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Aviation History
1963
1963 - 0667.PDF
SERVICE DOOR GALLEY COATS AND STOWAGE EMERGENCY EXITS TOILET PASSENGER DOOR ;A__E • PASSENGER DOOR iALLEY EMERGENCY EXITS Typical interior section with ten TOILET layout for the Trident IE, with seating for 85 passengers mixed-class. Behind the flight deck (standard m all versions) is a first-class seats four-abreast at 40in pitch; then follow 75 tourist seats at 34in. Broken lines indicate open positions of upward-sliding doors flight. Tankage has been extended to fill the whole inter-spar box, and the inboard end of the ailerons has been moved 18in nearer to the wing tips to permit a similar increase in the span of the outer flaps. The triple aileron jacks are retained at the same station as in present aircraft, but drive the surface 18in nearer its inner end. The IE, and the proposed IF described in the next section (Accom modation), is the subject of the ensuing description. Where the 1C differs significantly, details are given. Accommodation Choosing the body cross-section is always one of the more difficult compromises in the design of a new airliner. BEA's original specification still left much room for manoeuvre, and de Havilland spent many months on alternative schemes before deciding to use a simple circle. The only real disadvantage of this shape is that the floor is placed relatively higher than in a double- bubble, so that there is more tumblehome and a lower ceiling. It also* tends to restrict the depth of the underfloor cargo holds. On the other hand, the differences are unimportant: for example, at shoulder level the difference in cabin width is equivalent to 0.5in per passenger in the tourist-class configuration, and half this at arm-rest height. After weighing the matter with many airlines, de Havilland decided that the reduced weight and drag—and hence reduced operating cost—of the circular section could be reconciled with comfortable six-abreast seating, the flight time being relatively short, and with an adequate hold capacity. Internal length between the rear of the flight deck and the rear pressure bulkhead is approximately 65ft to port and 67ft to star board; in the projected Trident IF this is increased by 9ft 3in Width across the interior trim at floor level is 129|in (the same as in the large jets), and maximum interior width is 135£in. Aisle height is 79.6in. Numerous variations of interior layout are possible. In the Trident 1C the galley may be located beside the rear passenger door, to port, or at either of two positions on the starboard side (or at both), served by 48in by 24in doors which also act as emergency exits. In the IE the rear service door is deleted, and in the IF it is moved right aft. There are no structural bulkheads, and any part of the floor may be used for four-, five- or six-abreast seating. After discussing with their original customer the merits of a ventral rear stairway, de Havilland decided against such a feature, which would have incurred a 6001b weight penalty and been of doubtful advantage. (It is also the author's view that passengers tend in emergency to leave the aircraft by the way they entered, and rear stairs cannot be used after ditching or belly landing.) Instead the Trident has two passenger doors on the port side ahead of the wing; this arrangement keeps coaches clear of the busy rear of the aircraft, is compatible with jetways (extending walkway tubes) and enables all passengers to use a single coach without walking more than a few feet. Doors are opened by pulling in and sliding up inside the trim. In the Trident 1C the doors open inwards on hinged links. The projected IF has an arrangement similar to that of the IE. The forward passenger door is directly above the transverse nose-undercarriage bay, and at customer preference airstairs can be installed in the upper part of this bay. The lightweight all-metal stairs are extended horizontally by an electric actuator which may be run off the aircraft batteries (with emergency manual override). As the stairs begin to hinge down, the lower portion and handrails unfold and finally two wheels at the end rest on the ground. The nose-undercarriage bay is not pressurized, and the airstairs door opens outwards. Emergency exit is possible through the two doors to port, the two service doors (one in the IE) to starboard, and through two Class 3 emergency exits on each side above the wings (one per side in the 1C). Crew exit may be through either forward door or, via ropes attached to roof fittings, through the d.v. windows. Drop-out crew and passenger oxygen masks are served by two 2,100-litre bottles, and there are various portable bottles. There are comprehensive fire warning and extinguishing systems. Freight is carried beneath the floor in two compartments, one in front of and the other behind the wing. The forward hold is the larger, with a constant width of 81.9in and constant depth of 42.Sin, served by a plug-type door on the starboard side, 48in wide by 35in high and with sill 54in from the ground. Total hold volume of the 1C and IE aircraft can be up to 740 cu ft (dependent on the aircraft loading), and of the IF up to 950 cu ft. The forward part of the front hold can be ventilated for livestock. Great attention is being paid to achieving a low cabin noise level. The cabin styling of the Trident 1 has been carried out to BEA's requirements. Styling of the IE and IF is being designed by Charles Butler Associates, who are very well known for their airliner interiors. Structure It is doubtful that any other manufacturer in the world has as much hard-won knowledge of jet-transport structures as de Havil land Aircraft, and every bit of this knowledge is needed for an air liner intended to fly short stages in dense air at very high speed for 20 years or more. It is de Havilland's aim to demonstrate by test a mean life of 60,000hr (40,000 1 ihr flights) on all primary structure without any crack developing. Allowing for scatter, this would make it very unlikely that any aircraft in a fleet would develop a crack before 30,000hr. Testing will be continued for a further 30,000hr (20,000 1 ihr flights) to cover the fail-safe aspect of the design. This applies to the whole of the primary structure, where the redundant load-paths provided ensure that, after a crack has devel oped, the remaining structure can bear at least proof loads for a period greater than the maximum interval which could elapse between inspection of the part. Where such fail-safe design is impossible without unacceptable penalties, de Havilland are going on to show a safe life far in excess of anything which any aircraft could reasonably accomplish. Examples of such areas, together with the target life of the test specimen, are as follows: engine mountings, 180,000 l^hr flights, testing completed; nose landing gear, 120,000, 50 per cent complete; main landing gear 120,000, 40 per cent complete; and the main tailplane pivot fitting, 1,680,000 flights, complete. In de Havilland's view the truest demonstration of the way in which an airframe will stand up to service is provided by the use of a single specimen, made exactly like any other production airframe, for both fatigue and static-strength tests, switching from one type of test to the other at carefully chosen points. This ensures both that static tests do not have a favourable effect on the fatigue performance and that the airframe preserves adequate static strength in the later stages of its service life, i.e. between 30,000 and 60,000hr. Testing has been carried out with a nose fuselage, main fuselage and complete wing, rear fuselage and fin, and tail- plane. The three body sections all overlap. Testing has been according to the following programme: (1) stiff ness (resonance, and some stiffness, was also carried out on the first flight aircraft); (2) static to 50 per cent ultimate, to clear the first two flight aircraft; (3) fatigue to 10,000 lpr flights, including simulated taxying, landing and gust loads and cabin-pressure reversals; and (4) static to proof of 66 per cent ultimate. These four tests suffice for a Certificate of Airworthiness. The programme then includes: (5) further fatigue to 40,000 l£hr flights; (6) static beyond proof, to at least 75 per cent in all cases; (7) fail-safe testing,
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