Profile – Hawker Siddeley Trident

Some stand out as being successful in service and in the sales race -the Viscount, One-Eleven and HS. 748 spring to mind – but otherwise there has tended to be a litany of “also-rans” when it comes to the hard statistic of the number of aircraft sold. . . the Comet, Vanguard, Britannia, Herald, VC10, Hermes, Ambassador, Brabazon, Princess. . . even the greatest technical achievement of them all, Concorde. But one aircraft stands apart from even this esteemed company. Its rival, Boeing’s ubiquitous 727, became a best-seller with over 1800 built, while it – the origin of the species – ended its life with a mere 117 having rolled off the production line. That aircraft is the Hawker Siddeley Trident.

The Trident’s origins lie in a July 1956 British European Airways requirement for a short-haul jet to compliment the airline’s Vickers Vanguard turboprops then on order. De Havilland came up with the DH. 119 as its first proposal, an aircraft powered by four Rolls-Royce Avons. The DH. 120 design then followed an attempt to fill both BEA’s and BOAC’s requirements with one aircraft, BOAC naturally looking for a long-haul aeroplane. This specification was eventually met by the VC10, and de Havilland reconcentrated its efforts on an aircraft designed specifically for BEA and called the DH. 121.

This design became one of the three leading contenders for the order, its rivals being the Bristol 200 and Avro 740. All were advanced trijets designed to cruise at the then-high speed of 600 mph (966 km/h) and all were larger than the aircraft which eventually emerged.

Political interference crept into the Trident’s history in 1957 when it was announced that whichever manufacturer won the competition would have to merge with another company. To meet this requirement, de Havilland set up the Airco consortium with Fairey and Hunting to produce the DH. 121, for which BEA placed a preliminary order for 24 in February 1958. This consortium (which was a paper operation, anyway) only lasted until 1959 when de Havilland became part of Hawker Siddeley and Hunting disappeared into the British Aircraft Corporation.

At this stage the DH. 121 was a 111-seater with a 2070 mis (3331 km) range powered by three Rolls-Royce RB. 141/3 Medway engines of 13,790 lb (6255 kg) thrust each, a specification remarkably similar to that which Boeing produced for its 727 a couple of years later.

In fact Britain’s lead over the USA in the short-medium haul airliner field at this stage was quite substantial, as the major American manufacturers had been concentrating on the long-haul market with the Boeing 707 and Douglas DC-8, while Lockheed had committed a tactical error by ignoring the jet market entirely and building the medium-range turboprop Electra. But this important and unexpected chance to grab the lion’s share of that huge market over the next two decades disappeared from sight when, in March 1959, the BEA board did an about-face on the specification of their new airliner and asked de Havilland to build them a smaller, shorter range, less powerful version tailored precisely to BEA’s short, intercity Western European routes.

This immediately cut out any chance of the DH. 121 capturing any large proportion of the potential world market for two reasons. Firstly, the world wanted a jet closer to the original, larger specification – just ask a Boeing salesman of the time – and secondly, it further delayed the already lagging (thanks to the Airco merger waste of time) project and allowed the Americans to make up for time. If Boeing was five years behind when the BEA specification was first issued in 1956, they were just over twelve months behind by the time the first DH. 121 took to the air. . . and they had an aeroplane which the world’s airlines wanted.

The tragedy of the DH. 121’s emasculation reached further than just the airframe design. The RB. 141 engine was also lost, an engine which would have been a direct competitor to Pratt & Whitney’s JT8D, the engine which finally powered literally thousands of 727s, 737s, DC-9s and other airliners. Even BEA cannot be blamed entirely for the commercial fiasco that followed, as de Havilland’s Board couldn’t find sufficient strength to follow their instincts and fight the decision to reduce the 121’s specification. In addition, the company’s marketing teams were instructed to cease discussions with potential export customers until BEA decided exactly what they wanted.

As in all tragedies, there was a touch of the ironic in the 121’s history, too. Almost as soon as the aircraft entered service, the principal culprit, BEA, began demanding higher-capacity and longer-range versions!

With the dissolution of the Airco group in 1959 and the incorporation of de Havilland into the Hawker Siddeley organisation, the 121 was named Trident, and 24 of them were on order for BEA. Production was put in hand immediately against the BEA launch order and there was no prototype as such. The first Trident to fly was also the first for its so far only customer.

The name Trident was particularly appropriate. It not only referred to the three-engined configuration but also to the aircraft’s systems. The hydraulic system was in triplicate with a system connected to each of the three engines, thus ensuring continuity of supply, even with an engine out. When it appeared, the Trident was a very advanced aircraft and was the first airliner designed from the start to operate in very low weather minima. Smiths Autoland was the automatic landing system incorporated, and within one year of entering service, BEA’s aircraft were permitted to make Autoflare landings, a year later full Autoland capability was approved and then Category 2 and later full value Category 3B automatic landings were allowed. The Autoland operated the flying controls via the triplexed hydraulic system, thus ensuring blind landing capability even with an inoperative engine.

