Wikipedia

Hawker Siddeley Trident

TheHawker Siddeley HS-121 Trident(originally thede Havilland DH.121and briefly theAirco DH.121) is a Britishairlinerproduced byHawker Siddeley. In 1957,de Havillandproposed its DH.121trijetdesign to aBritish European Airways(BEA) request. By 1960, de Havilland had been acquired by Hawker Siddeley. The Trident'smaiden flighthappened on 9 January 1962, and it was introduced on 1 April 1964, two months after its main competitor, theBoeing 727. By the end of the programme in 1978, 117 Tridents had been produced. The Trident was withdrawn from service in 1995.

HS-121 Trident
British AirwaysTrident 3B
General information
TypeNarrow-body airliner
National originUnited Kingdom
ManufacturerHawker Siddeley
Designer
StatusRetired
Primary usersBritish European Airways
Number built117
History
Manufactured1962–1978
Introduction date1 April 1964 withBEA
First flight9 January 1962
Retired1995

The jetliner is powered by three rear-mountedRolls-Royce Speylow-bypass turbofans, it has a lowswept wingand aT-tail. Advancedavionicsallowed it to be the first airliner to make ablind landingin revenue service in 1965. The initial Trident 1/2 could seat 101–115 passengers over up to 2,350 nmi (4,350 km). The Trident 3 was stretched by 5 m (16 ft) to seat 180 over 1,940 nmi (3,590 km; 2,230 mi), and had an additionalRB.162booster engine in the tail.

Development

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Background and original specification

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In 1953, asBritish European Airways(BEA) introduced the world's firstturboprop-powered civil airliner – theVickers Viscount– into passenger service, the operator was already considering what would be required of a potential successor.[1]Following the entry into service of jet airliners in 1952, many airline managers and economists remained sceptical, and advocated turboprop airliners as replacements of piston-engined airliners.[2]In 1953, while several manufacturers across the world were investing in pure jet-powered aircraft, BEA chose to favour turboprops on the basis of their superior economics and produced a specification that called for an aircraft capable of seating 100 passengers and attaining a maximum speed of 370 knots.[3]As a result of the BEA specification, Vickers developed an enlarged derivative of the Viscount for BEA, theVickers Vanguard,which was ordered by the airline on 20 July 1956. By this point, however, the French-builtSud Aviation Caravellehad conducted itsmaiden flightduring the previous year, and BEA was beginning to recognise that jet aircraft could soon be providing stiff competition.[4]

In April 1956, Anthony Milward, chief executive of BEA, stated that he "would rather do without [jet airliners]". Nevertheless, in December of that same yearLord Douglas of Kirtleside,BEA's chairman, stated that a number of jet-powered short haul aircraft might need to be introduced while retaining turboprop aircraft as the mainstay of the company's inventory for the foreseeable future.[4]In July 1956, BEA had announced what it called "outline requirements" for a short-haul "second-generation jet airliner", to work alongside its turboprop fleet. It would carry a payload of some 20,000 lb (9,100 kg) or some 70 passengers up to 1,000 mi (1,600 km), weigh about 100,000 lb (45,000 kg), use 6,000-foot (1,800 m) runways, cruise at a very high speed of 610 to 620 mph (980 to 1,000 km/h), and have "more than two engines".[5][6][N 1][7]According to aviation author Derek Woods, BEA "wanted something that was faster than the Caravelle which was threatening to be highly competitive".[8]While they were not intended as an express requirement, commentators ever since have taken these figures to constitute a definite call to industry.[5]

The Trident was one of the firsttrijets,with all threeRolls-Royce Speyengines rear-mounted

Four companies prepared projects to match the BEA outline.Bristolproposed the initially four-enginedBristol Type 200.[1]Avroproposed the futuristicAvro 740trijet before shelving it and joining forces with Bristol and Hawker Siddeley.Vickersproposed the VC11 four-engined airliner, derived from its in-developmentVC10.Thede Havillandcompany considered three possible contenders for the specification; two of these were four-engined developments of the earlyComet,the world's first jet-powered airliner: the D.H.119 and the D.H.120, the latter being also intended to be offered toBritish Overseas Airways Corporation(BOAC). In July 1957, de Havilland made another submission in the form of the DH.121; this proposal was furnished with threeturbojets,Rolls-Royce Avonengines, and greatly resembled the eventual production aircraft.[9]By August 1957, the DH.121 proposal had been revised; differences included the adoption of the in-developmentturbofan,theRolls-Royce Medway,and an expansion to accommodate a maximum of 98 passengers.[9]

The DH.121 was to be the world's firsttrijetairliner. Its designers felt this configuration offered a trade-off between cruising economy and take-off safety in case of an engine failure; moreover, the BEA specification had called for "more than two engines". Each of the three engines would drive its own hydraulic system, offering triple redundancy in case of any of the other systems failing. The engines were to be 13,790 lbf (61.34 kN) Medway engines. The DH.121 was to have agross weightof 123,000 lb (56,000 kg) or optionally, up to 150,000 pounds (68,000 kg), a range of 2,070 mi (3,330 km), and seating for 111 in a two-class layout (or for over 140 in a high-density, single-class layout as typical from the 1960s onwards on inclusive-tourcharterflights).[10]The design initially included acruciformtail layout similar to that of the Caravelle.[9]The engines were clustered at the rear, with the centre engine situated in the extreme rear of the fuselage fed by air ducted through a large oval intake at the front of the fin, a configuration similar to the later Boeing 727; the design eventually settled on a variable-incidence T-tail.[11]

Offset nosewheel to accommodate a largeavionics baybeneath the flight deck

From the outset, the DH.121 was planned to employavionicsthat were very advanced for the period. Among other capabilities, they would offer automatic approach and landing within a few years of service entry. The avionics were also to have triplicated components for reliability and to allow "majority 2:1 voting" for aircraft guidance during automatic approach and landing.[12]The physical dimensions of most avionics of the period required them to be housed in a large compartment beneath the Trident's flight deck; the compartment's size was among the factors dictating a distinctive noseundercarriagedesign, with the nose landing gear offset by 2 ft (61 cm) to the port side and retracting sideways to stow across the DH.121's longitudinal axis.

