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Hawker Siddeley Trident

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Hawker Siddeley
IndustryAerospace
Predecessorde Havilland
Founded1960
Headquarters
United Kingdom


Template:EngvarB Template:Infobox aircraft

The Hawker Siddeley HS-121 Trident—initially designated the de Havilland DH.121 and briefly known as the Airco DH.121—is a British-built airliner manufactured by Hawker Siddeley. The design for the DH.121 trijet was first proposed by de Havilland in response to a specification from British European Airways (BEA) in 1957. Following de Havilland's acquisition by Hawker Siddeley in 1960, the aircraft’s development continued under the new company. Its inaugural flight took place on 9 January 1962, and the type entered commercial service on 1 April 1964, shortly after its principal rival, the Boeing 727. Production concluded in 1978 with a total of 117 units completed. The Trident was retired from operational use in 1995.

This aircraft features three rear-mounted Rolls-Royce Spey low-bypass turbofan engines, a low-positioned swept wing, and a distinctive T-tail configuration. Equipped with state-of-the-art avionics, it became the first commercial airliner to perform an automatic blind landing during revenue flights in 1965. The initial Trident 1 and 2 models accommodated between 101 and 115 passengers over distances up to 2,350 nmi (4,350 km). The later Trident 3 variant was lengthened by approximately 5 m (16 ft) to carry up to 180 passengers over a range of 1,940 nmi (3,590 km; 2,230 mi), incorporating an additional RB.162 booster engine mounted in the tail.

Background and original specification

When British European Airways (BEA) introduced the first civil turboprop airliner—the Vickers Viscount—in 1953, it was already contemplating the requirements for its eventual successor.[1] Despite jet airliners entering service as early as 1952, many airline executives and economists remained cautious and preferred turboprop aircraft over piston engines for their economic advantages.[2] Consequently, BEA issued a specification in 1953 calling for an airliner seating approximately 100 passengers with a maximum speed near 370 knots (690 km/h).[3] This led Vickers to develop the larger Vickers Vanguard turboprop, ordered by BEA on 20 July 1956. However, by then, the French Sud Aviation Caravelle had already flown its maiden flight in the previous year, prompting BEA to acknowledge that jet-powered aircraft would soon pose significant competition.[4]

In April of 1956, BEA's CEO Anthony Milward expressed a preference against adopting jet airliners. Nevertheless, by December that year, Lord Douglas of Kirtleside, BEA’s chairman, indicated that while turboprops would remain predominant for some time, several short-haul jet-powered aircraft might be integrated into the fleet.[4] In July 1956, BEA released "outline requirements" for a new short-range "second-generation jet airliner" to complement its turboprop models. The specification called for an aircraft capable of carrying roughly 20,000 lb (9,100 kg) payload or about seventy passengers over 1,000 mi (1,600 km), with an estimated weight near 100,000 lb (45,000 kg). It was expected to operate from runways approximately 6,000 feet (1,800 m) long and cruise at speeds between 610 to 620 mph (980 to 1,000 km/h), featuring more than two engines.[5][6][N 1][7] Aviation historian Derek Woods notes that BEA sought an aircraft faster than the Caravelle which was emerging as a strong competitor.[8] Although not explicitly mandated at the time, these specifications have since been interpreted as a clear direction for manufacturers.[5]

File:Channel Airways Hawker Siddeley HS-121 Trident 1E AN2388412.jpg
The Trident was among the earliest trijets with all three Rolls-Royce Spey engines mounted at the rear

Four manufacturers developed proposals responding to BEA’s outlined needs. The Bristol Aeroplane Company put forward the four-engine Bristol Type 200.[1] Meanwhile, Avro proposed the avant-garde trijet Avro 740 before shelving it and collaborating with Bristol and Hawker Siddeley. Vickers presented the VC11 four-engine design derived from its ongoing VC10 project. De Havilland explored three concepts: two four-engine variants based on earlier de Havilland Comet models—the D.H.119 and D.H.120 (the latter also intended for British Overseas Airways Corporation (BOAC))—and in July of 1957 submitted the DH.121 proposal featuring three turbojet Rolls-Royce Avon engines closely resembling what would become the production model.[9] By August that year, revisions to the DH.121 included switching to Rolls-Royce’s developing Medway turbofan engines and increasing passenger capacity to up to ninety-eight.[10]

The DH.121 was set to become the world’s first trijet airliner. Its designers believed this engine arrangement balanced fuel efficiency during cruise with improved safety during takeoff should an engine fail; additionally, BEA’s specification stipulated more than two engines. Each engine powered its own hydraulic system providing triple redundancy in case one system failed. The powerplants were planned as Medway engines producing approximately 13,790 lbf (61.34 kN) thrust each. The aircraft's maximum takeoff weight was projected at around 123,000 pounds (56,000 kg), optionally expandable up to 150,000 pounds (68,000 kg), with a range near 2,070 miles (3,330 km) and seating arranged for about one hundred eleven passengers in two classes or over one hundred forty in dense single-class configurations typical of charter operations from the mid-1960s onward.[11] The initial design included a cruciform tail similar to that of the Caravelle.[10] The three engines were grouped at the rear fuselage; notably, the centre engine was installed deep within the tail cone and fed by an oval intake integrated into the front of the vertical stabilizer—a layout comparable to that later adopted by Boeing's trijet design—but ultimately settled on a variable-incidence T-tail arrangement.[12]

File:G-awzk-front.jpg
The nosewheel is offset to port side allowing space for an extensive avionics compartment beneath the cockpit

From inception, advanced avionics were planned for the DH.121 well ahead of contemporaries; these systems would enable automatic approaches and landings within a few years after entering service. To ensure reliability during automatic landings and approaches, critical avionics components were triplicated allowing majority voting logic (2 out of3) to guide flight controls.[13] Due to their physical size at that time,the avionics equipment required installation in a sizable compartment beneath the flight deck.This necessity influenced an unusual nose landing gear design featuring a wheel offset approximately 2 feet (61 cm) to port side,retracting sideways along the longitudinal axis ofthe fuselage into its bay beneaththe avionics section.

