de Havilland Comet
The de Havilland DH.106 Comet was the world's first jet airliner. Built at Hatfield and first flown in 1949, it entered BOAC service in 1952, flying higher and faster than any airliner before it. In 1953 and 1954 two Comets broke up in flight, and the investigation traced the cause to metal fatigue in the pressurised cabin, a failure mode the industry had not understood. Grounded and redesigned with a stronger structure and oval windows, the Comet 4 returned in 1958 and opened the first transatlantic jet service, but larger American jets took the market it had created. Comets flew on with airlines, the RAF and research agencies until 1997, and the type's descendant, the Nimrod, served until 2011.
Why It Mattered
The de Havilland Comet was the world's first jet airliner, entering scheduled service with BOAC on 2 May 1952. It cruised at 450 mph, about twice the speed of the piston-engined airliners of its day, and cut long journey times in half. Its highly pressurised cabin carried passengers at altitudes no earlier airliner could use, in a smoothness piston types could not match. The early accidents that followed, and the investigation that explained them, then changed how every airliner after it would be designed, tested and certified. Britain gained the lead in civil aviation from this single design, and held it only briefly.
Design Notes
Four Ghost turbojets, developed from the Goblin engine of the Vampire fighter, were buried in the wing roots, keeping the airframe's lines clean. To keep weight down, the structure was glued as well as riveted, using the Redux bonding de Havilland had pioneered on its Hornet and Dove. The cabin was pressurised to 8.25 psi, then the highest differential on any airliner, and the Comet introduced fully hydraulic flying controls and high-pressure refuelling to airline service. The pressure cabin was pierced by windows, hatches and aerial openings, and it was at such openings that fatigue cracks later grew.
Operational History
The prototype first flew from Hatfield on 27 July 1949, with John Cunningham at the controls. On 2 May 1952 BOAC opened the first scheduled jet service, flying from London to Johannesburg, and within months its Comets were the envy of the world's airlines. In May 1953 a BOAC Comet broke up in a thunderstorm after leaving Calcutta, and all 43 people aboard were killed. On 10 January 1954 a second BOAC aircraft broke up minutes after leaving Rome; BOAC grounded its Comets the next day, but flights resumed on 23 March. On 8 April 1954 a third aircraft, flying for South African Airways between Rome and Cairo, fell into the Mediterranean, and the fleet was grounded again. The Royal Aircraft Establishment at Farnborough led the investigation: divers recovered about 70 per cent of one aircraft from the seabed for reconstruction, while a second airframe was cycled in a water tank until its skin failed. Together the wreckage and the tank test showed that repeated pressurisation had grown fatigue cracks in the pressure cabin until it failed. De Havilland strengthened the structure, fitting thicker skin and oval windows, and the redesigned, larger Comet 4 flew again in 1958. On 4 October 1958 the Comet 4 opened the first regular transatlantic jet service, between London and New York. The Boeing 707 entered service in the same year, far larger, and the Comet's early lead was gone for good.
Afterlife
In all, 114 Comets were built, including the two prototypes, before production ended in 1964. Airline aircraft passed to charter operators; Dan-Air eventually owned every remaining airworthy civil Comet. The RAF used Comets for transport and trials, and a research Comet 4C, Canopus, made the type's final flight on 14 March 1997. The Comet's maritime-patrol descendant, the Nimrod, remained in RAF service until 2011. The only complete Comet 1 survives at the RAF Museum, displayed in the BOAC colours of the first jet fleet, and six complete Comet 4s are held by other museums. The investigation's methods, including testing a whole airframe in a water tank, became part of standard practice, and de Havilland passed its fatigue findings to rival manufacturers.