The Tandem-Falke is a development of the SF-25C Falke wth the two seats in tandem positioned over the wings under a lengthened one-piece perspex canopy, instead of the side-by-side layout of the earlier Falke series. The Tandem-Falke can be flown solo from the front seat, with space for up to 198lb of baggage on the rear seat.
Design work on the SF-28 began in 1970 and the prototype, registered D-KAFJ, made its first flight in May 1971, powered by a 45hp Stamo MS 1500 modified Volkeswagen engine. The production SF-28A has a 65hp Limbach SI 1900EA1 engine, the same as fitted to the SF-25C Falke but fitted to drive a Hoffman two-blade variable-pitch feathering propeller; a fixed-pitch prop was available as an option and the fuel capacity totals 8.8 Imp gallons. Full electric system and starter were standard equipment.
The type has the same basic wooden construction with fabric covered welded steel tube fuselage as the SF-25 Falke series; both wing span and length are slightly greater than the SF-25C’s, the fin and rudder are now unswept. The single-spar wooden wings have spoilers in the upper surfaces and no flaps; there is an outrigger stabilising wheel on a nylon leg under each wing, as well as a faired non-retractable monowheel with internal brake and a steerable tailwheel. There is a trim tab in the elevator.
Altogether 112 Tandem-Falkes had been built by January 1980 and the Tandem-Falke has competed in the German Motor Glider Competition. In 1973, SF-28A’s took the first four places in the two-place class of the international motorglider contest at Burg Feuerstein in Germany. One flown by Peter Ross set up two United Kingdom records for motor gliders in 1976.
Tandem Falke SF-28A
Engine: Limbach SL 1700 EA1, 48 kW/ 65 bhp
Wing span: 16.28m / 53.4ft
Wing area: 18.49 sq.m / 199 sq.ft
Wing section: Gottingen 533
Length: 8.1 m / 27 ft 3 in
Height: 1.55 m / 5 ft 1 in
Empty Weight: 410kg / 903lb
Payload: 200kg / 441lb
Gross Weight: 610kg / 1344lb
Water ballast: None
Wing Load: 32.99 kg/sq.m / 6.75 lb/sq.ft
Aspect ratio: 14.5
Max speed: 118 mph / 102.5 kt / 190 km/h (in smooth air, power off)
Max cruising speed: 87 mph
Stall speed: 33.5 kt / 62 km/h
MinSink: 0.90 m/s / 2.95 fps / 1.75 kt at 43.5 mph / 37.5 kt / 70 km/h
L/DMax: 26 @ 85 kph / 46 kt / 53 mph
Best glide ratio: 27 at 51 kt / 95 km/h
Take-off run: 180 m / 591 ft
Max rate of climb S/L: 126 m/min / 413 ft/min
Range: 500 km / 270 nm
Range with max fuel: 261 miles
Seats: 2
Structure: steel-tube/ fabric fuselage, wood/ fabric wings and tail.
All Aero 