1957 - 1624

7/27/2019 1957 - 1624

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7 1 2  LI HT

  IRLINERS OF THE WORLD

FRIENDSHIP

Royal Netherlands Aircraft Factories Fokker Amsterdam

U.S. Licensees: F airchild Engine and Airplane Corp.

Hagerstown Maryland

 N aworld air transport building industry which is dominated

by afew big firms, it is remarkable that asmall country likeHolland should have come up with atransport as best-selling

as the Fokker F.27 Friendsh ip. Thi s aeroplane has been greatlysought by that most needy, if the poorest, category of air transport—the branchline feeder routes of not very h igh traffic densitywhich are still today largely flown by obsolete DC-3s and C-46s.

The Dutch firm of Fokker does not enjoy abig home marketfor diis type of aircraft (K.L.M. operate adozen DC-3s) but thisfact, frequently bewailed by other European manufacturers, doesnot seem to have handicapped world-wide sales of the Friendship.It was atremendous encouragement to Fokker when, last year,the Fairchild Engine and Airplane Corporation of America tookup alicence to produce the Friendship for the U.S. local serviceairlines. The aircraft may now be considered as ajoint marketingand production effort by the Dutch and American firms, with theBritish industry making asubstantial contribution (amounting tcabout 30 per cent of total aircraft value) in the form of the Rolls-Royce powerplant, Rotol propellers, Dowty undercarriage andcertain systems equipment. Fokker sum upthe case for th eFriend ship as follows: —

 The many twin-engined commercial aircraft of pre-war design,often bought from war surplus dumps, though still faithfullyserving short- and medium-range traffic, do not comply any morewith the present-day requirements of single-engine performance,economy and speed. Take-off and landing performance are nowdictated by stringent rules and regulations. Speed and economyare essentials for aprofitable operation. All these factors havebeen taken into account in the conception and development of theFokker F.27 Friends hip. T o cover the average dem and, standardseating capacity has been fixed to 32 passengers and 4,800 lb ofcargo with facilities for an increase to 36 or 40 passengers, withoutaffecting the basic airframe. T he com bination of a payload of abou tfour tons, arange variety of 300 to 1,000 miles, ahigh cruisingspeed and alew operating cost, make this propeller-turbine air-liner a revenue-earning prop osition which can be called attractive.

IRFR M The fuselage consists of apressurized hull,designed for adifferential pressure of 4.16 lb/ sq in(8,000ft at20,000ft).  large cargo door isincluded on the port forwardside of die fuselage. Extensive use is mad e of Redux b ond ing inthe attachment of stringers to skin. Th e high w ing arrangem entgives the advantage of low fuselage floor level for easy load ing.The wing is of stressed skin construction comprising acentresection carrying the engine nacelles and detachable outer wingsections. The spars are of particular inte rest: the booms arebonded angle laminations, and the change insection isachievedby progressively reducing the number of laminations to combinestrength with lightness and simplicity of construction. Th e outerwing iscovered by amachine-tapered skin over two inboardsections, and integral fuel tanks are located between the front andrear spars. The construction of the tailplane and fin isconven-tional, as are all control surfaces. T he main u ndercarriage is aDowty unit with twin Dunlop wheels incorporating Maxaretbrakes. Tyre pressure is 60 lb/s q in.

SY STE MS Flying Controls Duplicated cockpit controlsare fitted, and the control surfaces are conventionally operatedby cables and p ush-pull ro ds, each surface having a servo-trim tab .A gust-lock lever in the cockpit allows only one engine at atimeto be run to take-off r.p .m. with the flying controls locked. Th eflaps extend from fuselage toailerons, and are of single-slottedcompound type designed byFokker. They extend for almostthree-quarters of the total wing span, and are ab out one-thirdof the wing chord indep th. M axim um lift co-efficient fortake-off is 3.7.

Cabin Air System Th e Friendship ispressurized to amaxi-mum differential  of 4.16 Ib/sq in(8,000ft at 20,000ft). Tw oGodfrey cabin blowers, one driven by each engine, are the sourceof supply. The pressurized air enters through apertures underthe luggage racks and through aseparate duct to the cockpit, andis discharged  via relief valves from an outlet aft of the rear pressurebulkhead. Air conditioning equipm ent includes aturbine-expan-sion cold-air unit located behind the rear pressure bulkhead, andautomatic temperature control to maintain the cabin at 70 deg Fin the lowest outside air temperatures.

Electrical System Th e electrical installation comprises twoseparate systems, (1) a28V D.C. circuit, supplied by one engine-driven generator on each engine charging a24 Vbattery, and,

FOKKER F.27 FRIENDSHIPTwo Rolls-Royce Dart 511 of 1,740   e.p.h. each driving Rotol four-bladed.

12ft propellersDimensions:   Span, 95ft 2in; length, 75ft 9in; height, 27ft 6in; wing area,

754 sq ft ; aspect rat io, 12.Weights:   Operating weight em pty 32 seats), 22,0001b; max. payload,

10,200 Ib 32 passengers, catering and 4,792 Ib of baggage and c arg o); max. zerofuel weight, 32,200 Ib; max. landing weight, 34,000 Ib: max. take-off weioht34,250 Ib. 

Performance  at 33,000 Ib instandard condition*): Take-off balanced fieldlength, sea level, 3.600ft; rate of climb, sea level, 1, 80ft/min: 100ft/min ceiling,34,000ft; cruising speed at 20,000ft, 13,600 r.p.m., 275 m.p.h.; landing field length,sea le vel, 2,90Cft.

* A version wi th D art 528s 1,960 e.h.p.) wit h improved

performance, is offered also.

(2) an A.C. system using 115 V, 400 c/s main and auxiliary in-verters run off norm al aircraft D. C. su pply, and two engine-drivenalternators giving 208 V, 400 c/s.

Pneumatic System Th ere are no hydraulics in the Friendship;pneumatic power was chosen to operate the undercarriage, brakes,and nosewheel steering. The system ispowered by two Dunlopcompressors, one driven by each engine, at 3,000 lb/s q in pressure.All actuators operate at 1,000 lb /s q in . Th e system isdesignedso that each half isindependent inthe event of failure.  Theundercarriage air supply iscontrolled by an electro-pneumaticvalve which has amechanical over-ride to guard against electricalfailure; retraction time is 5 sec. Nosewheel steering is controlledby an infinitely variable valve coupled by lever and cable to thesteering wheel on the left of the instrument panel (duplication forthe first officer is option al). Power supply is cut off at asteeringangle of 58 deg, and the self-centring device in the steering motorensures that the whole assembly is centralized for retraction. Th ewheel-brakes are powered by the main storage system, with a small

supplementary air bottle to maintain full pressure should the mainair bottle pressure be low. Th e brakes are double-plate assemblies,and pneumatic Maxaret anti-skid units are fitted. Parking isachieved by depressing the toe-pedals and pulling alock lever.

An emergency pneumatic system provides power for loweringthe undercarriage and applying the brakes should there be a failurein the duplicated main supply system.