Industry consolidation and selection

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BEA soon selected the DH.121 as the basis for detailed negotiations, but these talks were protracted due to multiple factors, including wider policy decisions of the British government and indecision within BEA itself.[9]During the time that the DH.121 had emerged in the late 1950s, the British government came to view the airframe andaeroengineindustries as too fragmented into small companies; accordingly, a policy favouring mergers into a few large groups was adopted. De Havilland was keen to retain their independence and leadership of the DH.121, so approached the government with a proposal to form a consortium under which de Havilland would produce the fuselage, Bristol would manufacture the wings, and various other companies, includingHunting AircraftandFairey Aviation,would be responsible for other elements; however, Bristol strongly opposed this arrangement and chose to work with Hawker Siddeley in competition against de Havilland.[13]

Companies vigorously competed to be selected by BEA due to the lure of its £30 million contract (equivalent to £885,295,000 in 2023[14]), as well as the likelihood of lucrative overseas export sales.[15]On 4 February 1958, de Havilland, along with Hunting and Fairey, announced that they had agreed to form a partnership for the purpose of manufacturing and marketing the DH.121; the consortium adopted the corporate name of the defunctAircocompany, which had beenGeoffrey de Havilland's employer during theFirst World War.[15]TheMinister of Supplystated of the Airco consortium that "this is not quite what [he] had in mind". Nevertheless, both Airco and the rival Bristol-Hawker Siddeley team proceeded to conduct their own approaches to various overseas airlines; sufficiently interested, AmericanPan American World Airwaysinvited both teams to present their proposed airliners in January 1958.[15]SirMatthew Slattery,chairman of Bristol andShort Brothers,appealed for BEA to delay any decision until after one of the competing firms had already secured an export order for their airliner. In response, Lord Douglas stated that BEA wished to order the DH.121 and was awaiting approval from the government; Douglas's reply has been viewed as thedeath knellfor the rivalType 200proposal.[15]

Meanwhile, a rival airliner emerged, this time fromBoeingin the United States, in the form of the727,which also had a trijet configuration.[16]Boeing had begun its studies into this sector of the market in 1956, and elected to launch its own trijet programme in 1959. Airco executives, who were at the time intensely exploring various alternatives and further partnerships with other aircraft companies, considered the possibility that Boeing might choose to drop the 727 project and instead co-manufacture the DH.121 in the USA; Lord Douglas was one of the proponents of this initiative.[16]As a result, Airco invited a team of Boeing engineers and executives toHatfield;(Boeing later permitted a return visit by de Havilland representatives to Seattle); however, Boeing revealed few details of their plans for the 727, while virtually all information on the DH.121 had been shared with Boeing, an openness that had allegedly "amazed" them.[16]British commentators have tended to interpret this episode as involving the acquisition of sensitive proprietary data on the DH.121 by a direct competitor.[17]Woods remarked that "de Havilland solemnly handed all its research over to its rivals... the crowning piece of stupidity".[16]

On 12 February 1958, the British government authorised BEA to commence contractual negotiations along with the issuing of aletter of intentfor 24 aircraft.[15]Accordingly, that same month, BEA announced that the DH.121 had come closest to its requirements and that it would proceed to order 24 with options on 12 more.[18]A further six months were needed for the government to approve a formal BEA order for the DH.121; the government had favoured the Bristol 200 for industrial policy reasons.[19][20]Reportedly, BEA had a considerable interest in the Caravelle itself, but this would have been a politically unacceptable choice.[21]BEA also favouredde Havilland,and therefore the Trident submission, due to the firm's established experience with jet airliners with its prior development of the Comet.[9][21]

Six-abreast cabin

In April 1958, de Havilland firmed the general configuration of the DH.121 and established a development timetable, including a projected date for the type'smaiden flightto be conducted during mid-1961.[15]The company's market research department was forecasting that as many as 550 airliners in its category would be sold by 1965. Noting that a greater preference for the seating dimensions of what would becomeeconomy classwas emerging amongst airlines, design alterations were made to adopt a slightly larger diameter fuselage to accommodate six-abreast seating, providing for a maximum configuration of 111 seats.[22]According to Woods, this enlarged version of the DH.121 was "on the verge of building the right aeroplane for the market and the success of the Viscount looked like being repeated".[16]

Revised specification

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In March 1959, BEA, which had become concerned by a recent decline in passenger growth, concluded that the DH.121's payload-range capacity could be too great for their needs and petitioned de Havilland to reduce the scale of the design to suit their revised projections.[16]Fearing that the proposed scale of the Trident was too large, the airline had elected to effectively tear up the programme for its redesigning for their immediate situation. In 1959, BEA had a large fleet in operation and on order, and the issue of overcapacity was a critical concern.[23]The airline's concerns reflected three factors - a short-lived airline recession in the late 1950s; the imminent arrival into service of a large fleet of turbopropVickers Vanguards,which duplicated the DH.121's general payload-range area; and the growing trend to higher-density seating.[24]