Industry consolidation and selection

BEA quickly identified the DH.121 as the preferred candidate for detailed negotiations, though these discussions extended over a long period due to several reasons, including broader British government policies and internal uncertainty within BEA.[9] In the late 1950s, when the DH.121 first appeared, the British government regarded the aircraft and aeroengine sectors as excessively divided among numerous small firms. Consequently, a strategy was adopted to encourage mergers into a limited number of large conglomerates. De Havilland aimed to maintain its autonomy and lead on the DH.121 project, proposing to the government a consortium arrangement where de Havilland would handle fuselage production, Bristol would manufacture wings, and other companies like Hunting Aircraft and Fairey Aviation would take responsibility for additional components. Bristol, however, strongly rejected this plan and aligned itself with Hawker Siddeley in direct competition against de Havilland.[14]

The prospect of securing BEA’s £30 million contract (Template:InflationTemplate:Inflation-fn), coupled with potential profitable export opportunities abroad, sparked intense rivalry among companies vying for selection.[15] On 4 February 1958, de Havilland, together with Hunting and Fairey, declared their intention to form a partnership dedicated to producing and marketing the DH.121. This consortium revived the corporate identity of the defunct Airco company—the firm that had employed Geoffrey de Havilland during the First World War.[15] The Minister of Supply commented that this Airco consortium was "not quite what [he] had in mind". Nonetheless, both Airco and their rivals from Bristol-Hawker Siddeley proceeded independently to approach various international airlines; their efforts attracted sufficient interest that American carrier Pan American World Airways invited both groups to showcase their proposed aircraft in January 1958.[15] Sir Matthew Slattery, chairman of Bristol and Short Brothers, urged BEA to postpone any decision until one of the competing teams had secured an export contract. In reply, Lord Douglas affirmed that BEA intended to purchase the DH.121 pending government approval; this response has been interpreted as effectively ending the competing Type 200 bid.[15]

At the same time, a new competitor emerged from the United States: Boeing introduced its trijet design, the 727.[16] Boeing had initiated market research in this segment as early as 1956 and officially launched its trijet program in 1959. Executives at Airco—who were actively exploring various partnerships and alternative strategies—entertained the idea that Boeing might abandon the 727 project in favor of co-producing the DH.121 in America; Lord Douglas was among those supporting this concept.[16] Consequently, Airco invited Boeing engineers and executives to visit Hatfield. Boeing subsequently allowed de Havilland representatives to visit Seattle; however, Boeing disclosed minimal information about its plans for the 727, while sharing nearly all details about the DH.121 during the Hatfield meeting—an openness that reportedly "amazed" Boeing personnel.[16] British analysts have often viewed this episode as involving sensitive proprietary information about the DH.121 being obtained by a direct competitor.[17] Woods described this as "de Havilland solemnly handing all its research over to its rivals... the crowning piece of stupidity".[16]

On 12 February 1958, government authorization was granted for BEA to begin contractual discussions and issue a letter of intent for an initial batch of 24 aircraft.[15] That same month, BEA announced that the DH.121 best met its specifications and planned to order 24 units with options on an additional twelve.[18] A further six months were necessary before formal government approval of BEA’s order was secured; industrial policy considerations had inclined preference toward the Bristol Type 200.[19][20] Although BEA showed significant interest in the Caravelle itself, selecting it would have been politically untenable.[21] BEA also favored de Havilland and thus supported the Trident proposal due to that company’s established jet airliner expertise from developing the Comet.[9][21]

File:G-AWZK Trident 3 (5658146159).jpg
Six-abreast cabin

In April of that year, de Havilland finalized the general design layout for the DH.121 and set out a development schedule targeting a maiden flight by mid-1961.[15] Market research within the company predicted sales of up to approximately 550 aircraft in this category by 1965. Recognizing an increasing airline preference for wider seating arrangements typical of what became known as economy class, design modifications were made to enlarge the fuselage diameter slightly to accommodate six-abreast seating with a maximum capacity of around 111 passengers.[22] Woods noted that this expanded version of the DH.121 was poised to deliver an aircraft well-suited for market demands and anticipated a success comparable to that achieved by the Viscount.[16]

Revised specification

In March 1959, BEA, alarmed by a recent slowdown in passenger growth, determined that the DH.121's payload and range capabilities might exceed their requirements. Consequently, they requested de Havilland to scale down the design to align with their updated forecasts.[16] Concerned that the original Trident design was overly large, the airline opted to effectively cancel the initial program to allow for a redesign better suited to their immediate operational needs. At that time, BEA operated a substantial fleet and had numerous aircraft on order, making the issue of excess capacity particularly pressing.[23] The airline’s apprehensions were influenced by three main factors: a brief recession in the late 1950s affecting air travel; the impending deployment of a significant number of turboprop Vickers Vanguard aircraft, which overlapped with the DH.121’s intended payload-range profile; and an industry-wide shift toward higher-density seating arrangements.[24]

