| Akaflieg Darmstadt | |
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HW100 - 45000
UAW55 - 105000 RRW100 - 175000 PKRR - 7500 |
Akaflieg Darmstadt Akaflieg Darmstadt Type - Non-profit Headquarters - Darmstadt, Germany Field - Aviation research Membership (2010) - 53 Key people - Karl-Heinz "McHinz" Hinz - senior mastercraft Website - www.akaflieg.tu-darmstadt.de Akaflieg Darmstadt is one of approximately twenty aviation groups attached to German universities. Akaflieg is an abbreviation for Akademische Fliegergruppe, an academic group of students and faculty from a German University. Akaflieg history Otto Lilienthal published his book Der Vogelflug als Grundlage der Fliegekunst (Birdflight as the Basis of Aviation) in 1889, describing the basis of modern aerodynamics and aircraft construction. Lilienthal made many successful gliding flights from 1891 onwards. But the focus of attention shifted to powered flight after the Wright Brothers had demonstrated their Wright Flyer. Gliding re-emerged as a sport after the war because the building of powered aircraft was restricted in Germany by the Treaty of Versailles. The main originator of the gliding movement was Oskar Ursinus, who in 1920 organised the first contest, known as the Rhön-Contest, on the Wasserkuppe. Held annually, students of technical universities brought gliders which they had developed and built themselves for testing at these contests, developing an esprit de corps known as Rhöngeist. These informal beginnings stimulated the formation of groups of engineers at universities with the aim of scientific and practical education, with the first groups being formed, in 1920, at Aachen (Flugwissenschaftliche Vereinigung Aachen), Darmstadt (Akaflieg Darmstadt) and Berlin-Charlottenburg (Akaflieg Berlin), but others soon followed. Many of the first members had been pilots in the Luftstreitkräfte (Imperial German Air Service), but it was the love of flying rather than militarism or nationalism that motivated them, resulting in a fraternal spirit that has been maintained to this day. During the Nazi period some Akafliegs retained their autonomy through the patronage of the Deutsche Versuchsanstalt für Luftfahrt (DVL), a forerunner of the present-day German Aerospace Center (DLR). However, shortly before World War II the akafliegs were forced to integrate into the NS-Deutsche Studentenbund (Nazi-students-federation), with the Akaflieg projects having mostly military applications. Present day After the war, the Akafliegs re-formed in 1951, co-ordinated by Interessengemeinschaft Deutscher Akademischer Fliegergruppen e.V. (Idaflieg - interest group for German academic flying groups), with ten groups formed by 2009. The aim of the Akafliegs is scientific research into flight development, as well as design and construction of aeroplanes, especially gliders. Much of the practical work is done at the summer meetings of the 'Idaflieg' in co-operation with the German Aerospace Center (DLR), while the results of the research are presented at the winter meetings. The 'Idaflieg' also offers many events and courses to its members such as the specification, design and certification of aeroplanes. The quality of additional education provided by the Akafliegs is widely respected and so German glider manufacturers recruit almost exclusively from the Akafliegs. Once accepted as a member, students have to devote approximately 150 to 300-man-hours annually in the workshops to qualify for membership of the Akaflieg clubs, where the cost of flying is usually much lower than at other gliding/flying clubs. American Universities have also implemented programs similar to the Akafliegs but based around the American style of teaching, Pennsylvania State University's AERSP 404H is one example of this implementation. Akaflieg Darmstadt The Akademische Fliegergruppe Darmstadt e.V. (Academic Aviator Group Darmstadt) is a group of students enrolled at Darmstadt University of Technology, who are involved with the development and the design of gliders, as well as research in aerodynamics. Since the group was formed in 1920 over forty in-house designs have been created, with the D-43 trainer and Soteira pilot escape system being the latest. During research for and testing of new designs at Akaflieg Darmstadt the students get the opportunity to fly gliders in the Akaflieg fleet for recreation, as well as partake in the research flying programmes. Active members spend much of their free time in the workshop working towards reaching their academic goals. Aircraft Akaflieg Darmstadt D-1. Designed by Eugen von Lössl. First flight 1920. Construction: Wood, Wire and Fabric. Span 12.2 m (40 ft), Wing area 24.5 m2 (264 sq ft), Empty wt. 70 kg (150 lb) No. of seats 1. 