Although de Havilland stated that they generally concurred with BEA, its management also stated that they had worked "under terms more onerous than anything D.H. had previously undertaken".[25]Industry observers at the time felt that the British aircraft industry had again stumbled "into the pitfall of having designed exclusively for one customer an aeroplane that has potentially a much wider scope":[25]a sentiment which would be echoed throughout the Trident's subsequent history. The de Havilland board elected to submit to BEA's demand, over-riding input from its own sales and market research departments, which indicated that other airlines sought the larger model, instead.[16]Notably, de Havilland had not yet secured a formal and final BEA order and its competitor Bristol was actively promoting their 200[N 2]project, which was significantly smaller than the DH.121. At the timeBoeingandDouglaswere also downsizing their727andDC-9projects. It was felt the original large DH.121 would have to compete against theConvair 880andBoeing 720some four years after their service entries, whereas a cut-back design would be more competitive against the then-projected 75–100 seat, twin-engined DC-9.[26]

Downsizing the Trident involved substantial changes to the design being made, including a powerplant change from the Medway to a scaled-down derivative, the 40% less powerful 9,850 lbf(43.8 kN)Rolls-Royce Spey 505.[16]The gross weight was cut by about a third to 105,000 pounds (48,000 kilograms), while the range was cut by more than half to 930 mi (1,500 km), and mixed-class seating was cut by about a quarter to 75 or 80 (97 in a single-class layout). Wing span was reduced by roughly 17 ft (5.2 m), wing area by 30%, and overall length by 13 ft (4.0 m). The revised design retained some features of the original one, notably itsfuselagediameter. It had a smaller flight deck and single-axis, two-wheel, four-tyre main undercarriage legs in place of four-wheel bogies.[27]Woods summarised the BEA-mandated redesign as: "At one blow the 121 was emasculated in terms of size, power and range".[16]

Six months following BEA's request, de Havilland and the airline came to an agreement on the downsized DH.121.[16]Details of the emerging aircraft, including its pioneering avionics, were announced to the public in early 1960.[28]It was this revised aircraft that BEA ultimately ordered on 24 August 1959, initially in 24 examples with 12 options.[29]In September 1960, the future airliner's name, Trident, was announced at theFarnborough Airshow;this name had been chosen as a reflection of its then-unique three-jet, triple-hydraulicconfiguration.[30]

Further development and proposals

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By 1960, de Havilland had been acquired by the Hawker Siddeley group.[31]After the de Havilland takeover, Airco was disbanded. Hunting was marshalled into the competing newly formedBritish Aircraft Corporation(BAC); their departure removed any putative possibility of the Hunting 107 (later theBAC One-Eleven) being marketed alongside the DH.121 as a complementary, smaller member of the same airliner family. Fairey Aviation, partially incorporated intoWestland Aircraft,also left the DH.121 project.[N 3]With the move to Hawker Siddeley Aviation, the designation was eventually revised to the HS 121. The reorganisation of the industry had compounded upon the delays caused by BEA's changes to the specification, which had in turn harmed the Trident's competitiveness against the Boeing 727.

The rival Boeing 727 had quickly established a lead over the Trident.[32]The 727's early lead only strengthened it in subsequent competitions; one such example isTrans Australia Airlines,which had determined the Trident to be superior to the Boeing 727 from an operational standpoint, but it was also viewed as having been commercially risky to choose a different fleet from rival airlines such asAnsett Australia,which had already selected the 727.[33]In 1972, its unit cost was US$7.8M.[34]By 1975, only 117 Tridents had been sold against over 1,000 727s.[35]

According to Woods, a significant opportunity that may have enabled the Trident to catch up with the 727 was lost during the 1960s in the form of two competitions for amaritime patrol aircraft;aNATOdesign competition to replace theLockheed P-2 Neptune,andAir Staff Requirement 381,which sought a replacement for theRoyal Air Force's piston-enginedAvro Shackleton.[35]Amongst the various submissions that had been produced in response was a bid by Avro, part of the Hawker Siddeley Group, which was designated as the Avro 776. The proposed Avro 776 mated the Trident's fuselage with a redesigned and enlarged wing along with more powerfulRolls-Royce RB178engines capable of 16,300 lb of thrust.[36]In addition to the maritime patrol requirement, Avro envisioned that the aircraft could be used in various military roles, including as a 103-seat troop transport and as being armed with up to fourGAM-87 Skyboltair-launched ballistic missilesas anuclear-armedbomber.[37]In addition to Avro's proposals,Armstrong Whitworthhad also proposed their own military variants of the Trident.[37]

Later revisions of the Avro 776 substituted the RB.178 engine for the newerturbofan,theRolls-Royce RB211,the development of the latter being supported by the 776's procurement if selected.[38]Rolls-Royce Limited,having shelved development of the Medway following the Trident's redesign, was keen to develop an engine to slot between the 10,000 lb Spey engine and the 20,000 lbRolls-Royce Conwayengine; if such an engine had been produced, it could have equipped new versions of the civil Trident, as well. Furnished with a more capable engine that could provide more thrust than the Spey could, an extended fuselage could also have been adopted and existing landing restrictions could have been discarded; overall, the Trident would have been a far closer match to the 727.[39]Wood summarised the importance of this prospective development as: "For the Trident programme, the RB.177 would have been a God-send".[40]

