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HS121 Trident

Trident 1C

TypeJet airliner
ManufacturerHawker Siddeley
Maiden flight9 January 1962
Introduced1964
Primary usersBritish European Airways
British Airways
CAAC
Cyprus Airways
Number built117

The Trident, model DH121 or HS121, 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. An aerospace manufacturer is a company or individual involved in the various aspects of designing building testing selling and maintaining Aircraft, Aircraft parts The maiden flight of an Aircraft is the first occasion on which an aircraft leaves the ground of its own accord Events 475 - Byzantine Emperor Zeno is forced to flee his capital at Constantinople. This is a list of Aviation -related events from 1962: Events January US Army CH-21 Shawnees are dispatched to For the year see 1964 This is a list of Aviation -related events from 1964: Events January January British European Airways ( BEA) or British European Airways Corporation was a British Airline which existed from 1946 until 1974 British Airways plc ( is the national Airline and Flag carrier of the United Kingdom and one of the largest in Europe The Civil Aviation Administration of China ( CAAC) ( formerly General Administration of Civil Aviation of China ( is the aviation authority under the Cyprus Airways Public Ltd (Κυπριακές Αερογραμμές Kipriakes Aerogrammes Turkish Kıbrıs Hava Yolları) is the national Airline The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located A trijet is an Aircraft powered by three Jet engines Early twin-jet designs were limited by the FAA 's " 60-minute rule " whereby An airliner is a large Fixed-wing aircraft with the primary function of transporting paying passengers The de Havilland Aircraft Company (less commonly spelled de Haviland was a British aviation manufacturer founded in 1920 when Airco, of which Geoffrey Hawker Siddeley was a group of British manufacturing companies renowned for their aircraft production. Designed to a British European Airways (BEA) requirement, it had limited appeal to other airlines and sold in small numbers, with only 117 produced. British European Airways ( BEA) or British European Airways Corporation was a British Airline which existed from 1946 until 1974 It was an important airliner in Europe but high operational costs doomed it to a short lifespan. BEA's successor, British Airways chose to replace its fleet with the Boeing 737 and Boeing 757 in the early 1980s. British Airways plc ( is the national Airline and Flag carrier of the United Kingdom and one of the largest in Europe WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout In China the Trident remained active In Air China's service until the mid-1990s. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Not to be confused with China Airlines, the national airline of the Republic of China (Taiwan. The Trident is notable for being the first commercial airliner to make a fully automatic approach and landing in revenue paying service[1].

Contents

Design and development

British European Airways Hawker Siddeley Trident at London Heathrow Airport (in the background) in 1964. In the front is a BEA Vickers Viscount and on the right a BEA Vickers Vanguard
British European Airways Hawker Siddeley Trident at London Heathrow Airport (in the background) in 1964. British European Airways ( BEA) or British European Airways Corporation was a British Airline which existed from 1946 until 1974 In the front is a BEA Vickers Viscount and on the right a BEA Vickers Vanguard
Preserved Trident G-AWZK showing offset nosewheel
Preserved Trident G-AWZK showing offset nosewheel

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. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout The new aircraft would work beside a smaller design for shorter ranges, which would eventually emerge as the BAC One-Eleven. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 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 "tri-jet" design, a configuration which its designers felt offered a trade-off between cruising economy and take-off safety in case of an engine failure. A trijet is an Aircraft powered by three Jet engines Early twin-jet designs were limited by the FAA 's " 60-minute rule " whereby The plane included a cruciform tail design similar to the Sud Aviation Caravelle. For the resurrection device/parasite at the Hyperion Cantos see Cruciform (Hyperion Cantos. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 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. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout The production Trident had a variable incidence T-tail[2]. A T-tail is an aircraft tail stabilizer arrangement in which the horizontal surfaces ( Tailplane and elevators are mounted to the top of the The Trident has a distinctive offset, sidewards retracting front landing gear. In Aviation, the undercarriage or landing gear is the structure (usually wheels that supports an Aircraft on the ground and allows it to taxi 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 to seat 111 in a two-class layout. In the Physical sciences weight is a Measurement of the gravitational Force acting on an object

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. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout In the Physical sciences weight is a Measurement of the gravitational Force acting on an object This version gained the T-tail it would have from then on, 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 on 12 August 1959. Events 1099 - First Crusade: Battle of Ascalon - Crusaders under the command of Godfrey of Bouillon defeat Fatimid The year 1959 ( MCMLIX) was a Common year starting on Thursday (link will display full calendar of the Gregorian calendar.

