De Havilland Comet
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- This article is about the de Havilland Comet jet airliner. For the 1930s racing aircraft, see de Havilland DH.88.
| DH.106 Comet | |
|---|---|
 |
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| Royal Air Force Comet C.2 | |
| Type | Airliner |
| Manufacturer | de Havilland |
| Maiden flight | 1949-07-27 |
| Introduced | 1952-01-22 with BOAC |
| Status | military service only |
| Unit cost | UK£250,000 in 1952 |
| Variants | Hawker-Siddeley Nimrod |
- The correct title of this article is de Havilland Comet. The initial letter is shown capitalized due to technical restrictions.
The de Havilland Comet of Britain was the world's first commercial jet airliner. It is infamous for being the first to experience the metal fatigue of jet aircraft due to high flight altitudes. Despite that, the Comet and its military derivative, the Nimrod, enjoyed long and productive careers.
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[edit] History
The origins of the Comet lie in the report produced by the Brabazon Committee during the war. It looked forward to Britain's post war airliner needs and one of the aircraft identified as needing research was for a 100-seat jet airliner which was known as the "Type IV". That Geoffrey de Havilland, head of the de Havilland company, was on the committee and de Havilland were working on jet fighters for the RAF was not unrelated.
Design work began in 1946 under Ronald Bishop and the intention was to have a commercial aircraft by 1952. The DH 106 Comet first flew on 27 July 1949. At the controls was de Havilland test pilot, John Cunningham, the same man who set a new altitude record two years later in a de Havilland DH 100 Vampire. The design was similar to other airliners except that four of the new, albeit underpowered, de Havilland Ghost 50 Mk1 turbojets were mounted within the wings, in pairs close to the fuselage; this was thought to prove the aircraft more aerodynamic when flying at high speeds. (Unfortunately, the metal skin of the Comet was thinned to compensate for the lack of thrust from the Ghost turbojets; the consequences of this proved disastrous and will be discussed later.) The airliner underwent almost three years of tests and fixes and the first commercial flights did not begin until 22 January 1952 with British Overseas Airways Corporation (BOAC). It became an instant hit with the elite market at whom it was aimed. The first passenger flight was in May from London Heathrow Airport to Johannesburg. The airliner proved to be around twice as fast as contemporary craft and with almost 30,000 passengers carried in the first year over fifty Comets were ordered.
[edit] Design
The Comet is a low wing four engine jet aircraft of all metal construction. It is smaller than today's typical jet airliner (approximately the length of the smallest Boeing 737, the 737-100), though it held fewer people in more comfort. The earliest Comets had 11 rows for seats with four seats to a row. Each seat had its own ashtray. There was a galley able to serve hot and cold food and drink. There were separate men's and women's washrooms. A Comet had a quieter passenger cabin than the propeller driven planes it replaced.
The cockpit held space for two pilots, a flight engineer and a navigator. A modern plane of this size would only require a crew of two.
It has four de Havilland Ghost, Rolls-Royce Avon, or Rolls-Royce Spey jet engines embedded within the wings (which is a rare design feature). The engines are embedded near the middle of the wing where it is thickest. This placement is in strong contrast to the Boeing 707 and almost all other jet planes of this size which use podded engines.
Life rafts were embedded within the wing near the engines for use in an emergency. This is not done today. Below each seat bottom was a compartment holding a separate life vest.
Originally the Comet was to also have two hydrogen peroxide powered Sprite booster rockets for faster take-off, and in fact these were tested over thirty flights before it was decided the booster rockets were unnecessary.
The Comet had 7 (or 9) fuel tanks. They were:
- Outer left wing tank
- Middle left wing tank
- Left pinion tank (on later models, another unique Comet design feature)
- Inner left wing tank
- Centre tank
- Inner right wing tank
- Middle right wing tank
- Right pinion tank (on later models, another unique Comet design feature)
- Outer right wing tank
Pinion tanks are fuel tanks extending from the leading edge of the wing, and are never found on modern jet liners.
The Comet has four different hydraulic systems for redundancy:
- The Green system controlled everything.
- The Blue system was a backup for the primary flight controls.