At one point, the Avro 776 looked set to win the competition to be selected as the RAF's new maritime patrol aircraft.[41]Due to a desire to cut costs, though, the RAF decided to issue an entirely new operational requirement, under which the demands for speed, endurance, and capacity had all been diminished. As a result of the changes, the design team was recalled and the Avro 776 was entirely sidelined for a new proposal.[41]This new proposal, based upon the de Havilland Comet's fuselage, had little to do with the Trident save for the use of its existing Spey engines; this would go on to be selected and procured as theHawker Siddeley Nimrod.As a result of this loss, prospects for an enlarged, higher-power Trident effectively evaporated.[41]

A 35-m-long Trident 1C at the September 1962Farnborough Airshow,before its April 1964 introduction

Hawker Siddeley Aviation, which had absorbed de Havilland, needed additional customers for the Trident, so entered into discussions withAmerican Airlines(AA) in 1960. AA requested greater range than what the aircraft initially had, which meant that the original DH121 design would have fulfilled its requirements almost perfectly. In response, design began on a newTrident 1A,powered with up-rated Rolls-Royce Spey 510 engines 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 mi (2,900 km), but AA eventually declined the aircraft in favour of the Boeing 727.

Some of these changes were added into the original prototype, and it was renamed theTrident 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 mi (2,300 km). The first Trident 1,G-ARPA,made its maiden flight on 9 January 1962 fromHatfield Aerodrome.[42]

Design

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T-tail and retracted leading edge devices of a Hawker Siddeley Trident

Overview

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The Trident was ajet airlinerof all-metal construction with aT-tailand a low-mountedwingwith 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, with anS-shaped intake duct.One version, the 3B, had a fourth "boost" engine with a separate intake duct above the main S-duct. All versions were powered by versions of theRolls-Royce Spey,while the boost engine was aRolls-Royce RB162,originally intended as a lift engine forVTOLapplications.

The Trident was one of the fastest subsonic commercial airliners, cruising at over 610 mph (980 km/h). At introduction into service its cruise Mach Number was 0.88/ 380 knIAS.Designed for high speed, with acritical Mach numberof 0.93,[43]the wing produced relatively limited lift at lower speeds. This, and the aircraft's low thrust-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.[44]The aerodynamics and wing was developed by a team led byRichard Clarkson,who would later use the Trident wing design as the basis for the wing of theAirbus A300;for the Trident he won theMullard Awardin 1969.

The Trident normal descent rate was up to 4500 ft/min (23 m/s). In emergency descents of up to 10,000 ft/min, it was permissible to use reverse thrust. Below 280 kn IAS, it was also possible to extend the main landing gear for use as an airbrake. The Trident's first version, Trident 1C, had the unusual capability of using reverse thrust prior to touchdown. The throttles could be closed in the flare and reverse idle set to open the reverser buckets. At pilot discretion, up to full reverse thrust could then be used prior to touchdown. This was helpful to reduce hydroplaning and give very short landing runs on wet or slippery runways while preserving wheel brake efficiency and keeping wheel brake temperatures low. Brakes were fitted with theDunlop Maxaretanti-skidsystem.

Avionics

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Flight deck of a Trident 2E: there are orange "Triplex autoland fitted" placards on the control columns and themoving map displayon the centre instrument panel

The Trident had a complex, sophisticated and comprehensive avionics fit which was successful in service. This comprised a completelyautomatic blind landing systemdeveloped by Hawker Siddeley andSmiths Aircraft Instruments.[12][45]It was capable of guiding the aircraft automatically during airfield approach, flare, touchdown and even roll-out from the landing runway. The system was intended to offer autoland by 1970. In the event, it enabled the Trident to perform the first automatic landing by a civil airliner in scheduled passenger service on 10 June 1965[46]and the first genuinely "blind" landing in scheduled passenger service on 4 November 1966.[42][47][48]

The ability to land in fog solved a major problem atLondon Heathrowand other British airports. Delays were commonplace when Category 1 (Cat 1 = 200 ft (61 m) decision height and 600 metre runway visual range RVR)instrument landing system(ILS) was in use. The Trident's autoland system pioneered the use of lower landing minima, initially with Category 2 (100 ft decision height and 400 metres RVR) and soon after "zero-zero" (Category 3C) conditions. Since Tridents could operate safely to airfields equipped with suitable ILS installations, they could operate schedules regardless of weather, while other aircraft were forced to divert.[47]

The Trident's advanced avionics displayed the aircraft's current position relative to the ground on amoving map displayon the centre instrument panel. This electro-mechanical device also recorded the aircraft's track using a stylus plotting on a motor-driven paper map. Positional information was given by aDoppler navigationsystem which read groundspeed and drift data which, alongside heading data, drove the stylus.

The Trident was the first airliner fitted with a quick access flight data recorder. This sampled 64 variables, converted them into a digital format, and stored them on magnetic tape for ground analysis.[49]Later the system included a voice recorder.[50]

Operational history

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Introduction

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The first Trident entered service on 1 April 1964.[42]By 1965, 15 Tridents were in BEA's fleet, and by March 1966, the fleet had increased to 21.

