Hawker Siddeley Trident Trident 3B

BEA wanted a still larger Trident. Hawker Siddeley offered two new designs in 1965 — the 158-seat twin-engined HS132 and the 185-seat HS134 with underwing engines, very close to the Boeing 737 — but BEA preferred to buy 727s and 737s, and the British government vetoed that. The alternative was to stretch the Trident: a 5 m fuselage plug for 180 passengers and a greater wing chord. With the same Spey 512s the aircraft performed poorly at hot and high airports, and since the Spey 512 was the last of its line no more thrust was available.

Rather than change the three engines — awkward with one buried in the tail — the engineers added a fourth: the tiny Rolls-Royce RB.162 turbojet, fed from its own intake behind a pair of movable doors. It gave 15 per cent more take-off thrust for only 5 per cent more weight, and was used only when needed. BEA accepted the design as the Trident 3B and ordered 26.

It flew on 11 December 1969 and entered service on 1 April 1971. In some BEA and British Airways cabin layouts it carried rearward-facing seats, a rarity in an airliner. It was the most capable Trident and the last of the line before ICAO noise rules, in force from 1986, finished the type in Europe.