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Aviation History
1950
1950 - 0346.PDF
234 DE HAVILLAND HERON . . . Four main advantages ar* derived from incorporatingmany Dove components in the Heron: (i) It can be pro- duced quickly from existing tooling; (2) the cost of muchnew tooling is avoided, with resultant reduction in the price of the aircraft and spare parts ; (3) components whichare common to both types have been developed through their teething stages in four years of experience; (4) inter-changeability will reduce the stocks of spare parts neces- sary for Dove operators who add Herons to their fleets. The common components are wings, cockpit, main fuse-lage, tail units, controls, services and many internal parts. The Dove wing is, in fact, used intact with the additionof root extensions to carry the inboard Queen 30s. Control surfaces are Dove units, unaltered in the case of theailerons. The fuselage cdmprises Dove cockpit and tail sections between which is an enlarged cabin comprisingextended Dove side panels and keel member, and heightened and lengthened Dove roof member. As with the Dove, the low-wing configuration and shortundercarriage enable the engines and airscrews to be ser- viced from ground level, while, in addition, loading, re-fuelling and general servicing are simplified. A cost price of £35,000 without radio has been settledfor the Heron. The breakdown is as follows: — £.Airframe .. .. .. .. .. 24,700 Complete power units (£2,300 each).. 9,200 Airscrews (£275 each) .. .. .. 1,100 Radio installation 2,200 Total cost.. £37,200 Construction is naturally very similar to that of the Dove (which was originally illustrated in colour and des- cribed in Flight of May 30th, 1946). A brief description of the Heron structure provided by the de HavUland Company (for the first machine is not yet completed nor has examination yet been permitted) is given in the suc- ceeding paragraphs. The fuselage is of a deep oval cross-section constant over the main cabin portion and tapering in plan and elevation to the tail fairing. It is of monocoque construction com- posed of aluminium-alloy skin reinforced with frames and stringers of vee-section sheet. There are three main longerons on each side of the cabin portion of the fuselage ; two above and one below the window line, riveted to the fuselage skin. The main wing pick-up points are located at the fuselage sides. The nose, comprising the cockpit, the forward freight compartment and the nosewheel mounting, is separated from the cabin by a bulkhead which forms part of the main fuselage structure. A second structural bulkhead is located These graphs Indicate (I) variation of payload with stage length ; (2) variation of stage time and speed with length ; (3) direct opera- tion costs and payload with stage length. Breaks in the curves In Fig. I are due to the extra weight of tankage for 300 gallons, and in the curves in Fig. 3 to weight of crew's overnight baggage. TOTAL CABIN CAPACITY 4-7S CU fl 0003003 17 SEATS Alternative seating arrangements for the Heron. Dove-type seats at 32-Inch pitch are used for all the layout. at the rear of the luggage bay. This has a detachable panel which gives access to the rear fuselage for inspection. There are two further structural bulkheads in the rear fuselage which carry the attachment fittings for the tail. The cabin entrance door is on the port side of the fuselage behind the wing, and three emergency exits are in the roof. The floor of the main cabin is of sandwich construction stressed for carrying freight. One panel extends from the luggage bay bulkhead to the centre-section spar and the other from the front bulkhead aft to the centre-section spar. The floor is supported on transverse light-alloy members. Each wing is a cantilever structure of aluminium alloy with an I-section main spar and a built-up light-alloy false spar to carry the flap and aileron. Forward of the main spar, from the fuselage side to the outboard side of the outer engine nacelle, is another false spar to which the engine bearers are attached. The centre-section spar is a built-up box-section member, integral with the fuselage structure. Ribs and spanwise stringers, to which are riveted the skin panels, complete the structure. The lead- ing edge of the extension wing is a preformed light-alloy skin and is detachable. The wing tips are interchangeable. Ailerons and flaps are fabric covered and have light-alloy ribs and sectional spars. The fuel tanks are reached through quickly removable panels on the underside of the wing. Part of the leading edge of each wing hinges up to give access to pipe services, engine controls, and so forth. Both the tailplane and fin are of conventional design, the spars, ribs and skins being of light-alloy. The elevator and rudder are fabric covered. The main units of the undercarriage are easily removable, VOLUMETRIC CAPACITY I &YLOAD ''14R\SS.AT16Slb) O 200 400 600 8OO ipOO STAGE LENGTH: STATUTE MILES 110o "0 ZX> 400 600 8OO1DOO STAGE LENGTH:STATUTE MILES SO 40 30 UTILIZATION 1,000 hrv -(OTHERWISE STANDARD)- 1O °6 ?6O 4OO 6OO 800 1000 STAGE LENGTH: STATUTE MILES
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