While de Havilland generally agreed with BEA’s assessment, company leadership also emphasized that they had been operating "under terms more onerous than anything D.H. had previously undertaken".[25] At the time, industry analysts observed that the British aircraft sector had once again fallen into the trap of designing an airplane exclusively for one customer despite its broader market potential:[25] a critique that would resonate throughout the Trident’s later history. The de Havilland board chose to comply with BEA’s request, overruling advice from their sales and marketing teams who indicated demand from other airlines for a larger variant.[16] Importantly, de Havilland had not yet secured a definitive BEA contract, while rival Bristol was actively marketing their smaller Bristol 200 [N 2] project to BEA. Concurrently, American manufacturers Boeing and Douglas were also reducing the size of their 727 and DC-9 designs respectively. It was believed that retaining the original large DH.121 would position it against established aircraft like the Convair 880 and Boeing 720 several years after their introduction, whereas a scaled-down version would better compete with the anticipated 75–100 seat twin-engine DC-9.[26]

The process of shrinking the Trident entailed major design modifications, including replacing the Medway engines with a smaller derivative—the Rolls-Royce Spey 505—which delivered approximately 40% less thrust at 9,850 lbf (43.8 kN).[16] The maximum takeoff weight was reduced by roughly one-third to about 105,000 pounds (48,000 kilograms), while range dropped by more than half to around 930 mi (1,500 km). Seating capacity in mixed-class configurations decreased by approximately 25%, accommodating between 75 and 80 passengers (or up to 97 in an all-economy layout). The wingspan was shortened by about 17 ft (5.2 m), wing area decreased by nearly 30%, and overall length diminished by 13 ft (4.0 m). Despite these reductions, certain elements from the original design remained intact—most notably the fuselage diameter. The cockpit was made smaller, and the main landing gear was redesigned from four-wheel bogies to single-axis legs featuring two wheels and four tires.[27] Woods summarized this BEA-driven redesign bluntly: "At one blow the 121 was emasculated in terms of size, power and range".[16]

Approximately six months after BEA’s initial request, de Havilland and the airline reached consensus on the downsized DH.121 configuration.[16] Early in 1960, details about this updated aircraft—including its advanced avionics—were disclosed publicly.[28] This modified version became the basis for BEA’s eventual order placed on 24 August 1959 for an initial batch of 24 units with options for another dozen.[29] In September of the following year at the Farnborough Airshow, the airliner’s official name—Trident—was announced, chosen to highlight its distinctive three-jet propulsion and triple hydraulic system configuration.[30]

Continued development and proposals

By the year 1960, de Havilland had become part of the Hawker Siddeley group. Following this acquisition, Airco was dissolved, while Hunting was integrated into the newly established British Aircraft Corporation (BAC), a competitor. This shift eliminated any potential for the Hunting 107 (which later evolved into the BAC One-Eleven) to be marketed alongside the DH.121 as a smaller complement within the same airliner series. Fairey Aviation, which had been partially absorbed by Westland Aircraft, also withdrew from the DH.121 initiative.[N 3] With Hawker Siddeley Aviation taking over, the aircraft's designation was updated to HS 121. The industry restructuring compounded delays initially caused by BEA's specification revisions, which in turn diminished the Trident’s ability to compete effectively against the Boeing 727.

The Boeing 727 quickly gained a substantial advantage over the Trident early on.[31] This early lead solidified its position in subsequent procurement contests; for example, although Trans Australia Airlines considered the Trident operationally superior to the Boeing 727, it was deemed commercially risky to diverge from fleet choices made by competitors like Ansett Australia, which had already committed to the 727.[32] In 1972, the unit price for a Trident stood at US$7.8 million.[33] By 1975, total sales of Tridents reached only 117 units compared to over 1,000 Boeing 727s.[34]

Woods highlights a critical missed opportunity during the 1960s that could have allowed the Trident to narrow its gap with the 727: two maritime patrol aircraft competitions—the NATO program aimed at replacing the Lockheed P-2 Neptune and Air Staff Requirement 381, which sought a successor to the Royal Air Force's piston-powered Avro Shackleton.[34] Among various contenders was Avro’s submission—the Avro 776—part of Hawker Siddeley Group. This design combined the Trident’s fuselage with an enlarged and redesigned wing and more powerful Rolls-Royce RB178 engines delivering 16,300 lb of thrust.[35] Beyond maritime patrol duties, Avro envisioned multiple military applications for this aircraft, including a troop transport accommodating up to 103 personnel and a nuclear-capable bomber armed with up to four GAM-87 Skybolt air-launched ballistic missiles.[36] Additionally, Armstrong Whitworth proposed their own military adaptations based on the Trident platform.[36]

Subsequent versions of the Avro 776 replaced the RB178 engines with newer turbofans—the Rolls-Royce RB211—whose development was supported contingent on winning this procurement.[37] Rolls-Royce Limited had halted Medway engine development following changes to the Trident design but was eager to create an engine positioned between the Spey (10,000 lb thrust) and Conway (20,000 lb thrust) models. Such an engine could have powered updated civil Trident variants as well. Equipped with this more potent engine providing greater thrust than the Spey and an extended fuselage alongside removal of existing landing constraints, the Trident might have been significantly more competitive with the Boeing 727.[38] Wood summarized this potential advancement by stating: "For the Trident programme, the RB.177 would have been a God-send".[39]

At one stage, the Avro 776 appeared poised to win selection as the RAF's new maritime patrol aircraft.[40] However, cost-cutting priorities led the RAF to issue an entirely new operational requirement that reduced expectations for speed, endurance, and capacity. Consequently, Avro’s team was recalled and their design abandoned in favor of a new concept based on the de Havilland Comet fuselage but retaining Spey engines from the Trident; this design ultimately became the Hawker Siddeley Nimrod. As a result of this shift in direction, prospects for an enlarged and higher-thrust Trident variant disappeared.[40]

