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Metabolic Flux Analysis

Metabolic Flux Analysis: Methods and Protocols opens up the field of metabolic flux analysis to those who want to start a new flux analysis project but are overwhelmed by the complexity of the approach. Metabolic flux analysis emerged from the current limitation for the prediction of metabolic fluxes from a measured inventory of the cell. Divided into convenient thematic parts, topics in this essential volume include the fundamental characteristics of the underlying networks, the application of quantitative metabolite data and thermodynamic principles to constrain the solution space for flux balance analysis (FBA), the experimental toolbox to conduct different types of flux analysis experiments, the processing of data from 13C experiments, and three chapters that summarize some recent key findings. Written in the successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible protocols, and notes on troubleshooting and avoiding known pitfalls.

 

Authoritative and easily accessible, Metabolic Flux Analysis: Methods and Protocols presents protocols that cover a range of relevant organisms currently used in the field, providing a solid basis to anybody interested in the field of metabolic flux analysis.

Keywords

cell culture flux analysis metabolomics stoichiometry thermodynamics

Editors and affiliations

  • Jens O. Krömer
  • Lars K. Nielsen
  • Lars M. Blank
  1. 1.Centre for Microbial Electrosynthesis (CEMES), Advanced Water Management CentreUniversity of QueenslandSt. Lucia, BrisbaneAustralia
  2. 2.AIBNUniversity of QueenslandSt. Lucia, BrisbaneAustralia
  3. 3.Biology DepartmentRWTH Aachen UniversityAachenGermany

Bibliographic information

  • Book TitleMetabolic Flux Analysis
  • Book SubtitleMethods and Protocols
  • EditorsJens O. Krömer
    Lars K. Nielsen
    Lars M. Blank
  • Series TitleMethods in Molecular Biology
  • Series Abbreviated TitleMethods Molecular Biology
  • DOIhttps://doi.org/10.1007/978-1-4939-1170-7
  • Copyright InformationSpringer Science+Business Media New York2014
  • Publisher NameHumana Press, New York, NY
  • eBook PackagesSpringer Protocols
  • Hardcover ISBN978-1-4939-1169-1
  • Softcover ISBN978-1-4939-4159-9
  • eBook ISBN978-1-4939-1170-7
  • Series ISSN1064-3745
  • Series E-ISSN1940-6029
  • Edition Number1
  • Number of PagesXII, 316
  • Number of Illustrations19 b/w illustrations, 51 illustrations in colour
  • TopicsBiochemistry, general
    Enzymology
Источник: https://link.springer.com/content/pdf/10.1007%2F978-1-4939-1170-7.pdf

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de Havilland Comet

First commercial jet airliner

This article is about the jet airliner. For the 1930s racing aircraft, see de Havilland DH.88 Comet.

The de Havilland DH.106 Comet was the world's first commercial jet airliner. Developed and manufactured by de Havilland at its Hatfield Aerodrome in Hertfordshire, United Kingdom, the Comet 1 prototype first flew in 1949. It featured an aerodynamically clean design with four de Havilland Ghostturbojet engines buried in the wing roots, a pressurised cabin, and large square windows. For the era, it offered a relatively quiet, comfortable passenger cabin and was commercially promising at its debut in 1952.

Within a year of entering airline service, problems started to emerge, three Comets being lost within twelve months in highly publicised accidents, after suffering catastrophic in-flight break-ups. Two of these were found to be caused by structural failure resulting from metal fatigue in the airframe, a phenomenon not fully understood at the time; the other was due to overstressing of the airframe during flight through severe weather. The Comet was withdrawn from service and extensively tested. Design and construction flaws, including improper riveting and dangerous concentrations of stress around some of the square windows, were ultimately identified. As a result, the Comet was extensively redesigned, with oval windows, structural reinforcements and other changes. Rival manufacturers heeded the lessons learned from the Comet when developing their own aircraft.

Although sales never fully recovered, the improved Comet 2 and the prototype Comet 3 culminated in the redesigned Comet 4 series which debuted in 1958 and remained in commercial service until 1981. The Comet was also adapted for a variety of military roles such as VIP, medical and passenger transport, as well as surveillance; the last Comet 4, used as a research platform, made its final flight in 1997. The most extensive modification resulted in a specialised maritime patrol derivative, the Hawker Siddeley Nimrod, which remained in service with the Royal Air Force until 2011, over 60 years after the Comet's first flight.

Development[edit]

Origins[edit]

Design studies for the DH.106 Comet 1944–1947 (artist's impression)

On 11 March 1943, the Cabinet of the United Kingdom formed the Brabazon Committee, which was tasked with determining the UK's airliner needs after the conclusion of the Second World War.[4] One of its recommendations was for the development and production of a pressurised, transatlantic mailplane that could carry 1 long ton (2,200 lb; 1,000 kg) of payload at a cruising speed of 400 mph (640 km/h) non-stop.[5] Aviation company de Havilland was interested in this requirement, but chose to challenge the then widely held view that jet engines were too fuel-hungry and unreliable for such a role.[N 2] As a result, committee member Sir Geoffrey de Havilland, head of the de Havilland company, used his personal influence and his company's expertise to champion the development of a jet-propelled aircraft; proposing a specification for a pure turbojet-powered design.[4]

The committee accepted the proposal, calling it the "Type IV" (of five designs),[N 3] and in 1945 awarded a development and production contract to de Havilland under the designation Type 106. The type and design were to be so advanced that de Havilland had to undertake the design and development of both the airframe and the engines. This was because in 1945 no turbojet engine manufacturer in the world was drawing-up a design specification for an engine with the thrust and specific fuel consumption that could power an aircraft at the proposed cruising altitude (40,000 ft (12,000 m)), speed, and transatlantic range as was called for by the Type 106.[8] First-phase development of the DH.106 focused on short- and intermediate-range mailplanes with small passenger compartments and as few as six seats, before being redefined as a long-range airliner with a capacity of 24 seats.[5] Out of all the Brabazon designs, the DH.106 was seen as the riskiest: both in terms of introducing untried design elements and for the financial commitment involved.[4] Nevertheless, the British Overseas Airways Corporation (BOAC) found the Type IV's specifications attractive, and initially proposed a purchase of 25 aircraft; in December 1945, when a firm contract was created, the order total was revised to 10.[9]

"During the next few years, the UK has an opportunity, which may not recur, of developing aircraft manufacture as one of our main export industries. On whether we grasp this opportunity and so establish firmly an industry of the utmost strategic and economic importance, our future as a great nation may depend."

Duncan Sandys, Minister of Supply, 1952.[10]

A design team was formed in 1946 under the leadership of chief designer Ronald Bishop, who had been responsible for the Mosquito fighter-bomber.[9] Several unorthodox configurations were considered, ranging from canard to tailless designs;[N 4] All were rejected. The Ministry of Supply was interested in the most radical of the proposed designs, and ordered two experimental tailless DH 108s[N 5] to serve as proof of concept aircraft for testing swept-wing configurations in both low-speed and high-speed flight.[5][11] During flight tests, the DH 108 gained a reputation for being accident-prone and unstable, leading de Havilland and BOAC to gravitate to conventional configurations and, necessarily, designs with less technical risk.[12] The DH 108s were later modified to test the DH.106's power controls.[13]

In September 1946, before completion of the DH 108s, BOAC requests necessitated a redesign of the DH.106 from its previous 24-seat configuration to a larger 36-seat version.[5][N 6] With no time to develop the technology necessary for a proposed tailless configuration, Bishop opted for a more conventional 20-degree swept-wing design[N 7] with unswept tail surfaces, married to an enlarged fuselage accommodating 36 passengers in a four-abreast arrangement with a central aisle.[15] Replacing previously specified Halford H.1 Goblin engines, four new, more-powerful Rolls-Royce Avons were to be incorporated in pairs buried in the wing roots; Halford H.2 Ghost engines were eventually applied as an interim solution while the Avons cleared certification. The redesigned aircraft was named the DH.106 Comet in December 1947.[N 8] Revised first orders from BOAC and British South American Airways[N 9] totalled 14 aircraft, with delivery projected for 1952.[14]

Testing and prototypes[edit]

As the Comet represented a new category of passenger aircraft, more rigorous testing was a development priority.[17] From 1947 to 1948, de Havilland conducted an extensive research and development phase, including the use of several stress test rigs at Hatfield Aerodrome for small components and large assemblies alike. Sections of pressurised fuselage were subjected to high-altitude flight conditions via a large decompression chamber on-site [N 10] and tested to failure.[18] Tracing fuselage failure points proved difficult with this method,[18] and de Havilland ultimately switched to conducting structural tests with a water tank that could be safely configured to increase pressures gradually.[13][18][19] The entire forward fuselage section was tested for metal fatigue by repeatedly pressurising to 2.75 pounds per square inch (19.0 kPa) overpressure and depressurising through more than 16,000 cycles, equivalent to about 40,000 hours of airline service.[20] The windows were also tested under a pressure of 12 psi (83 kPa), 4.75 psi (32.8 kPa) above expected pressures at the normal service ceiling of 36,000 ft (11,000 m).[20] One window frame survived 100 psi (690 kPa),[21] about 1,250 percent over the maximum pressure it was expected to encounter in service.[20]

The first prototype DH.106 Comet (carrying Class B markings G-5-1) was completed in 1949 and was initially used to conduct ground tests and brief early flights.[18] The prototype's maiden flight, out of Hatfield Aerodrome, took place on 27 July 1949 and lasted 31 minutes.[22][23] At the controls was de Havilland chief test pilot John "Cats Eyes" Cunningham, a famous night-fighter pilot of the Second World War, along with co-pilot Harold "Tubby" Waters, engineers John Wilson (electrics) and Frank Reynolds (hydraulics), and flight test observer Tony Fairbrother.[24]

The prototype was registered G-ALVG just before it was publicly displayed at the 1949 Farnborough Airshow before the start of flight trials. A year later, the second prototype G-5-2 made its maiden flight. The second prototype was registered G-ALZK in July 1950 and it was used by the BOAC Comet Unit at Hurn from April 1951 to carry out 500 flying hours of crew training and route-proving.[25] Australian airline Qantas also sent its own technical experts to observe the performance of the prototypes, seeking to quell internal uncertainty about its prospective Comet purchase.[26] Both prototypes could be externally distinguished from later Comets by the large single-wheeled main landing gear, which was replaced on production models starting with G-ALYP by four-wheeled bogies.[27]

Design[edit]

Overview[edit]

The Comet was an all-metal low-wing cantilever monoplane powered by four jet engines; it had a four-place cockpit occupied by two pilots, a flight engineer, and a navigator.[28] The clean, low-drag design of the aircraft featured many design elements that were fairly uncommon at the time, including a swept-wing leading edge, integral wing fuel tanks, and four-wheel bogie main undercarriage units designed by de Havilland.[28] Two pairs of turbojet engines (on the Comet 1s, Halford H.2 Ghosts, subsequently known as de Havilland Ghost 50 Mk1s) were buried into the wings.[29]

The original Comet was the approximate length of, but not as wide as, the later Boeing 737-100, and carried fewer people in a significantly more-spacious environment. BOAC installed 36 reclining "slumberseats" with 45 in (1,100 mm) centres on its first Comets, allowing for greater leg room in front and behind;[30]Air France had 11 rows of seats with four seats to a row installed on its Comets.[31] Large picture window views and table seating accommodations for a row of passengers afforded a feeling of comfort and luxury unusual for transportation of the period.[32] Amenities included a galley that could serve hot and cold food and drinks, a bar, and separate men's and women's toilets.[33] Provisions for emergency situations included several life rafts stored in the wings near the engines, and individual life vests were stowed under each seat.[28]

One of the most striking aspects of Comet travel was the quiet, "vibration-free flying" as touted by BOAC.[34][N 11] For passengers used to propeller-driven airliners, smooth and quiet jet flight was a novel experience.[36]

Avionics and systems[edit]

For ease of training and fleet conversion, de Havilland designed the Comet's flight deck layout with a degree of similarity to the Lockheed Constellation, an aircraft that was popular at the time with key customers such as BOAC.[18] The cockpit included full dual-controls for the captain and first officer, and a flight engineer controlled several key systems, including fuel, air conditioning and electrical systems.[37] The navigator occupied a dedicated station, with a table across from the flight engineer.[38]

The flight deck of a Comet 4

Several of the Comet's avionics systems were new to civil aviation. One such feature was irreversible, powered flight controls, which increased the pilot's ease of control and the safety of the aircraft by preventing aerodynamic forces from changing the directed positions and placement of the aircraft's control surfaces.[39] Many of the control surfaces, such as the elevators, were equipped with a complex gearing system as a safeguard against accidentally over-stressing the surfaces or airframe at higher speed ranges.[40]

The Comet had a total of four hydraulic systems: two primaries, one secondary, and a final emergency system for basic functions such as lowering the undercarriage.[41] The undercarriage could also be lowered by a combination of gravity and a hand-pump.[42] Power was syphoned from all four engines for the hydraulics, cabin air conditioning, and the de-icing system; these systems had operational redundancy in that they could keep working even if only a single engine was active.[17] The majority of hydraulic components were centred in a single avionics bay.[43] A pressurised refuelling system, developed by Flight Refuelling Ltd, allowed the Comet's fuel tanks to be refuelled at a far greater rate than by other methods.[44]

The Comet 4 navigator's station

The cockpit was significantly altered for the Comet 4's introduction, on which an improved layout focusing on the onboard navigational suite was introduced.[45] An EKCO E160 radar unit was installed in the Comet 4's nose cone, providing search functions as well as ground and cloud-mapping capabilities,[38] and a radar interface was built into the Comet 4 cockpit along with redesigned instruments.[45]

Sud-Est's design bureau, while working on the Sud Aviation Caravelle in 1953, licensed several design features from de Havilland, building on previous collaborations on earlier licensed designs, including the DH 100 Vampire;[N 12] the nose and cockpit layout of the Comet 1 was grafted onto the Caravelle.[47] In 1969, when the Comet 4's design was modified by Hawker Siddeley to become the basis for the Nimrod, the cockpit layout was completely redesigned and bore little resemblance to its predecessors except for the control yoke.[48]

Fuselage[edit]

Diverse geographic destinations and cabin pressurisation alike on the Comet demanded the use of a high proportion of alloys, plastics, and other materials new to civil aviation across the aircraft to meet certification requirements.[49] The Comet's high cabin pressure and fast operating speeds were unprecedented in commercial aviation, making its fuselage design an experimental process.[49] At its introduction, Comet airframes would be subjected to an intense, high-speed operating schedule which included simultaneous extreme heat from desert airfields and frosty cold from the kerosene-filled fuel tanks, still cold from cruising at high altitude.[49]

The Comet's thin metal skin was composed of advanced new alloys[N 13] and was both riveted and chemically bonded, which saved weight and reduced the risk of fatigue cracks spreading from the rivets.[50] The chemical bonding process was accomplished using a new adhesive, Redux, which was liberally used in the construction of the wings and the fuselage of the Comet; it also had the advantage of simplifying the manufacturing process.[51]

When several of the fuselage alloys were discovered to be vulnerable to weakening via metal fatigue, a detailed routine inspection process was introduced. As well as thorough visual inspections of the outer skin, mandatory structural sampling was routinely conducted by both civil and military Comet operators. The need to inspect areas not easily viewable by the naked eye led to the introduction of widespread radiography examination in aviation; this also had the advantage of detecting cracks and flaws too small to be seen otherwise.[52]

Operationally, the design of the cargo holds led to considerable difficulty for the ground crew, especially baggage handlers at the airports. The cargo hold had its doors located directly underneath the aircraft, so each item of baggage or cargo had to be loaded vertically upwards from the top of the baggage truck, then slid along the hold floor to be stacked inside. The individual pieces of luggage and cargo also had to be retrieved in a similarly slow manner at the arriving airport.[53][54]

Propulsion[edit]

The Comet was powered by two pairs of turbojet engines buried in the wings close to the fuselage. Chief designer Bishop chose the Comet's embedded-engine configuration because it avoided the drag of podded engines and allowed for a smaller fin and rudder since the hazards of asymmetric thrust were reduced.[55] The engines were outfitted with baffles to reduce noise emissions, and extensive soundproofing was also implemented to improve passenger conditions.[56]

Placing the engines within the wings had the advantage of a reduction in the risk of foreign object damage, which could seriously damage jet engines. The low-mounted engines and good placement of service panels also made aircraft maintenance easier to perform.[57] The Comet's buried-engine configuration increased its structural weight and complexity. Armour had to be placed around the engine cells to contain debris from any serious engine failures; also, placing the engines inside the wing required a more complicated wing structure.[58]

The Comet 1 featured 5,050 lbf (22.5 kN) de Havilland Ghost 50 Mk1 turbojet engines.[29][59] Two hydrogen peroxide-powered de Havilland Sprite booster rockets were originally intended to be installed to boosttakeoff under hot and high altitude conditions from airports such as Khartoum and Nairobi.[31][60] These were tested on 30 flights, but the Ghosts alone were considered powerful enough and some airlines concluded that rocket motors were impractical.[13] Sprite fittings were retained on production aircraft.[61] Comet 1s subsequently received more powerful 5,700 lbf (25 kN) Ghost DGT3 series engines.[62]

From the Comet 2 onwards, the Ghost engines were replaced by the newer and more powerful 7,000 lbf (31 kN) Rolls-Royce Avon AJ.65 engines. To achieve optimum efficiency with the new powerplants, the air intakes were enlarged to increase mass air flow.[63] Upgraded Avon engines were introduced on the Comet 3,[63] and the Avon-powered Comet 4 was highly praised for its takeoff performance from high-altitude locations such as Mexico City.[64]

Operational history[edit]

Introduction[edit]

The earliest production aircraft, registered G-ALYP ("Yoke Peter"), first flew on 9 January 1951 and was subsequently lent to BOAC for development flying by its Comet Unit.[65] On 22 January 1952, the fifth production aircraft, registered G-ALYS, received the first Certificate of Airworthiness awarded to a Comet, six months ahead of schedule.[66] On 2 May 1952, as part of BOAC's route-proving trials, G-ALYP took off on the world's first jetliner[N 14] flight with fare-paying passengers and inaugurated scheduled service from London to Johannesburg.[68][69][70] The final Comet from BOAC's initial order, registered G-ALYZ, began flying in September 1952 and carried cargo along South American routes while simulating passenger schedules.[71]

Prince Philip returned from the Helsinki Olympic Games with G-ALYS on 4 August 1952. Queen Elizabeth, the Queen Mother and Princess Margaret were guests on a special flight of the Comet on 30 June 1953 hosted by Sir Geoffrey and Lady de Havilland.[72] Flights on the Comet were about 50 percent faster than on advanced piston-engined aircraft such as the Douglas DC-6 (490 mph (790 km/h) for the Comet compared to the DC-6's 315 mph (507 km/h)), and a faster rate of climb further cut flight times. In August 1953 BOAC scheduled the nine-stop London to Tokyo flights by Comet for 36 hours, compared to 86 hours and 35 minutes on its Argonaut piston airliner. (Pan Am's DC-6B was scheduled for 46 hours 45 minutes.) The five-stop flight from London to Johannesburg was scheduled for 21 hr 20 min.[73]

