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Aviation History
1964
1964 - 1648.PDF
FUOHT 901 International, 28 May 1964 IOO 2OO 3OO STAGE LENGTH (st miles) 4OO 5OO Direct operating cost (SBAC method). Assumptions:— Equipped airframe cost including radio, £89,850; bare engine cost (each), £7,525; maintenance labour per man-hour, £0.35; fuel cost per Imp gal, £0.094; landing fee up to 288 st miles, £1.25; over 288 st miles, £2.5; aircraft insurance, 5%; interest on investment, 4%; depreciation period, eight years; residual value, 10%; airframe spares holding, 10%; engine spares holding, 60%. 5.000 4.O IOO 2OO 3OO 400RANGE (st miles) 5OO BOO TOO Payloadlrange performance, ISA. Curve A, 4Smin holding at 5,000ft, plus ISO st miles diversion or return to base. B, 4Smin holding at 5,000ft. C, equivalent still-air range TURBO-SKYVAN ... half wing to the lower stub-wings. In view of the excellent skin finish possible with the corrugated stiffening, it was decided to use a laminar-flow profile. Eventually a NASA 63A section was chosen, and modified slightly to provide more internal space for flaps and control mechanisms by increasing thickness towards the trailing edge. The wing section and chord are constant from tip to tip, and there is no twist. Structurally the wing is a two-cell box, bounded by the leading- edge spar, rear spar and top and bottom skins, and divided internally by the main spar. The spars form shear webs only, bending being resisted entirely by the light-gauge stiffened skins. Torsional stiff- ness is provided by pressed-alloy, reinforced ribs spaced approxi- mately every 14in. At points of concentrated load, such as the engine mountings and flap-hinge pick-ups, the ribs are duplicated and reinforced. Each half-wing carries three single-slotted flaps the outermost of which acts also as an aileron and has two-fifths the angular flap movement of the two inboard surfaces. Empennage A twin-fin configuration was chosen to give maxi- mum rudder effectiveness by positioning the fins in the propeller slipstreams. An additional advantage of this layout is that fin and rudder loads do not impose heavy torsion on the fuselage, an im- portant factor with the Skyvan's large rear opening. The tailplane is made in two halves, and is attached by four bolts to the frame in the upper corner of the rear fuselage to which the rear door is hinged. The fins are bolted on to the ends of the tail- planes, and single-piece rudders are fitted above the tailplane level. The elevator is in three segments, the central one of which carries a movable fairing to align with the fuselage. Empennage com- ponents are constructed on conventional principles using light- alloy skins and pressed ribs. Powerplant The prototype Turbo-Skyvan is now flying with Turbomeca Astazou II engines delivering 520 s.h.p., but production aircraft will have the more powerful Astazou X of 632 s.h.p. The powerplant installation has been designed by SFERMA as a self-contained assembly to form a convenient engine-change unit. It is attached to the wing by four bolts passing through mating fittings on the wing anti on the welded-tube engine mounting structure. All marks of Astazou are constant-speed units running at a gov- erned speed of 43,000 r.p.m. The power output is controlled by adjustments to the propeller which are effected by the pilot through Ws pitch (throttle) levers, arrangements being incorporated to fine the pitch automatically to prevent excessive torque demands on the engine and to coarsen the pitch into feather in the event of engine failure. The Astazou's three-bladed electrically controlled, featheringand reversing propeller is by Ratier-Figeac, and in order to save height the propeller hub forms part of the reduction-gear assembly, tach blade is a machined duralumin forging detachable from thenu o. Blades and spinner are de-iced electrically. Flight Deck As to be expected in an aircraft of this type, the flight deck has been designed for solo operation, although provision is made for rapid conversion to dual control for pilot conversion. Particular care has been taken to give the pilot a good all-round view, and the broad panel has a convenient layout of instruments and controls. Fuel cocks and emergency propeller-feathering controls are located centrally in the roof, but the propeller-pitch levers and the auto- matic full-power selector have been moved from the roof (where they were on the prototype) to the central console. Systems Power for brakes and flaps is provided by an electrically driven hydraulic power pack, located forward of the flight deck where it is readily accessible through the hinging nose. A conventional electrical system provides power for radio and lighting and other minor services. A hot-air bleed from both engines is mixed with cold air from a single intake and circulated from a central overhead duct to various points in the flight deck for heating and window de- frosting. An extension of this duct supplies warm air to the freight hold. Development and Prospects For four painful years development of the aircraft was slowed almost to a halt by the inability of Short's financial resources to give the Turbo-Skyvan the impetus it deserved—coupled with re- fusal of the Government's Transport Aircraft Requirements Com- mittee to come to a decision on whether or not to allow the com- pany to apply to the project any of the £10m voted to assist them finance the Belfast programme (Short & Harland are 69 J% owned by the Ministry of Aviation, and so are hardly their own masters). Finally the MoA agreed last February that the project could go ahead, and work has now started on the first production batch. Impotent to do anything but listen to good friends like Mr Sigurd Wien and Mr Reg Ansett saying they'd "buy Skyvans to- morrow," the delay has nowhere been more frustrating than in Bel- fast. As previously noted, the prototype, G-ASCN, has flown over lOOhr since conversion to Astazou power. Flight development has proceeded satisfactorily to the point where a special category C of A was awarded in mid-April 1964 to permit demonstrations to poten- tial customers. The first overseas journey and demonstration was to the Hanover Air Show at the end of April. « The prototype was recently fitted with power braking, and is now undergoing airfield-performance-measurement trials. These will soon be followed by a visit to the Turbomeca works at Pau for engine/airframe matching trials and measurement of airfield per- formance at high temperatures. In recent months a sales team led by the company's technical sales manager, Mr Douglas Scoff ham, has visited a number of firmly interested operators in Alaska, Australia, New Zealand, and the Philippines. Although the first orders have yet to be signed, this event cannot be long removed now that firm plans for production have been laid. Deliveries are scheduled to begin early in 1966.
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