File:Trident 62a.jpg
A Trident 1C measuring approximately thirty-five meters in length displayed at the September 1962 Farnborough Airshow, prior to its introduction in April of 1964

Following de Havilland's absorption into Hawker Siddeley Aviation, efforts intensified to secure additional customers for the Trident. In discussions with American Airlines (AA) during 1960, AA expressed a need for increased range beyond what was initially available—requirements that would have been nearly met by the original DH121 design. This prompted development of a new Trident 1A, featuring uprated Rolls-Royce Spey Mk510 engines producing thrust of around10,700 lbf (47.6 kN), alongside a larger wing with greater fuel capacity. These enhancements raised maximum takeoff weight to 120,000 lb (54,000 kg) and extended range to approximately 1,800 mi (2,900 km); nevertheless, AA ultimately chose Boeing's competing model instead.

Some modifications intended for this version were incorporated into the original prototype aircraft—renamed Trident 1C. The primary upgrade involved enlarging fuel tanks within the wing's center section, increasing maximum weight to 115,000 lb (52,000 kg) and range up to about 1,400 mi (2,300 km). The first flight of Trident Series One aircraft G-ARPA took place on January 9, 1962 at Hatfield Aerodrome.[41]

Design

A left-quarter view of a jet airliner wing and tailplane. On the tail fin are the words 'Trident Two' and the letters 'BEA' and G-AFVB'.
T-tail and retracted leading edge devices of a Hawker Siddeley Trident

Overview

The Trident was an all-metal jet airliner featuring a distinctive T-tail configuration and a low-positioned wing with a quarter-chord sweep angle of 35 degrees. Its propulsion system consisted of three engines mounted at the rear: two housed in pods alongside the fuselage, and a third located within the tailcone, fed by an S-shaped intake duct. One variant, the 3B model, incorporated an additional fourth "boost" engine supplied through a separate intake positioned above the main S-duct. Power across all models was delivered by versions of the Rolls-Royce Spey engine, while the boost unit was a Rolls-Royce RB162, originally designed for use as a lift engine in VTOL aircraft.

Among subsonic commercial jets, the Trident ranked as one of the fastest, achieving cruising speeds exceeding 610 mph (980 km/h). At its service entry, it cruised at Mach 0.88 or 380 knots IAS. Engineered for high-speed performance with a critical Mach number of 0.93, its wing generated comparatively modest lift during lower-speed operations. Combined with a relatively low thrust-to-weight ratio, this characteristic necessitated extended takeoff distances. Despite this, the Trident met BEA’s requirement for field lengths up to 6,000 ft (1,800 m), and its moderate airfield capabilities were considered sufficient until later jets like the Boeing 727 emerged, which were designed around shorter 4,500 ft (1,400 m) runway criteria. The aircraft’s aerodynamic design and wing development were overseen by a team led by Richard Clarkson, who later adapted the Trident’s wing concept for the Airbus A300. For his work on the Trident wing, Clarkson received the prestigious Mullard Award in 1969.

The normal descent rate for the Trident could reach up to 4500 ft/min (23 m/s). In situations requiring emergency descents as steep as 10,000 ft/min, pilots were authorized to engage reverse thrust. When flying below 280 kn IAS, extending the main landing gear served as an effective airbrake. The initial Trident model, the 1C, featured an uncommon ability to deploy reverse thrust before touchdown: throttles could be closed during flare with reverse idle set to activate reverser buckets. Pilots could then apply full reverse thrust prior to landing if desired. This technique helped minimize hydroplaning risks and enabled very short landing distances on wet or slippery surfaces while maintaining brake effectiveness and preventing excessive brake temperatures. The braking system incorporated the Dunlop Maxaret anti-skid technology.

Avionics

File:TridentFlightDeck.JPG
Flight deck of a Trident 2E: orange "Triplex autoland fitted" placards are visible on the control columns, alongside the moving map display positioned on the central instrument panel

The Trident was equipped with an intricate and highly advanced avionics suite that proved effective throughout its operational life. This included a fully integrated automatic blind landing system co-developed by Hawker Siddeley and Smiths Aircraft Instruments. The system was engineered to autonomously manage the aircraft’s approach to the runway, flare, touchdown, and even the rollout phase after landing. Although initially targeted for introduction by 1970, the technology enabled the Trident to achieve the first automatic landing by a commercial airliner in scheduled passenger service on 10 June 1965, as well as the inaugural true "blind" landing in such service on 4 November 1966.

The capability to land safely in foggy conditions addressed a significant operational challenge at airports like London Heathrow and other UK facilities. Prior to this, delays were frequent under Category 1 (Cat 1 = 200 ft (61 m) decision height with a 600-metre runway visual range RVR) instrument landing system (ILS) conditions. The Trident’s autoland innovation broke new ground by enabling operations under lower visibility minima, initially achieving Category 2 (100 ft decision height and 400 metres RVR) standards and soon advancing to "zero-zero" or Category 3C conditions. This capability allowed Tridents to reliably maintain schedules at airfields fitted with compatible ILS equipment regardless of adverse weather, whereas other aircraft often had to divert.

A notable feature of the Trident’s avionics was its moving map display located on the central instrument panel, which visually represented the aircraft’s position relative to the terrain. This electro-mechanical device also tracked the flight path by plotting it via a stylus on a motor-driven paper chart. The positional data was derived from a Doppler navigation system that measured groundspeed and drift; combined with heading information, these inputs controlled the stylus movement.

