De Havilland Comet
Comet C. Mk2 of the Royal Air Force in 1964. This aircraft (XK715) made its first flight in 1957 and was scrapped in 1972.
Description
Role	Civil air transport
Crew	4
First Flight	July 27, 1949
Entered Service	January 22, 1952
Manufacturer	de Havilland
Dimensions (Comet 1)
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
Weights
Empty	0 lb	0 kg
Loaded	105,000 lb	47,620 kg
Maximum takeoff	lb	kg
Capacity	36-44 passengers
Powerplant
Engines	4 × de Havilland Ghost 50 turbojets
Thrust (each)	5,000 lb	22.3 kN
Performance
Maximum speed	450 mph	725 km/h
Range	1,500 miles	2,415 km
Ferry range	km	miles
Service ceiling	42,000 ft	12,800 m
Rate of climb	ft/min	m/min
Wing loading	51.8 lb/ft²	252.9 kg/m²
Thrust/Weight	0.19
Avionics
Avionics
Dimensions (Comet 4)
Length	111 ft 6 in	34 m
Wingspan	114 ft 10 in	35 m
Height	29 ft 6 in	9 m
Wing Area	2,121 ft²	197 m²
Weights
Empty	75,400 lb	34,200 kg
Loaded	162,000 lb	73,470 kg
Maximum takeoff	lb	kg
Capacity	56-109 passengers
Powerplant
Engine	4 × Rolls-Royce Avon Mk 524 turbojets
Thrust (each)	10,500 lb	46.8 kN
Performance
Maximum speed	500 mph	805 km/h
Range	3,225 miles	5,190 km
Ferry range	km	miles
Service ceiling	40,000 ft	12,200 m
Rate of climb	ft/min	m/min
Wing loading	76.4 lb/ft²	372.9 kg/m²
Thrust/weight	0.26

This article deals with the de Havilland Comet jet airliner. For the 1930s racing aircraft see de Havilland DH.88

The de Havilland Comet of Britain was the world's first commercial jet airliner.

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 July 27, 1949. The design was similar to other airliners except that four of the new, albeit underpowered, de Havilland Ghost 50 turbojets were mounted within the wings, in pairs close to the fuselage. The airliner underwent almost three years of tests and fixes and the first commercial flights did not begin until January 22, 1952 with BOAC. 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.

The first sign of a flaw in the Comet came on May 2, 1953 when a Comet crashed soon after take-off from Calcutta; further crashes (January 1954 and April 1954) with no clear cause led to the entire fleet being grounded for investigation. It was found in February 1955 that, as suspected, metal fatigue was the problem; after thousands of pressurized climbs and descents the thin fuselage metal around the Comet's distinctive right-angled large windows would begin to crack eventually causing sudden depressurization and catastrophic structural failure.

All the extant Comets were either scrapped or modified 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, but the Comet did not resume commercial airline service until 1958, when the much improved Comet 4 was introduced.

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 April 27, 1958, and deliveries to BOAC began that September. BOAC initiated Comet 4 service with a flight from London to New York via Gander on October 4, 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 June 27, 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 October 31, 1959, and Mexicana started Comet 4C services in 1960.

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 jetliner in service, the interruption of commercial service and the damage to the aircraft's reputation caused by the Comet 1 fatigue failures meant that the jetliner market was dominated by Boeing, which flew the first prototype 707 in 1954, and Douglas, which launched the DC-8 program in 1955. Only fifteen airlines ever used the Comet, the proposed Comet 5 was never built, and the Comet 4s were slowly withdrawn from service.

Perhaps as a mark of respect, a preserved Comet 4 in BOAC livery is on display at the Museum of Flight, next to Boeing's Seattle factory.

The Nimrod, a military maritime patrol aircraft, is a larger and heavily modified variation on the Comet design. It is the only large aircraft still in service that has engines built into its wings rather than slung beneath them or mounted either side of the rear fuselage.

Units Using the Comet

Royal Air Force

• No. 2 Squadron
• No. 4 Squadron
• No. 51 Squadron
• No. 192 Squadron
• No. 216 Squadron

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