Rolls Royce came up with the 9850 lb (4468 kg) RB. 163 Spey 505 engine to power the now-103 seater aircraft with its six abreast cabin, although BEA’s standard configuration was for 88 passengers. With a maximum take-off weight of 115,000 lb (52,164 kg), the aircraft’s payload/range flexibility was limited and all efforts would soon be directed to improving this substantially.

The Trident featured some other items of interest, like the sideways-retracting, offset-to-port nosewheel, the swivelling on retraction single axle four-wheel main undercarriage, noise suppressing (by early 1960s standards!) jet pipes, thrust reversers on the outer engines and 35 degree swept wing with drooped leading edges and double-slotted flaps.

The first Trident 1 C (as BEA’s version was designated), GARPA, made its maiden flight on January 9, 1962. The type made its first revenue flight for BEA on March 11, 1964 and entered full service on the airline’s European routes on April Fool’s Day of the same year.

The maker’s market research had indicated a need for some 550 aircraft of the Trident’s type by the end of 1965 – another factor that makes the readiness with which they submitted to BEA’s demands even more difficult to understand – but it was obvious that the aircraft’s specification would have to be substantially improved to even get a toe in the door of that market.

ROOM FOR IMPROVEMENT – 1

As a result of further design work, the first improved Trident, the 1E, was offered to the airlines. Several fundamental improvements were required: increased payload/range, greater passenger capacity, better hot-and-high performance and greater range. . . in other words, an aircraft that matched the Boeing 727. The basis for the new variant was the Rolls-Royce Spey 511 engine of 11,400 lb (5171 kg) thrust, an engine developed originally for the BAC One-Eleven.

The increased thrust coupled with a longer span wing (with leading edge slats) allowed an increase in maximum take-off weight to 134,000 lb (60,782 kg), while the revised wing also allowed fuel capacity to be increased from 3800 gallons (17,275 litres) to 6000 gals (27,276 1). The same fuselage length as the Trident 1 C was retained, but clever rearranging of the interior and installation of an extra emergency exit allowed up to 139 passengers to be squeezed in, although 115 was a more normal (and comfortable) configuration.

Where the Trident 1Cs range with maximum payload was just under 1000 miles (1600 km), the 1 E could nearly double that, while the maximum fuel range increased by 50 per cent for only a slight drop in payload.

The first Trident 1 E flew in November 1964 (nine months after the Boeing 727 entered service), and began operations with Iraqi Airways on October 1, 1965. What was once a substantial time advantage over the main rival had become a distinct disadvantage.

Only 15 Trident 1 Es were sold, three to Iraqi Airways (delivered from October 1965), four to Pakistan International (from March 1966), three to Kuwait Airways (from March 1966), two to BKS, two to Channel Island Airways and one to Air Ceylon. All were delivered by mid-1968, by which time the Boeing 727 order book stood at around 700, the high-capacity 727-200 was established in service, the economically very attractive Advanced 727 was being planned and the next Trident, the vastly better but too late 2E, had just begun operations with BEA.

ROOM FOR IMPROVEMENT – 2

Hawker Siddeley’s planned successor to the Trident 1 E was a greatly stretched derivative designated the 1F, but instead the type evolved into the rather less radical 2E for BEA. The Trident 2E (called simply Trident Two by BEA) featured the same fuselage as the earlier models with 115 the normal passenger complement (although a further internal rearrangement allowed for up to _ 149 at a pinch), but detail structural and design changes made this mark the most attractive of the lot so far. Available power was increased by the installation of 11,960 lb (5425 kg) thrust Spey 512 engines, the maximum take-off weight went up to 143,500 lb (65,090 kg) and the fuel capacity increased to 6400 gallons (29,094 litres) by virtue of an integral tank in the fin.

A further range improvement came about thanks to a substantial aerodynamic clean-up, and the maximum payload range was now Just under 2500 miles (4023 km) with reserves, while the maximum fuel range exceeded 3000 miles (4828 km) with 100 passengers and their baggage. Structurally, the 2E differed from its predecessors by having a further increase 1n wing span, strengthened wing, the fin fuel tank mentioned above and some weight saving by using titanium instead of steel in certain areas. BEA was the launch customer for the 2E, ordering 15 in 1965

of yet another Trident variant tailored expressly to their needs, although it appeared their needs had changed completely in only one year since the original Trident 1Cs had entered service! If you think the Trident’s sales teams and designers may have proffered the odd wry grin at this time, you’d probably be right. . . The first 2E flew on July 27, 1967 and the type entered service with BEA during April of the following year. As it turned out, this Trident variant was the most successful of all in the export stakes, with 35 being sold to two overseas customers. Cyprus Airways took two, while The Peoples Republic of China’s airline, CAAC, entered the scene in 1971 with a substantial order that kept the Trident line alive for several more years and in fact made the 2E the last of the Tridents to come off the production line, despite the advent in 1969 of the stretched 3B.