In their first year, Comets carried 30,000 passengers. As the aircraft could be profitable with a load factor as low as 43 percent, commercial success was expected.[27] The Ghost engines allowed the Comet to fly above weather that competitors had to fly through. They ran smoothly and were less noisy than piston engines, had low maintenance costs and were fuel-efficient above 30,000 ft (9,100 m).[N 15] In summer 1953, eight BOAC Comets left London each week: three to Johannesburg, two to Tokyo, two to Singapore and one to Colombo.[74]

In 1953, the Comet appeared to have achieved success for de Havilland.[75]Popular Mechanics wrote that Britain had a lead of three to five years on the rest of the world in jetliners.[70] As well as the sales to BOAC, two French airlines, Union Aéromaritime de Transport and Air France, each acquired three Comet 1As, an upgraded variant with greater fuel capacity, for flights to West Africa and the Middle East.[76][77] A slightly longer version of the Comet 1 with more powerful engines, the Comet 2, was being developed,[78] and orders were placed by Air India,[79]British Commonwealth Pacific Airlines,[80]Japan Air Lines,[81]Linea Aeropostal Venezolana,[81] and Panair do Brasil.[81] American carriers Capital Airlines, National Airlines, and Pan Am placed orders for the planned Comet 3, an even-larger, longer-range version for transatlantic operations.[82][83] Qantas was interested in the Comet 1 but concluded that a version with more range and better takeoff performance was needed for the London to Canberra route.[84]

Early hull losses[edit]

On 26 October 1952, the Comet suffered its first hull loss when a BOAC flight departing Rome's Ciampino airport failed to become airborne and ran into rough ground at the end of the runway. Two passengers sustained minor injuries, but the aircraft, G-ALYZ, was a write-off. On 3 March 1953, a new Canadian Pacific Airlines Comet 1A, registered CF-CUN and named Empress of Hawaii, failed to become airborne while attempting a night takeoff from Karachi, Pakistan, on a delivery flight to Australia. The aircraft plunged into a dry drainage canal and collided with an embankment, killing all five crew and six passengers on board.[85][86] The accident was the first fatal jetliner crash.[81] In response, Canadian Pacific cancelled its remaining order for a second Comet 1A and never operated the type in commercial service.[81]

Both early accidents were originally attributed to pilot error, as over-rotation had led to a loss of lift from the leading edge of the aircraft's wings. It was later determined that the Comet's wing profile experienced a loss of lift at a high angle of attack, and its engine inlets also suffered a lack of pressure recovery in the same conditions. As a result, de Havilland re-profiled the wings' leading edge with a pronounced "droop",[87] and wing fences were added to control spanwise flow.[88] A fictionalised investigation into the Comet's takeoff accidents was the subject of the novel Cone of Silence (1959) by Arthur David Beaty, a former BOAC captain. Cone of Silence was made into a film in 1960, and Beaty also recounted the story of the Comet's takeoff accidents in a chapter of his non-fiction work, Strange Encounters: Mysteries of the Air (1984).[89]

The Comet's second fatal accident occurred on 2 May 1953, when BOAC Flight 783, a Comet 1, registered G-ALYV, crashed in a severe thundersquall six minutes after taking off from Calcutta-Dum Dum (now Netaji Subhash Chandra Bose International Airport), India,[90] killing all 43 on board. Witnesses observed the wingless Comet on fire plunging into the village of Jagalgori,[91] leading investigators to suspect structural failure.[92]

India Court of Inquiry[edit]

After the loss of G-ALYV, the Government of India convened a court of inquiry[91] to examine the cause of the accident.[N 16] Professor Natesan Srinivasan joined the inquiry as the main technical expert. A large portion of the aircraft was recovered and reassembled at Farnborough,[92] during which the break-up was found to have begun with a left elevator spar failure in the horizontal stabilizer. The inquiry concluded that the aircraft had encountered extreme negative G forces during takeoff; severe turbulence generated by adverse weather was determined to have induced down-loading, leading to the loss of the wings. Examination of the cockpit controls suggested that the pilot may have inadvertently over-stressed the aircraft when pulling out of a steep dive by over-manipulation of the fully powered flight controls. Investigators did not consider metal fatigue as a contributory cause.[93]

The inquiry's recommendations revolved around the enforcement of stricter speed limits during turbulence, and two significant design changes also resulted: all Comets were equipped with weather radar and the "Q feel" system was introduced, which ensured that control column forces (invariably called stick forces) would be proportional to control loads. This artificial feel was the first of its kind to be introduced in any aircraft.[92] The Comet 1 and 1A had been criticised for a lack of "feel" in their controls,[94] and investigators suggested that this might have contributed to the pilot's alleged over-stressing of the aircraft;[95] Comet chief test pilot John Cunningham contended that the jetliner flew smoothly and was highly responsive in a manner consistent with other de Havilland aircraft.[96][N 17]

Comet disasters of 1954[edit]

Main articles: BOAC Flight 781 and South African Airways Flight 201

Just over a year later, Rome's Ciampino airport, the site of the first Comet hull loss, was the origin of a more-disastrous Comet flight. On 10 January 1954, 20 minutes after taking off from Ciampino, the first production Comet, G-ALYP, broke up in mid-air while operating BOAC Flight 781 and crashed into the Mediterranean off the Italian island of Elba with the loss of all 35 on board.[97][98] With no witnesses to the disaster and only partial radio transmissions as incomplete evidence, no obvious reason for the crash could be deduced. Engineers at de Havilland immediately recommended 60 modifications aimed at any possible design flaw, while the Abell Committee met to determine potential causes of the crash.[99][N 18] BOAC also voluntarily grounded its Comet fleet pending investigation into the causes of the accident.[101]

Abell Committee Court of Inquiry[edit]

Media attention centred on potential sabotage;[87] other speculation ranged from clear-air turbulence to an explosion of vapour in an empty fuel tank. The Abell Committee focused on six potential aerodynamic and mechanical causes: control flutter (which had led to the loss of DH 108 prototypes), structural failure due to high loads or metal fatigue of the wing structure, failure of the powered flight controls, failure of the window panels leading to explosive decompression, or fire and other engine problems. The committee concluded that fire was the most likely cause of the problem, and changes were made to the aircraft to protect the engines and wings from damage that might lead to another fire.[102]

During the investigation, the Royal Navy conducted recovery operations.[104] The first pieces of wreckage were discovered on 12 February 1954[105] and the search continued until September 1954, by which time 70 percent by weight of the main structure, 80 percent of the power section, and 50 percent of the aircraft's systems and equipment had been recovered.[106][107] The forensic reconstruction effort had just begun when the Abell Committee reported its findings. No apparent fault in the aircraft was found, [N 19] and the British government decided against opening a further public inquiry into the accident.[101] The prestigious nature of the Comet project, particularly for the British aerospace industry, and the financial impact of the aircraft's grounding on BOAC's operations both served to pressure the inquiry to end without further investigation.[101] Comet flights resumed on 23 March 1954.[108]

On 8 April 1954, Comet G-ALYY ("Yoke Yoke"), on charter to South African Airways, was on a leg from Rome to Cairo (of a longer route, SA Flight 201 from London to Johannesburg), when it crashed in the Mediterranean near Naples with the loss of all 21 passengers and crew on board.[97] The Comet fleet was immediately grounded once again and a large investigation board was formed under the direction of the Royal Aircraft Establishment (RAE).[97] Prime Minister Winston Churchill tasked the Royal Navy with helping to locate and retrieve the wreckage so that the cause of the accident could be determined.[109] The Comet's Certificate of Airworthiness was revoked, and Comet 1 line production was suspended at the Hatfield factory while the BOAC fleet was permanently grounded, cocooned and stored.[87]

Cohen Committee Court of Inquiry[edit]

BOAC Comet 1 cocooned and stored in the maintenance area at London Heathrow Airport in September 1954

On 19 October 1954, the Cohen Committee was established to examine the causes of the Comet crashes.[110] Chaired by Lord Cohen, the committee tasked an investigation team led by Sir Arnold Hall, Director of the RAE at Farnborough, to perform a more-detailed investigation. Hall's team began considering fatigue as the most likely cause of both accidents and initiated further research into measurable strain on the aircraft's skin.[97] With the recovery of large sections of G-ALYP from the Elba crash and BOAC's donation of an identical airframe, G-ALYU, for further examination, an extensive "water torture" test eventually provided conclusive results. This time, the entire fuselage was tested in a dedicated water tank that was built specifically at Farnborough to accommodate its full length.[101] Stress around the window corners was found to be much higher than expected and stresses on the skin were generally more than previously expected or tested.[111] The windows' square shape caused stress concentration by generating levels of stress two or three times greater than across the rest of the fuselage.[112] In 2012 a finite element analysis was carried out to find the stress values in a digital model of the Comet's cabin window loaded to a pressure differential of 8.25 psi. In this model, the maximum stress level at the margin of one of the outer row of rivet holes near the corner of the window was almost five times greater than in the areas of skin remote from the windows.[113]

In water-tank testing, engineers subjected G-ALYU to repeated repressurisation and over-pressurisation, and on 24 June 1954, after 3,057 flight cycles (1,221 actual and 1,836 simulated),[114] G-ALYU burst open. Hall, Geoffrey de Havilland and Bishop were immediately called to the scene, where the water tank was drained to reveal that the fuselage had ripped open at a bolt hole, forward of the forward left escape hatch cutout. The failure then occurred longitudinally along a fuselage stringer at the widest point of the fuselage (accident report Fig 7).[115] The fuselage frames did not have sufficient strength to prevent the crack from propagating. Although the fuselage failed after a number of cycles that represented three times the life of G-ALYP at the time of the accident, it was still much earlier than expected.[116] A further test reproduced the same results.[117] Based on these findings, Comet 1 structural failures could be expected at anywhere from 1,000 to 9,000 cycles. Before the Elba accident, G-ALYP had made 1,290 pressurised flights, while G-ALYY had made 900 pressurised flights before crashing. Dr P. B. Walker, Head of the Structures Department at the RAE, said he was not surprised by this, noting that the difference was about three to one, and previous experience with metal fatigue suggested a total range of nine to one between experiment and outcome in the field could result in failure.[114]

The RAE also reconstructed about two-thirds of G-ALYP at Farnborough and found fatigue crack growth from a rivet hole at the low-drag fibreglass forward aperture around the Automatic Direction Finder, which had caused a catastrophic break-up of the aircraft in high-altitude flight.[118] The punch-rivet construction technique employed in the Comet's design had exacerbated its structural fatigue problems;[97] the aircraft's windows had been engineered to be glued and riveted, but had been punch-riveted only. Unlike drill riveting, the imperfect nature of the hole created by punch-riveting could cause fatigue cracks to start developing around the rivet. Principal investigator Hall accepted the RAE's conclusion of design and construction flaws as the likely explanation for G-ALYU's structural failure after 3,060 pressurisation cycles.[N 20]

Response[edit]

In responding to the report de Havilland stated: "Now that the danger of high level fatigue in pressure cabins has been generally appreciated, de Havillands will take adequate measures to deal with this problem. To this end we propose to use thicker gauge materials in the pressure cabin area and to strengthen and redesign windows and cut outs and so lower the general stress to a level at which local stress concentrations either at rivets and bolt holes or as such may occur by reason of cracks caused accidentally during manufacture or subsequently, will not constitute a danger."[120]

The Cohen inquiry closed on 24 November 1954, having "found that the basic design of the Comet was sound",[110] and made no observations or recommendations regarding the shape of the windows. De Havilland nonetheless began a refit programme to strengthen the fuselage and wing structure, employing thicker-gauge skin and replacing the square windows and panels with rounded versions.[109] The fuselage escape hatch cut-outs retained their rectangular shape.[121]

Following the Comet enquiry, aircraft were designed to "Fail safe" or "Safe Life" standards,[122] though several subsequent catastrophic fatigue failures, such as Aloha Airlines Flight 243 of April 28, 1988 have occurred.[123]

In June 1956, some more wreckage from G-ALYP was accidentally trawled up from an area about 15 miles south of where the original wreckage had been found. This wreckage was from the starboard side of the cabin just above the three front windows. Subsequent examination at Farnborough suggested that the primary failure was probably near to this area rather than at the rear automatic direction finding window on the roof of the cabin, as had been previously thought. These findings were kept secret until the details were published in 2015.[124]

Resumption of service[edit]

With the discovery of the structural problems of the early series, all remaining Comets were withdrawn from service, while de Havilland launched a major effort to build a new version that would be both larger and stronger. All outstanding orders for the Comet 2 were cancelled by airline customers.[63] The square windows of the Comet 1 were replaced by the oval versions used on the Comet 2, which first flew in 1953, and the skin thickness was increased slightly.[125] Remaining Comet 1s and 1As were either scrapped or modified with oval windows and rip-stop doublers.

All production Comet 2s were also modified to alleviate the fatigue problems (most of these served with the RAF as the Comet C2); a programme to produce a Comet 2 with more powerful Avons was delayed. The prototype Comet 3 first flew in July 1954 and was tested in an unpressurised state pending completion of the Cohen inquiry.[63] Comet commercial flights would not resume until 1958.[126]

Development flying and route proving with the Comet 3 allowed accelerated certification of what was destined to be the most successful variant of the type, the Comet 4. All airline customers for the Comet 3 subsequently cancelled their orders and switched to the Comet 4,[63] which was based on the Comet 3 but with improved fuel capacity. BOAC ordered 19 Comet 4s in March 1955, and American operator Capital Airlines ordered 14 Comets in July 1956.[127] Capital's order included 10 Comet 4As, a variant modified for short-range operations with a stretched fuselage and short wings, lacking the pinion (outboard wing) fuel tanks of the Comet 4.[82] Financial problems and a takeover by United Airlines meant that Capital would never operate the Comet.[citation needed]

The Comet 4 first flew on 27 April 1958 and received its Certificate of Airworthiness on 24 September 1958; the first was delivered to BOAC the next day.[125][128] The base price of a new Comet 4 was roughly £1.14 million (£24.81 million in 2019).[129] The Comet 4 enabled BOAC to inaugurate the first regular jet-powered transatlantic services on 4 October 1958 between London and New York (albeit still requiring a fuel stop at Gander International Airport, Newfoundland, on westward North Atlantic crossings).[68] While BOAC gained publicity as the first to provide transatlantic jet service, by the end of the month rival Pan American World Airways was flying the Boeing 707 on the New York-Paris route, with a fuel stop at Gander in both directions,[130] and in 1960 began flying Douglas DC-8's on its transatlantic routes as well. The American jets were larger, faster, longer-ranged and more cost-effective than the Comet.[131] After analysing route structures for the Comet, BOAC reluctantly cast-about for a successor, and in 1956 entered into an agreement with Boeing to purchase the 707.[132]

Comet 4 of East African Airways at London Heathrow in 1964

The Comet 4 was ordered by two other airlines: Aerolíneas Argentinas took delivery of six Comet 4s from 1959 to 1960, using them between Buenos Aires and Santiago, New York and Europe, and East African Airways received three new Comet 4s from 1960 to 1962 and operated them to the United Kingdom and to Kenya, Tanzania, and Uganda.[133] The Comet 4A ordered by Capital Airlines was instead built for BEA as the Comet 4B, with a further fuselage stretch of 38 in (970 mm) and seating for 99 passengers. The first Comet 4B flew on 27 June 1959 and BEA began Tel Aviv to London-Heathrow services on 1 April 1960.[134]Olympic Airways was the only other customer to order the type.[135] The last Comet 4 variant, the Comet 4C, first flew on 31 October 1959 and entered service with Mexicana in 1960.[136] The Comet 4C had the Comet 4B's longer fuselage and the longer wings and extra fuel tanks of the original Comet 4, which gave it a longer range than the 4B. Ordered by Kuwait Airways, Middle East Airlines, Misrair (later United Arab Airlines), and Sudan Airways, it was the most popular Comet variant.[81][137]

Later service[edit]

In 1959 BOAC began shifting its Comets from transatlantic routes[N 21] and released the Comet to associate companies, making the Comet 4's ascendancy as a premier airliner brief. Besides the 707 and DC-8, the introduction of the Vickers VC10 allowed competing aircraft to assume the high-speed, long-range passenger service role pioneered by the Comet.[138] In 1960, as part of a government-backed consolidation of the British aerospace industry, de Havilland itself was acquired by Hawker Siddeley, within which it became a wholly owned division.[139]

In the 1960s, orders declined, a total of 76 Comet 4s being delivered from 1958 to 1964. In November 1965, BOAC retired its Comet 4s from revenue service; other operators continued commercial passenger flights with the Comet until 1981. Dan-Air played a significant role in the fleet's later history and, at one time, owned all 49 remaining airworthy civil Comets.[140] On 14 March 1997 a Comet 4C serialXS235 and named Canopus,[141] which had been acquired by the British Ministry of Technology and used for radio, radar and avionics trials, made the last documented production Comet flight.[1]

Legacy[edit]

Dan-Air Comet 4C, G-BDIW exhibited at the Flugausstellung Hermeskeilin Germany

The Comet is widely regarded as both an adventurous step forward and a supreme tragedy; the aircraft's legacy includes advances in aircraft design and in accident investigations. The inquiries into the accidents that plagued the Comet 1 were perhaps some of the most extensive and revolutionary that have ever taken place, establishing precedents in accident investigation; many of the deep-sea salvage and aircraft reconstruction techniques employed have remained in use within the aviation industry.[142] In spite of the Comet being subjected to what was then the most rigorous testing of any contemporary airliner, pressurisation and the dynamic stresses involved were not thoroughly understood at the time of the aircraft's development, nor was the concept of metal fatigue. Though these lessons could be implemented on the drawing board for future aircraft, corrections could only be retroactively applied to the Comet.[143]

According to de Havilland's chief test pilot John Cunningham, who had flown the prototype's first flight, representatives from American manufacturers such as Boeing and Douglas privately disclosed that if de Havilland had not experienced the Comet's pressurisation problems first, it would have happened to them.[144] Cunningham likened the Comet to the later Concorde and added that he had assumed that the aircraft would change aviation, which it subsequently did.[96] Aviation author Bill Withuhn concluded that the Comet had pushed "'the state-of-the-art' beyond its limits."[57]

Aeronautical-engineering firms were quick to respond to the Comet's commercial advantages and technical flaws alike; other aircraft manufacturers learned from, and profited by, the hard-earned lessons embodied by de Havilland's Comet.[10][147] The Comet's buried engines were used on some other early jet airliners, such as the Tupolev Tu-104,[148] but later aircraft, such as the Boeing 707 and Douglas DC-8, differed by employing podded engines held on pylons beneath the wings.[149] Boeing stated that podded engines were selected for their passenger airliners because buried engines carried a higher risk of catastrophic wing failure in the event of engine fire.[150] In response to the Comet tragedies, manufacturers also developed ways of pressurisation testing, often going so far as to explore rapid depressurisation; subsequent fuselage skins were of a greater thickness than the skin of the Comet.[151]

Variants[edit]

Comet 1[edit]

The square-windowed Comet 1 was the first model produced, a total of 12 aircraft in service and test. Following closely the design features of the two prototypes, the only noticeable change was the adoption of four-wheel bogie main undercarriage units, replacing the single main wheels. Four Ghost 50 Mk 1 engines were fitted (later replaced by more powerful Ghost DGT3 series engines). The span was 115 ft (35 m), and overall length 93 ft (28 m); the maximum takeoff weight was over 105,000 lb (48,000 kg) and over 40 passengers could be carried.[62]

