Designed by Dipl-lng Otto Funk especially for weak thermal conditions, the FK-3 is distinguished by a pod-and-boom fuselage and a very tall fin and rudder. The cantilever shoulder wings have a thickness/chord ratio of 15.3% and are of an unusual metal and foamed honeycomb construction, bending loads being carried by a single metal spar which tapers from a T-section to a U profile, and drag and torsion loads being carried by a light alloy nose spar which transmits these loads to the fuselage fittings. The wing ribs are of light alloy and plastic foam sandwich construction, spaced at intervals of approximately 4ft 7in, and supporting a 0.5mm thick light alloy skin. Between the ribs a foamed honeycomb known as Conticell 60 gives additional support to protect the skin from minor damage, and the overall wing finish is very smooth. The camber-changing flaps are divided into inner and outer sections and Schempp-Hirth air brakes are fitted. Up to 110lb of water ballast can be carried if desired in two rubber tanks in the wings with the dump valve positioned in the fuselage aft of the retractable monowheel. The fuselage nose section is of steel tube construction covered with a glassfibre-reinforced shell, and the tail boom, of small cross section, is built of riveted light metal sheet without frames or stringers, the lower part incorporating a rubbing strip to minimise damage in a rough landing. The tail unit is similar in construction to the wings, the rudder being fabric covered. The monowheel is manually-retracted and has a drum brake; there is also a tailwheel. The pilot sits in a semi-reclining position on an adjustable seat and has adjustable rudder pedals; the long onepiece Plexiglas canopy is removable, except for a small front portion.

A high performance Open Class single-seater, the prototype was built by apprentices at VFW-Fokker’s Speyer plant in Germany in the course of their regular training.

It first flew on 24 April 1968 and production started in January 1969, soon building up to a rate of three or four per month. In its first competition, flown by Dr Rolf Spa’nig, the prototype won the Open Class in the 1968 Italian Championships, and two FK-3s later gained first and second places in the Austrian Championships.

FK-3
Span: 17.4m / 57 ft 1 in
Wing area: 13.8 sq.m / 148.54 sq ft
Length: 7.2 m / 23 ft 7.5 in
Empty Weight: 260 kg / 529 lb
Height over tailplane: 5 ft 11 in
Gross Weight: 400 kg / 882 lb
Water ballast: 50 kg / 110 lb
Wing Load: 29.0 kg/sq.m / 5.94 lb/sq ft
Max speed: 168 mph / 146 kt / 270 km/h
Max aero-tow speed: 87 mph
Max rough air speed: 146 kt / 270 km/h
Stalling speed: 27-30 kt / 50-55 km/h
MinSink: 0.50 m/s / 1.64 ft/sec at 34.5 kt / 64 kph / 40 mph
L/DMax: 42 at 47.5 kt / 88 kph / 55 mph
Aspect ratio: 21.9
Airfoil: Wortmann FX 61-K-153
Seats: 1
No. Built: 11