CAAC ordered no fewer than 33 Trident 2Es in several batches following experience with four ex-Pakistan International 1Es, the first order being placed in 1971 and the last at the end of 1974. The first Chinese delivery was affected in November 1972, and the last 117th and final Trident built-was first flown on April 17, 1978 and delivered in June.

FOUR-PRONGED TRIDENT

The final Trident variant to enter production was the stretched and four-engined 3B. Built to another BEA specification for an aircraft suitable for high-density routes, the main problem facing the designers was that of the powerplants. Any existing or planned version of the Spey would not be powerful enough to propel this much larger and heavier Trident, and a change of engines was not considered economically viable.

After a lengthy series of design studies, Hawker Siddeley came up with the idea of retaining the three main engines of the 2E (Spey 512s) but adding a fourth, smaller engine for use as a booster during the take-off and initial climb phases of flight. The engine chosen was the Rolls-Royce RB. 162-86, a unit designed for V/STOL applications with a favourable thrust/weight ratio. It produced 5250 lb (2381 kg) of thrust, was already flying in the Dornier Do31 experimental V/STOL transport and was mounted fairly easily in the Trident’s tail immediately above the fuselage.

Although a direct evolution of the Trident 2E, the 3B featured many detail changes, apart from the obvious 16 ft 5 in _ (5. 01 m) fuselage stretch, the increase in passenger accomodat1on up to a maximum of 180 (with 130 to 140 the norm) and the fourth engine.

Maximum take-off weight increased again to 150,000 lb (68,040 kg), the structure was strengthened, flap and lift dumper areas increased, wing incidence increased and the fuel capacity was reduced to 5620 gallons (25,548 litres) due to the deletion of the fin and centre-section extension tanks. Although the wing span remained the same as the 2E, the wing area increased slightly due to the fitting of a full-span trailing-edge chord extension.

Optimised for high-density short-haul routes, the 3B could carry its maximum payload over 1100 miles (1771 km) with full reserves and a normal load of 128 passengers over 1600 miles (2575 km).

The first of BEA’s 26 aircraft made its maiden flight on December 11, 1969 and the mark entered service on – yet again – April Fool’s Day, 1971.

The Trident 3 carried on the autoland tradition of the earlier marks but took its capability to the ‘nth’ degree, being certified to carry out autoland operations down to a 12 feet decision height and 885 feet (269. 7 m) runway visual range. Full Category 3A take-offs were also permitted with an RVR of 295 feet (90 metres). BEA began operations to these standards in May 1973.

Despite being virtually a match for the Boeing 727 by now, the Trident 3B was simply too late to share in the massive market captured by Boeing’s best-seller, for by the time it appeared, there was simply no market left for the biggest Trident. Boeing, of course, reaped many hundreds of repeat orders for the 727 over the next decade, while the Trident 3B’s only exports were two to CAAC, ordered in 1972 and delivered in 1975. These aircraft were designated Trident Super 3B, and although externally identical to BEA’s aircraft they featured higher weights and slightly increased fuel capacity. In CAAC service they normally accommodate 152 passengers.

Further Trident variants were mooted in the mid-1970s, as were more orders-notably from North Korea, an idea which fell through due to the lack of suitable financial terms being arranged – and extra aircraft for CAAC. Interestingly, Hawker Siddeley announced in 1976 they were no longer even attempting to market the aircraft in the West.

Two paper Tridents at one time investigated by Hawker Siddeley were the further stretched Marks 4 and 5 with refined Speys and a new engine in the ten-tonne class, respectively. Neither progressed beyond the designer’s preliminary sketches.

Although it was reasonably trouble-free and popular 1n service, commercially the Trident was always behind the eight ball. The moment BEA reduced the initial model’s specification it was all certain over and Seattle’s there boardroom must have at been the same time, because gleeful! hand-rubbing that decision in not only gave Boeing some time to catch up but also allowed them _ to build the aeroplane the world’s airlines actually wanted, and build it without any competition. By the time the Trident was the right aircraft for the airlines, it was too late.

BENBritish Airways began breaking up their early Tridents in the mid-1970s and their service with the airline will formally end on December 31 this year, noise restrictions finally seeing the end of them. BA had actually scheduled to dispose of most of their remaining fleet a year ago, but increased traffic demands gave them a temporary reprieve.

The only major operational problem to face the Trident during its career was the discovery of wing cracks in 1977, this grounded a large proportion of BEA’s fleet at a given time over a two-year period while extensive modifications were performed. The modifications entailed remanufacturing the outer wing in a way which imposed lower stresses than the efficient Kuchemann tips as originally installed on Trident 2s and 3s.

At the time of writing their seemed to be little future for the surviving Tridents, although some of British Airways’ fleet will be saved from complete extinction thanks to Zaire-based freight operator, Air Charter Services, who have signed for four aircraft. Also, CAAC is looking at taking some of BA’s Trident 3s for short term use as transports and then as a source of spares for its existing aircraft.