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Prometheus 1


Prometheus 1, HB-2020, takes off from Olten-Gheid on the 12th August, 1972. Source : VGC New Spring 2015, Photo: Erich Gandet

The Prometheus 1 was an experimental powered sailplane, based on the airframe of the FFA Diamant 18. Design and construction began in late 1970, and the aircraft flew for the first time on 21 June 1971, powered by a 176 lb (80 kg) Microturbo Eclair II turbojet engine. This had been later replaced by a more powerful TRS 25 engine.

EEF Prometheus 1 powered sailplane
Fligth Archives 1972 - Prometheus I

General description

Wings, Fuselage, tail units and landing gear are coming from an original Diamant 18.

Power Plant

One 264 lb (120 kg) st Microturbo TRS 25 turbojet, mounted on a pylon above the wing center-section.

Total fuel capacity 

Fuel in two 8-75 Imp gallon (40 litre) wing tanks and one 0.4 Imp gallon (1.8 litre) fuselage tank. 

Total : 17.9 Imp gallons (81.8 litres). 

Oil capacity 

0.11 Imp gallons (0.5 litres).

Dimensions and areas

Wing span18,0 m59 ft 0.5 in 
Wing aspect ratio22,5
Length overall 7,56 m24 ft 9.5 in 
Height over tail4 ft 5 in 1,35 m
Tailplane span9 ft 6,25 in 2,90 m 
Weight empty 290 kg639 lb 
Max T-0 weight500 kg1,102 lb


Max level and living speed270 km/h146 knots168 mph
Max cruising speed at S/L210 km/h113 knots130 mph
con cruising speed at S/L170 km/h92 knots106 mph
Stalling speed, flaps up80 km/h43.5 knots50 mph
Stalling speed, flaps down68 km/h37 knots42.5 mph
Max rate of climb at S/L (/min)180 m591 ft
Service ceiling11,000 m36,100 ft
T-0 run300 m984 ft
T-0 to 50 ft (15 m)450 m1,476 ft
Landing from 50 ft (15 m)150 m492 ft
Landing run50 m164 ft
Range with max fuel> 135 nm> 250 km> 155 miles