Il 12 gennaio, il New York Times riferì che la BOAC aveva temporaneamente ritirato dal servizio tutti i suoi de Havilland Comet a causa dell'incidente, insieme alle due compagnie aeree francesi che utilizzavano i Comet, Air France e l'Union Aero Maritime des Transports.  A further test reproduced the same results. 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. The MoT subsequently backed BOAC's order of Conway-powered Boeing 707s. , In 1953 the Comet appeared to have achieved success for de Havilland. The last two Comet 4C fuselages were used to build prototypes of the Hawker Siddeley Nimrod maritime patrol aircraft.  The Ghost engines allowed the Comet to fly above weather which competitors had to fly through.  The Comet's Certificate of Airworthiness was revoked, and Comet 1 line production was suspended at the Hatfield factory while the BOAC fleet was permanently grounded, cocooned and stored. , 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. "De Havilland DH.106 Comet.  However, because of financial problems and a takeover by United Airlines, Capital would never operate the Comet. , The prototype was registered G-ALVG just before it was publicly displayed at the 1949 Farnborough Airshow prior to the start of flight trials. , The Comet 1 featured 5,050 lbf (22.5 kN) de Havilland Ghost 50 Mk1 turbojet engines.  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). Hall: "In the light of known properties of the aluminium alloy D.T.D. 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). 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). ", This page was last edited on 23 November 2020, at 23:35.  Based on these findings, Comet 1 structural failures could be expected at anywhere from 1,000 to 9,000 cycles. Nine additional Comet 3 airframes were not completed and their construction was abandoned at Hatfield. ", "De Havilland Comet 4B airliner, serial no 6438, 1960. BOAC installed 36 reclining "slumberseats" with 45-inch (1,100 mm) centres on its first Comets, allowing for greater leg room in front and behind; Air France had 11 rows of seats with four seats to a row installed on its Comets. "Preludes and Overtures: de Havilland Comet 1".  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.  While the Comet's buried engines were used on some other early jet airliners, such as the Tupolev Tu-104, later aircraft, such as the Boeing 707 and Douglas DC-8, would differ by employing podded engines held on pylons beneath the wings. , In military service the United Kingdom's Royal Air Force was the largest operator, with the 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. 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. , The cockpit was significantly altered for the Comet 4's introduction, on which an improved layout focusing on the onboard navigational suite was introduced.  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.  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. ", "De Havilland Comet 4C G-BDIX Interior View Scottish Museum of Flight. , 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. [N 23], 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. 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.  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.  Only two Comet 3s began construction with G-ANLO, the only airworthy Comet 3, demonstrated at the Farnborough SBAC Show in September 1954. endstream
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 The punch rivet construction technique employed in the Comet's design had exacerbated its structural fatigue problems; the aircraft's windows had been engineered to be glued and riveted, but had been punch riveted only. , 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.  The engines were outfitted with baffles to reduce noise emissions, and extensive soundproofing was also implemented to improve passenger conditions. We were in 1959 on 27th of August when a Comet 4 (LV-AHP) - operated by Aerolineas Argentinas - during a final approach to Asuncion airport (Paraguay ) encountered marginal weather conditions with … Entering service in 1969, five Nimrod variants were produced.  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. Following its first flight, the special order Comet 4C was described as "the world's first executive jet. , 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).  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.  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. , 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. ", "De Havilland DH.106 Comet 4, G-APDJ, Air Ceylon. , A design team was formed in 1946 under the leadership of chief designer Ronald Bishop, who had been responsible for the Mosquito fighter-bomber. , The Comet is widely regarded as both an adventurous step forward and a supreme tragedy; nevertheless, the aircraft's legacy does include numerous advances in aircraft design and in accident investigations. Il velivolo coinvolto nell'incidente era un De Havilland Comet DH. , 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.  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. A de Havilland DH-106 Comet 4C passenger plane, registered SU-ALC, was damaged beyond repair in an accident 7 km N of Tripoli International Airport (TIP), Libya. , The committee accepted the proposal, calling it the "Type IV" (of five designs),[N 3] and awarded a development and production contract to de Havilland under the designation Type 106 in February 1945. Four Ghost 50 Mk 1 engines were fitted (later replaced by more powerful Ghost DGT3 series engines). ", 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. %%EOF
