Hawker Siddeley Trident: Wikis

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HS121 Trident
Trident 1 at the SBAC Farnborough Airshow, 8 September 1962.
Role Jet airliner
Manufacturer Hawker Siddeley
First flight 9 January 1962
Introduced 1964
Primary users British European Airways
British Airways
CAAC
Cyprus Airways
Number built 117

The Hawker Siddeley HS.121 Trident, or DH.121, was a British short/medium-range three-engined airliner designed by de Havilland in the 1950s, and built by Hawker Siddeley Aviation in the 1960s, after the former became part of that group in 1960. Designed to a British European Airways (BEA) requirement, it sold in small numbers, with 117 produced.

BEA's successor, British Airways, chose to replace its fleet with the Boeing 737 and Boeing 757 in the early 1980s. In China the Trident remained active in Air China's service until the mid-1990s. The Trident is notable for being the first commercial airliner to make a fully automatic approach and landing in revenue paying service.[1]

Contents

Development

British European Airways Hawker Siddeley Trident at London Heathrow Airport (in the centre background) in 1964. In front is a BEA Vickers Viscount and on the right a BEA Vickers Vanguard

In July 1956 BEA offered a contract for a new medium-haul jet aircraft to replace the turboprop Vickers Viscount on its longer European routes. The new aircraft would work beside a smaller design for shorter ranges, which would eventually emerge as the BAC One-Eleven. Several designs were submitted for the longer-range role, including the Bristol 200, the Avro 740, the Vickers VC11 and de Havilland's DH121. The DH121 was selected as the winner in 1958.

The DH121 was the first trijet design, a configuration which its designers felt offered a trade-off between cruising economy and take-off safety in case of an engine failure. The design initially included a cruciform tail layout similar to the Sud Aviation Caravelle. With the engines clustered at the rear, also like the Caravelle, the wing was left free from engine mounts and was designed with high-speed cruising in mind, a speed of over 600 mph being the goal. The Trident has a distinctive offset, sideways-retracting front landing gear. The DH121 was to be powered by 13,790 lbf (61.34 kN) Rolls-Royce Medway engines, with a gross weight of 150,000 lb (63 000 kg), a range of 2,070 miles (3330 km), and seating for 111 in a two-class layout.

At this point BEA decided that the 111-seat aircraft was too large for its routes, so it tried to tailor its aircraft to its exact needs. The result was a downsizing of the Trident, powered by much smaller 9,850 lbf (43.8 kN) Rolls-Royce Spey 505 engines, with a gross weight of 105,000 pounds (48 000 kilograms), a range of 930 miles (1500 kilometres), and seating for 97. This version gained the variable-incidence T-tail it would have from then on,[2] as well as a new nose design, both of which made it look very different from the Comet-like original version. BEA was happier with this smaller design (now known as the Trident 1 after BEA had held a competition to name it) and placed a contract for 24 aircraft on 12 August 1959.

Design

The Trident is a jet airliner of all-metal construction with a T-tail and low-mounted swept wing. It has three rear-mounted engines: two in side-fuselage pods, with the third in the fuselage, fed intake air through an S-shaped duct. Some versions featured a fourth 'boost' engine fed from a separate duct on top of the normal one. All versions were powered by versions of the Rolls-Royce Spey, the fourth engine being another Rolls-Royce design, the small RB162.

The Trident was one of the fastest subsonic commercial airliners, regularly cruising at over 610 mph (965 km/h). On initial introduction the standard cruise Mach Number was 0.88/ 380kts IAS, probably the highest of any of its contemporaries. The wing, designed for high speed, gave limited lift at lower speeds. This, and its low power, required long takeoff rolls. The aircraft gained the nickname "ground gripper" for the way it stuck to the runway; and it was also joked that Tridents only became airborne because of the curvature of the Earth.

ex-British European Airways Trident 3B (G-AWZK) preserved at Manchester Airport, England. Delivered new in 1971, it flew for BEA and British Airways, retiring in 1985.
Preserved Trident G-AWZK showing offset nosewheel

The Trident was the first commercial aircraft to be fitted with a Quick access flight data recorder. It sampled 13 variables, converted them to a digital format and stored them on tape for ground analysis.[3]

