https://en.wikipedia.org/wiki/Hawker_Siddeley_Trident

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. The airline's requirements fluctuated
greatly in the 1950s and a decade later evolved radically away from what the
Trident could offer. Adherence to BEA's changing specification was widely seen
as limiting the Trident's appeal to other airlines and delaying its service
entry.

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, 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.

The Trident was a jet airliner of all-metal construction with a T-tail and a
low-mounted wing with a quarter-chord sweepback of 35 degrees. It had three
rear-mounted engines: two in side-fuselage pods, and the third in the fuselage
tailcone, aspirating through an S-shaped duct. One version, the 3B, had a fourth
"boost" engine aspirated through a separate intake duct above the main S-duct.
All versions were powered by versions of the Rolls-Royce Spey, while the boost
engine was also by Rolls-Royce: the RB.162, originally intended as a lift engine
for VTOL applications.

The Trident was one of the fastest subsonic commercial airliners, regularly
cruising at over 610 mph (980 km/h). At introduction into service its standard
cruise Mach Number was 0.88/ 380 kn IAS, probably the highest of any of its
contemporaries. Designed for high speed, with a critical Mach number of 0.93,
the wing produced relatively limited lift at lower speeds. This, and the
aircraft's low power-to-weight ratio, called for prolonged takeoff runs.
Nevertheless, the Trident fulfilled BEA's 6,000 ft (1,800 m) field length
criterion and its relatively staid airfield performance was deemed adequate
before the arrival into service of the Boeing 727 and later jet airliners built
to 4,500 ft (1,400 m) field length criteria. The aerodynamics and wing was
developed by a team led by Richard Clarkson, who would later take the Trident's
wing design for the wing of the Airbus A300; for the Trident he won the Mullard
Award in 1969.


Role
Narrow-body jet airliner

National origin
United Kingdom

Manufacturer
Hawker Siddeley

First flight
9 January 1962

Introduction
1 April 1964

Status
Retired

Primary users
British European Airways
British Airways
CAAC Airlines
Cyprus Airways

Number built
117

Unit cost

US$7.8M (1972)

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. On 1 January 1986, new ICAO noise legislation came
into force, requiring operators of first- and second-generation jet airliners to
have hush kits fitted to their engines; the main British operator of the type,
British Airways, viewed the refit as unviable and instead they chose to phase
the Trident out of their fleet. A total of 117 Tridents were produced, while the
Boeing 727, built to the original specification for the Trident, sold 1,832
units.

Variants

Trident 1C Production version for British European Airways, 24 built

Trident 1E Increased seating capacity uprated engines and addition of leading
edge slats, 15 built

Trident 2E As Trident 1E version with triplex autoland system, 50 built

Trident 3B High-capacity short-medium range version of the 2E with a 16 ft 5
in (5.00 m) stretch, 1 RB.162 booster engine in the tail; 26 builtSuper Trident
3BExtended range by 692 km (430 miles), two built

Specifications Trident 3B

Cockpit Crew Three (Captain, First Officer and System Panel Operator)
Seating Capacity (Typical) 180 Passengers
Length 131 ft 2 in (39.98 m)
Wingspan 98 ft (30 m)
Wing Area 1,462 sq ft (135.8 m2)
Overall Height 28 ft 3 in (8.61 m)
Operating Empty Weight, typical 83,000 lb (38,000 kg)
Maximum Takeoff Weight 150,000 lb (68,000 kg)
Cruise Speed Mach 0.84 – 495 kn (570 mph; 917 km/h) at 30,000 ft (9,100 m)
Range 2,235 mi (1,942 nmi; 3,597 km)
Service Ceiling 35,000 ft (11,000 m)
Powerplant 3 x Rolls Royce Spey RB163-25 Mk512-5 + 1 x Rolls-Royce RB162-86
Booster




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