The de Havilland DH.106 "Comet" holds the distinction of becoming the world's first commercial marketplace passenger jet airliner. The design originated from work begun during World War 2 (1939-1945) in 1943 looking to the future of British passenger air travel. Including prototypes used in the flight-testing phase of the program, a total of 114 Comets were completed with primary customers being BOAC, British European Airways, Dan-Air, and the Royal Air Force (RAF). The last example was retired on March 14th, 1997. A first-flight, in prototype form, was recorded on July 27th, 1949.
The Comet enjoyed a period of early success and high-level publicity, giving the British a head start in the jet-driven, passenger-hauling marketplace but the series was done-in by equally high-profile crashes and accidents. This period eventually allowed competitors in the United States to take-over with their own storied designs. For the British, the Comet did influence another major Cold War player, the Hawker Siddeley "Nimrod" (detailed elsewhere on this site) of the late-1960s as forty-nine of these were built for the RAF to a maritime patrol standard..
During the Comet's design study phase, several forms of the what would become the DH.106 emerged including a version with twin tail booms, one with canard foreplanes, and another lacking horizontal tailplanes altogether while relying on a wide-area, swept-back wing mainplane. Many of these early offerings were influenced by "blank canvas" thinking in the late-World War 2 period as it revolved around the prospect of jet-powered flight. As the decade wore on, however, the Comet's design began to materialize along more traditional lines - giving us the tried-and-true jet airliner form still in play today.
A tubular fuselage was envisioned to act as the center point of the aircraft in which a short nosecone gave pilots excellent vision over the frontal section. The passenger section then took up most of the internal volume of the tube which tapered at the aft-end to form the empennage. The tail unit consisted of a single, rounded vertical tail fin complemented by low-set horizontal planes. The wing mainplanes were also set low, this at about midships, and featuring sweepback of the leading wing edges. Within each wingroot was buried paired turbojet engines, aspirated through ports at the wing leading edges and exhausting through ports beyond the trailing edges. Their position within the wing allowed the aircraft to retain considerable aerodynamic efficiency by basic streamlining. For ground-running, multi-wheeled landing gear members were used which were wholly retractable.
There were four notable series variants in the Comet line named simply as "Comet 1", "Comet 2", "Comet 3, and "Comet 4". The original 40-seat Comet 1 emerged in production through a dozen airframes and were detailed with square windows, the overall appearance based heavily on the original de Havilland prototype. However, by this time, the design had incorporated multi-bogie main landing gear members over the original's single-wheeled forms. Original models were fielded with 4 x Ghost 50 Mk 1 series turbojet engines but these later gave way to 4 x Ghost FGT3 series engines.
From this initial model arrived the Comet 1A which increased performance allowing for greater take-off weights, speed, and range. Ten examples followed to the standard. The Royal Canadian Air Force (RCAF) was the recipient of a pair of Comet 1 models and these were taken on with reinforced skins and operated under the Comet 1X name. The follow-up Comet 1XB standard was nothing more than the Comet 1A with a strengthened fuselage understructure and more rounded windows.
The Comet 1 series enjoyed a maximum speed of 460 miles per hour with an MTOW of 110,000lb, a range out to 1,500 miles, and a cruising altitude of 42,000 feet. With these specifications, it clearly outpaced prop-driven developments of the period - garnering much interest from a public thirsty for flight.
The Comet 2 was given modified wing mainplanes which incorporated greater surface area and switched to more powerful Rolls-Royce "Avon" turbojets to better handle proposed cross-Atlantic / overwater routes. This also increased operational ranges but not to the extent required for such travel. The variant was some three feet longer than the original Comet 1 and was also differentiated by having the rounded windows of the later Comet 1 marks. The initial Comet 2 went airborne for the first time on August 27th, 1953 and deliveries followed in 1955. Variants went on to include the one-off Comet 2X development model (with its RR Avon 502 turbojets), a pair of Comet 2E aircraft (with mixed RR Avon 504/Avon 524 turbojet parings), a pair of Comet T2 marks (to serve the RAF as crew trainers), eight RAF-bound Comet 2C platforms, and a trio of Comet 2R developmental-minded platforms.
Both the Comet 1 and Comet 2 marks could be equipped to carry 36 and 44 passengers. Maximum speed for the Comet 2 was 490 miles per hour with an MTOW of 120,000lb, a range out to 2,600 miles, and a cruising altitude of 42,000 feet.
The Comet 3, first appearing in 1954, was the next logical offshoot of the series. It was over 15 feet longer than the earlier Comet 2 and was completed with 4 x RR Avon M502 turbojet engines of greater power. This, naturally, led the mark to exhibit better range and overall performance when compared to previous Comet marks but only two Comet 3 airframes were built. These went on to live largely developmental lives for their part in the Comet story and nine additional airframes went unfinished. Reduced-span wing mainplanes were used in the related Comet 3B and this model was flown publically at Farnborough 1958.
The Comet 3 was arranged to carry between 58 and 76 passengers. Maximum speed was 520 miles per hour with an MTOW of 150,000lb, a range out to 2,700 miles, and a cruising altitude of 45,000 feet.
The Comet 4 continued the development avenue of the Comet 3 series and increased fuel capacity even more, leading to better operational ranges, and there were improvements to performance, take-off weight, and internal seating capacity as well. First-deliveries of the mark, with reduced wingspans and a longer fuselage, began in September of 1958 with eighteen examples going to carrier BOAC. A further twenty-three, produced under the Comet 4C designation, were given the wing of the Comet 4 standard with the fuselage of the Comet 4B. A pair of prototypes were forged from the Comet 4C work and these served the all-important Hawker Siddeley "Nimrod" project detailed elsewhere on this site.
The Comet 4 held the capacity to carry 56 to 81 passengers. Maximum speed was 520 miles per hour with an MTOW of 156,000lb, a range out to 3,225 miles, and a cruising altitude of 42,000 feet miles.
The Comet 5 mark was a proposed, improved form of the Comet line and set to include a wider fuselage for additional seating, a revised wing mainplane with greater sweepback, and more efficient Rolls-Royce "Conway" turbofan engines held in wing nacelles/pods. This design fell to naught.
The Comet Bomber
Back in 1946, the British Air Ministry drew up Specification B.35/46 calling for a nuclear-capable, high-altitude reconnaissance platform and the DH.106 was briefly considered in the DH.111 "Comet Bomber" guise. The design emerged in 1948 but the effort was dropped in favor of the V-Bomber force which took control of the British nuclear arsenal for the foreseeable future.
Operators and Service Career
Operators of the Comet were global and ranged from Argentina and Australia to Sudan and the United Kingdom. The British, as well as the Canadians, operated the platform at the military level as well which put the airframe through the rigors of defense-minded service during the Cold War period (1947-1991). In the former, the Comet C2, Comet 2R, and the Comet C4 were all the marks used from a period spanning 1956 until 1975. In the latter, the Comet 1A was the choice mount though the aircraft fleet were later upgraded to the Comet 1XB standard. The RCAF operated its Comets from 1953 until 1963.
Operation of the Comet was marred by accidents and fatalities numbering thirteen crashes and 426 lives lost. From the period of May 1953 until April of 1954, there were three high-profile crashes alone which force the entire fleet to be grounded pending review. This period was then used to enact revisions to the design and it was not until 1958 that the series was allowed back into the air. The lull in operations allowed American competitors in Boeing and Douglas time to centralize their efforts and leap ahead of the British in the jet-powered passenger market.