- The Yellow system was also a backup for the primary flight controls.
- The Red system was able to extend (but not retract) the landing gear.
- Additionally, a hand pump was also able to extend (but not retract) the landing gear.
The early model Comets required about five or six man-hours of maintenance labour per flight hour, which was better than the propeller driven planes it replaced.
[edit] Design flaws
Two separate incidents involving Comets occurred near the end of 1952 and beginning of 1953: a BOAC flight failed to become airborne at Ciampino airport near Rome, Italy on 26 October 1952, resulting in minor injuries to passengers, while a Canadian Pacific Airlines Comet 1A collided with a bridge and was destroyed with all hands on takeoff from Karachi, Pakistan the following March. These were attributed to a loss of lift from the leading edge of the plane's wing, which was subsequently redesigned.
The first indication of a more serious design flaw, however, came later, on 2 May 1953 when a Comet 1, again of BOAC crashed soon after take-off from Calcutta (now Kolkata), India; further crashes (January and April 1954) off the Italian island of Elba (BOAC Flight 781) and in Stromboli (South African Airways Flight 201) with no clear cause led to the entire fleet being grounded for investigation. In February 1955, the remnants of the Italian crashes were brought to the surface. Analysis showed the cause of the crashes to be metal fatigue: after thousands of pressurised climbs and descents, the fuselage metal (which was thinner than standard due to the need to save weight, resulting from the aircraft's underpowered de Havilland Ghost engines) around the Comet's distinctive rectangular, large windows would begin to crack and eventually cause explosive decompression of the cabin and catastrophic structural failure.
All remaining Comets were either scrapped or modified with window rip-stop doublers and the program to produce a Comet 2 with more powerful Rolls-Royce Avon engines was put on hold. Some Comet 2s were modified to alleviate the fatigue problems and served with the RAF as the Comet C.2. The Comet did not resume commercial airline service until 1958, when the much-improved Comet 4 was introduced.
[edit] Variants
[edit] Comet 1
The Comet 1 was the first model of the Comet produced. An update Comet 1A was offered, and some of these were modified to Comet 1XB standard, with strengthened fuselages and round windows, in the wake of the fatigue accidents.
[edit] Comet 2
The Comet 2 was a development of the Comet 1, featuring a slightly larger wing, and more powerful Rolls-Royce Avon engines, which improved the aircraft's range and performance. The Comet 2s were allocated to the RAF, where they were known as the Comet Mk. 2s. Eight Comet C.Mk 2 transport aircraft and two Comet T.Mk 2 crew trainers were delivered to the RAF in 1955.
[edit] Comet 3
The Comet 3 was a lengthened Comet, with greater capacity and greater range. In the wake of the fatigue accidents, orders dried up, and only two Comet 3s were built, only one of which flew, the other being used for structural testing. The Comet 3 paved the way for the similarly sized Comet 4, serving as a test bed for new technology being developed for that aircraft.
[edit] Comet 4
The Comet 4 included many modifications compared to the original Comet 1. It used a strengthened fuselage and round windows to alleviate the metal fatigue problems of the Comet 1. The Comet 4 was also a considerably larger aircraft, 5.64 m (18 ft 6 in) longer than the Comet 1 and typically seating 74 to 81 passengers, compared to the Comet 1's 36 to 44. It also had a longer range, higher cruising speed, and higher maximum takeoff weight. These improvements were possible largely due to the use of Rolls-Royce Avon engines with over twice the thrust of the Comet 1's de Havilland Ghosts.
BOAC ordered 19 Comet 4s in March 1955, despite the Comet 1's problems. The Comet 4 first flew on 27 April 1958, and deliveries to BOAC began that September. BOAC initiated Comet 4 service with a flight from London to New York via Gander on 4 October 1958. That flight was the first scheduled trans-Atlantic passenger jet service, beating Pan Am's inaugural 707 service by three weeks.
Two other variants of the Comet 4 were developed. The Comet 4B included a stretched fuselage and shorter wings; it was targeted to the fairly short-range operations of British European Airways, which placed an initial order for it in 1958. The Comet 4B first flew on 27 June 1959, and BEA inaugurated services with it in April 1960. The final Comet 4 variant was the Comet 4C, with the longer fuselage of the Comet 4B but the larger wings and fuel tanks of the original Comet 4, which gave it a longer range than the 4B. It first flew on 31 October 1959, and Mexicana started Comet 4C services in 1960.