 Additionally, a large number 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.  One window frame survived 100 psi (690 kPa), about 1,250 percent over the maximum pressure it was expected to encounter in service. The Ministry of Supply's order for DH 108s was listed as Operational Requirement OR207 to Specification E.18/45.  The DH 108s were later modified to test the DH.106's power controls.  Design changes had been made to make the aircraft more suitable for transatlantic operations. Short take-off and landing capabilities.  The majority of hydraulic components were centred in a single avionics bay. The prototype Comet 3 first flew in July 1954, and was tested in an unpressurised state pending completion of the Cohen inquiry. 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.  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. , 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.  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. The wing was drastically redesigned from a 40˚ sweep. In April, another Comet, this one operated by South African Airways, came apart in midair, again over the Mediterranean.  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. Smith, Adrian. The Dash 8-400 is the most productive turboprop aircraft on the market.  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.  Comet flights resumed on 23 March 1954. The fuselage sections and nose simulated a flight up to 70,000 ft at a temperature of −70˚C, with 2,000 lb pressure applications at 9 lb pressure/square in. The American jets were larger, faster, longer-ranged, and more cost-effective than the Comet. The Comet design was finalized in 1945, as the British aircraft industry was attempting to establish a commercial aircraft industry post-World War II.  Comet commercial flights would not resume until 1958.. , Prince Philip returned from the Helsinki Olympic Games with G-ALYS on 4 August 1952. ", 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.  Popular Mechanics wrote that Britain had a lead of three to five years on the rest of the world in jetliners. 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.  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. Winchester, Jim, ed. As the aircraft could be profitable with a load factor as low as 43 percent, commercial success was expected.  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.  The base price of a new Comet 4 was roughly £1.14 million (£22.97 million in 2016).  In BOAC colours, G-ANLO was flown by John Cunningham in a marathon round-the-world promotional tour in December 1955. BOAC's requested capacity increase was known as Specification 22/46. 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. After design modifications were implemented, Comet services resumed in 1958. 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. 1–4.". 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 thousand feet), speed, and transatlantic range as was called for by the Type 106. Download the PDF.  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. 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. Without support from the Ministry of Transport, the proposal languished as a hypothetical aircraft and was never realised.  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 same route, and in 1960 the Douglas DC-8 as well.  With no witnesses to the disaster and only partial radio transmissions as incomplete evidence, no obvious reason for the crash could be deduced.  Deliveries to BOAC began on 30 September 1958 with two 48-seat aircraft, which were used to initiate the first scheduled transatlantic services. ", "ASN Aircraft accident de Havilland DH-106 Comet 4 G-APDN Sierra del Montseny", "de Havilland DH106 Comet 1A – de Havilland Aircraft Museum", "Gate Guardian Comet C2 Sagittarius – XK699 – RAF Lyneham. ", "Commercial Aircraft 1953: De Havilland Comet.  The undercarriage could also be lowered by a combination of gravity and a hand-pump.  A slightly longer version of the Comet 1 with more powerful engines, the Comet 2, was being developed, and orders were placed by Air India, British Commonwealth Pacific Airlines, Japan Air Lines, Linea Aeropostal Venezolana, and Panair do Brasil. A de Havilland DH-106 Comet 1 passenger plane, registered G-ALYP, was destroyed in an accident 16 km S off Elba, Italy. Survivors: Yes. 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. 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.  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.  The prototype's maiden flight, out of Hatfield Aerodrome, took place on 27 July 1949 and lasted 31 minutes.  