Hawker Siddeley then proposed an improved 1C, theTrident 1E.This would be powered by 11,400 lbf (50.7 kN) Spey 511s, have a gross weight of 135,600 lb (61,500 kg), an increased wing area by extending thechord,leading-edge slats for improved field performance, different takeoff flap settings (a 23 degree setting shortened the runway length required but imposed a 59,900kg MTOW), 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 with 7,000 lbf (31 kN) less thrust. Only a few sales of the new design were made, three each forKuwait AirwaysandIraqi Airways,four forPakistan International Airlines(later sold to CAAC), two each forChannel AirwaysandNortheast Airlines,and one forAir Ceylon.Channel Airways' aircraft were equipped with cramped, 21 in (53 cm)seat pitch,[citation needed]seven-abreast seating in the forward section, seating 149 passengers.

Trident 2E

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At this point, BEA decided that the Trident was too short-legged for its ever-expanding routes, and that an even longer-ranged version was needed.Hawker Siddeleyresponded with another upgrade designatedTrident 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 anoptionfor 14 further aircraft.

As work continued on the 1F the changes became so widespread that it was renamed theTrident 2E,E forExtended Range.Now powered by newer Spey 512s with 11,930 lbf (53.1 kN) thrust, it also replaced wingleading-edge droop flapswith slats, and extended the span withKüchemann-style tips.[citation needed]It had a gross weight of 142,400 lb (64,600 kg) and a 2,000 miles (3,200 kilometres) range.

BEA bought 15,[51]while two were bought byCyprus Airways.CAAC, the Chinese national airline, bought 33. The first flight of this version was made on 27 July 1967 and it entered service with BEA in April 1968.

Trident 3B

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The Trident 3B, stretched by 5 m (16 ft) for up to 180 seats

Subsequently, the Trident was becoming the backbone of BEA's fleet and BEA wanted an even larger aircraft.Hawker Siddeleyoffered 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 theBoeing 737.Both were to be powered by a new high-bypass engine under development at the time, theRolls-Royce RB178.BEA instead opted forBoeing 727sand737sto 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, theTrident 3.A fuselage stretch of 5 m (16 ft 5 in) made room for up to 180 passengers;Hawker Siddeleyraised the gross weight to 143,000 lb (65,000 kg) and made modifications to the wing to increase itschord;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 tinyRolls-Royce RB162turbojet, 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 theTrident 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 theSuper Trident 3B.

The Trident experienced some key export sales, particularly to China. Following a thawing of relations between Britain and thePeople's Republic of China,China completed several purchase deals and more than 35 Tridents were eventually sold.[52][53]

In 1977, fatigue cracks were discovered in the wings of British Airways Tridents. The aircraft were ferried back to the manufacturer and repaired, then returned to service.[54]

The beginning of the Trident's end came in the early 1980s, sinceICAObegan drafting noise regulations that would require first- and second-generation jet airliners to fithush kitsto the engines. These regulations would go into effect on 1 January 1986.British Airways,the type's main operator, saw the required refits as not viable and instead chose to phase the Trident out of their fleet in 1985, the final flights were made on 31st December 1985. The Trident's services in China ended in 1995, marking its permanent retirement from service.[55]

Only 117 Tridents were produced and all are no longer in service. In contrast, 1832Boeing 727aircraft (designed to the Trident's original specification) were built and the last continued in passenger service until 2019.[56]

Variants

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Trident 1C
Production version for British European Airways; 24 built
Trident 1E
Increasedseating capacity,uprated engines, and addition of leading edge slats over the Trident 1C; 15 built
Trident 2E
An improved Trident 1E 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 and one additionalRB.162booster engine in the tail; 26 built
Super Trident 3B
Extended range by 692 km (430 miles); two built[57]

Operators

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Air CeylonTrident 1E, March 1978
Iraqi AirwaysTrident 1E
A Trident 3B in crossoverBEA/British Airwayslivery.

Civil operators

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Ceylon
  • Air Ceylonreceived one of the cancelled Channel Airlines Trident 1Es in 1969, and operated it until 1978.[58]
China
Cyprus
  • Cyprus Airwaysreceived two Trident 2Es in 1969/70, one of which was damaged in 1972 and swapped for a similar BEA aircraft. Two former Kuwait Airlines Trident 1Es were acquired via BEA in 1973. Two aircraft were damaged beyond repair during theTurkish Invasion of Cyprusin 1974, one of which was left on the abandoned Nicosia airport and remains. The two survivors passed to British Airways in 1977.[58]
Iraq
Kuwait
  • Kuwait Airwaysreceived three Trident 1Es in 1965/66. One was written off in 1966 and the others were sold to BEA in 1972.[58]
Pakistan
United Kingdom
  • BKS/Northeast Airlinesreceived two of the cancelled Channel Airways Trident 1Es in 1969 and acquired a third example from Channel in 1971. One was written off in 1975 and the others passed to British Airways when Northeast was taken over in 1976.[58]
  • British Airwaysinherited 20 Trident 1Cs, one Trident 1E, 15 Trident 2Es and 26 Trident 3Bs from British European Airways in 1974. Two more 1Es were added when Northeast Airlines was absorbed in 1976, and a 1E and a 2E (both one-time BEA machines) came from Cyprus Airways in 1977. BA retired its Trident fleet between 1974 and 1985.[58]
  • British European Airwaysreceived 23 Trident 1Cs in 1964–66, a 24th aircraft having crashed on its test flight. These were followed by 15 Trident 2E (1968–70) and 26 Trident 3Bs (1971–73). A Trident 1E was acquired from Channel Airways in 1971. One of the 2Es was swapped for a damaged Cyprus Airlines example in 1972, while two former Kuwait Airlines 1Es were operated in 1972 before passing to Cyprus Airways in 1973. Three Trident 1Cs were written off whilst in BEA ownership and the rest of the fleet passed to British Airways upon its formation in 1974.[58]
  • Channel Airwaysordered five Trident 1Es but only two were delivered, in 1968. These were sold to BEA and Northeast Airways in 1971.[58]
Zaire
  • Air Charter Service of Zaire received five former British Airways Trident 3Bs in 1984–86.[58]