A notable feature of the Trident was its use in the development of a completely automatic blind landing system, the "Autoflare", developed by Hawker Siddeley and Smiths Aircraft Instruments[1].[4]

The Trident performed the first automatic blind landing by a civil airliner in fog on 4 November 1966,[5] pioneering the ability to land in fog, a major problem at London Heathrow. These delays were relatively common during the period when Category 1 (Cat 1 = 200 ft decision height and 600 metre runway visual range RVR) instrument landing system (ILS) was in use. The Trident, its autoland system and three pilots pioneered the use of lower landing limits starting with Cat 2 (100 ft decision height and 400 metres RVR). Because the Trident fleet could make successful approaches and landings to airfields equipped with suitable Cat 2 ILS installations it frequently operated to its intended destination, while other aircraft were forced to divert.

The Trident also had the unusual capability to use reverse thrust in flight (certified for Trident 1C only). This was limited to the two "pod" engines, and the normal landing procedure was to close the throttles in the flare, and immediately open the reverser buckets by selecting reverse idle. At the pilot's discretion, up to full power could then be selected in reverse prior to touchdown. Useful on wet or slippery runways, it produced a firm but well-controlled touchdown, and reduced hydroplaning, giving a very short landing. This compensated for its rather poor braking characteristics.

The use of reverse thrust up to 10,000 rpm was also permitted for emergency descent purposes. At indicated airspeeds below 280 kts it was also permissible to extend the main landing gear (but not the nosewheel) as an emergency airbrake, and when combined with conventional speedbrakes and reverse thrust this produced a phenomenal rate of emergency descent in the region of 12,000 ft per minute.[citation needed].

Another advanced feature for the era was a moving map display on the centre instrument panel. This was an electro-mechanical system with a stylus indicating the aircraft position over a motor-driven paper roll. Position was derived from a doppler navigation system which produced groundspeed and drift data, which combined with heading data could drive motors moving the stylus from side to side for lateral position, and the paper roll for the track.

Operational history

Hawker Siddeley Aviation, by this time the parent of de Havilland, needed additional customers for the Trident, so entered into discussions with American Airlines (AA) in 1960. They demanded an aircraft with a longer range, which meant that the original DH121 design would have fulfilled American's requirements almost perfectly. To fill AA's needs, design began on a new Trident 1A, powered with uprated Rolls-Royce Spey 510s of 10,700 lbf (47.6 kN) thrust, and a larger wing with more fuel, raising gross weight to 120,000 lb (54 000 kg) and range to 1,800 miles (2900 km). American Airlines eventually declined the aircraft in favour of the Boeing 727, an aircraft which filled the original DH121 specifications almost exactly. In fact, de Havilland had invited a group of engineers from Boeing to see the DH121 design and development program in its early stages, partly because Boeing was looking to develop a similar medium-range version of its 707 design.

Trident 1E

Some of these changes were nevertheless added into the original prototype, and it was renamed the Trident 1C. The main difference was a larger fuel tank in the centre section of the wing, raising weights to 115,000 lb (52 000 kg) and range to 1,400 miles (2250 km). The first Trident 1, G-ARPA, made its maiden flight on 9 January 1962 from Hatfield Aerodrome[5], and entered service on 1 April 1964.[5] By 1965 there were 15 Tridents in BEA's fleet and by March 1966 this had risen to 21.

Hawker-Siddeley then proposed an improved 1C, the Trident 1E. This would use 11,400 lbf (50.7 kN) Spey 511s, have a gross weight of 128,000 lb (58 000 kg), an increased wing area by extending the chord, and the same fuselage but with up to 140 seats in a six-abreast configuration. This specification took the 1C closer to the larger concept of the original DH121, but powered with 7,000 lbf (31 kN) less thrust. There were only a few sales of the new design: three each for Kuwait Airways and Iraqi Airways, four for PIA (later sold to CAAC), two each for Channel Airways and Northeast Airlines, and one for Air Ceylon.