1 built. Single-seat Hang glider with a parasol monoplane wing and rectangular section aerofoil profiled fuselage. Bequeathed, unfinished, by Eugen von Lössl after his death on 9 August 1920 to Akaflieg Darmstadt, where it was completed. Flew in the 1921 and 1922 Rhön competitions. Originally intended for centre of gravity style control, wing warping was added after much discussion. Akaflieg Darmstadt D-2 Pumpelmeise. Designed by E. Schatzki and F. Hoppe. First flight 1920. Construction: Wood, Wire and Fabric. Span 11 m (36 ft 1 in), Wing area 24.5 m2 (264 sq ft), Empty wt. 43 kg (95 lb) No. of seats 1. 1 built. Cantilever monoplane hang-glider with undercarriage skids, intended for the 1921 Rhön competitions but not flown there. The pilot was supported at the extreme nose of the fuselage which terminated at the wing leading edge. Akaflieg Darmstadt D-3 Nolleputzchen. Designed by F. Nicolaus. First flight 1921. Construction: Wood, Plywood and Fabric. Aerofoil: Göttingen 441 10 m (32 ft 10 in), Wing area 16 m2 (170 sq ft), Empty wt. 43 kg (95 lb) No. of seats 1. 1 built. This shoulder-winged cantilever monoplane had a conventional cockpit forward of the wing centre section and dual main skids. Constructed from wood with fabric and plywood covering, the D-3 had moderately tapered trapezoidal wings attached to a square section fuselage that tapered to nose and tail from the wing attachments. Akaflieg Darmstadt D-4 Edith. Designed by E. Thomas. First flight 1922. Construction: Wood, Plywood and Fabric. Aerofoil: Göttingen 426 12.6 m (41 ft 4 in), Wing area 18.8 m2 (202 sq ft), Empty wt. 110 kg (240 lb) No. of seats 1. 1 built. This single-seat strut braced parasol glider was used for training and is the direct precedent of the "Bremen". RRG Prüfling, RRG Falke and Grunau Baby. Akaflieg Darmstadt D-5 Flohschwanz. Designed by A.Botsch and W. Hübner. First flight 1922. Construction: Wood, Wire and Fabric 7.5 m (24 ft 7 in), Wing area 18 m2 (190 sq ft), Empty wt. 45 kg (99 lb) No. of seats 1. 1 built. This ultralight biplane glider was originally planned as a hang-glider but was completed with a cockpit nacelle and twin main skids. Akaflieg Darmstadt D-6 Geheimrat. Designed by L. Hoffmann and F. Nicolaus. First flight 1922. Construction: Wood, Plywood and Fabric 12.1 m (39 ft 8 in), Wing area 14.8 m2 (159 sq ft), Empty wt. 98 kg (216 lb) No. of seats 1. 1 built. This cantilevered monoplane glider employed an innovative control system, with pitch controlled through altering the angle of attack of the mainplane. Roll was achieved through altering the area of the wingtips, the after portions of which hinged at the inner front corner, sliding in and out of the forward portion of the wingtips, to alter area and thus lift, raising or lowering the wingtips. Akaflieg Darmstadt D-7 Margarete. Designed by E. Schatzki, R. Kercher and F. Hoppe. First flight 1923. Construction: Wood, Plywood and Fabric. Aerofoil: root Göttingen 533, tip symmetrical 15.3 m (50 ft 2 in), Wing area 22.5 m2 (242 sq ft), Empty wt. 200 kg (440 lb) No. of seats 2. 1 built. One of the first practical two-seaters, with a strut-braced high wing, and structure built from wood and fabric. Akaflieg Darmstadt D-8 Karl der Grosse. Designed by K. Plauth. First flight 1923. Construction: Wood, Plywood and Fabric. Powered by 1 x 22 kW (30 hp). Aerofoil: Göttingen 426 14 m (45 ft 11 in), Wing area 17.9 m2 (193 sq ft), Empty wt. 270 kg (600 lb) No. of seats 2. 1 built. A two-seat motorglider with a strut braced high wing, tandem cockpits under the wing centre section, tractor engine installation in the fuselage nose and twin mainwheels either side of the fuselage. Akaflieg Darmstadt D-9 Konsul. Designed by A. Botsch, R. Spies and F. Hoppe. First flight 1923. Construction: Wood, Plywood and Fabric. Aerofoil: Root Göttingen 535, Tip Symmetrical 18.2 m (59 ft 9 in), Wing area 21 m2 (230 sq ft), Empty wt. 200 kg (440 lb) No. of seats 1. built. This single-seat cantilever high winged glider illustrated the incremental progress in aerodynamic knowledge and construction techniques, using rounded sections and smooth skinning to reduce drag and improve performance. Weight reduction was also achieved by using a single main-skid, in what was to become the norm through to the 1940s when single wheeled undercarriages became the norm. The most impressive performance gain would have come from the (relatively) high aspect ratio long span wings, which at 18.2m were among the biggest up to that time. "The best glider of his time, which showed all the characteristics of today's gliders." (Brütting, 1972). Akaflieg Darmstadt D-10 Hessen. Designed by A. Botsch, R. Spies and G. Loew. First flight 1923. Construction: Wood, Plywood and Fabric. Aerofoil: Göttingen 429, Göttingen 430, Göttingen 431 or Göttingen 432 11.1 m (36 ft 5 in), Wing area 13.2 m2 (142 sq ft), Empty wt. 76 kg (168 lb) No. of seats 1. 