The Trident was the first commercial aircraft to be fitted with a flight data recorder, it sampled 13 variables, converted them to a digital format and stored them on tape for ground analysis[3]. The flight data recorder ( FDR) or Black Box is a Flight recorder used to record specific Aircraft performance parameters The Trident was the first airliner to be fitted with an automatic blind landing system[4]; the Autoflare, developed by Hawker Siddeley and Smiths Aircraft Instruments[1]. Smiths Group ( is a leading British engineering company involved in wide-ranging speciality engineering activities

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 in 1960. American Airlines Inc (AA is a US -based airline and the world's Largest airline in total passenger miles transported and passenger fleet size Though the original DH121 design would have fulfilled American's requirements almost perfectly, they demanded an aircraft with a longer range. Design began on a new Trident 1A, powered with uprated Rolls-Royce Spey 510s of 10,700 lbf (47. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 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). Thrust is a reaction force described quantitatively by Newton 's Second and Third Laws. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object American Airlines eventually declined the aircraft in favour of the Boeing 727, an aircraft which filled the original DH121 specifications almost exactly. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

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]. Events 475 - Byzantine Emperor Zeno is forced to flee his capital at Constantinople. Year 1962 ( MCMLXII) was a Common year starting on Monday (the link is to a full 1962 calendar of the Gregorian calendar. Hatfield Aerodrome, formerly, was an airfield and Aircraft factory located in the town of Hatfield Hertfordshire from 1930 until its closure and redevelopment in Events 527 - Byzantine Emperor Justin I names his nephew Justinian I as co-ruler and successor to the throne Year 1964 ( MCMLXIV) was a Leap year starting on Wednesday (link will display full calendar of the 1964 Gregorian calendar. By 1965 there were 15 Tridents in BEA's fleet and by March 1966 this had risen to 21. 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, something that had previously caused many problems at London Heathrow and resulted in cancellations and delays. Events 1333 - Flood of the Arno River, causing massive damage in Florence as recorded by the Florentine chronicler Giovanni Villani Year 1966 ( MCMLXVI) was a Common year starting on Saturday (link will display full calendar of the 1966 Gregorian calendar. These delays were relatively common during the period when Category 1 (Cat 1 = 200 ft decision height and 600 metre runway visual range RVR) 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.

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. In reference to Aircraft, chord refers to the distance between the leading edge and trailing edge of a Wing, Horizontal stabilizer or Vertical stabilizer This specification took the 1C closer to the larger concept of the original DH. 121, but powered with 7,000 lbf (31 kN) less thrust. The Trident was one of the fastest subsonic commercial airliners, regularly cruising at over 600mph. 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 and this, combined with the low power, meant takeoffs tended to be very long. The aircraft gained the nickname the "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. 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. Kuwait Airways (الخطوط الجوية الكويتية is the national Airline of Kuwait, based in Kuwait City and wholly owned by Iraqi Airways ( Arabic: الخطوط الجوية العراقية also known as Air Iraq) is the National carrier of Iraq, based in Channel Airways was formed in 1946 as East Anglian Flying Services. Northeast Airlines was an American airline based in Boston, Massachusetts. Air Ceylon was Ceylon 's (later Sri Lanka's national carrier that began as Ceylon Airways in 1947, and was fully state-owned

Trident 1E
Trident 1E

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. Cyprus Airways Public Ltd (Κυπριακές Αερογραμμές Kipriakes Aerogrammes Turkish Kıbrıs Hava Yolları) is the national Airline The first flight of this version was made on 27 July 1967 and it entered service with BEA in April 1968. Events 1214 - Battle of Bouvines: In France, Philip II of France defeats John of England. Year 1967 ( MCMLXVII) was a Common year starting on Sunday (link will display full calendar of the 1967 Gregorian calendar.

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. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 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 HS121 or 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. In Aviation, hot and high refers to very warm climates or very high Elevations that may compromise an aircraft's ability to operate safely 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. BEA 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. British European Airways ( BEA) or British European Airways Corporation was a British Airline which existed from 1946 until 1974 British Airways plc ( is the national Airline and Flag carrier of the United Kingdom and one of the largest in Europe The first flight was on 11 December 1969 and the aircraft entered service on 1 April 1971. Events 359 - Honoratus, the first known Prefect of the City of Constantinople, takes office Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. Events 527 - Byzantine Emperor Justin I names his nephew Justinian I as co-ruler and successor to the throne Year 1971 ( MCMLXXI) was a Common year starting on Friday (link will display full calendar of the 1971 Gregorian calendar. Addition of extra fuel capacity resulted in the Super Trident 3B, two of which were sold to CAAC.