  • An updated Comet 1A was offered with higher-allowed weight, greater fuel capacity,[76] and water-methanol injection; 10 were produced. In the wake of the 1954 disasters, all Comet 1s and 1As were brought back to Hatfield, placed in a protective cocoon and retained for testing.[152] All were substantially damaged in stress testing or were scrapped entirely.[153]
  • Comet 1X: Two RCAF Comet 1As were rebuilt with heavier-gauge skins to a Comet 2 standard for the fuselage, and renamed Comet 1X.[110]
  • Comet 1XB: Four Comet 1As were upgraded to a 1XB standard with a reinforced fuselage structure and oval windows. Both 1X series were limited in number of pressurisation cycles.[153]
  • The DH 111 Comet Bomber, a nuclear bomb-carrying variant developed to Air Ministry specification B35/46, was submitted to the Air Ministry on 27 May 1948. It had been originally proposed in 1948 as the "PR Comet", a high-altitude photo reconnaissance adaptation of the Comet 1. The Ghost DGT3-powered airframe featured a narrowed fuselage, a bulbous nose with H2S Mk IX radar, and a four-crewmember pressurised cockpit under a large bubble canopy. Fuel tanks carrying 2,400 imperial gallons (11,000 L) were added to attain a range of 3,350 miles (5,390 km). The proposed DH 111 received a negative evaluation from the Royal Aircraft Establishment over serious concerns regarding weapons storage; this, along with the redundant capability offered by the RAF's proposed V bomber trio, led de Havilland to abandon the project on 22 October 1948.[154]

Comet 2[edit]

Comet C2, XK671 Aquilaat RAF Waterbeach, fitted with revised round windows

The Comet 2 had a slightly larger wing, higher fuel capacity and more-powerful Rolls-Royce Avon engines, which all improved the aircraft's range and performance;[155] its fuselage was 3 ft 1 in (0.94 m) longer than the Comet 1's.[156] Design changes had been made to make the aircraft more suitable for transatlantic operations.[155] Following the Comet 1 disasters, these models were rebuilt with heavier-gauge skin and rounded windows, and the Avon engines featuring larger air intakes and outward-curving jet tailpipes.[N 22][157] A total of 12 of the 44-seat Comet 2s were ordered by BOAC for the South Atlantic route.[158] The first production aircraft (G-AMXA) flew on 27 August 1953.[159] Although these aircraft performed well on test flights on the South Atlantic, their range was still not suitable for the North Atlantic. All but four Comet 2s were allocated to the RAF, deliveries beginning in 1955. Modifications to the interiors allowed the Comet 2s to be used in several roles. For VIP transport, the seating and accommodations were altered and provisions for carrying medical equipment including iron lungs were incorporated. Specialised signals intelligence and electronic surveillance capability was later added to some airframes.[160]

  • Comet 2X: Limited to a single Comet Mk 1 powered by four Rolls-Royce Avon 502 turbojet engines and used as a development aircraft for the Comet 2.[155]
  • Comet 2E: Two Comet 2 airliners were fitted with Avon 504s in the inner nacelles and Avon 524s in the outer ones. These aircraft were used by BOAC for proving flights during 1957–1958.[155]
  • Comet T2: The first two of 10 Comet 2s for the RAF were fitted out as crew trainers, the first aircraft (XK669) flying initially on 9 December 1955.[160]
  • Comet C2: Eight Comet 2s originally destined for the civil market were completed for the RAF and assigned to No. 216 Squadron.[160]
  • Comet 2R: Three Comet 2s were modified for use in radar and electronic systems development, initially assigned to No. 90 Group (later Signals Command) for the RAF.[160] In service with No. 192 and No. 51 Squadrons, the 2R series was equipped to monitor Warsaw Pact signal traffic and operated in this role from 1958.[161][N 23]

Comet 3[edit]

The Comet 3, which flew for the first time on 19 July 1954, was a Comet 2 lengthened by 15 ft 5 in (4.70 m) and powered by Avon M502 engines developing 10,000 lbf (44 kN).[162] The variant added wing pinion tanks, and offered greater capacity and range.[163] The Comet 3 was destined to remain a development series since it did not incorporate the fuselage-strengthening modifications of the later series aircraft, and was not able to be fully pressurised.[164] Only two Comet 3s began construction; G-ANLO, the only airworthy Comet 3, was demonstrated at the Farnborough SBAC Show in September 1954. The other Comet 3 airframe was not completed to production standard and was used primarily for ground-based structural and technology testing during development of the similarly sized Comet 4. Another nine Comet 3 airframes were not completed and their construction was abandoned at Hatfield.[165] In BOAC colours, G-ANLO was flown by John Cunningham in a marathon round-the-world promotional tour in December 1955.[163] As a flying testbed, it was later modified with Avon RA29 engines fitted, as well as replacing the original long-span wings with reduced span wings as the Comet 3B and demonstrated in British European Airways (BEA) livery at the Farnborough Airshow in September 1958.[164] Assigned in 1961 to the Blind Landing Experimental Unit (BLEU) at RAE Bedford, the final testbed role played by G–ANLO was in automatic landing system experiments. When retired in 1973, the airframe was used for foam-arrester trials before the fuselage was salvaged at BAE Woodford, to serve as the mock-up for the Nimrod.[166]

Comet 4[edit]

The Comet 4 was a further improvement on the stretched Comet 3 with even greater fuel capacity. The design had progressed significantly from the original Comet 1, growing by 18 ft 6 in (5.64 m) and typically seating 74 to 81 passengers compared to the Comet 1's 36 to 44 (119 passengers could be accommodated in a special charter seating package in the later 4C series).[15] The Comet 4 was considered the definitive series, having a longer range, higher cruising speed and higher maximum takeoff weight. These improvements were possible largely because of Avon engines, with twice the thrust of the Comet 1's Ghosts.[134] Deliveries to BOAC began on 30 September 1958 with two 48-seat aircraft, which were used to initiate the first scheduled transatlantic services.

  • Comet 4B: Originally developed for Capital Airlines as the 4A, the 4B featured greater capacity through a 2m longer fuselage, and a shorter wingspan; 18 were produced.
  • Comet 4C: This variant featured the Comet 4's wings and the 4B's longer fuselage; 23 were produced.

The last two Comet 4C fuselages were used to build prototypes of the Hawker Siddeley Nimrod maritime patrol aircraft.[167] A Comet 4C (SA-R-7) was ordered by Saudi Arabian Airlines with an eventual disposition to the Saudi Royal Flight for the exclusive use of King Saud bin Abdul Aziz. Extensively modified at the factory, the aircraft included a VIP front cabin, a bed, special toilets with gold fittings and was distinguished by a green, gold and white colour scheme with polished wings and lower fuselage that was commissioned from aviation artist John Stroud. Following its first flight, the special order Comet 4C was described as "the world's first executive jet."[168]

Comet 5 proposal[edit]

The Comet 5 was proposed as an improvement over previous models, including a wider fuselage with five-abreast seating, a wing with greater sweep and podded Rolls-Royce Conway engines. Without support from the Ministry of Transport, the proposal languished as a hypothetical aircraft and was never realised.[169][N 24]

Hawker Siddeley Nimrod[edit]

Main article: Hawker Siddeley Nimrod

The last two Comet 4C aircraft produced were modified as prototypes (XV148 & XV147) to meet a British requirement for a maritime patrol aircraft for the Royal Air Force; initially named "Maritime Comet", the design was designated Type HS 801.[167] This variant became the Hawker Siddeley Nimrod and production aircraft were built at the Hawker Siddeley factory at Woodford Aerodrome. Entering service in 1969, five Nimrod variants were produced.[170] The final Nimrod aircraft were retired in June 2011.[171]

Operators[edit]

Main article: List of de Havilland Comet operators

The original operators of the early Comet 1 and the Comet 1A were BOAC, Union Aéromaritime de Transport and Air France. All early Comets were withdrawn from service for accident inquiries, during which orders from British Commonwealth Pacific Airlines, Japan Air Lines, Linea Aeropostal Venezolana, National Airlines, Pan American World Airways and Panair do Brasil were cancelled.[80][81] When the redesigned Comet 4 entered service, it was flown by customers BOAC, Aerolíneas Argentinas, and East African Airways,[172] while the Comet 4B variant was operated by customers BEA and Olympic Airways [172] and the Comet 4C model was flown by customers Kuwait Airways, Mexicana, Middle East Airlines, Misrair Airlines and Sudan Airways.[81]

Other operators used the Comet either through leasing arrangements or through second-hand acquisitions. BOAC's Comet 4s were leased out to Air Ceylon, Air India, AREA Ecuador, Central African Airways[173] and Qantas Empire Airways;[80][174] after 1965 they were sold to AREA Ecuador, Dan-Air, Mexicana, Malaysian Airways, and the Ministry of Defence.[81][172][175] BEA's Comet 4Bs were chartered by Cyprus Airways, Malta Airways and Transportes Aéreos Portugueses.[176]Channel Airways obtained five Comet 4Bs from BEA in 1970 for inclusive tour charters.[177] Dan-Air bought all of the surviving flyable Comet 4s from the late 1960s into the 1970s; some were for spares reclamation, but most were operated on the carrier's inclusive-tour charters; a total of 48 Comets of all marks were acquired by the airline.[178]

In military service, the United Kingdom's Royal Air Force was the largest operator, with 51 Squadron (1958–1975; Comet C2, 2R), 192 Squadron (1957–1958; Comet C2, 2R), 216 Squadron (1956–1975; Comet C2 and C4), and the Royal Aircraft Establishment using the aircraft.[110][179] The Royal Canadian Air Force also operated Comet 1As (later retrofitted to 1XB) through its 412 Squadron from 1953 to 1963.[153]

Accidents and incidents[edit]

The Comet was involved in 26 hull-loss accidents, including 13 fatal crashes which resulted in 426 fatalities.[180] Pilot error was blamed for the type's first fatal accident, which occurred during takeoff at Karachi, Pakistan, on 3 March 1953 and involved a Canadian Pacific Airlines Comet 1A.[81] Three fatal Comet 1 crashes due to structural problems, specifically BOAC Flight 783 on 2 May 1953, BOAC Flight 781 on 10 January 1954 and South African Airways Flight 201 on 8 April 1954, led to the grounding of the entire Comet fleet. After design modifications were implemented, Comet services resumed on October 4, 1958 with Comet 4's.[81][181]

Comet 4 G-APDN crashedin the Spanish Montseny range in July 1970 during a Dan-Air flight.[180]

Pilot error resulting in controlled flight into terrain was blamed for five fatal Comet 4 accidents: an Aerolíneas Argentinas crash near Asunción, Paraguay, on 27 August 1959, Aerolíneas Argentinas Flight 322 at Campinas near São Paulo, Brazil, on 23 November 1961, United Arab Airlines Flight 869 in Thailand's Khao Yai mountains on 19 July 1962, a Saudi Arabian Government crash in the Italian Alps on 20 March 1963, and United Arab Airlines Flight 844 in Tripoli, Libya, on 2 January 1971.[81] The Dan-Air de Havilland Comet crash in Spain's Montseny range on 3 July 1970 was attributed to navigational errors by air traffic control and pilots.[182] Other fatal Comet 4 accidents included a British European Airways crash in Ankara, Turkey, following instrument failure on 21 December 1961, a United Arab Airlines Flight 869 crash during inclement weather near Bombay, India, on 28 July 1963, and the terrorist bombing of Cyprus Airways Flight 284 off the Turkish coast on 12 October 1967.[81]

Nine Comets, including Comet 1s operated by BOAC and Union Aeromaritime de Transport and Comet 4s flown by Aerolíneas Argentinas, Dan-Air, Malaysian Airlines and United Arab Airlines, were irreparably damaged during takeoff or landing accidents that were survived by all on board.[81][180] A hangar fire damaged a No. 192 Squadron RAF Comet 2R beyond repair on 13 September 1957, and three Middle East Airlines Comet 4Cs were destroyed by Israeli troops at Beirut, Lebanon, on 28 December 1968.[81]

Aircraft on display[edit]

Since retirement, three early-generation Comet airframes have survived in museum collections. The only complete remaining Comet 1, a Comet 1XB with the registration G-APAS, the very last Comet 1 built, is displayed at the RAF Museum Cosford.[183] Though painted in BOAC colours, it never flew for the airline, having been first delivered to Air France and then to the Ministry of Supply after conversion to 1XB standard;[183] this aircraft also served with the RAF as XM823. The sole surviving Comet fuselage with the original square-shaped windows, part of a Comet 1A registered F-BGNX, has undergone restoration and is on display at the de Havilland Aircraft Museum in Hertfordshire, England.[184] A Comet C2 Sagittarius with serialXK699, later maintenance serial 7971M, was formerly on display at the gate of RAF Lyneham in Wiltshire, England since 1987.[185][186] In 2012, with the planned closure of RAF Lyneham, the aircraft was slated to be dismantled and shipped to the RAF Museum Cosford where it was to be re-assembled for display. The move was cancelled due to the level of corrosion and the majority of the airframe was scrapped in 2013, the cockpit section going to the Boscombe Down Aviation Collection at Old Sarum Airfield[187]

Six complete Comet 4s are housed in museum collections. The Imperial War Museum Duxford has a Comet 4 (G-APDB), originally in Dan-Air colours as part of its Flight Line Display, and later in BOAC livery at its AirSpace building.[188] A Comet 4B (G-APYD) is stored in a facility at the Science Museum at Wroughton in Wiltshire, England.[189] Comet 4Cs are exhibited at the Flugausstellung Peter Junior at Hermeskeil, Germany (G-BDIW),[190] the Museum of Flight Restoration Center near Everett, Washington (N888WA),[175] and the National Museum of Flight near Edinburgh, Scotland (G-BDIX).[191]

The last Comet to fly, Comet 4C Canopus (XS235),[1] is kept in running condition at Bruntingthorpe Aerodrome, where fast taxi-runs are regularly conducted.[192] Since the 2000s, several parties have proposed restoring Canopus, which is maintained by a staff of volunteers,[193] to airworthy, fully flight-capable condition.[141] The Bruntingthorpe Aerodrome also displays a related Hawker Siddeley Nimrod MR2 aircraft.[193]

Specifications[edit]

Variant[194]Comet 1Comet 2Comet 3Comet 4
Cockpit crew 4 (2 pilots, flight engineer and radio operator/navigator)[195]
Passengers36–44[15][158]58–76[162]56–81[196]
Length 93 ft (28 m)[156]96 ft 1 in (29.29 m)[156]111 ft 6 in (33.99 m)[162][197]
Tail height 29 ft 6 in (8.99 m)[197]
Wingspan115 ft (35 m)[197][198]
Wing area2,015 sq ft (187.2 m2)[156]2,121 sq ft (197.0 m2)[197]
Aspect ratio6.566.24
Airfoil NACA 63A116 mod root, NACA 63A112 mod tip[199]
MTOW110,000 lb (50,000 kg)[156]120,000 lb (54,000 kg)[156]150,000 lb (68,000 kg)[156]156,000 lb (71,000 kg)[197]
Turbojets (x 4) Halford H.2 Ghost 50 R-R Avon Mk 503/504 R-R Avon Mk 502/521 R-R Avon Mk 524
Unit thrust 5,000 lbf (22 kN)[156]7,000 lbf (31 kN)[156]10,000 lbf (44 kN)[162]10,500 lbf (47 kN)[200]
Range1,300 nmi; 2,400 km[69]2,300 nmi; 4,200 km[198]2,300 nmi; 4,300 km[201]2,802 nmi; 5,190 km[195]
Cruisingspeed400 kn (740 km/h)[156]430 kn (790 km/h)[198]450 kn (840 km/h)[198][200]
Cruise altitude42,000 ft (13,000 m)[156][198]45,000 ft (14,000 m)[198]42,000 ft (13,000 m)[195]

In popular culture[edit]

Main article: De Havilland Comet in fiction

See also[edit]

Comet 4B 3-view schematic (front, side, and dorsal views)

Comet 1 3-view in silhouette (note differences in Comet 4 insert, reproduced in same scale)

Related development

Aircraft of comparable role, configuration, and era

Related lists

References[edit]