[edit] Comet 5
The Comet 5 was a proposed development that would have been a marked improvement over the previous models. Features of the design included a wider fuselage allowing 5 abreast seating, a wing with greater sweep, and pod mounted Rolls-Royce Conway engines, all producing a similar configuration to the Boeing 707 and Douglas DC-8 which were being developed on the other side of the Atlantic. Support from the Ministry of Transport was not forthcoming, and the project did not proceed. Ironically, BOAC, backed by the Department, went on to order Conway powered Boeing 707s.
[edit] Hawker Siddeley Nimrod
The Comet 4 was heavily modified to become the Hawker-Siddeley Nimrod, a military plane which has been the Royal Air Force's primary maritime patrol aircraft since 1969. Before its introduction, maritime patrol aircraft generally used piston or turboprop engines because of better fuel economy, which gave longer flight duration and range. The Nimrod is powered by turbofans, two of its four Spey engines being able to be shut down in flight to reduce fuel consumption and allow extended "loiter" time, the four engines used together allowing for a high-speed "dash" to a suspected submarine contact.
Nimrod was originally designed and built by Hawker-Siddeley who had incorporated de Havilland, but is now produced by BAE Systems (formerly British Aerospace which had been formed out of Hawker-Siddeley and other companies). Nimrod serves the RAF in two variants: the Maritime Reconnaissance (MR) role, currently as the MR.2 variant, and the Reconnaissance (R1) variant, with an electronic intelligence (ELINT) gathering capacity; officially, these were originally coyly designated "radar calibration aircraft". The R1 is distinguished from the MR2 by the lack of a MAD boom. A new Nimrod, the Nimrod MRA4, is entering service.
[edit] Production and service summary
In total, 76 Comet 4 family aircraft were delivered from 1958 to 1964. Although BOAC retired its Comet 4s from revenue service in 1965, other operators (of which Dan-Air was the largest and last) continued flying commercial passenger services with the aircraft until 1980. The last Comet flight was conducted in 1997 by a Comet 4C that had been owned by the British government.
Although the Comet was the first jet airliner in service, the interruption of commercial service and the damage to the aircraft's reputation caused by the Comet 1 fatigue failures led to the domination of the jetliner market by Boeing, which flew the first prototype 707 in 1954, and Douglas, which launched the DC-8 program in 1955. Also, for a brief period, the Soviet Union's Tupolev Tu-104 was the only jet airliner flying commercially.
Both the 707 and DC-8 had better ranges and passenger accommodations as compared to the Comet, and the American manufacturers also had the huge advantage of a large (and often highly patriotic) domestic airline market. The USA has enjoyed a large share of the commercial jetliner market ever since, with their only real competition coming from the later formed Airbus consortium (although Tupolev still manufacture jet airliners at a slow pace).
Only fifteen airlines ever used the Comet. The proposed Comet 5 was never built, and the Comet 4 was slowly withdrawn from service.
[edit] Preserved Aircraft
[edit] Comet 1
The only complete surviving Comet 1 is a Comet 1XB on display at the RAF Museum Cosford. It is painted in BOAC colours and displays the registration G-APAS, although it never flew for that airline, having been delivered to Air France, and then to the Ministry of Supply after conversion to 1XB standard.
The nose of BOAC Comet 1A G-ANAV is displayed at London's Science Museum, while the fuselage of Air France Comet 1A F-BGNX is preserved at the De Havilland Aircraft Heritage Centre in Hertfordshire.
[edit] Comet 4
- Comet C2 'Sagittarius' (Serial XK699 and later maintenance serial 7971M) is the current Gate Guardian at RAF Lyneham in Wiltshire. Lyneham, was previously the operational base for all RAF operated Comets.
- Comet 4B (Registration G-APYD) is stored at the Science Museum facility at Wroughton in Wiltshire.