A notable feature of the Trident was its use in the development of a completely automatic blind landing system. In Aviation, autoland describes a system that fully automates the Landing phase of an Aircraft 's flight with the human crew merely supervising This allowed the plane to land itself in conditions that would cause other planes to have to divert to alternate airports. The Trident also had the unusual capability to use reverse thrust in flight. This was limited to the two "pod" engines, and the normal landing procedure was to close the thrust levers 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. This was an extremely useful facility on wet or slippery runways resulting in a firm but well-controlled touchdown significantly reducing the probability of acquaplaning and producing a very short landing run. This compensated for the rather poor braking characteristics of the double wheel pairs on each axle main gear.

The use of reverse thrust up to 10,000 rpm was also permitted away from the landing flare essentially 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 10,000 feet per minute. > However use of this facility was restricted after it was realised that this facility was being used by crews more often than had been envisaged by the manufacturers.

Other advanced features for the era included provision of a cockpit moving map display on the main 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 itself for along track.

In 1977, fatigue cracks were discovered in the wings of British Airways' Trident1's 2s and 3s. The aircraft were ferried back to the manufacturer, where repairs were made, and the aircraft returned to service.

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

Preserved aircraft

Three complete aircraft are preserved in the United Kingdom: a Trident 2E, G-AVFB, at Duxford near Cambridge; a Trident 3B, G-AWZM, in the Science Museum's exhibit store at Wroughton in Wiltshire; and another Trident 3B, G-AWZK, at the Aviation Viewing Park at Manchester Airport; this aircraft is open to the public every weekend from April to October for an admission charge. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Duxford is a village in Cambridgeshire, England, some ten miles south of Cambridge. For science museums in general check out Science museum. The Science Museum on Exhibition Road, South Kensington, London is part Etymology The county formerly 'Wiltonshire' or 'Wiltunscir' (9th century is named after the former county town of Wilton (itself named after the River Wylye Manchester Airport is a major Airport in the vicinity of Manchester, England, and the largest airport in the United Kingdom outside the All these aircraft served in the BEA and British Airways fleet. Additionally, there are a number of cockpits or forward fuselage sections either in museums or private ownership in the UK, several aircraft or sections in use as fire service training aids and aircraft either preserved or in store in locations in China (three airframes, one with a broken back, can be seen at the Beijing Aeroplane Museum at Xiao Tang Shan, north of Beijing). A Spey engine taken from a Trident is on display at the Scottish Museum of Flight. The National Museum of Flight is an Aerospace Museum at East Fortune Airfield (formerly RAF East Fortune) just south of the village of East Fortune There has been an abandoned Trident at Nicosia International Airport ever since the airport stopped operating due to civil strife in 1974. Nicosia International Airport is an abandoned Airport. It lies to the west of the Cypriot capital city of Nicosia.

Accidents

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, 26 built
Super Trident 3B
Extended range by 692 (430) miles, two built

Janes Encyclopedia of Aviation. IBSN 1-85170-342-1

Operators

Civil operators

Flag of Sri Lanka Sri Lanka (Ceylon)
Flag of the People's Republic of China People's Republic of China
Flag of Cyprus Cyprus
Flag of Iraq Iraq
Flag of Kuwait Kuwait
Flag of Pakistan Pakistan
Flag of the United Kingdom United Kingdom
Flag of Zaire Zaire

Military operators

Flag of the People's Republic of China People's Republic of China
Flag of Pakistan Pakistan

Specifications

Specifications (Trident 2E)

General characteristics

Performance


Specifications (Trident 3B)

General characteristics

Performance

See also

Comparable aircraft

Related lists

References

Notes

  1. ^ a b Time Magazine | Touchdown by Computer | Friday, Jun. 18, 1965
  2. ^ Concept to Reality | Deep-Stall Avoidance
  3. ^ Smiths Industries Flight Data/Cockpit Voice Recorders
  4. ^ Flight Control Systems: Practical Issues in Design and Implementation, Roger Pratt, 2000 ISBN 0852967667
  5. ^ a b c Jackson 1973, p. In Aviation, V-speeds or Velocity-speeds are standard terms used to define Airspeeds important or useful to the operation of Aircraft, such The maximal total range is the distance an Aircraft can fly between Takeoff and Landing, as limited by fuel capacity in powered aircraft or cross-country In Aeronautics, a ceiling is the maximum Density altitude an aircraft can reach under a set of conditions British European Airways Flight 548 was a scheduled air service operated by British European Airways (BEA from London Heathrow Airport to Brussels Zaventem WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout This list of aircraft is sorted alphabetically beginning with the name of the manufacturer (or in certain cases designer 272–276.

Bibliography

External links

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