Notes
  1. ^Total of Comets in production: 114,[2] or 136 (when including refitting of original airframes and conversions).[3]
  2. ^ During the same era, both Lockheed with their Lockheed L-188 Electra and Vickers with the ground-breaking Vickers Viscount discounted the advantages of "pure" jet power to develop turboprop-powered airliners.[6]
  3. ^The "Type IV" Specifications issued on 3 February 1943 provided for a "high-speed mail-carrying airliner, gas-turbine powered."[7]
  4. ^From 1944 to 1946, the design group prepared submissions on a three-engined twin-boom design, a three-engined canard design with engines mounted in the rear, and a tailless design that featured a swept wing and four "podded" engines.[9]
  5. ^The Ministry of Supply's order for DH 108s was listed as Operational Requirement OR207 to Specification E.18/45.[11]
  6. ^BOAC's requested capacity increase was known as Specification 22/46.[5]
  7. ^The wing was drastically redesigned from a 40˚ sweep.[14]
  8. ^The name "Comet", previously used by the de Havilland DH.88 racing aircraft, was revived.[16]
  9. ^British South American Airways merged with BOAC in 1949.[5]
  10. ^The fuselage sections and nose simulated a flight up to 70,000 ft (21,000 m) at a temperature of −70 °C (−94 °F), with 2,000 lb (910 kg) pressure applications at 9 psi (62 kPa).[13]
  11. ^BOAC flight crew revelled in standing a pen on end and pointing that out to passengers; invariably, the pen remained upright throughout the entire flight.[35]
  12. ^The Sud-Est SE 530/532/535 Mistral (FB 53) was a single-seat fighter-bomber version of the de Havilland Vampire jet fighter, used by L'Armée de l'Air.[46]
  13. ^Fuselage alloys detailed in Directorate of Technical Development 564/L.73 and DTD 746C/L90.
  14. ^The Avro Canada C102 Jetliner, for which it was coined, first used the term; "jetliner" later became a generic term for all jet airliners.[67]
  15. ^Depending on weight and temperature, cruise fuel consumption was 6 to 10 kg (13 to 22 lb) per per nautical mile (1.2 miles; 1.9 km), the higher figure being at the lower altitude needed at high weight.[citation needed]
  16. ^The court acted under the provisions of Rule 75 of the Indian Aircraft Rules 1937.[92]
  17. ^Cunningham: "[the Comet] flew extremely smoothly and responded to the controls in the best way de Havilland aircraft usually did."[96]
  18. ^The Abell Committee, named after chairman C. Abell, Deputy Operations Director (Engineering) of BOAC, consisted of representatives of the Allegation Review Board (A.R.B.), BOAC, and de Havilland.[100]
  19. ^On 4 April, Lord Brabazon wrote to the Minister of Transport, "Although no definite reason for the accident has been established, modifications are being embodied to cover every possibility that imagination has suggested as a likely cause of the disaster. When these modifications are completed and have been satisfactorily flight-tested, the Board sees no reason why passenger services should not be resumed."[101]
  20. ^Hall: "In the light of known properties of the aluminium alloy D.T.D. 546 or 746 of which the skin was made and in accordance with the advice I received from my Assessors, I accept the conclusion of RAE that this is a sufficient explanation of the failure of the cabin skin of Yoke Uncle by fatigue after a small number, namely, 3,060 cycles of pressurisation."[119]
  21. ^The Feb 1959 OAG shows eight transatlantic Comets a week out of London, plus 10 BOAC Britannias and 11 DC-7Cs. In April 1960, 13 Comets, 19 Britannias and 6 DC-7Cs. Comets quit flying the North Atlantic in October 1960 (but reportedly made a few flights in summer 1964).[citation needed]
  22. ^Avon-powered Comets were distinguished by larger air intakes and curved tailpipes that reduced the thermal effect on the rear fuselage.[157]
  23. ^The 2R ELINT series was operational until 1974, when replaced by the Nimrod R1, the last Comet derivative in RAF service.[161]
  24. ^The MoT subsequently backed BOAC's order of Conway-powered Boeing 707s.[169]
Citations
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  9. ^ abcJones 2010, p. 62.
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  13. ^ abcdBirtles 1970, p. 125.
  14. ^ abJones 2010, pp. 62–63.
  15. ^ abcWinchester 2004, p. 109.
  16. ^Jackson 1988, p. 356.
  17. ^ abDarling 2001, p. 17.
  18. ^ abcdeDarling 2001, p. 18.
  19. ^"Tank Test Mk 2.", Flight, Iliffe, pp. 958–959, 30 December 1955, archived from the original on 31 January 2019, retrieved 26 April 2012
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  21. ^"Comet Engineering", Flight, Iliffe, p. 552, 1 May 1953, archived from the original on 2 February 2017, retrieved 23 March 2019 – via FlightGlobal Archive
  22. ^Dick and Patterson 2010, pp. 134–137.
  23. ^Green and Swanborough April 1977, p. 174.
  24. ^Prins 1998, p. 43.
  25. ^Swanborough 1962, p. 45.
  26. ^Gunn 1987, p. 268.
  27. ^ abWalker 2000, p. 25.
  28. ^ abcFrancis 1950, p. 99.
  29. ^ abFrancis 1950, pp. 100–101.
  30. ^Hill 2002, p. 27.
  31. ^ abCookman, Aubery O. Jr. "Commute by Jet."Popular Mechanics, 93(4), April 1950, pp. 149–152.
  32. ^Smith 2010. 30(4), pp. 489, 506.
  33. ^Francis 1950, p. 98.
  34. ^Walker 2000, p. 69.
  35. ^Windsor-Liscombe, Rhodri. "Usual Culture: The Jet."Topia: Canadian Journal of Cultural Studies (Toronto: York University), Number 11, Spring 2004. Retrieved 26 April 2012.
  36. ^Francis 1950, p. 100.
  37. ^Darling 2001, pp. 35–36.
  38. ^ abDarling 2001, p. 36.
  39. ^Abzug and Larrabee 2002, pp. 80–81.
  40. ^Darling 2001, p. 2.
  41. ^Darling 2001, pp. 16–17.
  42. ^Darling 2001, p. 40.
  43. ^Darling 2001, p. 45.
  44. ^"F.R. equipment speeds refuelling."Flight, 11 May 1951. Retrieved 26 April 2012.
  45. ^ abDarling 2001, pp. 40–41.
  46. ^Watkins 1996, pp. 181–182.
  47. ^Motem 1990, p. 143.
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  49. ^ abc"Comet Engineering: The Performance of Airframe, Engines, and Equipment in Operational Service."Flight International, 1 May 1953, p. 551. Retrieved 26 April 2012.
  50. ^"Comet Enters Service."Archived 22 September 2009 at the Wayback MachineRoyal Air Force Museum Cosford. Retrieved 1 November 2010.
  51. ^Moss, C. J. "Metal to Metal Bonding – For Aircraft Structures: Claims of the Redux Process."Flight International, 8 February 1951, p. 169. Retrieved 26 April 2012.
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  60. ^Francis 1950, pp. 98–102.
  61. ^Gunn 1987, p. 269.
  62. ^ abWalker 2000, p. 190.
  63. ^ abcdeDarling 2001, p. 33.
  64. ^"Comet Gets Stronger Engines."Popular Science, 160(6), June 1952, p. 142.
  65. ^Davies and Birtles 1999, p. 31.
  66. ^Davies and Birtles 1999, p. 34.
  67. ^Floyd 1986, p. 88.
  68. ^ abMcNeil 2002, p. 39.
  69. ^ ab"On This Day: Comet inaugurates the jet age."BBC News, 2 May 1952. Retrieved 26 April 2012.
  70. ^ abCookman, Aubrey O. Jr. "I Rode The First Jet Airliner."Popular Mechanics, July 1952, pp. 90–94. Retrieved 26 April 2012.
  71. ^Jackson 1988, pp. 173–174.
  72. ^Lane 1979, p. 205.
  73. ^"Jet Air-Routes", Flight, p. 547, 1 May 1953, archived from the original on 5 March 2016
  74. ^Davies and Birtles 1999, p. 22 (Route map illustration).
  75. ^Schnaars 2002, p. 71.
  76. ^ abSchnaars 2002, p. 70.
  77. ^"Preludes and Overtures: de Havilland Comet 1".Flight, 4 September 1953. Retrieved 30 May 2012.
  78. ^Darling 2001, p. 20.
  79. ^Cacutt 1989, p. 146.
  80. ^ abcDarling 2005, p. 119.
  81. ^ abcdefghijklmnoRoach and Eastwood 1992, pp. 331–335.
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  85. ^"Comet Accident Record."Aviation Safety Network. Retrieved: 22 September 2010.
  86. ^"CF-CUN"Ed Coates' Civil Aircraft Photograph Collection. Retrieved: 18 February 2011.
  87. ^ abcWithuhn 1976, p. 85.
  88. ^Birtles 1970, p. 127.
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  90. ^Darling 2005, p. 36.
  91. ^ abLokur, N. S. "Report of the court investigation on the accident to COMET G-ALYV"(PDF). Lessons Learned. Federal Aviation Administration. Archived from the original(PDF) on 15 April 2015. Retrieved 23 February 2015.
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  93. ^Lo Bao 1996, p. 7.
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  95. ^Darling 2001, p. 26.
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  97. ^ abcdeWithey, P.A (1997), "Fatigue Failure of the de Havilland Comet I",
Источник: https://en.wikipedia.org/wiki/De_Havilland_Comet

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Non-solvent Flux Augmentation of an LDPE-Coated Polytetrafluoroethylene Hollow Fiber Membrane for Direct Contact Membrane Distillation

4. Materials and Methods


4.1. Membrane and Chemicals

A PTFE-HF membrane (OD/ID: 0.8/0.5 μm) of 0.2 μm pore was supplied by PLC Solution (Malaysia). The PTFE HF membrane is hydrophobic and has been selected as the substrate as it allows surface modification through LDPE via indirect coating from our previous work. (2) Xylene (>98.5% of the mixture isomers + ethyl benzene base, France) as a solvent, ethanol, acetone, and cyclohexanone were purchased from Sigma-Aldrich (St. Louis, MO, USA) to be used as non-solvent additives, while sodium chloride (NaCl) as a feed solution was supplied from Merck Sdn. Bhd.

4.2. Preparation of the Non-solvent Additive Coating Solution

The optimum concentration of the coating solution (30 g/L) from the previous work was further studied to enhance the surface hydrophobicity of the PTFE HF membrane by adding non-solvent additives (ethanol, acetone, and cyclohexanone). The percentage volume of ethanol, acetone, and cyclohexanone was fixed at 10% (v/v) and slowly added to the polymeric solution (mixture of LDPE and xylene) below the non-solvent boiling point by controlling the circulated water at the same temperature. The above steps varied from 10% (v/v) to 50% (v/v) to study the effect on membrane wettability. The PTFE HF membrane was coated and dried at room temperature in a vacuum oven.

4.3. Membrane Characterization and Performance Test

The hollow fiber-modified membrane was characterized by wetting properties, surface morphology, surface roughness, LEP, and porosity. In addition, the effect of the preparation parameters was assessed in terms of hydrophobicity.

4.3.1. Water Contact Angle

The membrane wettability was measured with goniometer equipment, Rame-Hart 250-FI USA, based on the sessile drop method at ambient temperatures (24 ± 1 °C). The PTFE HF membrane was placed on top of a platform, and DI water (2 μL) was dropped on the membrane surface using a microsyringe. The digital image was analyzed by determining the average values of WCA to minimize experimental errors. This step was repeated at five different positions for each sample.

4.3.2. Scanning Electron Microscopy

The surface morphology of each modified membrane was examined by scanning electron microscopy (SEM) using table-top SEM, HITACHI (TM3000), Japan, to analyze the flat and curved surface of the modified PTFE HF membrane. The modified membranes were immersed into liquid nitrogen, N2, and then cracked to obtain a brittle and clean (57) fracture to measure the coating thickness of the membranes. The membrane was initially coated with gold using a Quorum SC7620 sputter-coater (USA). (58)

4.3.3. Surface Roughness

AFM (Model XE 100, Park System) was used to analyze the topographic map of the membrane surface via the non-contact mode at room temperature. The membrane samples with a dimension of 5 μm × 5 μm were fixed on a magnetic holder. All AFM images were observed using XEI software to determine the roughness parameter, Ra.

4.3.4. Liquid Entry Pressure

LEP is defined by the minimum TMP at which the first drop of the feed solution enters the pore by overcoming the forces of the PTFE HF membrane. The membrane was equipped with water inserted in the lumen shell side in a stainless steel tubular module. The value of LEP was analyzed using PMI software.

4.3.5. Membrane Porosity

Porosity measurement (ε) of the modified membrane was determined by the gravimetric method mentioned in our previous publication; (2)three PTFE HF membranes were cut into 3 cm long pieces for each measurement to reduce the error and immersed in Porefil for 24 h. Then, the total porosity was averaged for three fibers and was calculated according to eq 1(1)where Wwand Wdare the weight of the wet and dry membranes (g), ρwrepresents the density of Porefil (1.78 g/cm3), r is the inner radius (cm), hfis the length of the fiber (3 cm), and ρpis the polymer density (2.2 g/cm3).

4.3.6. Pore Size Distribution

The size of the membrane pores was estimated using a capillary flow porometer POROLUX 1000 and a gas flow/liquid displacement method (Benelux Scientific, Germany). First, Porefil was used to moisten the membrane samples measuring 5 cm in length completely. The samples were then connected to the instrument, where tests were performed using the “dry/wet” procedure, and pore sizes were calculated using PMI software.

4.3.7. Direct Contact Membrane Distillation

The experimental DCMD study was conducted to determine the separation performance for modified membranes at different feed temperatures. In this experiment, 35 g/L of sodium chloride (NaCl)-simulated seawater was used as a feeding solution. The temperature of the hot feed varied from 60 to 80 °C, and the cold permeate side was set at 20 °C. The permeation flux (L m–2h–1) and salt rejection (%) of the membrane by MD were calculated from the following equations, respectively(2)(3)where Jdenotes the permeate flux (L m–2h–1), ΔVis the permeate volume (L), Ais the membrane surface area (m2), Δtis the time interval (h), Ris the rejection coefficient (%), and Cpand Cfare the feed’s concentration and permeate solution (g L–1), respectively.

Author Information


    • Mohamad Razif Mohd Ramli - School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, 14300 Pulau Pinang, Malaysia

    • Ebenezer Idowu Oluwasola - School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, 14300 Pulau Pinang, Malaysia;  Food Technology Department, The Federal Polytechnic Ado Ekiti, Ado Ekiti, 360231 Ekiti state, Nigeria

  • The authors declare no competing financial interest.

Acknowledgments


This study was funded by the Ministry of Higher Education of Malaysia for the Long Term Research Grant Scheme 1/2018, LRGS (203/PJKIMIA/67215002). The authors would like to acknowledge the financial support of Mr. Mohamad Razif Mohd Ramli by Universiti Sains Malaysia under fellowship scheme.

This article references 58 other publications.

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    Reischer, G. H.; Kollanur, D.; Vierheilig, J.; Wehrspaun, C.; Mach, R. L.; Sommer, R.; Stadler, H.; Farnleitner, A. H.

    Environmental Science & Technology (2011), 45 (9), 4038-4045CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)

    Water resource management must strive to link catchment information with water quality monitoring. This study attempted this for the field of microbial fecal source tracking (MST). A fecal pollution source profile based on catchment data (e.g., prevalence of fecal sources) was used to formulate a hypothesis about the dominant sources of pollution in an Austrian mountainous karst spring catchment. This allowed a statistical definition of methodical requirements necessary for an informed choice of MST methods. The hypothesis was tested in a 17-mo study of spring water quality. The study followed a nested sampling design in order to cover the hydrol. and pollution dynamics of the spring and to assess effects such as differential persistence between parameters. Genetic markers for the potential fecal sources as well as microbiol., hydrol., and chemo-phys. parameters were measured. The hypothesis that ruminant animals were the dominant sources of fecal pollution in the catchment was clearly confirmed. It was also shown that the concn. of ruminant markers in feces was equally distributed in different ruminant source groups. The developed approach provides a tool for careful decision-making in MST study design and might be applied on various types of catchments and pollution situations.

    >> More from SciFinder ®

    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXkt1Cqur8%253D&md5=8c465c3ba5605b9690fc6b98f1bcf1b7
  8. 8
    Sumpter, J. P.; Johnson, A. C.Lessons from Endocrine Disruption and Their Application to Other Issues Concerning Trace Organics in the Aquatic Environment. Environ. Sci. Technol.2005, 39, 4321– 4332,  DOI: 10.1021/es048504a
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    8

    Lessons from Endocrine Disruption and Their Application to Other Issues Concerning Trace Organics in the Aquatic Environment

    Sumpter, John P.; Johnson, Andrew C.

    Environmental Science and Technology (2005), 39 (12), 4321-4332CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)

    A review. In the past 10 years, many thousands of research papers covering the many different aspects of endocrine disruption in the environment have been published. As to what has been learned from all this research, we have tried to reduce this very large vol. of material into a relatively small no. of "lessons.". Hence, this paper is not a typical review, but instead it summarizes our personal opinions on what we consider are the major messages to have come from all this research. We realize that what has been a lesson to us may have been obvious from the outset to someone more knowledgeable about that particular aspect of the burgeoning field of endocrine disruption. In addn., it is inevitable that others will consider that we have "missed" some lessons that they would have expected to find included in our list. If so, we encourage them to submit them as responses to our paper. Our own lessons range widely, from the design and interpretation of data from fieldwork studies, through some key messages to come out of the very many lab. studies that have been conducted, to issues around the sources and fates in the environment of endocrine-disrupting chems., and finally to the key role of sewage treatment in controlling the concns. of these chems. in the aquatic environment. Having (hopefully) learned our lessons, we have then applied them to the difficult issue of how best to approach future concerns about the potential impacts of other new and emerging contaminants (e.g., pharmaceuticals) on wildlife.

    >> More from SciFinder ®

    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXjvF2hs7s%253D&md5=97313ffd3ce90c8c051ed1e7c123a534
  9. 9
    Dacre, J. C.; Rosenblatt, D. H.; Cogley, D. R.Preliminary Pollutant Limit Values for Human Health Effects. Environ. Sci. Technol.1980, 14, 778– 784,  DOI: 10.1021/es60167a007
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    9

    Preliminary pollutant limit values for human health effects

    Dacre, Jack C.; Rosenblatt, David H.; Cogley, David R.

    Environmental Science and Technology (1980), 14 (7), 778-80, 782-4CODEN: ESTHAG; ISSN:0013-936X.

    An approach to det. preliminary pollutant limit values in the environment is discussed. The approach includes detns. of pollutants, pathways, acceptable daily dose of toxicants, and calcn. of single-pathway preliminary pollutant limit values.

    >> More from SciFinder ®

    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3cXmtV2nsrc%253D&md5=8e90a4be829ee6c8c1b33bec8a6d09e8
  10. 10
    Famurewa, J. A. V.; Oluwasola, E. I.Development of a Biomass Fuelled Household Water Distiller, 2020.report
  11. 11
    Xu, W.-T.; Zhao, Z.-P.; Liu, M.; Chen, K.-C.Morphological and Hydrophobic Modifications of PVDF Flat Membrane with Silane Coupling Agent Grafting via Plasma Flow for VMD of Ethanol–water Mixture. J. Membr. Sci.2015, 491, 110– 120,  DOI: 10.1016/j.memsci.2015.05.024
    [Crossref], [CAS], Google Scholar
    11

    Morphological and hydrophobic modifications of PVDF flat membrane with silane coupling agent grafting via plasma flow for VMD of ethanol-water mixture

    Xu, Wan-Ta; Zhao, Zhi-Ping; Liu, Min; Chen, Kang-Cheng

    Journal of Membrane Science (2015), 491 (), 110-120CODEN: JMESDO; ISSN:0376-7388. (Elsevier B.V.)

Источник: https://pubs.acs.org/doi/full/10.1021/acsomega.1c02887

Hydrogen Flux And Corrosion Rate Measurements On Hydrogen Induced Cracking Susceptible And Resistant A516 Steels In Various Sour Environments

ABSTRACT

Two A516 16 mm plate steels were simultaneously exposed to various sour saturated solutions at 20oC over two week trials. One plate was known to be highly resistant to HIC cracking, the other to be highly susceptible to HIC cracking. Flux and corrosion rates of the two plates decreased after a few days in non-buffered acid solutions, whereas in buffered acid conditions they maintained a steady state. Crack surface ratios of HIC susceptible plates post-trial were approximately proportional to the total wall flux passed. In ammonium bisulfide solutions, flux was only induced by addition of cyanide. In all trials, flux from the two plates co-trended extremely closely. Computed hydrogen diffusivities, entry concentrations, and permeabilities of the HIC resistant Cyrobo Hidden Disk Pro For Windows susceptible plates were similar. Diffusion coefficients varied between 8 and 12 x 10-6 cm2.s-1, consistent with other data for A516 steels. There was good correlation between corrosion rate and steady state flux for the first day of measurement, except from pH 2.7 solutions, where an additional, non-hydrogen occluding corrosion of 0.5 mm/yr corrosion rate was attributed to similar corrosion measured prior to sour saturation. Apart from this, no pH effect on the correlation was evident between pH 2.7 and pH 9.

OBJECTIVES

The objectives of the work reported here, were to correlate corrosion rate and hydrogen flux through simultaneously tested hydrogen induced cracking (HIC) susceptible and resistant A516 grade steels in sour solutions at ambient temperatures, and to investigate the influence, if any, of plate HIC susceptibility and damage, on through wall hydrogen flux.

INTRODUCTION

  • Steel susceptibility to HIC

  • Conditions which increase or decrease sour corrosion and HIC

  • The effectiveness of inhibitors or barriers in preventing sour corrosion

  • The correlation of flux measurements with corrosion rates

  • Steel HIC susceptibility is the objective of most studies presented in the literature and accordingly, emphasis is placed upon hydrogen in steel bulk, as characterized by a steel's hydrogen diffusion D (cm2/s) and solubility S (ppm wt/wt, but see Table 1a for other units)obtained from hydrogen permeation measurements.

