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Aviation History
1956
1956 - 0917.PDF
FLIGHT, 6 July 1956 63 Airliners of the World TWIN PIONEER SCOTTISH AVIATION, LTD.. PRESTWICK AIRPORT, AYRSHIRE FIRST commercial aircraft to be designed in Scotland, theTwin Pioneer is a larger, twin-engined development of amulti-purpose type widely used for short-field or jungle operations by the Royal Air Force. Scottish Aviation, Ltd., sumup the Twin Pioneer's reason d'etre as follows: — "The basic design philosophy of the Pioneer series of aircraft wasto produce aircraft capable of using unprepared surfaces in restricted spaces, thereby providing the means of extension of services to thoseareas in which it would be either uneconomical to provide the necessary runways for the operation of aircraft with higher take-off and landingspeeds such as are in general use today, or where geographical conditions were such that normal length runway strips are just not possible. Inaddition it was felt that such an aircraft had many potential uses in the military field in the transport of troops and equipment into areas remotefrom points where such troops and equipment would be landed on main airfields by the larger long-range military transports. It was also evidentthat this type of aircraft, capable of using smaller airfields closer in to city centres, could, despite its relatively low cruising speed, consider-ably reduce the city-centre-to-centre times of inter-city services." Airframe. The whole airframe is very simply built up from standardsheet and strip, mainly of 20, 22, or thinner gauge, using mushroom- head rivets. The wing comprises a centre section and two outer panels,all three sections having two spars and closely pitched pressed-sheet ribs. Each outer panel is braced by an extruded, streamline-sectionstrut, and carries powered slats which open when the flaps arc depressed to 12 deg or more. There are four Fowler-type flap portions, runningout to a maximum of 30 deg by a double-acting hydraulic ram, torque- tubes and chain drives. Of basically square section, the fuselage is built in front and rearportions joined at station 158. The multiple-channel half-frames are butt-jointed together along the upper centre line and the keel member;those at stations 185.5 and 249.6 are heavy frames in line with the wing spars. The tail is a conventional all-metal assembly, with inter-changeable outer vertical surfaces. The ailerons are fabric covered, all controls being manual. Electro-Hydraulics supply the three under-carriage units, the main gear having twin wheels on each leg with Dunlop three-cylinder, single-plate hydraulic brakes. Powerplant. Each engine is an Alvis Leonides 503/8 nine-cylinderradial, rated at 540 h.p. They are geared (0.5 : 1) to lift three-blade de Havilland constant-speed airscrews and are installed as complete engine-change units, interchangeable port and starboard. Starting can be by electric motor (which can also act as the feathering pump) or cartridge,and methyl bromide bottles are mounted in both of the two bays in each nacelle. Behind each firewall is a 7-gal magnesium oil tank. Systems. Each engine drives a Newton 1.5 kW D.C. generatorwhich serves a 28-volt system. Electrical equipment includes starter (optional), tank booster pumps, feathering pumps, and the pumpdriving the hydraulic system of the Dunlop wipers. Each engine also drives a Lockheed Mk 7 hydraulic pump which energizes a 2,500 lb/sq in system driving the slats and flaps and also charging an emergency air bottle. Standard tankage comprises four Fireproof Tanks bags between thewing spars, two housing 55 gal and two 30 gal apiece. This total of 170 gal can be increased by the addition of a 30-gal tank in eachouter wing. Interior cabin heating is provided by a new pattern of Delaney Gallay exhaust heat-exchanger, and de-icing (an optional extra)is of the T.K.S. fluid type. Payload Accommodation. The interior is quite unobstructed by anystructural members. The pain door is 62 x 47m and an emergency door is provided on the opposite (starboard) side, supplemented by a thirdemergency hatch in the roof, forward. Interior measurements, aft of the cockpit bulkhead, are 19ft long and 5ft 8in high. The standardpassenger accommodation is for 16 in lightweight seats: five to port and one single and five double seats to starboard. As an ambulance theTwin Pioneer can carry nine stretcher cases, two walking casualties and two attendants, and corresponding loads can be worked out for otherspecialized roles. Projects exist for floatplane versions and for a true freighter, capable of fulfilling important military and commercialrequirements, with large clamshell doors at the rear. Commercial History. The first prototype has now been flying sinceJune 1955 and has logged some 300 hours. On April 24th of this year a second machine (illustrated in the heading picrure)_ flew and otheraircraft are approaching completion. All have been built in production jigs and preparations are in hand for a run of 200 aircraft. The typehas attracted substantial interest in all parts of the world, and quantity deliveries are virtually assured. TWIN PIONEER Two 540 h.p. Alvis Leonids* 503/8 Dimamion*: Span, 76ft 6in; length, 45ft 3in: height. 13ft 8in; wing area, 657 sq ft; vertical tail area, 166 sq ft; horizontal tail area, 161 sq ft. Waightt: Empty, 8,936 Ib; 16-passenger, furnished, 9,376 Ib; operating weight, 10,921 Ib; max. weight, 13.500 Ib. Performance: Take-off (see p. 10), minimum unstick distance, 312-380ft; to 50ft, 1,128-1,170ft; landing, 1,101ft from 50ft with 420ft ground run; w.m. cruise, 141 m.p.h., or 107 m.p.h. for 3.55 a.m./gal. 4.OOO ; 3.OOO < 2,000 1.OOO A B 1OO 2OO 3OO 4OO STAGE DISTANCE In.ml 5OO Payload/range and cost assumptions: cruise at 40 per cent power, i.s.a. at 73,500 Ib, still air at 5,000ft; 100 n.m. diversion+ 15 min + five per cent; S.B.A.C. costs, with A, B and C being annual utilizations of lflOO, 2,000 and 3<000 hours. Payload: upper curves, freighter, lower curves are for 76 seater with toilet; A = 170 gal, B=230 gal. 25 a 2a 2O 15 B A- C • — —.——- —-— 2-O a. o si fSul 1-5 1OO 2OO 3OO 4OO STAGE DISTANCE (st mile) 5OO1O
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