M.Hardy. Gliders & Sailplanes of the world

Akaflieg Stuttgart FS-24 Phonix

  Notable as being the first sailplane to be built of glassfibre, design of the Phonix was started at the Stuttgart Akademische Fliegergruppe under R. Eppler and H. Nagele back in 1951. Originally balsa wood ДальшеMore>>> construction with a strengthened outer skin of paper-and-glue layers was decided upon with the idea of reducing weight, but the Phonix project had to be abandoned for a time. Work was continued when the Stuttgart Fliegergruppe was given a grant for further research, and by now the new glassfibre strengthened polyester resins were available as a constructional material. The Phonix was redesigned to a basically balsa wood/glassfibre sandwich form of construction, and made its first flight on 27 November 1957. At first a conventional tail unit with low-set tailplane was featured, but this was later replaced by a T-tail; the landing gear is retractable. Altogether eight Phonixes were built and all of them were still flying 21 years after the prototype first took to the air. The monocoque fuselage is built in two pieces with a sandwich skin with balsa wood filling and an outer skin of glassfibre. The wing attachment, controls and fittings are installed before the two pieces are glued together with the glassfibre skin overlapping; weight carrying points and the edge of the cockpit canopy are strengthened with plywood. The wings and tail unit are of similar balsa wood/glassfibre sandwich construction, the ailerons, flaps and rudder being cut out after the glueing process is completed.


Data: FS-24 Phonix
Span: 52 ft 6 in
Length: 22 ft 5 1/4 in
Wing area: 154.6 sq ft
Aspect ratio: 17.83
Empty weight: 362 lb
Max weight: 584 lb
Max speed: 107 mph
Min sinking speed: 1.7 ft/sec at 43 mph
Best glide ratio: 40:1 at 48 mph



Akaflieg Stuttgart FS-29

  For the sailplane pilot a variable geometry wing offers the exciting prospect of being able to vary the wing's area and geometry in flight to make the most of the soaring conditions encountered. A high aspect ratio could be selected for ascending in a thermal and a low aspect ratio (and hence a smaller area) for getting the maximum speed in cross-country flying. The Stuttgart Akaflieg's bold solution to this problem in the high-performance single-seater FS-29 is a telescopic wing in which the span can be varied in flight from 43ft 7 1/2 in to 62ft 4in by outer telescopic wing sections sliding over fixed inner sections. These outer wing sections are of glassfibre/foam/carbon-fibre sandwich construction and are extended and retracted manually by means of push-rods. A stub spar protrudes from each inner wing to provide a mounting for the guide rails on which the outer panels move. The inner wing is built up from a box spar of glassfibre/Conticell foam sandwich and is fitted with Schempp-Hirth air brakes on the upper surface which are only effective when the outer panels are extended. The plain ailerons are of similar construction to the outer wings. The fuselage is very similar to that of the Schempp-Hirth Nimbus 2, using the same landing gear and cockpit canopy, while the tail unit is the same as the Nimbus 2's. Design work on the FS-29 began in 1972 and the difficult problem of devising a wing which could be varied in span solely by manual power, and yet keep to the required aerodynamic and structural safety factors, meant that the first flight was not made until June 1975.


Data: FS-29
Span: 43 ft 7 1/2 in to 62 ft 4 in
Length: 23 ft 5 3/4 in
Height: 4 ft 2 in
Wing area: 92.2 to 136.2 sq ft
Aspect ratio: 20.67 to 28.54
Empty weight: 787 lb
Max weight: 992 lb
Max speed: 155 mph
Min sinking speed: 1.8 ft/sec at 46 mph
Best glide ratio: 44:1 at 62 mph