Hydrogen flux measurements on sour corroding steels are performed Adobe Photoshop CS6 Serial Number Crack and Free Download the laboratory to study:The rate of diffusion of hydrogen in a metal is proportional to the concentration gradient of mobile hydrogen in the metal, according to Fick's Law. If the diffusion is in one dimension (eg through plate):

(Equation in full paper)

To apply equation (2), the steady state flux should be converted to Ncm3.cm2.s-1 (Table 1b) and c0 from Ncm3.cm3 to ppm (Table 1a). Equation (2) can be derived from (1) at steady state, that is, when a uniform mobile hydrogen concentration gradient is established through a steel, assuming the exit face sub-surface concentration (cw) is zero, and the diffusion coefficient is independent of concentration. Some literature examples are presented1-14 in Table 2. For the hydrogen collection method of flux measurement technology used in this work, the validity of these assumptions has been broadly demonstrated15,16.

Источник: https://onepetro.org/NACECORR/proceedings-pdf/CORR10/All-CORR10/NACE-10179/1717855/nace-10179.pdf

Non-solvent Flux Augmentation of an LDPE-Coated Polytetrafluoroethylene Hollow Fiber Membrane for Direct Contact Membrane Distillation

4. Materials and Methods


4.1. Membrane and Chemicals

A PTFE-HF membrane (OD/ID: 0.8/0.5 μm) of 0.2 μm pore was supplied by PLC Solution (Malaysia). The PTFE HF membrane is hydrophobic and has been selected as the substrate as it allows surface modification through LDPE via indirect coating from our previous work. (2) Xylene (>98.5% of the mixture isomers + ethyl benzene base, France) as a solvent, ethanol, acetone, and cyclohexanone were purchased from Sigma-Aldrich (St. Louis, MO, USA) to be used as non-solvent additives, while sodium chloride (NaCl) as a feed solution was supplied from Merck Sdn. Bhd.

4.2. Preparation of the Non-solvent Additive Coating Solution

The optimum concentration of the coating solution (30 g/L) from the previous work was further studied to enhance the surface hydrophobicity of the PTFE HF membrane by adding non-solvent additives (ethanol, acetone, and cyclohexanone). The percentage volume of ethanol, acetone, and cyclohexanone was fixed at 10% (v/v) and slowly added to the polymeric solution (mixture of LDPE and xylene) below the non-solvent boiling point by controlling the circulated water at the same temperature. The above steps varied from 10% (v/v) to 50% (v/v) to study the effect on membrane wettability. The PTFE HF membrane was coated and dried at room temperature in a vacuum oven.

4.3. Membrane Characterization and Performance Test

The hollow fiber-modified membrane was characterized by wetting properties, surface morphology, surface roughness, LEP, and porosity. In addition, the effect of the preparation parameters was assessed in terms of hydrophobicity.

4.3.1. Water Contact Angle

The membrane wettability was measured with goniometer equipment, Rame-Hart 250-FI USA, based on the sessile drop method at ambient temperatures (24 ± 1 °C). The PTFE HF membrane was placed on top of a platform, and DI water (2 μL) was dropped on the membrane surface using a microsyringe. The digital image was analyzed by determining the average values of WCA to minimize experimental errors. This step was repeated at five different positions for each sample.

4.3.2. Scanning Electron Microscopy

The surface morphology of each modified membrane was examined by scanning electron microscopy (SEM) using table-top Nova Launcher Prime 7.0.42 Crack + Serial Key Free Download 2021, HITACHI (TM3000), Japan, to analyze the flat and curved surface of the modified PTFE HF membrane. The modified membranes were immersed into liquid nitrogen, N2, and then cracked to obtain a brittle and clean (57) fracture to measure the coating thickness of the membranes. The membrane was initially coated with gold using a Quorum SC7620 sputter-coater (USA). (58)

4.3.3. Surface Roughness

AFM (Model XE 100, Park System) was used to analyze the topographic map of the membrane surface via the non-contact mode at room temperature. The membrane samples with a dimension of 5 μm × 5 μm were fixed on a magnetic holder. All AFM images were observed using XEI software to determine the roughness parameter, Ra.

4.3.4. Liquid Entry Pressure

LEP is defined by the minimum TMP at which the first drop of the feed solution enters the pore by overcoming the forces of the PTFE HF membrane. The membrane was equipped with water inserted in the lumen shell side in a stainless steel tubular module. The value of LEP was analyzed using PMI software.

4.3.5. Membrane Porosity

Porosity measurement (ε) of the modified membrane was determined by the gravimetric method mentioned in our previous publication; (2)three PTFE HF membranes were cut into 3 cm long pieces for each measurement to reduce the error and immersed in Porefil for 24 h. Then, the total porosity was averaged for three fibers and was calculated according to eq 1(1)where Wwand Wdare the weight of the wet and dry membranes (g), ρwrepresents the density of Porefil (1.78 g/cm3), r is the inner radius (cm), hfis the length of the fiber (3 cm), and ρpis the polymer density (2.2 g/cm3).

4.3.6. Pore Size Distribution

The size of the membrane pores was estimated using a capillary flow porometer POROLUX 1000 and a gas flow/liquid displacement method (Benelux Scientific, Germany). First, Porefil was used to moisten the membrane samples measuring 5 cm in length completely. The samples were then connected to the instrument, where tests were performed using the “dry/wet” procedure, and pore sizes were calculated using PMI software.

4.3.7. Direct Contact Membrane Distillation

The experimental DCMD study was conducted to determine the best folder lock software - Activators Patch performance for modified membranes at different feed temperatures. In this experiment, 35 g/L of sodium chloride (NaCl)-simulated seawater was used as a feeding solution. The temperature of the hot feed varied from 60 to 80 °C, and the cold permeate side was set at 20 °C. The permeation flux (L m–2h–1) and salt rejection (%) of the membrane by MD were calculated from the following equations, respectively(2)(3)where Jdenotes the permeate flux (L m–2h–1), ΔVis the permeate volume (L), Ais the membrane surface area (m2), Δtis the time interval (h), Ris the rejection coefficient (%), and Cpand Cfare the feed’s concentration and permeate solution (g L–1), respectively.

Author Information


    • Mohamad Razif Mohd Ramli - School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, 14300 Pulau Pinang, Malaysia

    • Ebenezer Idowu Oluwasola - School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, 14300 Pulau Pinang, Malaysia;  Food Technology Department, The Federal Polytechnic Ado Ekiti, Ado Ekiti, 360231 Ekiti state, Nigeria

  • The authors declare no competing financial interest.

Acknowledgments


This study was funded by the Ministry of Higher Education of Malaysia for the Long Term Research Grant Scheme 1/2018, LRGS (203/PJKIMIA/67215002). The authors would like to acknowledge the financial support of Mr. Mohamad Razif Mohd Ramli by Universiti Sains Malaysia under fellowship scheme.

This article references 58 other publications.

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    ACS Omega (2021), 6 (7), 4609-4618CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)

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    A review. Membrane distn. (MD) is a thermally driven process that uses low-grade energy to operate and has been extensively explored as an alternative cost-effective and efficient water treatment process compared to conventional membrane processes. MD membranes are synthesized from hydrophobic polymers, e.g. polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or polypropylene (PP), using various methods including phase inversion and electrospinning techniques. Recent literature on MD membranes clearly shows their important role in surface water/wastewater treatment and seawater desalination. Modification of MD membranes with nanoscale materials significantly improves their performance, preventing wetting and fouling. This review presents a crit. assessment of the progress on the use of nanomaterials for the modification of MD membranes. The techniques commonly used to synthesize MD membranes, the modifications that have been adopted for the incorporation of nanomaterials onto membranes, and the unique properties these nanomaterials impart on the membranes are discussed. The use of modified membranes in different MD configurations and their application in groundwater, surface water, wastewater, brackish water and seawater treatment is reviewed. Finally, cost implications, com. viability, environmental sustainability, and future prospects of MD are also discussed to elucidate promising approaches for a future and successful implementation of MD at an industrial scale.

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    Water resource management must strive to link catchment information with water quality monitoring. This study attempted this for the field of microbial fecal source tracking (MST). A fecal pollution source profile based on catchment data (e.g., prevalence of fecal sources) was used to formulate a hypothesis about the dominant sources of pollution in an Austrian mountainous karst spring catchment. This allowed a statistical definition of methodical requirements necessary for an informed choice of MST methods. The hypothesis was tested in a 17-mo study of spring water quality. The study followed a nested sampling design in order to cover the hydrol. and pollution dynamics of the spring and to assess effects such as differential persistence between parameters. Genetic markers for the potential fecal sources as well as microbiol., hydrol., and chemo-phys. parameters were measured. The hypothesis that ruminant animals were the dominant sources of fecal pollution in the catchment was clearly confirmed. It was also shown that the concn. of ruminant markers in feces was equally distributed in different ruminant source groups. The developed approach provides a tool for careful decision-making in MST study design and might be applied on various types of catchments and pollution situations.

    >> More from SciFinder ®

    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXkt1Cqur8%253D&md5=8c465c3ba5605b9690fc6b98f1bcf1b7
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    [ACS Full Text ACS Full Text], [CAS], Google Scholar
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    Lessons from Endocrine Disruption and Their Application to Other Issues Concerning Trace Organics in the Aquatic Environment

    Sumpter, John P.; Johnson, Andrew C.

    Environmental Science and Technology (2005), 39 (12), 4321-4332CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)

    A review. In the past 10 years, many thousands of research papers covering the many different aspects of endocrine disruption in the environment have been published. As to what has been learned from all this research, we have tried to reduce this very large vol. of material into a relatively small no. of "lessons.". Hence, this paper is not a typical review, but instead it summarizes our personal opinions on what we consider are the major messages to have come from all this research. We realize that what has been a lesson to us may have been obvious from the outset to someone more knowledgeable about that particular aspect of the burgeoning field of endocrine disruption. In addn., it is inevitable that others will consider that we have "missed" some lessons that they would have expected to find included in our list. If so, we encourage them to submit them as responses to our paper. Our own lessons range widely, from the design and interpretation of data from fieldwork studies, through some key messages to come out of the very many lab. studies that have been conducted, to issues around the sources and fates in the environment of endocrine-disrupting chems., and finally to the key role of sewage treatment in controlling the concns. of these chems. in the aquatic environment. Having (hopefully) learned our lessons, we have then applied them to the difficult issue of how best to approach future concerns about the potential impacts of other new and emerging contaminants (e.g., pharmaceuticals) on wildlife.

    >> More from SciFinder ®

    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXjvF2hs7s%253D&md5=97313ffd3ce90c8c051ed1e7c123a534
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    Preliminary pollutant limit values for human health effects

    Dacre, Jack C.; Rosenblatt, David H.; Cogley, David R.

    Environmental Science and Technology (1980), 14 (7), 778-80, 782-4CODEN: ESTHAG; ISSN:0013-936X.

    An approach to det. preliminary pollutant limit values in the environment is discussed. The approach includes detns. of pollutants, pathways, acceptable daily dose of toxicants, and calcn. of single-pathway preliminary pollutant limit values.

    >> More from SciFinder ®

    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3cXmtV2nsrc%253D&md5=8e90a4be829ee6c8c1b33bec8a6d09e8
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    [Crossref], [CAS], Google Scholar
    11

    Morphological and hydrophobic modifications of PVDF flat membrane with silane coupling agent grafting via plasma flow for VMD of ethanol-water mixture

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Metabolic Flux Analysis

Metabolic Flux Analysis: Methods and Protocols opens up the field of metabolic flux analysis to those who want to start a new flux analysis project but are overwhelmed by the complexity of the approach. Metabolic flux analysis emerged from the current limitation for the prediction of metabolic fluxes from a measured inventory of the cell. Divided into convenient thematic parts, topics in this essential volume include the fundamental characteristics of the underlying networks, the application of quantitative metabolite data and thermodynamic principles to constrain the solution space for flux balance analysis (FBA), the experimental toolbox to conduct different types of flux analysis experiments, the processing of data from 13C experiments, and three chapters that summarize some recent key findings. Written in the successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible protocols, and notes on troubleshooting and avoiding known pitfalls.

 

Authoritative and easily accessible, Metabolic Flux Analysis: Methods and Protocols presents protocols that cover a range of relevant organisms currently used in the field, providing a solid basis to anybody interested in the field of metabolic flux analysis.

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cell culture flux analysis metabolomics stoichiometry thermodynamics

Editors and affiliations

  • Jens O. Krömer
  • Lars K. Nielsen
  • Lars M. Blank
  1. 1.Centre for Microbial Electrosynthesis (CEMES), Advanced Water Management CentreUniversity of QueenslandSt. Lucia, BrisbaneAustralia
  2. 2.AIBNUniversity of QueenslandSt. Lucia, BrisbaneAustralia
  3. 3.Biology DepartmentRWTH Aachen UniversityAachenGermany

Bibliographic information

  • Book TitleMetabolic Flux Analysis
  • Book SubtitleMethods and Avast premier full version with crack free download - Free Activators O. Krömer
    Lars K. Nielsen
    Lars M. Blank
  • Series TitleMethods in Molecular Biology
  • Series Abbreviated TitleMethods Molecular Biology
  • DOIhttps://doi.org/10.1007/978-1-4939-1170-7
  • Copyright InformationSpringer Science+Business Media New York2014
  • Publisher NameHumana Press, New York, NY
  • eBook PackagesSpringer Protocols
  • Hardcover ISBN978-1-4939-1169-1
  • Softcover ISBN978-1-4939-4159-9
  • eBook ISBN978-1-4939-1170-7
  • Series ISSN1064-3745
  • Series E-ISSN1940-6029
  • Edition Number1
  • Number of PagesXII, 316
  • Number of Illustrations19 b/w illustrations, 51 illustrations in colour
  • TopicsBiochemistry, general
    Enzymology
Источник: https://link.springer.com/content/pdf/10.1007%2F978-1-4939-1170-7.pdf

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de Havilland Comet

First commercial jet airliner

This article is about the jet airliner. For the 1930s racing aircraft, see de Havilland DH.88 Comet.

The de Havilland DH.106 Comet was the world's first commercial jet airliner. Developed and manufactured by de Havilland at its Hatfield Aerodrome in Hertfordshire, United Kingdom, the Comet 1 prototype first flew in 1949. It featured an aerodynamically clean design with four de Havilland Ghostturbojet engines buried in the wing roots, a pressurised cabin, and large square windows. For the era, it offered a relatively quiet, comfortable passenger cabin and was commercially promising at its debut in 1952.

Within a year of entering airline service, problems started to emerge, three Comets being lost within twelve months in highly publicised accidents, after suffering catastrophic in-flight break-ups. Two of these were found to be caused by structural failure resulting from metal fatigue in the airframe, a phenomenon not fully understood at the time; the other was due to overstressing of the airframe during flight through severe weather. The Comet was withdrawn from service and extensively tested. Design and construction flaws, including improper riveting and dangerous concentrations of stress around some of the square windows, were ultimately identified. As a result, the Comet was extensively redesigned, with oval windows, structural reinforcements and other changes. Rival manufacturers heeded the lessons learned from the Comet when developing their own aircraft.

Although sales never fully recovered, the improved Comet 2 and the prototype Comet 3 culminated in the redesigned Comet 4 series which debuted in 1958 and remained in commercial service until 1981. The Comet was also adapted for a variety of military roles such as VIP, medical and passenger transport, as well as surveillance; the last Comet 4, used as a research platform, made its final flight in 1997. The most extensive modification resulted in a specialised maritime patrol derivative, the Hawker Siddeley Nimrod, which remained in service with the Royal Air Force until 2011, over 60 years after the Comet's first flight.

Development[edit]

Origins[edit]

Design studies for the DH.106 Comet 1944–1947 (artist's impression)

On 11 March 1943, the Cabinet of the United Kingdom formed the Brabazon Committee, which was tasked with determining the UK's airliner needs after the conclusion of the Second World War.[4] One of its recommendations was for the development and production of a pressurised, transatlantic mailplane that could carry 1 long ton (2,200 lb; 1,000 kg) of payload at a cruising speed of 400 mph (640 km/h) non-stop.[5] Aviation company de Havilland was interested in this requirement, but chose to challenge the then widely held view that jet engines were too fuel-hungry and unreliable for such a role.[N 2] As a result, committee member Sir Geoffrey de Havilland, head of the de Havilland company, used his personal influence and his company's expertise to champion the development of a jet-propelled aircraft; proposing a specification for a pure turbojet-powered design.[4]

The committee accepted the proposal, calling it the "Type IV" (of five designs),[N 3] and in 1945 awarded a development and production contract to de Havilland under the designation Type 106. The type and design were to be so advanced that de Havilland had to undertake the design and development of both the airframe and the engines. This was because in 1945 no turbojet engine manufacturer in the world was drawing-up a design specification for an engine with the thrust and specific fuel consumption that could power an aircraft at the proposed cruising altitude (40,000 ft (12,000 m)), speed, and transatlantic range as was called for by the Type 106.[8] First-phase development of the DH.106 focused on short- and intermediate-range mailplanes with small passenger compartments and as few as six seats, before being redefined as a long-range airliner with a capacity of 24 seats.[5] Out of all the Brabazon designs, the DH.106 was seen as the riskiest: both in terms of introducing untried design elements and for the financial commitment involved.[4] Nevertheless, the British Overseas Airways Corporation (BOAC) found the Type IV's specifications attractive, and initially proposed a purchase of 25 aircraft; in December 1945, when a firm contract was created, the order total was revised to 10.[9]

"During the next few years, the UK has an opportunity, which may not recur, of developing aircraft manufacture as one of our main export industries. On whether we grasp this opportunity and so establish firmly an industry of the utmost strategic and economic importance, our future as a great nation may depend."

