The Hawker Siddeley HS 121 Trident (originally the de Havilland D.H.121 and the Airco DH 121) was a British short- (and later medium-) range airliner. It was the first T-tail rear-engined three-engined jet airliner to be designed. It was also the first airliner to make a blind landing in revenue service in 1965.
The Trident emerged in response to a call by the state-owned British European Airways Corporation (BEA) for a jet airliner for its premier West European routes. BEA had been induced by the government to issue this call despite its unwillingness to buy a large jet fleet. Adherence to BEA's changing specification was widely seen as limiting the Trident's appeal to other airlines and delaying its service entry. BEA's requirements fluctuated greatly in the 1950s and in the 1960's and 1970's ended up differing considerably from what the Trident could offer.
During its gestation, the Trident was also involved in a government drive to rationalise the British aircraft industry. The resulting corporate moves and government interventions contributed to delays causing it to enter service two months after its major competitor, the Boeing 727, losing further potential sales as a result. By the end of the programme in 1978, only 117 Tridents had been produced. BEA's successor British Airways withdrew its Tridents by the mid-1980s. Trident services ended in China in the early 1990s.
While the Trident was becoming the backbone of the BEA fleet, BEA wanted an even larger aircraft. Hawker Siddeley offered two new designs in 1965: a larger 158-seat two-engine aircraft otherwise similar to the Trident known as the HS132; and the 185-seat HS134, which moved the engines under the wings, a design very similar to the Boeing 757. Both were to be powered by a new high-bypass engine under development at the time, the Rolls-Royce RB178. BEA instead opted for Boeing 727s and 737s to fill the roles of both the BAC 1–11 and Trident, but this plan was vetoed by the British government.
BEA returned to Hawker Siddeley and chose a stretched version of the basic Trident, the Trident 3. A fuselage stretch of 5 m (16 ft 5 in) made room for up to 180 passengers; Hawker Siddeley raised the gross weight to 143,000 lb (65,000 kg) and made modifications to the wing to increase its chord; the engines remained the same. BEA rejected the design as being unable to perform adequately in "hot and high" conditions, in light of such issues experienced with the Trident 2E. Since the Spey 512 was the last of the Spey line, extra thrust would be difficult to obtain. Instead of attempting to replace the three engines with a completely different type, which would have been difficult with one engine buried in the tail, Hawker Siddeley's engineers decided to add a fourth engine in the tail, the tiny Rolls-Royce RB162 turbojet, fed from its own intake behind a pair of movable doors. The engine added 15% more thrust for takeoff, while adding only 5% more weight, and it would only be used when needed. BEA accepted this design as the Trident 3B, and ordered 26. The first flight was on 11 December 1969 and the aircraft entered service on 1 April 1971. Addition of extra fuel capacity resulted in the Super Trident 3B.
The Trident experienced some key export sales, particularly to China. Following a thawing of relations between Britain and the People's Republic of China, China completed several purchase deals and more than 35 Tridents were eventually sold.
In 1977, fatigue cracks were discovered in the wings of the British Airways Trident fleet. The aircraft were ferried back to the manufacturer and repaired, then returned to service. The beginning of the Trident's end came in the early 1980's, because on 1 January 1986 ICAO noise legislation came into force, requiring operators of first- and second-generation jet airliners to have hush kits fitted to their engines. British Airways, the type's main operator, viewed the refit as not viable and instead chose to phase the Trident out of their fleet in 1985.
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The aircraft on display: after a long process, Trident G-AWZK finally made the move to the Aviation Viewing Park at Manchester Airport from London Heathrow on 11/9/05. Work to piece together G-AWZK continued throughout January and February 2007 with the aircraft ready for public viewing from April 2007.
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