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Trident 2E

Flight deck of a Trident 2E

At this point BEA decided that the Trident was now too short-legged for its ever-expanding routes, and that an even longer-ranged version was needed. Hawker-Siddeley responded with another upgrade as the Trident 1F. It would have the Spey 511 engines, a 2.8 m fuselage stretch, a gross weight of 132,000 lb (60 000 kg) and up to 128 seats in the original five-abreast configuration. BEA planned to buy 10 1Fs, plus an option for 14 further aircraft. As work continued on the 1F the changes became so widespread that it was renamed the Trident 2E, E for Extended Range. Now powered by newer Spey 512s with 11,930 lbf (53.1 kN) thrust, it also replaced wing leading-edge droops with slats, and extended the span with Kuchemann-style tips. It had a gross weight of 142,400 lb (65 000 kg) and a 2,000 mile (3200 km) range. BEA bought 15, two were bought by Cyprus Airways and 33 by CAAC, the Chinese national airline. The first flight of this version was made on 27 July 1967 and it entered service with BEA in April 1968.

Trident 3B

By this point the Trident was becoming the backbone of the BEA fleet and 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 and led to a modern-looking design very similar to the Boeing 757. Both were to be powered by a new high-bypass engine currently under development, the Rolls-Royce RB178. BEA instead opted for Boeing 727s and 737s to fill the role of both the BAC 1-11 and Trident, but this plan was later vetoed by the British government (the owners of BEA).

BEA returned to Hawker Siddeley and instead chose a stretched version of the basic Trident, the Trident 3. This included a fuselage stretch of 5 m for up to 180 passengers, raised the gross weight to 143,000 lb (65 000 kg), and made modifications to the wing to increase its chord. However the engines remained the same, and BEA rejected the design as being unable to get off the ground in "hot and high" conditions, given that the 2E was having so many problems already. Since the Spey 512 was the last of the Spey line, extra power would be difficult to add. Instead of attempting to fit a new engine, which would be difficult given that one was buried in the tail, Hawker-Siddeley decided to add a fourth engine in the tail, the tiny RB162 turbojet, fed from its own intake behind a pair of moveable doors. The engine added 15% more thrust for takeoff, while adding only 5% more weight, and would only be used when needed. BEA accepted this somewhat odd mixture as the Trident 3B, and ordered 26. In some configurations, BEA (later British Airways) Trident aircraft had a number of rearward-facing passenger seats, an uncommon seating arrangement for civil aircraft. 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, two of which were sold to CAAC.

In 1977, fatigue cracks were discovered in the wings of the British Airways Trident fleet. The aircraft were ferried back to the manufacturer, where repairs were made, and the aircraft returned to service.

In total, 117 Tridents were produced, while the Boeing 727, built to the original airline specification for the Trident, sold over 1,700.

During the type's operational history, no Trident ever crashed due to a design flaw or mechanical failure.[citation needed]

Variants

Trident 1C
Production version for British European Airways, 24 built
Trident 1E
Increased seating capacity version, 15 built
Trident 2E
Production version with triplex autoland system, 50 built
Trident 3B
High-capacity short-range version of the 1E with a 16 ft 5 in (5m) stretch, 1 RB162 booster engine in the tail; 26 built
Super Trident 3B
Extended range by 692 (430) miles, two built[6]

Operators

Civil operators

 Sri Lanka (Ceylon)
 People's Republic of China
 Cyprus
 Iraq
 Kuwait
 Pakistan
 United Kingdom
British Airways Trident in the early 1980s
 Zaire
  • Air Charter Service of Zaire

Military operators

 People's Republic of China
 Pakistan

Aircraft on display

Three complete aircraft are preserved in the United Kingdom:

Survivors

Several aircraft or sections in use as fire service training aids and aircraft either preserved or in storage at various locations in China (three airframes, one with a broken back, can be seen at the Beijing Aeroplane Museum at Datangshan, north of Beijing). In 2008, the personal plane of Mao Zedong was offered for sale after a decision by merchants at a market in Zhuhai that the plane, formerly a tourist attraction, was limiting business[9].