Duncan Sandys, Minister of Supply, 1952.[10]

A design team was formed in 1946 under the leadership of chief designer Ronald Bishop, who had been responsible for the Mosquito fighter-bomber.[9] Several unorthodox configurations were considered, ranging from canard to tailless designs;[N 4] All were rejected. The Ministry of Supply was interested in the most radical of the proposed designs, and ordered two experimental tailless DH 108s[N 5] to serve as proof of concept aircraft for testing swept-wing configurations in both low-speed and high-speed flight.[5][11] During flight tests, the DH 108 gained a reputation for being accident-prone and unstable, leading de Havilland and BOAC to gravitate to conventional configurations and, necessarily, designs with less technical risk.[12] The DH 108s were later modified to test the DH.106's power controls.[13]

In September 1946, before completion of the DH 108s, BOAC requests necessitated a redesign of the DH.106 from its previous 24-seat configuration to a larger 36-seat version.[5][N 6] With no time to develop the technology necessary for a proposed tailless configuration, Bishop opted for a more conventional 20-degree swept-wing design[N 7] with unswept tail surfaces, married to an enlarged fuselage accommodating 36 passengers in a four-abreast arrangement with a central aisle.[15] Replacing previously specified Halford H.1 Goblin engines, four new, more-powerful Rolls-Royce Avons were to be incorporated in pairs buried in the wing roots; Halford H.2 Ghost engines were eventually applied as an interim solution while the Avons cleared certification. The redesigned aircraft was named the DH.106 Comet in December 1947.[N 8] Revised first orders from BOAC and British South American Airways[N 9] totalled 14 aircraft, with delivery projected for 1952.[14]

Testing and prototypes[edit]

As the Comet represented a new category of passenger aircraft, more rigorous testing was a development priority.[17] From 1947 to 1948, de Havilland conducted an extensive research and development phase, including the use of several stress test rigs at Hatfield Aerodrome for small components and large assemblies alike. Sections of pressurised fuselage were subjected to high-altitude flight conditions via a large decompression chamber on-site [N 10] and tested to failure.[18] Tracing fuselage failure points proved difficult with this method,[18] and de Havilland ultimately switched to conducting structural tests with a water tank that could be safely configured to increase pressures gradually.[13][18][19] The entire forward fuselage section was tested for metal fatigue by repeatedly pressurising to 2.75 pounds per square inch (19.0 kPa) overpressure and depressurising through more than 16,000 cycles, equivalent to about 40,000 hours of airline service.[20] The windows were also tested under a pressure of 12 psi (83 kPa), 4.75 psi (32.8 kPa) above expected pressures at the normal service ceiling of 36,000 ft (11,000 m).[20] One window frame survived 100 psi (690 kPa),[21] about 1,250 percent over the maximum pressure it was expected to encounter in service.[20]

The first prototype DH.106 Comet (carrying Class B markings G-5-1) was completed in 1949 and was initially used to conduct ground tests and brief early flights.[18] The prototype's maiden flight, out of Hatfield Aerodrome, took place on 27 July 1949 and lasted 31 minutes.[22][23] At the controls was de Havilland chief test pilot John "Cats Eyes" Cunningham, a famous night-fighter pilot of the Second World War, along with co-pilot Harold "Tubby" Waters, engineers John Wilson (electrics) and Frank Reynolds (hydraulics), and flight test observer Tony Fairbrother.[24]

The prototype was registered G-ALVG just before it was publicly displayed at the 1949 Farnborough Airshow before the start of flight trials. A year later, the second prototype G-5-2 made its maiden flight. The second prototype was registered G-ALZK in July 1950 and it was used by the BOAC Comet Unit at Hurn from April 1951 to carry out 500 flying hours of crew training and route-proving.[25] Australian airline Qantas also sent its own technical experts to observe the performance of the prototypes, seeking to quell internal uncertainty about its prospective Comet purchase.[26] Both prototypes could be externally distinguished from later Comets by the large single-wheeled main landing gear, which was replaced on production models starting with G-ALYP by four-wheeled bogies.[27]

Design[edit]

Overview[edit]

The Comet was an all-metal low-wing cantilever monoplane powered by four jet engines; it had a four-place cockpit occupied by two pilots, a flight engineer, and a navigator.[28] The clean, low-drag design of the aircraft featured many design elements that were fairly uncommon at the time, including a swept-wing leading edge, integral wing fuel tanks, and four-wheel bogie main undercarriage units designed by de Havilland.[28] Two pairs of turbojet engines (on the Comet 1s, Halford H.2 Ghosts, subsequently known as de Havilland Ghost 50 Mk1s) were buried into the wings.[29]

The original Comet was the approximate length of, but not as wide as, the later Boeing 737-100, and carried fewer people in a significantly more-spacious environment. BOAC installed 36 reclining "slumberseats" with 45 in (1,100 mm) centres on its first Comets, allowing for greater leg room in front and behind;[30]Air France had 11 rows of seats with four seats to a row installed on its Comets.[31] Large picture window views and table seating accommodations for a row of passengers afforded a feeling of comfort and luxury unusual for transportation of the period.[32] Amenities included a galley that could serve hot and cold food and drinks, a bar, and separate men's and women's toilets.[33] Provisions for emergency situations included several life rafts stored in the wings near the engines, and individual life vests were stowed under each seat.[28]

One of the most striking aspects of Comet travel was the quiet, "vibration-free flying" as touted by BOAC.[34][N 11] For passengers used to propeller-driven airliners, smooth and quiet jet flight was a novel experience.[36]

Avionics and systems[edit]

For ease of training and fleet conversion, de Havilland designed the Comet's flight deck layout with a degree of similarity to the Lockheed Constellation, an aircraft that was popular at the time with key customers such as BOAC.[18] The cockpit included full dual-controls for the captain and first officer, and a flight engineer controlled several key systems, including fuel, air conditioning and electrical systems.[37] The navigator occupied a dedicated station, with a table across from the flight engineer.[38]

The flight deck of a Comet 4

Several of the Comet's avionics systems were new to civil aviation. One such feature was irreversible, powered flight controls, which increased the pilot's ease of control and the safety of the aircraft by preventing aerodynamic forces from changing the directed positions and placement of the aircraft's control surfaces.[39] Many of the control surfaces, such as the elevators, were equipped with a complex gearing system as a safeguard against accidentally over-stressing the surfaces or airframe at higher speed ranges.[40]

The Comet had a total of four hydraulic systems: two primaries, one secondary, and a final emergency system for basic functions such as lowering the undercarriage.[41] The undercarriage could also be lowered by a combination of gravity and a hand-pump.[42] Power was syphoned from all four engines for the hydraulics, cabin air conditioning, and the de-icing system; these systems had operational redundancy in that they could keep working even if only a single engine was active.[17] The majority of hydraulic components were centred in a single avionics bay.[43] A pressurised refuelling system, developed by Flight Refuelling Ltd, allowed the Comet's fuel tanks to be refuelled at a far greater rate than by other methods.[44]

The Comet 4 navigator's station

The cockpit was significantly altered for the Comet 4's introduction, on which an improved layout focusing on the onboard navigational suite was introduced.[45] An EKCO E160 radar unit was installed in the Comet 4's nose cone, providing search functions as well as ground and cloud-mapping capabilities,[38] and a radar interface was built into the Comet 4 cockpit along with redesigned instruments.[45]

Sud-Est's design bureau, while working on the Sud Aviation Caravelle in 1953, licensed several design features from de Havilland, building on previous collaborations on earlier licensed designs, including the DH 100 Vampire;[N 12] the nose and cockpit layout of the Comet 1 was grafted onto the Caravelle.[47] In 1969, when the Comet 4's design was modified by Hawker Siddeley to become the basis for the Nimrod, the cockpit layout was completely redesigned and bore little resemblance to its predecessors except for the control yoke.[48]

Fuselage[edit]

Diverse geographic destinations and cabin pressurisation alike on the Comet demanded the use of a high proportion of alloys, plastics, and other materials new to civil aviation across the aircraft to meet certification requirements.[49] The Comet's high cabin pressure and fast operating speeds were unprecedented in commercial aviation, making its fuselage design an experimental process.[49] At its introduction, Comet airframes would be subjected to an intense, high-speed operating schedule which included vpn unlimited full crack - Activators Patch extreme heat from desert airfields and frosty cold from the kerosene-filled fuel tanks, still cold from cruising at high altitude.[49]

The Comet's thin metal skin was composed of advanced new alloys[N 13] and was both riveted and chemically bonded, which saved weight and reduced the risk of fatigue cracks spreading from the rivets.[50] The chemical bonding process was accomplished using a new adhesive, Redux, which was liberally used in the construction of the wings and the fuselage of the Comet; it also had the advantage of simplifying the manufacturing process.[51]

When several of the fuselage alloys were discovered to be vulnerable to weakening via metal fatigue, a detailed routine inspection process was introduced. As well as thorough visual inspections of the outer skin, mandatory structural sampling was routinely conducted by both civil and military Comet operators. The need to inspect areas not easily viewable by the naked eye led to the introduction of widespread radiography examination in aviation; this also had the advantage of detecting cracks and flaws too small to be seen otherwise.[52]

Operationally, the design of the cargo holds led to considerable difficulty for the ground crew, especially baggage handlers at the airports. The cargo hold had its doors located directly underneath the aircraft, so each item of baggage or cargo had to be loaded vertically upwards from the top of the baggage truck, then slid along the hold f.lux 4.75 - Crack Key For U to be stacked inside. The individual pieces of luggage and cargo also had to be retrieved in a similarly slow manner at the arriving airport.[53][54]

Propulsion[edit]

The Comet was powered by two pairs of turbojet engines buried in the wings close to the fuselage. Chief designer Bishop chose the Comet's embedded-engine configuration because it avoided the drag of podded engines and allowed for a smaller fin and rudder since the hazards of asymmetric thrust were reduced.[55] The engines were outfitted with baffles to reduce noise emissions, and extensive soundproofing was also implemented to improve passenger conditions.[56]

Placing the engines within the wings had the advantage of a reduction in the risk of foreign object damage, which could seriously damage jet engines. The low-mounted engines and good placement of service panels also made aircraft maintenance easier to perform.[57] The Comet's buried-engine configuration increased its structural weight and complexity. Armour had to be placed around the engine cells to contain debris from any serious engine failures; also, placing the engines inside the wing required a more complicated wing structure.[58]

The Comet 1 featured 5,050 lbf (22.5 kN) de Havilland Ghost 50 Mk1 turbojet engines.[29][59] Two hydrogen peroxide-powered de Havilland Sprite booster rockets were originally intended to be installed to boosttakeoff under hot and high altitude conditions from airports such as Khartoum and Nairobi.[31][60] These were tested on 30 flights, but the Ghosts alone were considered powerful enough and some airlines concluded that rocket motors were impractical.[13] Sprite fittings were retained on production aircraft.[61] Comet 1s subsequently received more powerful 5,700 lbf (25 kN) Ghost DGT3 series engines.[62]

From the Comet 2 onwards, the Ghost engines were replaced by the newer and more powerful 7,000 lbf (31 kN) Rolls-Royce Avon AJ.65 engines. To achieve optimum efficiency with the new powerplants, the air intakes were enlarged to increase mass air flow.[63] Upgraded Avon engines were introduced on the Comet 3,[63] and the Avon-powered Comet 4 was highly praised for its takeoff performance from high-altitude locations such as Mexico City.[64]

Operational history[edit]

Introduction[edit]

The earliest production aircraft, registered G-ALYP ("Yoke Peter"), first flew on 9 January 1951 and was subsequently lent to BOAC for development flying by its Comet Unit.[65] On 22 January 1952, the fifth production aircraft, registered G-ALYS, received the first Certificate of Airworthiness awarded to a Comet, six months ahead of schedule.[66] On 2 May 1952, as part of BOAC's route-proving trials, G-ALYP took off on the world's first jetliner[N 14] flight with fare-paying passengers and inaugurated scheduled service from London to Johannesburg.[68][69][70] The final Comet from BOAC's initial order, registered G-ALYZ, began flying in September 1952 and carried cargo along South American routes while simulating passenger schedules.[71]

Prince Philip returned from the Helsinki Olympic Games with G-ALYS on 4 August 1952. Queen Elizabeth, the Queen Mother and Princess Margaret were guests on a special flight of the Comet on 30 June 1953 hosted by Sir Geoffrey and Lady de Havilland.[72] Flights on the Comet were about 50 percent faster than on advanced piston-engined aircraft such as the Douglas DC-6 (490 mph (790 km/h) for the Comet compared to the DC-6's 315 mph (507 km/h)), and a faster rate of climb further cut flight times. In August 1953 BOAC scheduled the nine-stop London to Tokyo flights by Comet for 36 hours, compared to 86 hours and 35 minutes on its Argonaut piston airliner. (Pan Am's DC-6B was scheduled for 46 hours 45 minutes.) The five-stop flight from London to Johannesburg was scheduled for 21 hr 20 min.[73]

In their first year, Comets carried 30,000 passengers. As the aircraft could be profitable with a load factor as low as 43 percent, commercial success was expected.[27] The Ghost engines allowed the Comet to fly above weather that competitors had to fly through. They ran smoothly and were less noisy than piston engines, had low maintenance costs and were fuel-efficient above 30,000 ft (9,100 m).[N 15] In summer 1953, eight BOAC Comets left London each week: three to Johannesburg, two to Tokyo, two to Singapore and one to Colombo.[74]

In 1953, the Comet appeared to have achieved success for de Havilland.[75]Popular Mechanics wrote that Britain had a lead of three to five years on the rest of the world in jetliners.[70] As well as the sales to BOAC, two French airlines, Union Aéromaritime de Transport and Air France, each acquired three Comet 1As, an upgraded variant with greater fuel capacity, for flights to West Africa and the Middle East.[76][77] A slightly longer version of the Comet 1 with more powerful engines, the Comet 2, was being developed,[78] and orders were placed by Air India,[79]British Commonwealth Pacific Airlines,[80]Japan Air Lines,[81]Linea Aeropostal Venezolana,[81] and Panair do Brasil.[81] American carriers Capital Airlines, National Airlines, and Pan Am placed orders for the planned Comet 3, an even-larger, longer-range version for transatlantic operations.[82][83] Qantas was interested in the Comet 1 but concluded that a version with more range and better takeoff performance was needed for the London to Canberra route.[84]

Early hull losses[edit]

On 26 October 1952, the Comet suffered its first hull loss when a BOAC flight departing Rome's Ciampino airport failed to become airborne and ran into rough ground at the end of the runway. Two passengers sustained minor injuries, but the aircraft, G-ALYZ, was a write-off. On 3 March 1953, a new Canadian Pacific Airlines Comet 1A, registered CF-CUN and named Empress of Hawaii, failed to become airborne while attempting a night takeoff f.lux 4.75 - Crack Key For U Karachi, Pakistan, on a delivery flight to Australia. The aircraft plunged into a dry drainage canal and collided with an embankment, killing all five crew and six passengers on board.[85][86] The accident was the first fatal jetliner crash.[81] In response, Canadian Pacific cancelled its remaining order for a second Comet 1A and never operated the type in commercial service.[81]

Both early accidents were originally attributed to pilot error, as over-rotation had led to a loss of lift from the leading edge of the aircraft's wings. It was later determined that the Comet's wing profile experienced a loss of lift at a high angle of attack, and its engine inlets also suffered a lack of pressure recovery in the same conditions. As a result, de Havilland re-profiled the wings' leading edge with a pronounced "droop",[87] and wing fences were added to control spanwise flow.[88] A fictionalised investigation into the Comet's takeoff accidents was the subject of the novel Cone of Silence (1959) by Arthur David Beaty, a former BOAC captain. Cone of Silence was made into a film in 1960, and Beaty also recounted the story of the Comet's takeoff accidents in a chapter of his non-fiction work, Strange Encounters: Mysteries of the Air (1984).[89]

The Comet's second fatal accident occurred on 2 May 1953, when BOAC Flight 783, a Comet 1, registered G-ALYV, crashed in a severe thundersquall six minutes after taking off from Calcutta-Dum Dum (now Netaji Subhash Chandra Bose International Airport), India,[90] killing all 43 on board. Witnesses observed the wingless Comet on fire plunging into the village of Jagalgori,[91] leading investigators to suspect structural failure.[92]

India Court of Inquiry[edit]

After the loss of G-ALYV, the Government of India convened a court of inquiry[91] to examine the cause of the accident.[N 16] Professor Natesan Srinivasan joined the inquiry as the main technical expert. A large portion of the aircraft was recovered and reassembled at Farnborough,[92] during which the break-up was found to have begun with a left elevator spar failure in the horizontal stabilizer. The inquiry concluded that the aircraft had encountered extreme negative G forces during takeoff; severe turbulence generated by adverse weather was determined to have induced down-loading, leading to the loss of the wings. Examination of the cockpit controls suggested that the pilot may have inadvertently over-stressed the aircraft when pulling out of a steep dive by over-manipulation of the fully powered flight controls. Investigators did not consider metal fatigue as a contributory cause.[93]

The inquiry's recommendations revolved around the enforcement of stricter speed limits during turbulence, and two significant design changes also resulted: all Comets were equipped with weather radar and the "Q feel" system was introduced, which ensured that control column forces (invariably called stick forces) would be proportional to control loads. This artificial feel was the first of its kind to be introduced in any aircraft.[92] The Comet 1 and 1A had been criticised for a lack of "feel" in their controls,[94] and investigators suggested that this might have contributed to the pilot's alleged over-stressing of the aircraft;[95] Comet chief test pilot John Cunningham contended that the jetliner flew smoothly and was highly responsive in a manner consistent with other de Havilland aircraft.[96][N 17]

Comet disasters of 1954[edit]

Main articles: BOAC Flight 781 and South African Airways Flight 201

Just over a year later, Rome's Ciampino airport, the site of winx hd video converter deluxe 5.16.2 license key first Comet hull loss, was the origin of a more-disastrous Comet flight. On 10 January 1954, 20 minutes after taking off from Ciampino, the first production Comet, G-ALYP, broke up in mid-air while operating BOAC Flight 781 and crashed into the Mediterranean off the Italian island of Elba with the loss of all 35 on board.[97][98] With no witnesses to the disaster and only partial radio transmissions as incomplete evidence, no obvious reason for the crash could be deduced. Engineers at de Havilland immediately recommended 60 modifications aimed at any possible design flaw, while the Abell Committee met to determine potential causes of the crash.[99][N 18] BOAC also voluntarily grounded its Comet fleet pending investigation into the causes of the accident.[101]

Abell Committee Court of Inquiry[edit]

Media attention centred on potential sabotage;[87] other speculation ranged from clear-air turbulence to an explosion of vapour in an empty fuel tank. The Abell Committee focused on six potential aerodynamic and mechanical causes: control flutter (which had led to the loss of DH 108 prototypes), structural failure due to high loads or metal fatigue of the wing structure, failure of the powered flight controls, failure of the window panels leading to explosive decompression, or fire and other engine problems. The committee concluded that fire was the most likely cause of the problem, and changes were made to the aircraft to protect the engines and wings from damage that might lead to another fire.[102]

During the investigation, the Royal Navy conducted recovery operations.[104] The first pieces of wreckage dvdfab crack version free download discovered on 12 February 1954[105] and the search continued until September 1954, by which time 70 percent by weight of the main structure, 80 percent of the power section, and 50 percent of the aircraft's systems and equipment had been recovered.[106][107] The forensic reconstruction effort had just begun when the Abell Committee reported its findings. No apparent fault in the aircraft was found, [N 19] and the British government decided against opening a further public inquiry into the accident.[101] The prestigious nature of the Comet project, particularly for the British aerospace industry, and the financial impact of the aircraft's grounding on BOAC's operations both served to pressure the inquiry to end without further investigation.[101] Comet flights resumed on 23 March 1954.[108]

On 8 April 1954, Comet G-ALYY ("Yoke Yoke"), on charter to South African Airways, was on a leg from Rome to Cairo (of a longer route, SA Flight 201 from London to Johannesburg), when it crashed in the Mediterranean near Naples with the loss of all 21 passengers and crew on board.[97] The Comet fleet was immediately grounded once again and a large investigation board was formed under the direction of the Royal Aircraft Establishment (RAE).[97] Prime Minister Winston Churchill tasked the Royal Navy with helping to locate and retrieve the wreckage so that the cause of the accident could be determined.[109] The Comet's Certificate of Airworthiness was revoked, and Comet 1 line production was suspended at the Hatfield factory while the BOAC fleet was permanently grounded, cocooned and stored.[87]

Cohen Committee Court of Inquiry[edit]

BOAC Comet 1 cocooned and stored in the maintenance area at London Heathrow Airport in September 1954