The Trident was pioneering in installing a quick access flight data recorder (QAR) onboard. This device captured 64 parameters, digitized them, and stored the information on magnetic tape for subsequent analysis once on the ground. Later enhancements incorporated a cockpit voice recorder into the system as well.

Introduction

The inaugural Trident was introduced into service on 1 April 1964. By 1965, BEA's fleet included 15 Tridents, expanding to 21 by March 1966. Hawker Siddeley presented an enhanced model, the Trident 1E, powered by 11,400 lbf (51,000 N) Spey 511 engines. This variant featured an increased maximum takeoff weight of 135,600 lb (61,500 kg), a larger wing area achieved by extending the chord, leading-edge slats to improve performance on shorter runways, and modified take-off flap settings—specifically a 23-degree setting that reduced runway length requirements but limited the MTOW to 59,900 kg (132,100 lb). The fuselage remained unchanged but was configured to accommodate up to 140 passengers in a six-abreast seating arrangement. This design brought the 1C closer to the original DH121’s larger concept, albeit with 7,000 lbf (31,000 N) less thrust. Sales of this improved version were limited: three units each went to Kuwait Airways and Iraqi Airways, four were delivered to Pakistan International Airlines (later transferred to CAAC), two each were sold to Channel Airways and Northeast Airlines, and one to Air Ceylon. Channel Airways’ Tridents were outfitted with cramped seven-abreast seating in the forward cabin, featuring a tight 21 in (530 mm) seat pitch, accommodating 149 passengers.

Trident 2E

BEA determined that the Trident’s range was insufficient for its growing route network and requested a model with extended range capabilities. In response, Hawker Siddeley developed the Trident 1F, which retained Spey 511 engines, stretched the fuselage by 2.8 m (9 ft 2 in), increased gross weight to 132,000 lb (60,000 kg), and offered seating for up to 128 passengers in the original five-abreast layout. BEA initially intended to purchase ten units with an option for fourteen additional aircraft.

As development progressed, modifications became substantial enough to warrant renaming the aircraft as the Trident 2E—the "E" denoting Extended Range. This version utilized upgraded Spey 512 engines delivering 11,930 lbf (53,100 N) thrust, replaced wing leading-edge droop flaps with slats, and incorporated span extensions featuring Küchemann-style wingtip devices. The aircraft's maximum takeoff weight rose to 142,400 lb (64,600 kg), enabling a range of approximately 2,000 mi (3,200 km).

BEA acquired fifteen units, while two were sold to Cyprus Airways. The Chinese national carrier CAAC purchased thirty-three aircraft. The Trident 2E first flew on 27 July 1967 and entered BEA service in April 1968.

Trident 3B

File:British Airways Trident Marmet.jpg
The Trident 3B featured a fuselage stretch of 5 m (16 ft) allowing up to 180 seats

As the Trident became central to BEA’s operations, the airline sought a larger capacity aircraft. In 1965, Hawker Siddeley proposed two new models: the HS132, a larger two-engine aircraft seating 158 passengers similar in design to the Trident; and the HS134, which accommodated 185 seats and relocated engines beneath the wings in a configuration resembling the Boeing 737. Both designs were intended to use the then-developmental high-bypass Rolls-Royce RB178 engines. However, BEA ultimately opted for Boeing 727s and Boeing 737s to replace both BAC One-Eleven and Trident roles—a decision blocked by the British government.

Subsequently, BEA selected an extended version of the standard Trident labeled the Trident 3. The fuselage was lengthened by approximately 5 m (16 ft 5 in), increasing capacity up to 180 passengers; gross weight was raised to 143,000 lb (65,000 kg); and wing chord modifications were implemented. The original engines remained unchanged. Nevertheless, BEA found this design inadequate for "hot and high" operating environments due to performance limitations experienced with the Trident 2E. Since Spey 512 engines were at their performance limit and replacing them was challenging given one engine’s tail-mounted position, engineers at Hawker Siddeley innovated by adding a fourth engine—a compact Rolls-Royce RB162 turbojet—mounted in the tail with its own intake behind movable doors. This auxiliary engine provided an additional 15% thrust during takeoff while increasing overall weight by only about 5%, operating solely when extra power was necessary. BEA approved this configuration as the Trident 3B and placed orders for twenty-six units. Its maiden flight occurred on 11 December 1969, with entry into service on 1 April 1971. An enhanced fuel capacity variant was later introduced as the Super Trident 3B.

The Trident secured notable export success, especially in China. Following improved diplomatic relations between Britain and the People's Republic of China, over thirty-five Tridents were sold there.

In 1977, British Airways discovered fatigue cracks in their Tridents’ wings; these aircraft were returned to Hawker Siddeley for repairs before re-entering service.

The early 1980s marked the beginning of the Trident’s phase-out as new noise regulations drafted by ICAO mandated installation of hush kits on first- and second-generation jets effective from January 1986. British Airways—the primary operator—deemed retrofitting uneconomical and chose to retire its fleet by late 1985, with final flights on December 31 of that year. Chinese operations concluded in 1995, signaling complete retirement from commercial use. A total of only one hundred seventeen Tridents were manufactured; all have since been withdrawn from service. By comparison, Boeing produced one thousand eight hundred thirty-two Boeing 727s—an aircraft originally designed around similar specifications—and these remained in passenger operation until as late as 2019.

