The de Havilland DH 106 Comet was the first production commercial jetliner. Developed and manufactured by de Havilland at its Hatfield Aerodrome, Hertfordshire, United Kingdom headquarters, the Comet 1 prototype first flew on 27 July 1949. It featured an aerodynamically clean design with four de Havilland Ghost turbojet engines buried in the wings, a pressurised fuselage, and large square windows. For the era, it offered a relatively quiet, comfortable passenger cabin and showed signs of being a commercial success at its 1952 debut.
A year after entering commercial service the Comets began suffering problems, with three of them breaking up during mid-flight in well-publicised accidents. This was later found to be due to catastrophic metal fatigue in the airframes, not well understood at the time. The Comet was withdrawn from service and extensively tested to discover the cause; the first incident had been incorrectly blamed on adverse weather. Design flaws, including dangerous stresses at the corners of the square windows and installation methodology, were ultimately identified. As a result, the Comet was extensively redesigned with oval windows, structural reinforcement and other changes. Rival manufacturers meanwhile heeded the lessons learned from the Comet while developing their own aircraft.
Although sales never fully recovered, the improved Comet 2 and the prototype Comet 3 culminated in the redesigned Comet 4 series which debuted in 1958 and had a productive career of over 30 years. The Comet was adapted for a variety of military roles such as VIP, medical and passenger transport, as well as surveillance. The most extensive modification resulted in a specialised maritime patrol aircraft variant, the de Havilland Nimrod. The Nimrod remains service with the Royal Air Force today, over 60 years after the Comet's first flight.
Variants[]
- De-Havilland DH-106 Comet 1: The Comet 1 was the first model produced, a total of 12 aircraft in service and test. Following closely the design features of the two prototypes, the only noticeable change was the adoption of four-wheel bogie main undercarriage units, replacing the single main wheels. Four Ghost 50 Mk 1 engines were fitted (later replaced by more powerful Ghost DGT3 series engines). The span was 115 ft (35 m), and overall length 93 ft (28 m); the maximum takeoff weight was over 105,000 lb (48,000 kg) and over 40 passengers could be carried
- De-Havilland DH-106 Comet 1A: An updated Comet 1A was offered with higher-allowed weight, greater fuel capacity and water-methanol injection; 10 were produced. In the wake of the 1954 disasters, all Comet 1s and 1As were brought back to Hatfield, placed in a protective cocoon and retained for testing. All were substantially damaged in stress testing or were scrapped entirely
- De-Havilland DH-106 Comet 1X: Two RCAF Comet 1As were rebuilt with heavier-gauge skins to a Comet 2 standard for the fuselage and renamed Comet 1X.
- De-Havilland DH-106 Comet 1XB: Four Comet 1As were upgraded to a 1XB standard with a reinforced fuselage structure and oval windows. Both 1X series were limited in number of pressurisation cycles.
- De-Havilland DH-106 Comet 2: 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. Design changes had been made to make the aircraft more suitable for transatlantic operations. Following the Comet 1 disasters, these models were rebuilt with heavier-gauge skin and rounded windows, and the Avon engines featuring larger air intakes and outward-curving jet tailpipes. A total of 12 of the 44-seat Comet 2s were ordered by BOAC for the South Atlantic route. The first production aircraft (G-AMXA) flew on August 27th 1953. Although these aircraft performed well on test flights on the South Atlantic, their range was still not suitable for the North Atlantic. All but four Comet 2s were allocated to the RAF, deliveries beginning in 1955. Modifications to the interiors allowed the Comet 2s to be used in several roles. For VIP transport, the seating and accommodations were altered and provisions for carrying medical equipment including iron lungs were incorporated. Specialised signals intelligence and electronic surveillance capability was later added to some airframes
- De-Havilland DH-106 Comet 2X: Limited to a single Comet Mk 1 powered by four Rolls-Royce Avon 502 turbojet engines and used as a development aircraft for the Comet 2.