On 19 October 1954, the Cohen Committee was established to examine the causes of the Comet crashes.[110] Chaired by Lord Cohen, the committee tasked an investigation team led by Sir Arnold Hall, Director of the RAE at Farnborough, to perform a more-detailed investigation. Hall's team began considering fatigue as the most likely cause of both accidents and initiated further research into measurable strain on the aircraft's skin.[97] With the recovery of large sections of G-ALYP from the Elba crash and BOAC's donation of an identical airframe, G-ALYU, for further examination, an extensive "water torture" test eventually provided conclusive results. This time, the entire fuselage was tested in a dedicated water tank that was built specifically at Farnborough to accommodate its full length.[101] Stress around the window corners was found to be much higher Active@ Data Studio Free Download expected and stresses on the skin were generally more than previously expected or tested.[111] The windows' square shape caused stress concentration by generating levels of stress two or three times greater than across the rest of the fuselage.[112] In 2012 a finite element analysis was carried out to find the stress values in a digital model of the Comet's cabin window loaded to a pressure differential of 8.25 psi. In this model, the maximum stress level at the margin of one of the f.lux 4.75 - Crack Key For U row of rivet holes near the corner of the window was almost five times greater than in the areas of skin remote from the windows.[113]

In water-tank testing, engineers subjected G-ALYU to repeated repressurisation and over-pressurisation, and on 24 June 1954, after 3,057 flight cycles (1,221 actual and 1,836 simulated),[114] G-ALYU burst open. Hall, Geoffrey de Havilland and Bishop were immediately called to the scene, where the water tank was drained to reveal that the fuselage had ripped open at a bolt hole, forward of the forward left escape hatch cutout. The failure then occurred longitudinally along a fuselage stringer at the widest point of the fuselage (accident report Fig 7).[115] The fuselage frames did not have sufficient strength to prevent the crack from propagating. Although the fuselage failed after a number of cycles that represented three times the life of G-ALYP at the time of the accident, it was still much earlier than expected.[116] A further test reproduced the same results.[117] Based on these findings, Comet 1 structural failures could be expected at anywhere from 1,000 to 9,000 cycles. Before the Elba accident, G-ALYP had made 1,290 pressurised flights, while G-ALYY had made 900 pressurised flights before crashing. Dr P. B. Walker, Head of the Structures Department at the RAE, said he was not surprised by this, noting that the difference was about three to one, and previous experience with metal fatigue suggested a total range of nine to one between experiment and outcome in the field could result in failure.[114]

The RAE also reconstructed about two-thirds of G-ALYP at Farnborough and found fatigue crack growth from a rivet hole at the low-drag fibreglass forward aperture around the Automatic Direction Finder, which had caused a catastrophic break-up of the aircraft in high-altitude flight.[118] The smadav 12.0.1 serial key - Crack Key For U construction technique employed in the Comet's design had exacerbated its structural fatigue problems;[97] the aircraft's windows had been engineered to be glued and riveted, but had been punch-riveted only. Unlike drill riveting, the imperfect nature of the hole created by punch-riveting could cause fatigue cracks to Reason 10 Full Download - Free Activators developing around the rivet. Principal investigator Hall accepted the RAE's conclusion of design and construction flaws as the likely explanation for G-ALYU's structural failure after 3,060 pressurisation cycles.[N 20]

Response[edit]

In responding to the report de Havilland stated: "Now that the danger of high level fatigue in pressure cabins has been generally appreciated, de Havillands will take adequate measures to deal with this problem. To this end we propose to use thicker gauge materials in the pressure cabin area and to strengthen and redesign windows and cut outs and so lower the general stress to a level at which local stress concentrations either at rivets and bolt holes or as such may occur by reason of cracks caused accidentally during manufacture or subsequently, will not constitute a danger."[120]

The Cohen inquiry closed on 24 November 1954, having "found that the basic design of the Comet was sound",[110] and made no observations or recommendations regarding the shape of the windows. De Havilland nonetheless began a refit programme to strengthen the fuselage and wing structure, employing thicker-gauge skin and replacing the square windows and panels with rounded versions.[109] The fuselage escape hatch cut-outs retained their rectangular shape.[121]

Following the Comet enquiry, aircraft were designed to "Fail safe" or "Safe Life" standards,[122] though several subsequent catastrophic fatigue failures, such as Aloha Airlines Flight 243 of April 28, 1988 have occurred.[123]

In June 1956, some more wreckage from G-ALYP was accidentally trawled up from an area about 15 miles south of where the original wreckage had been found. This wreckage was from the starboard side of the cabin just above the three front windows. Subsequent examination at Farnborough suggested that the primary failure was probably near to this area rather than at the rear automatic direction finding window on the roof of the cabin, as had been previously thought. These findings were kept secret until the details were published in 2015.[124]

Resumption of service[edit]

With the discovery of the structural problems of the early series, all remaining Comets were withdrawn from service, while de Havilland launched a major effort to build a new version that would be both larger and stronger. All outstanding orders for the Comet 2 were cancelled by airline customers.[63] The square windows of the Comet 1 were replaced by the oval versions used on the Comet 2, which first flew in 1953, and the skin thickness was increased slightly.[125] Remaining Comet 1s and 1As were either scrapped or modified with oval windows and rip-stop doublers.

All production Comet 2s were also modified to alleviate the fatigue problems (most of these served with the RAF as the Comet C2); a programme to produce a Comet 2 with more powerful Avons was delayed. The prototype Comet 3 first flew in July 1954 and was tested in an unpressurised state pending completion of the Cohen inquiry.[63] Comet commercial flights would not resume until 1958.[126]

Development flying and route proving with the Comet 3 allowed accelerated certification of what was destined to be the most successful variant of the type, the Comet 4. All airline customers for the Comet 3 subsequently cancelled their orders and switched to the Comet 4,[63] which was based on the Comet 3 but with improved fuel capacity. BOAC ordered 19 Comet 4s in March 1955, and American operator Capital Airlines ordered 14 Comets in July 1956.[127] Capital's order included 10 Comet 4As, a variant modified for short-range operations with a stretched fuselage and short wings, lacking the pinion (outboard wing) fuel tanks of the Comet 4.[82] Financial problems and a takeover by United Airlines meant that Capital would never operate the Comet.[citation needed]

The Comet 4 first flew on 27 April 1958 and received its Certificate of Airworthiness on 24 September 1958; the first was delivered to BOAC the next day.[125][128] The base price of a new Comet 4 was roughly £1.14 million (£24.81 million in 2019).[129] The Comet 4 enabled BOAC to inaugurate the first regular jet-powered transatlantic services on 4 October 1958 between London and New York (albeit still requiring a fuel stop at Gander International Airport, Newfoundland, on westward North Atlantic crossings).[68] While BOAC gained publicity as the first to provide transatlantic jet service, by the end of the month rival Pan American World Airways was flying the Boeing 707 on the New York-Paris route, with a fuel stop at Gander in both directions,[130] and in 1960 began flying Douglas DC-8's on its transatlantic routes as well. The American jets were larger, faster, longer-ranged and more cost-effective than the Comet.[131] After analysing route structures for the Comet, BOAC reluctantly cast-about for a successor, and in 1956 entered into an agreement with Boeing to krisp crack windows 10 - Free Activators the 707.[132]

Comet 4 of East African Airways at London Heathrow in 1964

The Comet 4 was ordered by two other airlines: Aerolíneas Argentinas took delivery of six Comet 4s from 1959 to 1960, using them between Buenos Aires and Santiago, New York and Europe, and East African Airways received three new Comet 4s from 1960 to 1962 and operated them to the United Kingdom and to Kenya, Tanzania, and Uganda.[133] The Comet 4A ordered by Capital Airlines was instead built for BEA as the Comet 4B, with a further fuselage stretch of 38 in (970 mm) and seating for 99 passengers. The first Comet 4B flew on 27 June 1959 and BEA began Tel Aviv to London-Heathrow services on 1 April 1960.[134]Olympic Airways was the only other customer to order the type.[135] The last Comet 4 variant, the Comet 4C, first flew on 31 October 1959 and entered service with Mexicana in 1960.[136] The Comet 4C had the Comet 4B's longer fuselage and the longer wings and extra fuel tanks of the original Comet 4, which gave it a longer range than the 4B. Ordered by Kuwait Airways, Middle East Airlines, Misrair (later United Arab Airlines), and Sudan Airways, it was the most popular Comet variant.[81][137]

Later service[edit]

In 1959 BOAC began shifting its Comets from transatlantic routes[N 21] and released the Comet to associate companies, making the Comet 4's ascendancy as a premier airliner brief. Besides the 707 and DC-8, the introduction of the Vickers VC10 allowed competing aircraft to assume the high-speed, long-range passenger service role pioneered by the Comet.[138] In 1960, as part of a government-backed consolidation of the British aerospace industry, de Havilland itself was acquired by Hawker Siddeley, within which it became a wholly owned division.[139]

In the 1960s, orders declined, a total of 76 Comet 4s being delivered from 1958 to 1964. In November 1965, BOAC retired its Comet 4s from revenue service; other operators continued commercial passenger flights with the Comet until 1981. Dan-Air played a significant role in the fleet's later history and, at one time, owned all 49 remaining airworthy civil Comets.[140] On 14 March 1997 a Comet 4C serialXS235 and named Canopus,[141] which had been acquired by the British Ministry of Technology and used for radio, radar and avionics trials, made the last documented production Comet flight.[1]

Legacy[edit]

Dan-Air Comet 4C, G-BDIW exhibited at the Flugausstellung Hermeskeilin Germany

The Comet is widely regarded as both an adventurous step forward and a supreme tragedy; the aircraft's legacy includes advances in aircraft design and in accident investigations. The inquiries into the accidents that plagued the Comet 1 were perhaps some of the most extensive and revolutionary that have ever taken place, establishing precedents in accident investigation; many of the deep-sea salvage and aircraft reconstruction techniques employed have remained in use within the aviation industry.[142] In spite of the Comet being subjected to what was then the most rigorous testing of any contemporary airliner, pressurisation and the dynamic stresses involved were not thoroughly understood at the time of the aircraft's development, nor was the concept of metal fatigue. Though these lessons could be implemented on the drawing board for future aircraft, corrections could only be retroactively applied to the Comet.[143]

According to de Havilland's chief test pilot John Cunningham, who had flown the prototype's first flight, representatives from American manufacturers such as Boeing and Douglas privately disclosed that if de Havilland had not experienced the Comet's pressurisation problems first, it would have happened to them.[144] Cunningham likened the Comet to the later Concorde and added that he had assumed that the aircraft would change aviation, which it subsequently did.[96] Aviation author Bill Withuhn concluded that the Comet had pushed "'the state-of-the-art' beyond its limits."[57]

Aeronautical-engineering firms were quick to respond to the Comet's commercial advantages and technical flaws alike; other aircraft manufacturers learned from, and profited by, the hard-earned lessons embodied by de Havilland's Comet.[10][147] The Comet's buried engines were used on some other early jet airliners, such as the Tupolev Tu-104,[148] but later aircraft, such as the Boeing 707 and Douglas DC-8, differed by employing podded engines held on pylons beneath the wings.[149] Boeing stated that podded engines were selected for their passenger airliners because buried engines carried a higher risk of catastrophic wing failure in the event of engine fire.[150] In response to the Comet tragedies, manufacturers also developed ways of pressurisation testing, often going so far as to explore rapid depressurisation; subsequent fuselage skins were of a greater thickness than the skin of the Comet.[151]

Variants[edit]

Comet 1[edit]

The square-windowed Comet 1 was the first model produced, a total of 12 aircraft in service and test. Following closely the design features of the two prototypes, the only noticeable change was the adoption of four-wheel bogie main undercarriage units, replacing the single main wheels. Four Ghost 50 Mk 1 engines were fitted (later replaced by more powerful Ghost DGT3 series engines). The span was 115 ft (35 m), and overall length 93 ft (28 m); the maximum takeoff weight was over 105,000 lb (48,000 kg) and over 40 passengers could be carried.[62]

  • An updated Comet 1A was offered f.lux 4.75 - Crack Key For U higher-allowed weight, greater fuel capacity,[76] and water-methanol injection; 10 were produced. In the wake of the 1954 disasters, all Comet 1s and 1As were brought back to Hatfield, placed in a protective cocoon and retained for testing.[152] All were substantially damaged in stress testing or were scrapped entirely.[153]
  • Comet 1X: Two RCAF Comet 1As were rebuilt with heavier-gauge skins to a Comet 2 standard for the fuselage, and renamed Comet 1X.[110]
  • Comet 1XB: Four Comet 1As were upgraded to a 1XB standard with a reinforced fuselage structure and oval windows. Both 1X series were limited in number of pressurisation cycles.[153]
  • The DH 111 Comet Bomber, a nuclear bomb-carrying variant developed to Air Ministry specification B35/46, was submitted to the Air Ministry on 27 May 1948. It had been originally proposed in 1948 as the "PR Comet", a high-altitude photo reconnaissance adaptation of the Comet 1. The Ghost DGT3-powered airframe featured a narrowed fuselage, a bulbous nose with H2S Mk IX radar, and a four-crewmember pressurised cockpit under a large bubble canopy. Fuel tanks carrying 2,400 imperial gallons (11,000 L) were added to attain a range of 3,350 miles (5,390 km). The proposed DH 111 received a negative evaluation from the Royal Aircraft Establishment over serious concerns regarding weapons storage; this, along with the redundant capability offered by the RAF's proposed V bomber trio, led de Havilland to abandon the project on 22 October 1948.[154]

Comet 2[edit]

Comet C2, XK671 Aquilaat RAF Waterbeach, fitted with revised round windows

The Comet 2 had a slightly larger wing, higher fuel capacity and more-powerful Rolls-Royce Avon engines, which all improved the aircraft's range and performance;[155] its fuselage was 3 ft 1 in (0.94 m) longer than the Comet 1's.[156] Design changes had been made to make the aircraft more suitable for transatlantic operations.[155] Following the Comet 1 disasters, these models were rebuilt with heavier-gauge skin and rounded windows, and the Avon engines featuring larger air intakes and outward-curving jet tailpipes.[N 22][157] A total of 12 of the 44-seat Comet 2s were ordered by BOAC for the South Atlantic route.[158] The first production aircraft (G-AMXA) flew on 27 August 1953.[159] Although these aircraft performed well on test flights on the South Atlantic, their range was still not suitable for the North Atlantic. All but four Comet 2s were allocated to the RAF, deliveries beginning in 1955. Modifications to the interiors allowed the Comet 2s to be used in several roles. For VIP transport, the seating and accommodations were altered and provisions for carrying medical equipment including iron lungs were incorporated. Specialised signals intelligence and electronic surveillance capability was later added to some airframes.[160]

  • Comet 2X: Limited to a single Comet Mk 1 powered by four Rolls-Royce Avon 502 turbojet engines and used as a development aircraft for the Comet 2.[155]
  • Comet 2E: Two Comet 2 airliners were fitted with Avon 504s in the inner nacelles and Avon 524s in the outer ones. These aircraft were used by BOAC for proving flights during 1957–1958.[155]
  • Comet T2: The first two of 10 Comet 2s for the RAF were fitted out as crew trainers, the first aircraft (XK669) flying initially on 9 December 1955.[160]
  • Comet C2: Eight Comet 2s originally destined for the civil market were completed for the RAF and assigned to No. 216 Squadron.[160]
  • Comet 2R: Three Comet 2s were modified for use in radar and electronic systems development, initially assigned to No. 90 Group (later Signals Command) for the RAF.[160] In service with No. 192 and No. 51 Squadrons, the 2R series was equipped to monitor Warsaw Pact signal traffic and operated in this role from 1958.[161][N 23]

Comet 3[edit]

The Comet 3, which flew for the first time on 19 July 1954, was a Comet 2 lengthened by 15 ft 5 in (4.70 m) and powered by Avon M502 engines developing 10,000 lbf (44 kN).[162] The variant added wing pinion tanks, and offered greater capacity and range.[163] The Comet 3 was destined to remain a development series since it did not incorporate the fuselage-strengthening modifications of the later series aircraft, and was not able to be fully pressurised.[164] Only two Comet 3s began construction; G-ANLO, the only airworthy Comet 3, was demonstrated at the Farnborough SBAC Show in September 1954. The other Comet 3 airframe was not completed to production standard and was used primarily for ground-based structural and technology testing during development of the similarly sized Comet 4. Another nine Comet 3 airframes were not completed and their construction was abandoned at Hatfield.[165] In BOAC colours, G-ANLO was flown by John Cunningham in a marathon round-the-world promotional tour in December 1955.[163] As a flying testbed, it was later modified with Avon RA29 engines fitted, as well as replacing the original long-span wings with reduced span wings as the Comet 3B and demonstrated in British European Airways (BEA) livery at the Farnborough Airshow in September 1958.[164] Assigned in 1961 to the Blind Landing Experimental Unit (BLEU) at RAE Bedford, the final testbed role played by G–ANLO was in automatic landing system experiments. When retired in 1973, the airframe was used for foam-arrester trials before the fuselage was salvaged at BAE Woodford, to serve as the mock-up for the Nimrod.[166]

Comet 4[edit]

The Comet 4 was a further improvement on the stretched Comet 3 with even greater fuel f.lux 4.75 - Crack Key For U. The design had progressed significantly from the original Comet 1, growing by 18 ft 6 in (5.64 m) and typically seating 74 to 81 passengers compared to the Comet 1's 36 to 44 (119 passengers could be accommodated in a special charter seating package in the later 4C series).[15] The Comet 4 was considered the definitive series, having a longer range, higher cruising speed and higher maximum takeoff weight. These improvements were possible largely because of Avon engines, with twice the thrust of the Comet 1's Ghosts.[134] Deliveries to BOAC began on 30 September 1958 with two 48-seat aircraft, which were used to initiate the first scheduled transatlantic services.

  • Comet 4B: Originally developed for Capital Airlines as the 4A, the 4B featured greater capacity through a 2m longer fuselage, and a shorter wingspan; 18 were produced.
  • Comet 4C: This variant featured the Comet 4's wings and the 4B's longer fuselage; 23 were produced.