Military operators

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China
Pakistan
  • Pakistan Air Forcewas the intended operator of the presidential Trident 1E, but it was delivered to Pakistan International Airways instead.[58]

Aircraft on display

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Trident 2 atChina Aviation Museum,Beijing
  • Trident 1C G-ARPH (Nose Section) at Museum of Flight East Fortune Scotland.
  • Trident 1C G-ARPO at North East Land, Sea and Air Museums[59]Sunderland,UK inNortheast Airlines (UK)livery.
  • Trident 1C G-ARPP (Nose Section) at Solway Aviation Museum Carlisle Airport UK.
  • Trident 1E B-2207 at theMilitary Museum of the Chinese People's Revolution,Beijing, China.[60]
  • Trident 1E 50051 at Beijing Air And Space Museum.
  • Trident 2E 50057 at Zhuhai.
  • Trident 2E G-AVFB atImperial War Museum Duxford,Duxford,Cambridgeshire,UK; on display inBritish European Airwayslivery.
  • Trident 2E G-AVFH (Forward Fuselage Section) at the De Havilland Museum Hertfordshire.
  • Trident 2E G-AVFM (Nose Section) at South Wales Aviation Museum St Athan Wales.
  • Trident 3B G-AWZI (Nose Section) at Farnborough Air Sciences Trust Museum.
  • Trident 3B G-AWZJ (Forward Fuselage Section) Dumfries and Galloway Aviation Museum.
  • Trident 3B G-AWZK at Runway Visitor Park atManchester Airport,Manchester, UK; moved from Heathrow in September 2005 after fund raising campaign by The Trident Preservation Society and Neil Lomax on display inBritish European Airwayslivery.[61]
  • Trident 3B G-AWZM at theScience Museum'sNational Collections Centreexhibit store at Wroughton,Wiltshire,UK; preserved in British Airways 'Negus' livery.
  • Trident 3B G-AWZP (Nose Section) at the De Havilland Museum Hertfordshire.
  • Trident 3B G-AWZU (Nose Section) at Jet Age Museum Gloucester.

Accidents and incidents

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Accidents with fatalities

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Hull losses

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  • On 30 June 1966, Kuwait Airways Trident 1E registration 9K-ACG crash-landed 3 miles short of the runway at Kuwait International Airport. Fortunately there were no fatalities, and only minor injuries amongst the 83 passengers & crew. The aircraft which was just over one year old was written off.[71]
  • On 3 July 1968, whilst parked at Heathrow Terminal 1, Trident 1s G-ARPI and G-ARPT were struck by anAirspeed AmbassadorG-AMAD operatingBKS Air Transport Flight C.6845,which crashed whilst landing on runway 28R, thereafter departing from the runway. Trident G-ARPI was severely damaged, but repaired and returned to service, whereas G-ARPT was written off.[72]
  • On 15 September 1975 Trident 1EG-AVYDwas damaged beyond repair & written off at Bilbao after aborting its take-off at or close toV1,and failing to stop on the remaining length of (wet) runway. It was operating British Airways (Northeast Airlines) flightNS552with 110 passengers and 7 crew, all of whom evacuated the aircraft safely.[73][74]

Incidents

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Specifications

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Hawker Siddeley Trident 3B side view
Variant comparison[76][77][78][79]
Variant Trident 1/1C Trident 1E Trident 2E Trident 3B
Cockpit crew Three (Captain, First Officer, and Flight Engineer)
Typical seats 101 seats 108 seats 115 seats 180 seats
Length 114 ft 9 in (34.98 m) 131 ft 2 in (39.98 m)
Wingspan 89 ft 10 in (27.38 m) 95 ft (29 m) 98 ft (30 m)
Wing area 1,358 sq ft (126.2 m2) 1,415 sq ft (131.5 m2) 1,462 sq ft (135.8 m2)
Wingsweep 35 degrees
Height 27 ft 0 in (8.23 m) 28 ft 3 in (8.61 m)
Max. cabin width 11 ft 3.5 in (3.442 m)
TypicalOEW 66,700 lb (30.3 t)
1C: 67,200 lb (30.5 t) 		70,000 lb (31.8 t) 73,200 lb (33.2 t) 83,000 lb (37.6 t)
MTOW 107,000 lb (48.5 t)
1C: 115,000 lb (52.2 t) 		128,000 lb (58.1 t) 142,500 lb (64.6 t) 150,000 lb (68.0 t)
Fuel capacity 3,840 imperial gallons (17,500 L)
1C: 4,840 imp gal (22,000 L) 		5,440 imp gal
(24,700 L) 		5,774 imp gal
(26,250 L) 		5,440 imp gal
(24,700 L)
Engines 3 xSpeyRB163-1 Mk505-5 3 x Spey RB163-25 Mk511-5 3 x Spey RB.163-25 Mk512-5 3 x Spey RB.163-25 Mk512-5

1 xRB.162-86

Thrust 3 x 10,400 lbf (46 kN) 3 x 11,400 lbf (51 kN) 3 x 11,960 lbf (53.2 kN) 3 x 11,960 lbf (53.2 kN)

1 x (5,250) lbf (23.4 kN)

FL300 cruise Mach 0.86 – 506 kn (937 km/h) Mach 0.84 – 495 kn (917 km/h)
Ceiling 35,000 ft (11,000 m)
Range 1,170 nmi; 2,170 km
1C: 1,760 nmi; 3,260 km 		1,910 nmi; 3,540 km 2,350 nmi; 4,350 km 1,940 nmi; 3,600 km

See also

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Aircraft of comparable role, configuration, and era

Related lists

Notes

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  1. ^"B.E.A.'s feelings on these points were not inflexible. Their specification constituted a basis for discussion"
  2. ^A later revision of the Bristol 200 proposal that was being promoted to BEA was designated as the Bristol 205
  3. ^Hunting and Fairey remained DH.121 subcontractors.

