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Aviation History
1968
1968 - 0695.PDF
fLIGHT International, 2 May I96S 669 IN THE AIR By Neil Harrison: Number 230 of this series SPORTAVIA FOURNIER RF-4D (One 39 h.p. Rectimo AR 1,200 VW, 52in dia two-blade fixed-pitch Hoffman wooden propeller) Dimensions Span, 37ft; length, 19ft lOin; height, 5ft 2 in; wing area, 122 sq ft. Fuel Capacity, 8.4 Imp gal; octane, 80/87. Weights Gross (normal) 8601b; gross (aerobatic, +4.4g and — 1.8g), 8161b; typical basic empty, 5951b; wing loading, 7.11b sq ft; power loading, 22lb/h.p. Performance (handbook figures at gross weight, see text for observed performance): Take-off to 50ft (ISA, s.l., still air), 885ft; rate of climb, 690ft/min at sea level; service ceiling (powered flight) 19,000ft; gliding ratio (prop stopped), 20: I at 240ft/min; max cruise TAS/fuel consumption, 110 m.p.h./ 2.12 Imp gal/hr; landing distance from 50ft, 755ft. Airspeed limitations Never exceed speed (Vne), 155 m.p.h. IAS; (Vno), 130 m.p.h.; manceuvring speed (Va), 124 m.p.h. IAS; spoiler extension, 130 m.p.h.; gear lowering speed, 66 m.p.h. (spoilers and wheel cleaned for flight to Vne)- Engine limitations take-off and Smin con- tinuous, 3,600 r.p.m.; maximum continuous, 3,400 r.p.m. FOURNIER RF-4D THE IDEA WAS that I would just whistle the Fournier RF-4Daround for air-to-air photography, gather impressions ofthe new ailerons, and then back down again. After all, we had reported on the otherwise almost identical version of this French-designed, German-made powered sailplane in some de- tail before (RF-3, In the Air No 215, Flight, October 27, 1966). But it didn't work out quite like that. I became so enchanted by the superb handling and changed characteristics of the air- craft that I just didn't want to come down. It is almost un- believable how the switch from plain to Frise ailerons of iden- tical size has so completely transformed the appeal of this avion-planeur. The other important thing is that the airframe has been beefed up and tested to qualify for a fully aerobatic category Certificate of Airworthiness. The RF-3 has been well received in Britain and prospects must be very bright indeed for the RF-4D. It is a sporting machine par excellence, and should really be treated as such. Though it has extraordinarily good cruising efficiency and it might seem right to recommend it for touring, unfortunately the undercarriage arrangement is such that, for manceuvring on the ground, wing-tip helpers are usually needed even in moder- ately windy conditions—and that could be an embarrassment away from base. Anyway, in a club or syndicate there wall surely always be a terrific queue of people eager to get up and go soaring among the cu-nims with the engine off, or wheeling around doing the especially graceful ae'robatics characteristic of this beautiful aeroplane. To me this is one of the few aircraft in which everything feels just right. You sit in a nicely relaxed position, fairly well back from the large, clear instruments, with a generous canopy over your head and, below, a slenderly tapered wdng that is so obviously efficient. The substantial all-wooden airframe absorbs practically all the vibration of the Rectimo-VW 1,200 c.c. engine, and the noise level is quite low. The high aspect-ratio and slightly flexible wing give a smooth ride on days when other ultra-lights are being tossed all over the place. But it is the sheer harmony, smoothness and response of control that really delights. Whereas the heaviness of the plain ailerons on the RF-3 had positively discouraged rolling and made one con- scious of the unusually large span for so light an aeroplane, one is now just as eager to barrel roll as to loop—and the wings don't feel half so wide. At a reduced gross weight of 8161b, the RF-4D is cleared for all positive-g aerobatics, inverted gliding, and spinning, but not for flick manoeuvres. Normal category approval (including spin- ning, wing-overs and so forth) is granted up to 8601b gross weight. The typical RF-4DI flew had an empty weight of 5951b; at this figure a 14-stone pilot can take full fuel for nearly 3hr if he is doing aerobatics, or for 4hr of continuous running under normal flight. Most RF-4Ds have a spring-assisted mechanical engine starter operated by a lever situated on the box into which the main- wheel retracts. The machine I flew did not have it, and unfor- tunately I have yet to fly the Fournier as a sailplane with the prop stopped. One can, of course, set low power to simulate any desired gliding ratio, but it's not quite the same. The wide speed range, from a stall at less than 30 m.p.h. IAS to the design never-exceed 155 m.p.h., reflects the low wing- "Flight" photograph
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