Variants

Trident 1C
The production model supplied to British European Airways, with a total of 24 units manufactured
Trident 1E
Featured enhanced seating capacity, more powerful engines, and the addition of leading edge slats compared to the Trident 1C; 15 units produced
Trident 2E
An upgraded version of the Trident 1E incorporating a triplex autoland system; 50 units built
Trident 3B
A high-capacity short to medium-range variant based on the 2E, extended by 16 ft 5 in (5.00 m) and equipped with an additional RB.162 booster engine mounted in the tail; 26 units constructed
Super Trident 3B
Extended operational range by 692 km (430 miles); only two units built

Operators

File:Air Ceylon Hawker Siddeley HS-121 Trident Green.jpg
Air Ceylon Trident 1E, March 1978
File:Iraqi Airways Hawker Siddeley HS-121 Trident 1E at London Heathrow Airport.jpg
Iraqi Airways Trident 1E
File:British Airways Trident Three G-AWZA.jpg
Trident 3B displaying crossover BEA/British Airways livery

Civil operators

Ceylon
  • Air Ceylon acquired one of the cancelled Channel Airlines Trident 1Es in 1969 and operated it until 1978.
China
  • Air China flew five ex-CAAC Tridents from 1988 through 1991.
  • CAAC Airlines took delivery of four former Pakistan International Airlines Trident 1Es in 1970, followed by thirty-three new Trident 2Es between 1972 and 1978, as well as two Super Trident 3Bs in 1975.
  • China United Airlines operated previously CAAC-owned Tridents.
Cyprus
  • Cyprus Airways received two Trident 2Es during 1969/70, one of which was damaged in 1972 and replaced with a similar aircraft from BEA. Additionally, two former Kuwait Airlines Trident 1Es were obtained through BEA in 1973. Two aircraft were irreparably damaged during the Turkish Invasion of Cyprus in 1974, with one left abandoned at Nicosia airport. The remaining two were transferred to British Airways in 1977.
Iraq
  • Iraqi Airways operated three Trident 1Es acquired in 1965 until their retirement in 1977.
Kuwait
  • Kuwait Airways took delivery of three Trident 1Es between 1965 and 1966, with one lost in an accident in 1966 and the remaining two sold to BEA in 1972.
Pakistan
  • Pakistan International Airlines received four Trident 1Es during 1966–67, including a VIP-configured aircraft for presidential use. These were sold to China in 1970.
United Kingdom
  • BKS/Northeast Airlines obtained two of the cancelled Channel Airways Trident 1Es in 1969 and added a third from Channel in 1971. One was written off in 1975, with the others transferring to British Airways following Northeast’s acquisition in 1976.
  • British Airways inherited twenty Trident 1Cs, one Trident 1E, fifteen Trident 2Es, and twenty-six Trident 3Bs from British European Airways in 1974. Two additional Trident 1Es arrived when Northeast Airlines merged into BA in 1976, alongside a single Trident 1E and a Trident 2E acquired from Cyprus Airways in 1977. British Airways phased out its entire Trident fleet between 1974 and 1985.
  • British European Airways initially received twenty-three Trident 1Cs between 1964 and 1966 (a twenty-fourth was lost during testing). They later added fifteen Trident 2Es (1968–70) and twenty-six Trident 3Bs (1971–73). A single Trident 1E was purchased from Channel Airways in 1971. One of the Trident 2Es was exchanged for a damaged Cyprus aircraft in 1972, while two former Kuwait Airways Trident 1Es were operated briefly before transferring to Cyprus Airways in the following year. Three of BEA’s original Trident 1Cs were written off during their service period, with the remainder passing to British Airways upon its formation in 1974.
  • Channel Airways placed orders for five Trident 1Es but only took delivery of two units in 1968; these were subsequently sold to BEA and Northeast Airlines by 1971.
Zaire
  • Air Charter Service of Zaire operated five former British Airways Trident 3Bs between the years of 1984 and 1986.

Military operators

China
Pakistan
  • Although the Pakistan Air Force was initially designated to receive the presidential Trident 1E, the aircraft was ultimately delivered to Pakistan International Airways instead.

Fatal accidents

  • On 3 June 1966, a Trident 1C bearing the registration G-ARPY entered a deep stall during a test flight and crashed near Felthorpe, Norfolk, resulting in the deaths of all four crew members.
  • On 13 September 1971, a Trident 1E operated by the People's Liberation Army Air Force crashed in Mongolia under unclear conditions amidst an alleged defection attempt by Lin Biao and his family to the Soviet Union. Official Chinese government reports attribute the crash to fuel exhaustion, while alternative accounts suggest controlled flight into terrain during radar evasion.
  • On 18 June 1972, British European Airways Flight 548, a Trident 1 registered G-ARPI, stalled deeply due to pilot error shortly after departing from Heathrow Airport and crashed near Staines, killing all 118 occupants. This tragedy is known as the "Staines air disaster" and remains, as of 2025, the deadliest aviation accident on British soil (excluding terrorist acts such as Pan Am Flight 103).
  • On 10 September 1976, a midair collision occurred over Yugoslavia involving British Airways Flight 476, a Trident 3B registered G-AWZT, and Inex-Adria Aviopromet Flight 550, a McDonnell Douglas DC-9 registered YU-AJR. All passengers and crew on both aircraft perished. The accident was attributed to errors in air traffic control.
  • On 14 March 1979, a CAAC Airlines Trident 2E with registration B-274 crashed into a factory near Beijing after being flown by an unqualified pilot who had illicitly taken control of the aircraft. The incident resulted in at least 200 injuries and fatalities including all 12 onboard and 32 individuals on the ground.
  • On 26 April 1982, CAAC Flight 3303, operated by a Trident 2E registered B-266, crashed close to Yangsuo, China, causing the loss of all 112 passengers and crew aboard.
  • On 14 September 1983, a CAAC Airlines Trident 2E registered B-264 was struck by a military aircraft while positioned on the runway at Guilin Airport in China, leading to eleven passenger fatalities.
  • On 31 August 1988, during adverse weather conditions involving rain and fog at Hong Kong's Kai Tak Airport, the right outboard flap of a CAAC Trident 2B operating as CAAC Flight 301 contacted approach lights on runway 31. Subsequently, the right main landing gear collided with the seawall of the reclaimed land beneath the runway, causing it to collapse. The aircraft veered off the runway and submerged into the harbor, resulting in seven fatalities.