References

edit
  1. ^abWood 1975, p. 99.
  2. ^Staniland 2003, p. 149.
  3. ^Wood 1975, pp. 99–100.
  4. ^abWood 1975, p. 100.
  5. ^abMunson 1967, pp. 153–154.
  6. ^Wood 1975, pp. 100–101.
  7. ^"Thoughts on the D.H.121".Flight International28 February 1958, p. 267.
  8. ^Wood 1975, p. 101.
  9. ^abcdeWood 1975, p. 102.
  10. ^Wood 1975, pp. 97, 102.
  11. ^"Deep-Stall Avoidance".Concept to Reality.Retrieved: 13 November 2010.
  12. ^ab"Touchdown by Computer".Time,18 June 1965. Retrieved: 17 July 2009.
  13. ^Wood 1975, pp. 102–103.
  14. ^UKRetail Price Indexinflation figures are based on data fromClark, Gregory (2017)."The Annual RPI and Average Earnings for Britain, 1209 to Present (New Series)".MeasuringWorth.Retrieved7 May2024.
  15. ^abcdefWood 1975, p. 103.
  16. ^abcdefghijWood 1975, p. 104.
  17. ^Bacon, Roger. "Straight & Level".Flight International.16 December 1960, p. 953.
  18. ^"Airco D.H.121".Flight International,25 July 1958.
  19. ^"Bristol 200 – a Preliminary Appraisal".Flight International,24 January 1958, p. 109.
  20. ^"B.E.A.'s Jet: Cards on the Table".Flight International,February 1958, p. 167.
  21. ^abStaniland 2003, pp. 149–150.
  22. ^Wood 1975, pp. 103–104.
  23. ^Staniland 2003, p. 150.
  24. ^"B.E.A. versus Traffic Recession".Flight International.28 August 1958, p. 74.
  25. ^ab"Subsonic Setback?"Flight International,29 May 1959, p. 753.
  26. ^"A Smaller D.H.121".Flight International,14 August 1959, p. 26.
  27. ^"Airco D.H.121: Preliminary Details".Flight International.28 August 1959, p. 91.
  28. ^"D.H.121: Progress Report on Britain's 600 m.p.h. Viscount Replacement".Flight International22 January 1960, p. 102.
  29. ^"The D.H.121 and Automatic Landing".Flight International.22 January 1960, p. 120.
  30. ^"Commercial Aircraft of the World: D.H.121 Trident Mk 1".Flight International.18 November 1960, p. 798.
  31. ^"Hawker Siddeley Mergers".Flight International.12 February 1960, p. 196.Archived1 February 2014 at theWayback Machine
  32. ^Wood 1975, pp. 104–105.
  33. ^Gunn 1999, pp. 184–185.
  34. ^"Airliner price index".Flight International.10 August 1972. p. 183.
  35. ^abWood 1975, p. 105.
  36. ^Wood 1975, pp. 105–106.
  37. ^abWood 1975, p. 106.
  38. ^Wood 1975, pp. 106–107.
  39. ^Wood 1975, pp. 107–108.
  40. ^Wood 1975, p. 107.
  41. ^abcWood 1975, p. 108.
  42. ^abcJackson 1973, pp. 272–276.
  43. ^"1964 | 0946 | Flight Archive".Flightglobal.com. 2 April 1964.Retrieved7 December2019.
  44. ^"Talking to Mr. Beall: Boeing's Senior Vice-President in London".Flight International.14 October 1960, p. 603.
  45. ^Pratt, Roger, ed.Flight Control Systems: Practical Issues in Design and Implementation.Kidlington, Oxfordshire, UK: Elsevier Science Ltd., 2000.ISBN0-85296-766-7.
  46. ^"Trident Automatically".Flight International.17 June 1965, p. 972.
  47. ^abKenward, Michael."Cutting through the fog with autoland"Archived20 October 2023 at theWayback Machine.New Scientist,10 February 1972 Volume 53 Number 782. pp. 321–323. via Google Books
  48. ^Bearup, Benjamin."Flashback Friday: 50th Anniversary of Autolanding".Archived22 December 2015 at theWayback MachineAirways News,31 July 2015.
  49. ^Interaviaarticle 1976 page 863 "Autoland starts to pay off for British Airways" by Don Craig (Principle Development Engineer Autoflight, European Division). The Quick Access Recorder "can record 64 analogue parameters and 30 odd- event signals". The QAR was situated on the flight deck and the cassettes were changed every couple of flights. The data was analysed on a Honeywell computer system. Steve Mills (Development Engineer Autoflight).
  50. ^"Smiths Industries Flight Data/Cockpit Voice Recorders".ntsb.gov.Retrieved: 1 April 2010.
  51. ^"BEA orders more Tridents".Glasgow Herald,6 August 1965.
  52. ^"British bid to sell jets to China".The Age,10 May 1971.
  53. ^"After Trident, Concorde?"Glasgow Herald,5 December 1973.
  54. ^Imrie, Ian."New snag could again delay Tridents".Glasgow Herald,12 August 1977.
  55. ^Kingsley-Jones, Max."Analysis: Why there was more to the HS Trident than just a lot of noise".Flight International,14 December 2015.
  56. ^Guy, Jack (22 January 2019)."Boeing's famous trijet 727 makes last commercial flight".CNN.Retrieved23 January2019.
  57. ^Taylor 1980, p. 269.
  58. ^abcdefghijkl"Hawker Siddeley HS121 Trident production list".rzjets.net.
  59. ^Falcus, Matt."Save the Trident".savethetrident.org.Retrieved: 1 April 2010.
  60. ^"China People's Revolution Military Museum - Beijing - China".
  61. ^"HS.121 Trident series 3B-101 'G-AWZK'".Archived15 December 2009 at theWayback Machinewww.ringwayreports.co.uk,7 August 2007. Retrieved: 27 September 2009.
  62. ^"Accident description: Hawker Siddeley HS-121 Trident 1C, 3 June 1966".aviation-safety.net.Retrieved: 13 November 2010.
  63. ^"Criminal Occurrence description: Trident 1E crash, 13 September 1971".aviation-safety.net.Retrieved: 13 November 2010.
  64. ^Civil Aircraft Accident Report 4/73:Trident I G-ARPI: Report of the Public Inquiry into the Causes and Circumstances of the Accident near Staines on 18 June 1972 – Appendix AAccident Investigation Branch, Department of Trade and Industry. HMSO, London, 1973.
  65. ^"Accident description: Hawker Siddeley HS-121 Trident 1C, 18 June 1972".aviation-safety.net.Retrieved: 13 November 2010.
  66. ^"Accident description: Hawker Siddeley HS-121 Trident 3B, 10 September 1976".aviation-safety.net.Retrieved: 13 November 2010.
  67. ^"CAAC Trident 2E".planecrashinfo.com.Retrieved: 1 April 2010.
  68. ^"ASN Aircraft accident: Hawker Siddeley HS-121 Trident 2E B-266 Yangsuo".aviation-safety.net.Retrieved: 1 April 2010.
  69. ^Accident description for B-264at theAviation Safety Network.Retrieved on 30 August 2014.
  70. ^"Accident description: Hawker Siddeley HS-121 Trident 2E, 31 August 1988".aviation-safety.net.Retrieved: 13 November 2010.
  71. ^"Accident description: Hawker Siddeley HS-121 Trident 1E 9K-ACG, 30 June 1966".aviation-safety.net.Retrieved: 8 March 2024.
  72. ^"Hull-loss description: Hawker Siddeley HS-121 Trident 1s, 3 June 1966".aviation-safety.net.Retrieved: 13 November 2010.
  73. ^"Accident description: Hawker Siddeley HS-121 Trident 1E, 15 September 1975".aviation-safety.net.Reviewed: 12 March 2024.
  74. ^AAIB, gov.uk."8/1977 British Airways Trident G-AVYD, 15 Sept 1975".Retrieved12 March2024.
  75. ^Accident description for Hawker Siddeley HS-121 Trident 2E B-296 Chunchon Air Baseat theAviation Safety Network.Retrieved on 18 July 2021.
  76. ^Jackson 1973, p. 276.
  77. ^Green 1976, p. 117.
  78. ^"Commercial Aircraft of the World".Flight International.9 November 1962. p. 865. Archived fromthe originalon 11 July 2015.Retrieved7 December2019.
  79. ^"Aero Engines 1969".Flight International.Vol. 95, no. 3121. 2 January 1969. p. 27. Archived fromthe originalon 17 April 2015.Retrieved10 July2015.