The last two Comet 4C fuselages were used to build prototypes of the Hawker Siddeley Nimrod maritime patrol aircraft.[167] A Comet 4C (SA-R-7) was ordered by Saudi Arabian Airlines with an eventual disposition to the Saudi Royal Flight for the exclusive use of King Saud bin Abdul Aziz. Extensively modified at the factory, the aircraft included a VIP front cabin, a bed, special toilets with gold fittings and was distinguished by a green, gold and white colour scheme with polished wings and lower fuselage that was commissioned from aviation artist John Stroud. Following its first flight, the special order Comet 4C was described as "the world's first executive jet."[168]

Comet 5 proposal[edit]

The Comet 5 was proposed as an improvement over previous models, including a wider fuselage with five-abreast seating, a wing with greater sweep and podded Rolls-Royce Conway engines. Without support from the Ministry of Transport, the proposal languished as a hypothetical aircraft and was never realised.[169][N 24]

Hawker Siddeley Nimrod[edit]

Main article: Hawker Siddeley Nimrod

The last two Comet 4C aircraft produced were modified as prototypes (XV148 & XV147) to meet a British requirement for a maritime patrol aircraft for the Royal Air Force; initially named "Maritime Comet", the design was designated Type HS 801.[167] This variant became the Hawker Siddeley Nimrod and production aircraft were built at the Hawker Siddeley factory at Woodford Aerodrome. Entering service in 1969, five Nimrod variants were produced.[170] The final Nimrod aircraft were retired in June 2011.[171]

Operators[edit]

Main article: List of de Havilland Comet operators

The original operators of the early Comet 1 and the Comet 1A were BOAC, Union Aéromaritime de Transport and Air France. All early Comets were withdrawn from service for accident inquiries, during which orders from British Commonwealth Pacific Airlines, Japan Air Lines, Linea Aeropostal Venezolana, National Airlines, Pan American World Airways and Panair do Brasil were cancelled.[80][81] When the redesigned Comet 4 entered service, it was flown by customers BOAC, Aerolíneas Argentinas, and East African Airways,[172] while the Comet 4B variant was operated by customers BEA and Olympic Airways [172] and the Comet 4C model was flown by customers Kuwait Airways, Mexicana, Middle East Airlines, Misrair Airlines and Sudan Airways.[81]

Other operators used the Comet either through leasing arrangements or through second-hand acquisitions. BOAC's Comet 4s were leased out to Air Ceylon, Air India, AREA Ecuador, Central African Airways[173] and Qantas Empire Airways;[80][174] after 1965 they were sold to AREA Ecuador, Dan-Air, Mexicana, Malaysian Airways, and the Ministry of Defence.[81][172][175] BEA's Comet 4Bs were chartered by Cyprus Airways, Malta Airways and Transportes Aéreos Portugueses.[176]Channel Airways obtained five Comet 4Bs from BEA in 1970 for inclusive tour charters.[177] Dan-Air bought all of the surviving flyable Comet 4s from the late 1960s into the 1970s; some were for spares reclamation, but most were operated on the carrier's inclusive-tour charters; a total of 48 Comets of all marks were acquired by the airline.[178]

In military service, the United Kingdom's Royal Air Force was the largest operator, with 51 Squadron (1958–1975; Comet C2, 2R), 192 Squadron (1957–1958; Comet C2, 2R), 216 Squadron (1956–1975; Comet C2 and C4), and the Royal Aircraft Establishment using the aircraft.[110][179] The Royal Canadian Air Force also operated Comet 1As (later retrofitted to 1XB) through its 412 Squadron from 1953 to 1963.[153]

Accidents and incidents[edit]

The Comet was involved in 26 hull-loss accidents, including 13 fatal crashes which resulted in 426 fatalities.[180] Pilot error was blamed for the type's first fatal accident, which occurred during takeoff at Karachi, Pakistan, on 3 March 1953 and involved a Canadian Pacific Airlines Comet 1A.[81] Three fatal Comet 1 crashes due to structural problems, specifically BOAC Flight 783 on 2 May 1953, BOAC Flight 781 on 10 January 1954 and South African Airways Flight 201 on 8 April 1954, led to the grounding of the entire Comet fleet. After design modifications were implemented, Comet services resumed on October 4, 1958 with Comet 4's.[81][181]

Comet 4 G-APDN crashedin the Spanish Montseny range in July 1970 during a Dan-Air flight.[180]

Pilot error resulting in controlled flight into terrain was blamed for five fatal Comet 4 accidents: an Aerolíneas Argentinas crash near Asunción, Paraguay, on 27 August 1959, Aerolíneas Argentinas Flight 322 at Campinas near São Paulo, Brazil, on 23 November 1961, United Arab Airlines Flight 869 in Thailand's Khao Yai mountains on 19 July 1962, a Saudi Arabian Government crash in the Italian Alps on 20 March 1963, and United Arab Airlines Flight 844 in Tripoli, Libya, on 2 January 1971.[81] The Dan-Air de Havilland Comet crash in Spain's Montseny range on 3 July 1970 was attributed to navigational errors by air traffic control and pilots.[182] Other fatal Comet 4 accidents included a British European Airways crash in Ankara, Turkey, following instrument failure on 21 December 1961, a United Arab Airlines Flight 869 crash during inclement weather near Bombay, India, on 28 July 1963, and the terrorist bombing of Cyprus Airways Flight 284 off the Turkish coast on 12 October 1967.[81]

Nine Comets, including Comet 1s operated by BOAC and Union Aeromaritime de Transport and Comet 4s flown by Aerolíneas Argentinas, Dan-Air, Malaysian Airlines and United Arab Airlines, were irreparably damaged during takeoff or landing accidents that were survived by all on board.[81][180] A hangar fire damaged a No. 192 Squadron RAF Comet 2R beyond repair on 13 September 1957, and three Middle East Airlines Comet 4Cs were destroyed by Israeli troops at Beirut, Lebanon, on 28 December 1968.[81]

Aircraft on display[edit]

Since retirement, three early-generation Comet airframes have survived in museum collections. The only complete remaining Comet 1, a Comet 1XB with the registration G-APAS, the very last Comet 1 built, is displayed at the RAF Museum Cosford.[183] Though painted in BOAC colours, it never flew for the airline, having been first delivered to Air France and then to the Ministry of Supply after conversion to 1XB standard;[183] this aircraft also served with the RAF as XM823. The sole surviving Comet fuselage with the original square-shaped windows, part of a Comet 1A registered F-BGNX, has undergone restoration and is on display at the de Havilland Aircraft Museum in Hertfordshire, England.[184] A Comet C2 Sagittarius with serialXK699, later maintenance serial 7971M, was formerly on display at the gate of RAF Lyneham in Wiltshire, England since 1987.[185][186] In 2012, with the planned closure of RAF Lyneham, the aircraft was slated to be dismantled and shipped to the RAF Museum Cosford where it was to be re-assembled for display. The move was cancelled due to the level of corrosion and the majority of the airframe was scrapped in 2013, the cockpit section going to the Boscombe Down Aviation Collection at Old Sarum Airfield[187]

Six complete Comet 4s are housed in museum f.lux 4.75 - Crack Key For U. The Imperial War Museum Duxford has a Comet 4 (G-APDB), originally in Dan-Air colours as part of its Flight Line Display, and later in BOAC livery at its AirSpace building.[188] A Comet 4B (G-APYD) is stored in a facility at the Science Museum at Wroughton in Wiltshire, England.[189] Comet 4Cs are exhibited at the Flugausstellung Peter Junior at Hermeskeil, Germany (G-BDIW),[190] the Museum of Flight Restoration Center near Everett, Washington (N888WA),[175] and the National Museum of Flight near Edinburgh, Scotland (G-BDIX).[191]

The last Comet to fly, Comet 4C Canopus (XS235),[1] is kept in running condition at Bruntingthorpe Aerodrome, where fast taxi-runs are regularly conducted.[192] Since the 2000s, several parties have proposed restoring Canopus, which is maintained by a staff of volunteers,[193] to airworthy, fully flight-capable condition.[141] The Bruntingthorpe Aerodrome also displays a related Hawker Siddeley Nimrod MR2 aircraft.[193]

Specifications[edit]

Variant[194]Comet 1Comet 2Comet 3Comet 4
Cockpit crew 4 (2 pilots, flight engineer and radio operator/navigator)[195]
Passengers36–44[15][158]58–76[162]56–81[196]
Length 93 ft (28 m)[156]96 ft 1 in (29.29 m)[156]111 ft 6 in (33.99 m)[162][197]
Tail height 29 ft 6 in (8.99 m)[197]
Wingspan115 ft (35 m)[197][198]
Wing area2,015 sq ft (187.2 m2)[156]2,121 sq ft (197.0 m2)[197]
Aspect ratio6.566.24
Airfoil NACA 63A116 mod root, NACA 63A112 mod tip[199]
MTOW110,000 lb (50,000 kg)[156]120,000 lb (54,000 kg)[156]150,000 lb (68,000 kg)[156]156,000 lb (71,000 kg)[197]
Turbojets (x 4) Halford H.2 Ghost 50 R-R Avon Mk 503/504 R-R Avon Mk 502/521 R-R Avon Mk 524
Unit thrust 5,000 lbf (22 kN)[156]7,000 lbf (31 kN)[156]10,000 lbf (44 kN)[162]10,500 lbf (47 kN)[200]
Range1,300 nmi; 2,400 km[69]2,300 nmi; 4,200 km[198]2,300 nmi; 4,300 km[201]2,802 nmi; 5,190 km[195]
Cruisingspeed400 kn (740 km/h)[156]430 kn (790 km/h)[198]450 kn (840 km/h)[198][200]
Cruise altitude42,000 ft (13,000 m)[156][198]45,000 ft (14,000 m)[198]42,000 ft (13,000 m)[195]

In popular culture[edit]

Main article: De Havilland Comet in fiction

See also[edit]

Comet 4B 3-view schematic (front, side, and dorsal views)

Comet 1 3-view in silhouette (note differences in Comet 4 insert, reproduced in same scale)

Related development

Aircraft of comparable role, configuration, and era

Related lists

References[edit]

Notes
  1. ^Total of Comets in production: 114,[2] or 136 (when including refitting of original airframes and conversions).[3]
  2. ^ During the same era, both Lockheed with their Lockheed L-188 Electra and Vickers with the ground-breaking Vickers Viscount discounted the advantages of "pure" jet power to develop turboprop-powered airliners.[6]
  3. ^The "Type IV" Specifications issued on 3 February 1943 provided for a "high-speed mail-carrying airliner, gas-turbine powered."[7]
  4. ^From 1944 to 1946, the design group prepared submissions on a three-engined twin-boom design, a three-engined canard design with engines mounted in the rear, and a tailless design that featured a swept wing and four "podded" engines.[9]
  5. ^The Ministry of Supply's order for DH 108s was listed as Operational Requirement OR207 to Specification E.18/45.[11]
  6. ^BOAC's requested capacity increase was known as Specification 22/46.[5]
  7. ^The wing was drastically redesigned from a 40˚ sweep.[14]
  8. ^The name "Comet", previously used by the de Havilland DH.88 racing aircraft, was revived.[16]
  9. ^British South American Airways merged with BOAC in 1949.[5]
  10. ^The fuselage sections and nose simulated a flight up to 70,000 ft (21,000 m) at a temperature of −70 °C (−94 °F), with 2,000 lb (910 kg) pressure applications at 9 psi (62 kPa).[13]
  11. ^BOAC flight crew revelled in standing a pen on end and pointing that out to passengers; invariably, the pen remained upright throughout the entire flight.[35]
  12. ^The Sud-Est SE 530/532/535 Mistral (FB 53) was a single-seat fighter-bomber version of the de Havilland Vampire jet fighter, used by L'Armée de l'Air.[46]
  13. ^Fuselage alloys detailed in Directorate of Technical Development 564/L.73 and DTD 746C/L90.
  14. ^The Avro Canada C102 Jetliner, for which it was coined, first used the term; "jetliner" later became a generic term for all jet airliners.[67]
  15. ^Depending on weight and temperature, cruise fuel consumption was 6 to 10 kg (13 to 22 lb) per per nautical mile (1.2 miles; 1.9 km), the higher figure being at the lower altitude needed at high weight.[citation needed]
  16. ^The court acted under the provisions of Rule 75 of the Indian Aircraft Rules 1937.[92]
  17. ^Cunningham: "[the Comet] flew extremely smoothly and responded to the controls in the best way de Havilland aircraft usually did."[96]
  18. ^The Abell Committee, named after f.lux 4.75 - Crack Key For U C. Abell, Deputy Operations Director (Engineering) of BOAC, consisted of representatives of the Allegation Review Board (A.R.B.), BOAC, and de Havilland.[100]
  19. ^On 4 April, Lord Brabazon wrote to the Minister of Transport, "Although no definite reason for the accident has been established, modifications are being embodied to cover every possibility that imagination has suggested as a likely cause of the disaster. When these modifications are completed and have been satisfactorily flight-tested, the Board sees no reason why passenger services should not be resumed."[101]
  20. ^Hall: "In the light of known properties of the aluminium alloy D.T.D. 546 or 746 of which the skin was made and in accordance with the advice I received from my Assessors, I accept the conclusion of RAE that this is a sufficient explanation of the failure of the cabin skin of Yoke Uncle by fatigue after a small number, namely, 3,060 cycles of pressurisation."[119]
  21. ^The Feb 1959 OAG shows eight transatlantic Comets a week out of London, plus 10 BOAC Britannias and 11 DC-7Cs. In April 1960, 13 Comets, 19 Britannias and 6 DC-7Cs. Comets quit flying the North Atlantic in October 1960 (but reportedly made a few flights in summer 1964).[citation needed]
  22. ^Avon-powered Comets were distinguished by larger air intakes and curved tailpipes that reduced the thermal effect on the rear fuselage.[157]
  23. ^The 2R ELINT series was operational until 1974, when replaced by the Nimrod R1, the last Comet derivative in RAF service.[161]
  24. ^The MoT subsequently backed BOAC's order of Conway-powered Boeing 707s.[169]
Citations
  1. ^ abcWalker 2000, p. 169.
  2. ^ abLo Bao 1996, pp. 36–47.
  3. ^Walker 2000, pp. 185–190.
  4. ^ abcTrischler and Helmuth 2003, p. 88.
  5. ^ abcdefBirtles 1970, p. 124.
  6. ^Kodera et al. 2010, p. 16.
  7. ^Jones 2010, p. 60.
  8. ^Jackson 1988, p. 453.
  9. ^ abcJones 2010, p. 62.
  10. ^ abTrischler and Helmuth 2003, p. 90.
  11. ^ abWatkins 1996, p. 39.
  12. ^Darling 2001, p. 11.
  13. ^ abcdBirtles 1970, p. 125.
  14. ^ abJones 2010, pp. 62–63.
  15. ^ abcWinchester 2004, p. 109.
  16. ^Jackson 1988, p. 356.
  17. ^ abDarling 2001, p. 17.
  18. ^ abcdeDarling 2001, p. 18.
  19. ^"Tank Test Mk 2.", Flight, Iliffe, pp. 958–959, 30 December 1955, archived from the original on 31 January 2019, retrieved 26 April 2012
  20. ^ abcDavies and Birtles 1999, p. 30.
  21. ^"Comet Engineering", Flight, Iliffe, p. 552, 1 May 1953, archived from the original on 2 February 2017, retrieved 23 March 2019 – via FlightGlobal Archive
  22. ^Dick and Patterson 2010, pp. 134–137.
  23. ^Green and Swanborough April 1977, p. 174.
  24. ^Prins 1998, p. 43.
  25. ^Swanborough 1962, p. 45.
  26. ^Gunn 1987, p. 268.
  27. ^ abWalker 2000, p. 25.
  28. ^ abcFrancis 1950, p. 99.
  29. ^ abFrancis 1950, pp. 100–101.
  30. ^Hill 2002, p. 27.
  31. ^ abCookman, Aubery O. Jr. "Commute by Jet."Popular Mechanics, 93(4), April 1950, pp. 149–152.
  32. ^Smith 2010. 30(4), pp. 489, 506.
  33. ^Francis 1950, p. 98.
  34. ^Walker 2000, p. 69.
  35. ^Windsor-Liscombe, Rhodri. "Usual Culture: The Jet."Topia: Canadian Journal of Cultural Studies (Toronto: York University), Number 11, Spring 2004. Retrieved 26 April 2012.
  36. ^Francis 1950, p. 100.
  37. ^Darling 2001, pp. 35–36.
  38. ^ abDarling 2001, p. 36.
  39. ^Abzug and Larrabee 2002, pp. 80–81.
  40. ^Darling 2001, p. 2.
  41. ^Darling 2001, pp. 16–17.
  42. ^Darling 2001, p. 40.
  43. ^Darling 2001, p. 45.
  44. ^"F.R. equipment speeds refuelling."Flight, 11 May 1951. Retrieved 26 April 2012.
  45. ^ abDarling 2001, pp. 40–41.
  46. ^Watkins 1996, pp. 181–182.
  47. ^Motem 1990, p. 143.
  48. ^Darling 2001, p. 96.
  49. ^ abc"Comet Engineering: The Performance of Airframe, Engines, and Equipment in Operational Service."Flight International, 1 May 1953, p. 551. Retrieved 26 April 2012.
  50. ^"Comet Enters Service."Archived 22 September 2009 at the Wayback MachineRoyal Air Force Museum Cosford. Retrieved 1 November 2010.
  51. ^Moss, C. J. "Metal to Metal Bonding – For Aircraft Structures: Claims of the Redux Process."Flight International, 8 February 1951, p. 169. Retrieved 26 April 2012.
  52. ^Jefford 2001, pp. 123–125.
  53. ^Birtles 1970, p. 132.
  54. ^Jones 2010, p. 67.
  55. ^Francis 1950, pp. 101–102.
  56. ^Darling 2001, pp. 35, 46.
  57. ^ abWithuhn 1976, p. 88.
  58. ^Francis 1950, p. 103.
  59. ^"Ghost engine."Archived 4 February 2010 at the Wayback MachineRoyal Air Force Museum Cosford. Retrieved 1 November 2010.
  60. ^Francis 1950, pp. 98–102.
  61. ^Gunn 1987, p. 269.
  62. ^ abWalker 2000, p. 190.
  63. ^ abcdeDarling 2001, p. 33.
  64. ^"Comet Gets Stronger Engines."Popular Science, 160(6), June 1952, p. 142.
  65. ^Davies and Birtles 1999, p. 31.
  66. ^Davies and Birtles 1999, p. 34.
  67. ^Floyd 1986, p. 88.
  68. ^ abMcNeil 2002, p. 39.
  69. ^ ab"On This Day: Comet inaugurates the jet age."BBC News, 2 May 1952. Retrieved 26 April 2012.
  70. ^ abCookman, Aubrey O. Jr. "I Rode The First Jet Airliner."Popular Mechanics, July 1952, pp. 90–94. Retrieved 26 April 2012.
  71. ^Jackson 1988, pp. 173–174.
  72. ^Lane 1979, p. 205.
  73. ^"Jet Air-Routes", Flight, p. 547, 1 May 1953, archived from the original on 5 March 2016
  74. ^Davies and Birtles 1999, p. 22 (Route map illustration).
  75. ^Schnaars 2002, p. 71.
  76. ^ abSchnaars 2002, p. 70.
  77. ^"Preludes and Overtures: de Havilland Comet 1".Flight, 4 September 1953. Retrieved 30 May 2012.
  78. ^Darling 2001, p. 20.
  79. ^Cacutt 1989, p. 146.
  80. ^ abcDarling 2005, p. 119.
  81. ^ abcdefghijklmnoRoach and Eastwood 1992, pp. 331–335.
  82. ^ abDarling 2005, p. 128.
  83. ^Proctor et al. 2010, p. 23.
  84. ^Gunn 1987, pp. 268–270.
  85. ^"Comet Accident Record."Aviation Safety Network. Retrieved: 22 September 2010.
  86. ^"CF-CUN"Ed Coates' Civil Aircraft Photograph Collection. Retrieved: 18 February 2011.
  87. ^ abcWithuhn 1976, p. 85.
  88. ^Birtles 1970, p. 127.
  89. ^Beaty 1984, pp. 113–114.
  90. ^Darling 2005, p. 36.
  91. ^ abLokur, N. S. "Report of the court investigation on the accident to COMET G-ALYV"(PDF). Lessons Learned. Federal Aviation Administration. Archived from the original(PDF) on 15 April 2015. Retrieved 23 February 2015.
  92. ^ abcdWalker 2000, p. 37.
  93. ^Lo Bao 1996, p. 7.
  94. ^Job 1996, p. 14.
  95. ^Darling 2001, p. 26.
  96. ^ abcFaith 1996, pp. 63–64.
  97. ^ abcdeWithey, Geekbench Pro 5.4.1 Crack+ Serial Key Free Download 2021 (1997), "Fatigue Failure of the de Havilland Comet I",
Источник: https://en.wikipedia.org/wiki/De_Havilland_Comet

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