Hull losses

  • On 30 June 1966, a Kuwait Airways Trident 1E bearing registration 9K-ACG crash-landed approximately three miles short of the runway at Kuwait International Airport. Fortunately, all 83 passengers and crew escaped with only minor injuries. The aircraft, which was just over a year old at the time, was deemed a total loss.[42]
  • On 3 July 1968, while stationed at Heathrow Terminal 1, two Trident 1s, registrations G-ARPI and G-ARPT, were hit by an Airspeed Ambassador (G-AMAD) involved in BKS Air Transport Flight C.6845. The Ambassador crashed during its landing on runway 28R and subsequently left the runway area. Trident G-ARPI sustained significant damage but was repaired and returned to operation; however, G-ARPT was written off. Notably, G-ARPI later crashed in 1972 during British European Airways Flight 548.[43]
  • On 15 September 1975, British Airways Trident 1E G-AVYD was irreparably damaged and subsequently written off after aborting its takeoff near V1 at Bilbao. The aircraft failed to stop on the wet runway's remaining length. Operating as British Airways (Northeast Airlines) flight NS552, it carried 110 passengers and seven crew members, all of whom evacuated safely.[44][45]

Incidents

  • On 23 July 1974, a British Airways Trident experienced a bombing attempt while flying over the sea and subsequently diverted to Manchester Airport.
  • On 5 May 1983, CAAC Flight 296 was hijacked,[46] an event that contributed to the initiation of diplomatic ties between the People's Republic of China and South Korea.

Aircraft on display

File:Hawker Siddeley Trident 2.jpg
Trident 2 exhibited at the China Aviation Museum, Beijing
  • The nose section of Trident 1C G-ARPH is preserved at the Museum of Flight East Fortune in Scotland.
  • Trident 1C G-ARPO is exhibited at the North East Land, Sea and Air Museums in Sunderland, UK, painted in Northeast Airlines (UK) colors.[47]
  • The nose section of Trident 1C G-ARPP is displayed at the Solway Aviation Museum located near Carlisle Airport in the UK.
  • Trident 1E B-2207 is part of the collection at the Military Museum of the Chinese People's Revolution, Beijing.[48]
  • Trident model 1E with registration number 50051 is housed within the Beijing Air And Space Museum.
  • The Trident 2E with registration number 50057 is on display in Zhuhai.
  • At the Imperial War Museum Duxford in Duxford, Cambridgeshire, UK, Trident 2E G-AVFB is presented in British European Airways livery.
  • The forward fuselage section of Trident 2E G-AVFH can be found at the De Havilland Museum in Hertfordshire.
  • South Wales Aviation Museum in St Athan, Wales exhibits the nose section of Trident 2E G-AVFM.
  • Farnborough Air Sciences Trust Museum houses the nose section of Trident 3B G-AWZI.
  • Dumfries and Galloway Aviation Museum displays the forward fuselage segment of Trident 3B G-AWZJ.
  • The Runway Visitor Park at Manchester Airport, UK showcases Trident 3B G-AWZK in British European Airways livery; this aircraft was relocated from Heathrow in September 2005 following a fundraising campaign led by The Trident Preservation Society and Neil Lomax.[49]
  • The Science Museum's National Collections Centre at Wroughton, Wiltshire preserves Trident 3B G-AWZM painted in British Airways' 'Negus' scheme.
  • At Hertfordshire's De Havilland Museum, visitors can view the nose section of Trident 3B G-AWZP.
  • The Jet Age Museum in Gloucester exhibits the nose section of Trident 3B G-AWZU.

Specifications

File:Hawker Siddeley Trident.png
Side profile of the Hawker Siddeley Trident 3B
Comparison of Variants
Variant Trident 1/1C Trident 1E Trident 2E Trident 3B
Flight deck crew Three members (Captain, First Officer, and Flight Engineer)
Standard seating capacity 101 passengers 108 passengers 115 passengers 180 passengers
Aircraft 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 surface area 1,358 sq ft (126.2 m2) 1,415 sq ft (131.5 m2) 1,462 sq ft (135.8 m2)
Wing sweep angle 35 degrees
Aircraft height 27 ft (8.2 m) 28 ft 3 in (8.61 m)
Maximum cabin width 11 ft 3.5 in (3.442 m)
Typical operating empty weight (OEW) 66,700 lb ([convert: unknown unit])
1C: 67,200 lb ([convert: unknown unit]) 		70,000 lb ([convert: unknown unit]) 73,200 lb ([convert: unknown unit]) 83,000 lb ([convert: unknown unit])
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See also

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Notes

  1. ↑ "B.E.A.'s feelings on these points were not inflexible. Their specification constituted a basis for discussion"
  2. ↑ with a subsequent revision known as the Bristol 205
  3. ↑ Hunting and Fairey continued as DH.121 subcontractors.