Accidents

  • On 13 September 1971, a People's Liberation Army Air Force Trident 1E crashed in Mongolia under mysterious circumstances during an attempt by Lin Biao and his family to defect to the Soviet Union.[citation needed] Official PRC accounts claim that the plane ran out of fuel.[citation needed]
  • On 18 June 1972, British European Airways Flight 548, a Trident 1, G-ARPI, stalled and crashed at Staines shortly after takeoff from Heathrow Airport. All on board were killed. At the time this was the worst air crash to have occurred on British soil.
  • On 10 September 1976, a British Airways Trident 3B, G-AWZT, collided in midair with an Inex Adria McDonnell-Douglas DC-9, YU-AJR, over Yugoslavia, killing everyone on both aircraft. The 1976 Zagreb midair collision was attributed to an air traffic control error.
  • On 14 March 1979, a CAAC Trident 2E, B-274, crashed into a factory near Beijing, killing at least 200.[citation needed] The crash was caused by an unqualified pilot who stole and flew the plane.[10] Total fatalities were all 12 crew, 32 ground, and no passengers.
  • On 31 August 1988, the right outboard flap of a CAAC Trident 2B hit approach lights of runway 31 of Hong Kong's Kai Tak Airport while landing in rain and fog.[citation needed] The right main landing gear then struck a lip and collapsed, causing the aircraft to run off the runway and slip into the harbour. Seven people were killed.

Specifications (Trident 2E)

Data from [11][12]

General characteristics

  • Crew: 3
  • Capacity: 115 passengers
  • Length: 114 ft 9 in (35 m)
  • Wingspan: 98 ft (28.9 m)
  • Height: 27 ft (8.3 m)
  • Wing area: 1,462 sq ft (135.82 sq m)
  • Empty weight: 73,800 lb (33,475 kg)
  • Max takeoff weight: 142,500 lb (64,636 kg)
  • Powerplant: × Rolls-Royce RB.163-25 Spey 512 , 11,930 lbf (53.1 kN) each

Performance

Variant comparison

Trident 2E Trident 3B
Capacity 115 Passengers 180 Passengers
Length 35 m (114 ft 9 in) 40 m (131 ft 2 in)
Wingspan 28.9 m (98 ft)
Height 8.3 m (27 ft) 8.6 m (28 ft 2.5 in)
Max Takeoff Weight 143,500 lb (65,000 kg) 155,000 lb (70,300 kg)
Cruise Speed 604 MPH (972 km/h) 582 MPH (936 km/h)
Range 2,400 mi (3,860 km) 1,800 mi (3,060 km)

See also

Comparable aircraft

Related lists

References

Notes

  1. ^ a b "Touchdown by Computer." Time Magazine, 18 June 1965. Retrieved: 17 July 2009.
  2. ^ Concept to Reality | Deep-Stall Avoidance
  3. ^ Smiths Industries Flight Data/Cockpit Voice Recorders
  4. ^ Pratt, Roger, ed. Flight Control Systems: Practical Issues in Design and Implementation. Kidlington, Oxfordshire, UK: Elsevier Science Ltd., 2000. ISBN 0-85296-766-7.
  5. ^ a b c Jackson 1973, pp. 272–276.
  6. ^ Taylor 1980, p. 269.
  7. ^ "HS.121 TRIDENT SERIES 3B-101 'G-AWZK'". www.ringwayreports.co.uk/. 7 August 2007. http://www.ringwayreports.co.uk/G-AWZK.htm. Retrieved 2009-09-27. 
  8. ^ [1]
  9. ^ Mao's personal plane up for sale, ABC Online, 2 October 2008, accessed 3 October 2008
  10. ^ source
  11. ^ Jackson 1973, p. 276.
  12. ^ Green 1976, p. 117.

Bibliography

  • Green, William. The Observer's Book of Aircraft. London: Frederick Warne & Co. Ltd., 1976. ISBN 0-7232-1553-7.
  • Jackson, A.J. British Civil Aircraft since 1919, Volume 2. London: Putnam, 1973. ISBN 0-370-10107-X.
  • Taylor, Michael J.H., ed. Janes's Encyclopedia of Aviation, Vol. 2. Danbury, Connecticut: Grolier Educational Corporation, 1980. ISBN 0-7106-0710-5.
  • Varley, Helen, ed. The Air Traveller's Handbook: The Complete Guide to Air Travel, Airplanes and Airports. London: Fireside Book, 1998. ISBN 0-671-24393-8.
  • Winchester, Jim, ed. "Hawker Siddeley Trident." Civil Aircraft. Kent, UK: The Grange, 2004. ISBN 1-84013-642-1.

External links


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