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Aviation History
1956
1956 - 0892.PDF
36 FLIGHT Airliners of the World ACCOUNTA AVIATION TRADERS (ENGINEERING). LTD., LONDON, W.I. Standard Mk. 1 Accountant thawing forward-facing teats and inward-facing settee Drawn at Southmnd, June 19S6 FUSELAGE PRESSURIZED TO 5.5 Ib/sq in EMERGENCY CREW-EXIT RADIO STOWAGE ELECTRICS EMERGENCY EXITS RADIO REMOTE- CONTROL PANEL \ DIRECT-VISION WINDOW ROLLS-ROYCE DART 512 TURBOPROP WITH PETAL TYPE COWLINGROTOL 4-BLADED10ft dia AIRSCREW REARWARD-RETRACTING NOSEWHEEL STEERABLE, FULLY CASTORING (HALF WHEEL PROTRUDES) UNDER-WING PRESSURE RE-FUELLING POINT FORWARD-RETRACTING DOWTY UNDERCARRIAGE IT was felt by Aviation Traders that, due to the diversity ofroles undertaken by the DC-3, operators' requirements wouldbe widely divergent, to such an extent that no real conclusion could be drawn from them as to the actual specification for a replacement aircraft. The company, with its considerable oper- ating experience, felt that it was in a good position to produce the type of aircraft most likely to fulfil the various needs of prospective operators. Careful consideration had to be given to the obvious features whichhad to be retained in a successful replacement aircraft: (1) dependability and versatility; (2) a rugged structure of long life; (3) ability to loadfreight readily into some 1,300 cu ft of cabin space; (4) low purchase price and running costs; (5) ability to operate from short, poorlysurfaced strips. With sensible design, all these features (except price) could, it wasfelt, be reproduced in a new design, together with a great many additional advantages, including a higher standard of safety. The Aviation Traders design philosophy, accordingly, was to pro-duce an aircraft based on the following criteria. Size and weight would be substantially similar to the DC-3. Rolls-Royce Dart turbines would be used with standard accessories and equip- ment. (The wisdom of this early decision, with Viscounts now orderedby more than 30 airlines, became strongly apparent.) The airframe must be simple and rugged, designed on "fail-safe" principles to ensurelong life. The aircraft must be flexible in operation, capable of accom- modating a satisfactory payload over short distances, and provisionmust be made for sufficient fuel for stage lengths up to 2,000 miles. Considerable impovements in overall performance must be providedover a wider range of payload and stage-length in any condition of temperature and altitude. The aircraft must be designed to enableincreasing engine powers to be easily accommodated. In particular, the interior layout must be designed from the start to permit the greatest possible variation of operational role. The Account-ant can in fact be supplied with or without nose cargo-doors for, respectively, all-freight or all-passenger work; the interior lends itselfwell to mixed cargo-passenger operations, and furthermore has singular appeal in an executive role from the points of view of size and comfort. The Accountant is offered in Mk. 1 or Mk. 2 form. The Mk. 1 isnormally supplied in the bare condition to enable operators to equip the aircraft to their specific requirements. The Mk. 2 can be suppliedwith the hinging nose or the forward freight-loading door as required. This version is 10ft longer than the Mk. 1, having a cabin volume of1,698 cu ft compared with 1,275 cu ft. There is no significant differ- ence in performance between the two marks. Design work on theforegoing principles has now been virtually completed, and construc- tion is well advanced, toward a prototype first-flight at the end of thisyear. AIRFRAME. A structural break-down is employed which assiststhe sub-contracting of major components. The simple form of jigging required by the Heal method of construction, which provides a modestdegree of tension up to 5,000 lb/sq in, confers numerous benefits to construction and appearance. The problem of fatigue has been given primary consideration in thedesign of the Accountant's airframe. It was realized from the very beginning that if the aircraft was to have the economic life expected ofa DC-3 replacement, great care must be exercised in. the design of the pressure cabin, wing and control surfaces. A design policy of "fail-safe" on all components was adopted, the aim being that, should fatigue troubles start, they would remain localized and be readily found atnormal inspections, and repaired in the usual manner. The following points about airframe design are worth noting. The general membrane stresses of the pressure cabin have been keptdown to about 12,000 Ib/sq in, and attention has been paid to the design of the closely spaced radial formers to ensure continuity and freedomfrom notch effects. A minimum factor of 3.0 has been applied to
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