References

  1. ↑ 1.0 1.1 Wood 1975, p. 99.
  2. ↑ Staniland 2003, p. 149.
  3. ↑ Wood 1975, pp. 99–100.
  4. ↑ 4.0 4.1 Wood 1975, p. 100.
  5. ↑ 5.0 5.1 Munson 1967, pp. 153–154.
  6. ↑ Wood 1975, pp. 100–101.
  7. ↑ "Thoughts on the D.H.121". Flight International 28 February 1958, p. 267.
  8. ↑ Wood 1975, p. 101.
  9. ↑ 9.0 9.1 9.2 Wood 1975, p.102.
  10. ↑ 10.0 10.1 Cite error: Invalid <ref> tag; no text was provided for refs named wood102
  11. ↑ Wood1975,pages97and102.
  12. ↑ "Deep-Stall Avoidance". Concept to Reality. Retrieved: November13,2010.
  13. ↑ "Touchdown by Computer". Time, June18,1965.RetrievedJuly17,2009.
  14. ↑ Wood 1975, pp. 102–103.
  15. ↑ 15.0 15.1 15.2 15.3 15.4 15.5 Wood 1975, p. 103.
  16. ↑ 16.00 16.01 16.02 16.03 16.04 16.05 16.06 16.07 16.08 16.09 Wood 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. ↑ 21.0 21.1 Staniland 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. ↑ 25.0 25.1 "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 International 22 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. ↑ Wood 1975, pp. 104–105.
  32. ↑ Gunn 1999, pp. 184–185.
  33. ↑ Lua error in Module:Citation/CS1/Configuration at line 2123: attempt to index field '?' (a nil value).
  34. ↑ 34.0 34.1 Wood 1975, p. 105.
  35. ↑ Wood 1975, pp. 105–106.
  36. ↑ 36.0 36.1 Wood 1975, p. 106.
  37. ↑ Wood 1975, pp. 106–107.
  38. ↑ Wood 1975, pp. 107–108.
  39. ↑ Wood 1975, p. 107.
  40. ↑ 40.0 40.1 Wood 1975, p. 108.
  41. ↑ Jackson 1973, pp. 272–276.
  42. ↑ "Accident description: Hawker Siddeley HS-121 Trident 1E 9K-ACG, 30 June 1966". aviation-safety.net. Retrieved: 8 March 2024.
  43. ↑ "Hull-loss description: Hawker Siddeley HS-121 Trident 1s, 3 June 1966". aviation-safety.net. Retrieved: 13 November 2010.
  44. ↑ "Accident description: Hawker Siddeley HS-121 Trident 1E, 15 September 1975". aviation-safety.net. Reviewed: 12 March 2024.
  45. ↑ Lua error in Module:Citation/CS1/Configuration at line 2123: attempt to index field '?' (a nil value).
  46. ↑ Template:ASN accident
  47. ↑ Falcus, Matt. "Save the Trident". savethetrident.org. Retrieved: 1 April 2010.
  48. ↑ Lua error in Module:Citation/CS1/Configuration at line 2123: attempt to index field '?' (a nil value).
  49. ↑ "HS.121 Trident series 3B-101 'G-AWZK'". Archived 15 December 2009 at the Wayback Machine www.ringwayreports.co.uk, 7 August 2007. Retrieved: 27 September 2009.

Sources

  • Green, William. The Observer's Book of Aircraft. London: Frederick Warne & Co. Ltd., 1976. ISBN 0-7232-1553-7.
  • Gunn, John. Contested skies: Trans-Australian Airlines, Australian Airlines, 1946–1992. St Lucia, Queensland, Australia: University of Queensland Press, 1999. ISBN 0-7022-3073-1.
  • Jackson, A.J. British Civil Aircraft since 1919, Volume 2. London: Putnam, 1973. ISBN 0-370-10010-7.
  • 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. ISBN 0-7425-0124-8.
  • Taylor, Michael J.H., ed. Jane'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. New York: Simon & Schuster/Fireside, 1978. ISBN 0-671-24393-4.
  • Winchester, Jim, ed. "Hawker Siddeley Trident". Civil Aircraft. Kent, UK: The Grange, 2004. ISBN 1-84013-642-1.
  • Wood, Derek. Project Cancelled. Macdonald and Jane's Publishers, 1975. ISBN 0-356-08109-5.

Further reading

External links

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Maximum takeoff weight (MTOW) 107,000 lb ([convert: unknown unit])
1C: 115,000 lb ([convert: unknown unit]) 		128,000 lb ([convert: unknown unit]) 142,500 lb ([convert: unknown unit]) 150,000 lb ([convert: unknown unit])
Fuel storage capacity 3,840 imperial gallons (17,500 L)
1C: 4,840 imperial gallons (22,000 L) 		5,440 imperial gallons (24,700 L) 5,774 imperial gallons (26,250 L) 5,440 imperial gallons (24,700 L)
Powerplants 3 × Rolls-Royce Spey RB163-1 Mk505-5 engines 3 × Spey RB163-25 Mk511-5 engines 3 × Spey RB163-25 Mk512-5 engines 3 × Spey RB163-25 Mk512-5 engines
1 × Rolls-Royce RB.162-86 engine
Thrust output 3 × 10,400 lbf (46 kN) 3 × 11,400 lbf (51 kN) 3 × 11,960 lbf (53.2 kN) 3 × 11,960 lbf (53.2 kN)
1 × 5,250 lbf (23.4 kN)
Cruise speed at FL300 Mach 0.86 – approximately 506 kn (937 km/h) Mach 0.84 – about 495 kn (917 km/h)
Service ceiling Approximately 35,000 ft (11,000 m)
Operational range 1,350 miiles nautical miles kilometers[convert: unknown unit]
1C variant: 2,025 miiles nautical miles kilometers[convert: unknown unit] 		2,200 miiles nautical miles kilometers[convert: unknown unit] 2,700 miiles nautical miles kilometers[convert: unknown unit] 2,235 miiles nautical miles kilometers[convert: unknown unit]
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