The last Comet 4 variant, the Comet 4C, first flew on 31 October 1959 and entered service with Mexicana in 1960. This time, the entire fuselage was tested in a dedicated water tank that was built specifically at Farnborough to accommodate its full length. L'impennaggio orizzo… 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.  In addition to 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.  Sprite fittings were retained on production aircraft. L'incidente provocò la distruzione del velivolo e la morte di tutti i 112 a bordo. , In September 1946, prior to the 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. Developed and manufactured by de Havilland at its Hatfield Aerodrome in Hertfordshire, United Kingdom, the Comet 1 prototype first flew in 1949.  Two hydrogen peroxide-powered de Havilland Sprite booster rockets were originally intended to be installed to boost takeoff under hot and high altitude conditions from airports such as Khartoum and Nairobi. The airplane operated on a flight from Algiers-Dar el Beida Airport (ALG) to Tripoli International Airport (TIP). "The de Havilland Comet Srs.  The fuselage frames did not have sufficient strength to prevent the crack propagating. , 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. Categoría:Accidentes e incidentes de de Havilland Comet. 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. %PDF-1.5
Flight Phase: Takeoff (climb) Flight Type: Scheduled Revenue Flight. 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. While these lessons could be implemented on the drawing board for future aircraft, corrections could only be retroactively applied to the Comet. On April 8, 1954, another Comet broke up in air. BOAC ordered 19 Comet 4s in March 1955, while American operator Capital Airlines ordered 14 Comets in July 1956.  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. h�b``�e``2d T��,
This wreckage was from the starboard side of the cabin just above the three front windows.  Comet 1s subsequently received more powerful 5,700 lbf (25 kN) Ghost DGT3 series engines. 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. , In 1959 BOAC began shifting its Comets from transatlantic routes and released the Comet to associate companies, making the Comet 4's ascendancy as a premier airliner brief. 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). 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. Birtles, P.J. Efficient regional operations. Simons, Graham M. "Comet!  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, and a radar interface was built into the Comet 4 cockpit along with redesigned instruments. "Comet Service To South America Planned" (News). The Ministry of Supply was, however, 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.  A Comet 4C (SA-R-7) was ordered by Saudi Arabian Airlines with eventual disposition to the Saudi Royal Flight for the exclusive use of King Saud bin Abdul Aziz. , 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; its fuselage was 3 ft 1 in (0.94 m) longer than the Comet 1's. Developed and manufactured by de Havilland at its Hatfield Aerodrome in Hertfordshire, United Kingdom, the Comet 1 prototype first flew in 1949. ", "Metal to Metal Bonding – For Aircraft Structures: Claims of the Redux Process.  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. Cunningham: "[the Comet] flew extremely smoothly and responded to the controls in the best way de Havilland aircraft usually did.". Jones, Barry. 8 April 1954: Suid-Afrikaanse Lugdiens (South African Airways) Flight 201, a chartered British Overseas Airways Corporation de Havilland DH.106 Comet 1, departed Rome at 1832 UTC, bound for Cairo.  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. On January 10, 1954 a Comet broke up in mid-air. 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.  Aviation author Bill Withuhn concluded that the Comet had pushed "'the state-of-the-art' beyond its limits. It was the last leg of the new … G-ALYP crashed into the sea leaving Rome. The Comet Story. 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. As a result, the Comet was extensively redesigned, with oval windows, structural reinforcements and other changes. ", 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), During the same era, both Lockheed with their, The "Type IV" Specifications issued on 3 February 1943 provided for a "high-speed mail-carrying airliner, gas-turbine powered. "World Beater: Homage to the DH. 106 Comet.". 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. [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, during which the break-up was found to have begun with a left elevator spar failure in the stabilizer. "The Dawn of the Jet Age in Austerity Britain: David Lean's The Sound Barrier". Over the coming years, this small upstart would become one of the most accomplished aircraft designers and manufacturers in Canadian history.
 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. Unlike drill riveting, the imperfect nature of the hole created by punch riveting could cause fatigue cracks to start developing around the rivet. The low-mounted engines and good placement of service panels also made aircraft maintenance easier to perform.