Sources

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  • Green, William.The Observer's Book of Aircraft.London: Frederick Warne & Co. Ltd., 1976.ISBN0-7232-1553-7.
  • Gunn, John.Contested skies: Trans-Australian Airlines, Australian Airlines, 1946–1992.St Lucia, Queensland, Australia: University of Queensland Press, 1999.ISBN0-7022-3073-1.
  • Jackson, A.J.British Civil Aircraft since 1919, Volume 2.London: Putnam, 1973.ISBN0-370-10010-7.
  • Jerram, Michael and Cliff Barnet.Illustrated International Aircraft Guide 6: General Aviation.London: Phoebus Publishing Co., 1981. No ISBN.
  • Munson, Kenneth.Civil Airliners since 1946.London: Blandford Press, 1967.
  • Staniland, Martin.Government Birds: Air Transport and the State in Western Europe.Lanham, Maryland: Rowman & Littlefield, 2003.ISBN0-7425-0124-8.
  • Taylor, Michael J.H., ed.Jane's Encyclopedia of Aviation, Vol. 2.Danbury, Connecticut: Grolier Educational Corporation, 1980.ISBN0-7106-0710-5.
  • Varley, Helen, ed.The Air Traveller's Handbook: The Complete Guide to Air Travel, Airplanes and Airports.New York: Simon & Schuster/Fireside, 1978.ISBN0-671-24393-4.
  • Winchester, Jim, ed. "Hawker Siddeley Trident".Civil Aircraft.Kent, UK: The Grange, 2004.ISBN1-84013-642-1.
  • Wood, Derek.Project Cancelled.Macdonald and Jane's Publishers, 1975.ISBN0-356-08109-5.

Further reading

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