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Aviation History
1956
1956 - 0904.PDF
48 FLIGHT, 6 July 1956 , Airliners of the World FRIENDSHIP Fokker F.27 Friendship as specified by K.L.M. and Aer Linaus. Drawn at Amsterdam May 19S5, revised June 1956. incorporates radio control, engine starters and relight buttons, andelectrical switches. Layout of the flight deck was developed in close association withK.L.M., and appears to provide uncommon comfort, visibility and headroom. Flying Controls. Duplicated cockpit controls are fitted, and thecontrol surfaces are conventionally operated by cables and push-pull rods, each surface having a servo-trim tab. A gust-lock lever in thecockpit allows only one engine at a time to be run to take-off r.p.m. with the flying controls locked. The flaps extend from fuselage toailerons, and are of double-slotted compound type designed by Fokker. They extend for almost three-quarters of the total wing span, andare about one-third of the wing chord in depth. Maximum hit co- efficient for take-off is 3.7. Cabin Air System. The Friendship is pressurized to a maximumdifferential of 4.16 Ib/sq in (8,000ft at 20,000ft). Two Godfrey cabin blowers, one driven by each engine, are the source of supply. Thepressurized air enters through apertures under the luggage racks and through a separate duct to the cockpit, and is discharged via reliefvalves from an outlet aft of the rear pressure bulkhead. Air condition- ing equipment includes a turbine-expansion cold-air unit located behindthe rear pressure bulkhead, and automatic temperature control to main- tain the cabin at 70 deg F in the lowest outside air temperatures. Electrical System. The electrical installation comprises two separatesystems, (1) a 28 volt D.C. circuit, supplied by one engine-driven generator on each engine charging a 24 volt battery, and, (2) an A.C.system using 115 volt, 400-cycle main and auxiliary inverters run off normal aircraft D.C. supply, and two engine-driven alternators giving208 volts, 400 cycles. Pneumatic System. There are no hydraulics in the Friendship;pneumatic power was chosen to operate the undercarriage, brakes, and nosewheel steering. The system is powered by two Dunlop com-pressors, one driven by each engine, at 3,000 lb/sq in storage pressure. All actuators operate at 1,000 lb/sq in. The system is designed so thateach half is independent in the event of failure. The undercarriage air supply is controlled by an electro-pneumaticvalve which has a mechanical over-ride to guard against electrical failure; retraction time is 5 sec. Nose-wheel steering is controlled_byan infinitely variable valve coupled by lever and cable to the steering wheel on the left of the instrument panel (duplication for the firstofficer is optional). Power supply is cut off at a steering angle of 58 deg, and the self-centring device in the steering motor ensures thatthe whole assembly is centralized for retraction. The wheel-brakes are powered by the main storage system, with a small supplementary
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