Developed from the original Mistral, which first flew in 1975, the ISF Model 2 Mistral-C single-seat Club Class sailplane is a product of the German firm Ingenieur/Buro Dipling Strauber – Frommhold GmbH & Co KG. Design work on the Mistral-C, which was intended to conform with the new FAI Club regulations, started in October 1974 and the prototype made its first flight in October 1976; 20 examples of this glassfibre T-tailed sailplane had been completed by the beginning of 1979. The type took 3rd place out of 33 contestants in the first Club class international competition held in Sweden in 1979.
The Mistral-C is a cantilever shoulder wing monoplane with 1° forward sweep at the quarterchord line; the wings and tail unit are of glassfibre reinforced plastic/foam/Conticell CC60 sandwich construction, the ailerons being of glassfibre reinforced plastic (GRP). There are Schempp-Hirth aluminium air brakes in the wing upper surfaces.
The fuselage is a GRP monocoque structure, and the landing gear consists of a non-retractable monowheel with a brake, and a tailskid. The tailplane is a fixed incidence one with spring trim, and the pilot sits under a large flush-fitting one-piece canopy that opens sideways. There is a towing hook on the centre of gravity, and a nose-mounted hook is optional.
In 1980 Mistral Flugzeugbau was formed to continue production of the Mistral-C at Hassfurt/Main; it had previously been built at Bensheim.
Mistral-C
Span: 15.0 m / 49 ft 2.5 in
Length: 6.73 m / 22 ft 1 in
Height: 1.45 m / 4 ft 9 in
Wing area: 10.9 sq.m / 116.8 sqft
Aspect ratio: 20.7
Wing section: Wortmann FX-61-163
Empty weight: 230 kg / 510 lb
Max weight: 350 kg / 77 1 lb
Water ballast: None
Max speed: 155 mph 135 kt / 250 km/h (in smooth air)
Max aero-tow speed: 105 mph
Stalling speed: 33 kt / 62 km/h
Min sinking speed: 2.17 ft/sec at 43.5 mph
Min sinking speed: 0.60 m/sec / 1.96 ft/sec at 35 kt / 65 km/h
Best glide ratio: 35: 1 at 55.5 mph
Best glide ratio: 35 at 49 kt / 90 km/h