- De-Havilland DH-106 Comet 2E: Two Comet 2 airliners were fitted with Avon 504s in the inner nacelles and Avon 524s in the outer ones. These aircraft were used by BOAC for proving flights during 1957–1958
- De-Havilland DH-106 Comet 3: 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 10,000ibf. The variant added wing pinion tanks, and offered greater capacity and range. The Comet 3 was destined to remain a development series since it did not incorporate the fuselage-strengthening modifications of the later series aircraft, and was not able to be fully pressurised. Only two Comet 3s began construction; G-ANLO, the only airworthy Comet 3, was demonstrated at the Farnborough SBAC Show in September 1954. The other Comet 3 airframe was not completed to production standard and was used primarily for ground-based structural and technology testing during development of the similarly sized Comet 4. Another nine Comet 3 airframes were not completed and their construction was abandoned at Hatfield. In BOAC colours, G-ANLO was flown by John Cunningham in a marathon round-the-world promotional tour in December 1955. 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 Air show in September 1958 Assigned in 1961 to the Blind Landing Experimental Unit (BLEU) at RAE Bedford, the final testbed role played by G–ANLO was in automatic landing system experiments. When retired in 1973, the airframe was used for foam-arrester trials before the fuselage was salvaged at BAE Woodford, to serve as the mock-up for the Nimrod.
- De-Havilland DH-106 Comet 4: The Comet 4 was a further improvement on the stretched Comet 3 with even greater fuel capacity. 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). The Comet 4 was considered the definitive series, having a longer range, higher cruising speed and higher maximum take-off weight. These improvements were possible largely because of Avon engines, with twice the thrust of the Comet 1's Ghosts. Deliveries to BOAC began on September 30th 1958 with two 48-seat aircraft, which were used to initiate the first scheduled transatlantic services.
- De-Havilland DH-106 Comet 4A: Proposal for Trans Canada Airlines, 10 were ordered but not taken up.
- De-Havilland DH-106 Comet 4B: developed from the Comet 4A, the Comet 4B featured greater capacity through a 2m longer fuselage, and a shorter wingspan; 18 were produced.
- De-Havilland DH-106 Comet 4C: This variant featured the Comet 4's wings and the 4B's longer fuselage; 28 were produced. The last two Comet 4C fuselages were used to build prototypes of the De Havilland Nimrod maritime patrol aircraft.
- De-Havilland Comet 4C executive jet: A Comet 4C (SA-R-7) was ordered by Saudi Arabian Airlines with an eventual disposition to the Saudi Royal Flight for the exclusive use of King Saud bin Abdul Aziz. 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. Following its first flight, the special order Comet 4C was described as "the world's first executive jet
Military Variants[]
- De-Havilland DH-106 Comet C.2: Eight Comet 2s originally destined for the civil market were completed for the RAF and assigned to No. 216 Squadron.
- De-Havilland DH-106 Comet R.2: Three Comet 2s were modified for use in radar and electronic systems development, initially assigned to No. 90 Group (later Signals Command) for the RAF. In service with No. 192 and No. 51 Squadrons, the 2R series was equipped to monitor Wake Island Association signal traffic and operated in this role from 1958 until 1974, when replaced by the Nimrod R1, the last Comet derivative in RAF service.
- De-Havilland DH-106 Comet T.2: The first two of 10 Comet 2s for the RAF were fitted out as crew trainers, the first aircraft (XK669) flying initially on December 9th 1955.
- De-Havilland DH-106 Comet C.4: 5 De-Havilland DH-106 Comet 4C operated by the No.216 Squadron.
- De-Havilland DH-106 Comet KC.5: Aerial tanker based on the proposed De Havilland Comet 5.
Proposed variants[]
- De-Havilland DH-106 Comet 5: 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. Without support from the Ministry of Transport, the proposal languished as a hypothetical aircraft and was never realised.
- De-Havilland DH-111 Comet Bomber: DH 111 Comet Bomber was a proposal for a nuclear bomb-carrying variant developed to Air Ministry specification B35/46, was submitted to the Air Ministry on 27 May 1948. It had been originally proposed in 1948 as the "PR Comet", a high-altitude photo reconnaissance adaptation of the Comet 1. The Ghost DGT3-powered airframe featured a narrowed fuselage, a bulbous nose with H2S Mk IX radar, and a four-crewmember pressurised cockpit under a large bubble canopy. Fuel tanks carrying 2,400 imperial gallons (11,000 L) were added to attain a range of 3,350 miles (5,390 km). The proposed DH 111 received a negative evaluation from the Royal Aircraft Establishment over serious concerns regarding weapons storage; this, along with the redundant capability offered by the RAF's proposed V bomber trio, led de Havilland to abandon the project on October 22nd 1948
