M.Hardy. Gliders & Sailplanes of the world

Onishi OS-G3 Japan

  Designed and built by Mr Onishi, a Japanese sailplane pilot, the OS-G3 single-seater is unique in being powered by six model aircraft engines, mounted three on each side of the nose on a strut-braced boom in line with the front of the cockpit canopy; these engines are intended to overcome the need for winch-launching or aero tows. Each 10cc OS.60 two-stroke glow-plug engine drives a 12in diameter two-bladed propeller and develops 1.7hp at 14,000rpm, or 1.275hp at a rather less noisy 8,000rpm, the six together producing a total of 10.2hp for take-off, or 7.65hp for cruising flight. This is just enough for an unaided take-off, the take-off run being about 500ft when the OS-G3 made its first flight early in 1977, and this miniscule power output leaves a mere 3mph margin between the cruising speed of 24mph and the stalling speed! This and a payload of only 154lb, to say nothing of the noise these high-revving engines must produce, make this form of sailplane power an interesting but hardly a practical proposition. The OS-G3 itself is a cantilever shoulder-wing design with a swept back fin and rudder and the tailplane mounted on top; the engine slipstream is in line with the wing leading edge. There are no flaps or air brakes, and the landing gear consists of a fixed monowheel, a fixed nosewheel and a tailskid. The pilot sits under a one-piece canopy, and has six throttle levers and six cut-out switches for the engines.


Span: 46 ft 3 in
Length: 21 ft 3 1/2 in
Height: 5 ft 2 1/2 in
Wing area: 185 sqft
Aspect ratio: 11.6
Empty weight: 143 lb
Max gross weight: 297 lb
Cruising speed: 24 mph
Stalling speed: 21 mph