- Comet 4C (Registration N888WA) in Mexicana livery is being restored and on display at the restoration facility of the Museum of Flight, at Paine Field, next to Boeing's Everett, WA widebody plant.
- Comet 4C (Registration N777WA) is on display at the Parque Zoológico Irapuato in Mexico.
- Comet 4C (Registration G-APDB) in the colours of Dan-Air is on display at the Imperial War Museum Duxford, England. The plane is part of the Flight Line Display and made available for touring inside during specific times.
- Comet 4C (Registration G-BDIW) in the colours of Dan-Air is on display at the Flugausstellung Leo Junior at Hermeskeil in Germany.
- Comet 4C (Registration G-BDIX) in the colours of Dan-Air is on display at the Museum of Flight at East Fortune near Edinburgh in Scotland.
- The last Comet to fly, named Canopus (Military Serial XS235), is kept in running condition at Bruntingthorpe Aerodrome, where it regularly conducts fast taxi runs. There is a campaign to return Canopus to flight, with the current goal to have it in the air by the 50th anniversary of the first regular transatlantic jet service, which started on 4 October 1958.
[edit] Operators
- Aerolineas Argentinas.
- Air Ceylon.
- Air France.
- AREA.
- BEA Airtours.
- BOAC.
- British European Airways.
- Canadian Pacific Airlines, CAP.
- Capitol Airlines.
- Channel Airways.
- Dan Air.
- East African Airways.
- The Government of Saudi Arabia.
- Kuwait Airways.
- Malaysian Airways.
- Malaysian Singapore Airways.
- Mexicana.
- Middle East Airlines, MEA.
- Misrair Egyptair.
- Olympic Airways.
- Sudan Airways.
- Union des Transports Aeriens, UTA.
- United Arab Airlines.
[edit] Military Operators
[edit] Military Units using the Comet
[edit] Royal Air Force
- 51 Squadron (1958-1975) Comet C2 (RC)
- 192 Squadron (1957-1958) Comet C2 (RC)
- 216 Squadron (1956-1975) Comet C2 and C4
[edit] Royal Canadian Air Force
- 412 Squadron (1953-1963) Comet 1A
[edit] Specifications (Comet 1)
General characteristics
- Crew: 4
- Capacity: 36-44 passengers
- Length: 93 ft 10 in (28.61 m)
- Wingspan: 114 ft 9 in (34.98 m)
- Height: 29 ft 6 in (9 m)
- Wing area: 2,023 ft² (188.3 m²)
- Airfoil: NACA 63A116 mod root, NACA 63A112 mod tip
- Empty weight: lb (kg)
- Loaded weight: 105,000 lb (47,600 kg)
- Max takeoff weight: lb (kg)
- Powerplant: 4× de Havilland Ghost 50 turbojets, 5,000 lbf (22.2 kN) each
Performance
- Maximum speed: 450 mph (725 km/h)
- Range: 1,500 mi (2,400 km)
- Service ceiling: 42,000 ft (12,800 m)
- Rate of climb: ft/min (m/s)
- Wing loading: lb/ft² (kg/m²)
[edit] Specifications (Comet 4)
General characteristics
- Crew: 4
- Capacity: 56-109 passengers
- Length: 111 ft 6 in (34.0 m)
- Wingspan: 114 ft 10 in (35.0 m)
- Height: 29 ft 6 in (9.0 m)
- Wing area: 2,121 ft² (197 m²)
- Airfoil: NACA 63A116 mod root, NACA 63A112 mod tip
- Empty weight: 75,400 lb (34,200 kg)
- Loaded weight: 162,000 lb (73,470 kg)
- Max takeoff weight: lb (kg)
- Powerplant: 4× Rolls-Royce Avon Mk 524 turbojets, 10,500 lbf (46.8 kN) each
Performance
- Maximum speed: 500 mph (805 km/h)
- Range: 3,225 mi (5,190 km)
- Service ceiling: 40,000 ft (12,200 m)
- Rate of climb: ft/min (m/s)
- Wing loading: lb/ft² (kg/m²)
[edit] External links
- Terrible accidents involving De Havilland Comet
- Marc Schaeffer's Comet Website
- David Young's Comet Website
- Campaign to return Canopus to flight