1 built. Built purely as a flying wind tunnel with a simple rhomboidal section fuselage sitting on a single main skid. The section of the D-10 wings could be altered in flight, but results were never satisfactory, not least due to high friction in the variable section control system. Akaflieg Darmstadt D-11 Mohamed. Designed by D. v. Massenbach and F. Hoppe. First flight 1924. Construction: Wood, Plywood and Fabric. Powered by 1x 20 hp (15 kW)Blackburne Tomtit with metal propeller. Aerofoil: Joukowski 10.74 m (35 ft 3 in), Wing area 12 m2 (130 sq ft), Empty wt. 170 kg (370 lb) No. of seats 1. 1 built. "A cantilever low-winged ultralight aircraft with narrow track trousered fixed undercarriage, smooth plywood skinned fuselage and an all flying tailplane for pitch control. The D-11 Mohamed generated some interest when taking part in the 1924 Rhön-Leichtflugzeug-Wettbewerb (1924 Rhön light aircraft competition)." Akaflieg Darmstadt D-12 Roemryke Berge. Designed by E. Schatzki. First flight 1924. Construction: Wood, Plywood and Fabric 16 m (52 ft 6 in), Wing area 17.5 m2 (188 sq ft), Empty wt. 144 kg (317 lb) No. of seats 1. 1 built. The D-12 was built as a medium performance glider using the new construction techniques to minimise drag. Full span flaps and ailerons were also used as well as all-flying horizontal and vertical tails. Nehring completed the first successful out and return with this aircraft in 1926, flying from Darmstadt to Misleburg and back. Akaflieg Darmstadt D-13 Mohamed II. Designed by P. Laubenthal and G. Riedenbach. First flight 1926. Powered by 22 kW (30 hp) Blackburne Thrush. Aerofoil: Joukowski 10.7 m (35 ft 1 in), Wing area 12 m2 (130 sq ft), Empty wt. 170 kg (370 lb) No. of seats 1. 1 built. This single-seat lightweight aircraft, powered by a Blackburne engine, was intended for aerobatics, but with no improvement over the D-11 Mohamed plans for a small production run were abandoned. Akaflieg Darmstadt D-14. Designed by H. Koch and R. Preuschen. First flight 1927. Powered by 30 kW (40 hp) ABC Scorpion, MkII. Aerofoil: Joukowski, Lachmann 9 m (29 ft 6 in), Wing area 14 m2 (150 sq ft), Empty wt. 220 kg (490 lb) No. of seats 2. 1 built. This two-seat low-wing monoplane won 1st prize in the Idaflieg and Röhn-Rossitten-Gesellschaft construction competitions. Akaflieg Darmstadt D-15 Westpreussen. Designed by H.Hofmann. First flight 1926. Aerofoil: Göttingen 535 and/or Göttingen 430/Göttingen431 14.5 m (47 ft 7 in), Wing area 16 m2 (170 sq ft), Empty wt. 120 kg (260 lb) No. of seats 1. 1 built. Built following the "Darmstadt School", of cantilevered high wing with streamlined fuselage sections. The D-15 was designed and built for Ferdinand Schulz, who broke all the contemporary World glidings records whilst flying it. Akaflieg Darmstadt D-16. Designed by F. Fecher and F. Ritz. First flight 1927. Construction: Wood, plywood and fabric. Powered by 30 kW (40 hp) ABC Scorpion, MkII 7.8 m (25 ft 7 in), Wing area 16.2 m2 (174 sq ft), Empty wt. 210 kg (460 lb) No. of seats 2. 1 built. Developed from the 1st prize winning D-14, the D-16 was itself the precursor of the D-18. Akaflieg Darmstadt D-17 Darmstadt. Designed by H. Volker. First flight 1927. Construction: Wood, plywood and fabric. Aerofoil: Göttingen 535 16 m (52 ft 6 in), Wing area 16.6 m2 (179 sq ft), Empty wt. 155 kg (342 lb) No. of seats 1. 1 built. Built in the Darmstadt school fashion, the D-17 introduced automatic connection for the ailerons when rigging the glider. The D-17 was later taken to the United States (US) for an expedition in 1928. Hesselbach had a bad take-off, damaging the glider. The remnants were sold to Horace Wild, who hired Jack O'Meara to restore the glider. Wild renamed it "Chanute". In the next few years O'Meara gained many competition victories and broke many US gliding records. Akaflieg Darmstadt D-18. Designed by Dipl.Ing. F. Fecher. First flight 1929. Construction: Wood, plywood and fabric. Powered by 1x65.6 kW (88.0 hp) Armstrong-Siddeley Genet / 1x 78.3 kW (105.0 hp) Armstrong-Siddeley Genet Major. Aerofoil: Joukowski 7.2 m (23 ft 7 in), Wing area 12.1 m2 (130 sq ft), Empty wt. 320 kg (710 lb) / 374 kg (825 lb) No. of seats 1 or 2. 1 built. Built on experience with the D-14 and D-16, the D-18 was a cantilevered, (with the exception of cabane struts for the upper mainplane), heavily staggered biplane with clean lines, built from wood and plywood and covered with fabric. After the first few promising flights at the Darmstadt airfield the D-18 was transferred to the DLV (Deutsche Versuchsanstalt für Luftfahrt-German research establishment for flying) at Berlin. The D-18 then took part in the 1929 Europa-Rundflug, giving excellent results until a crash forced withdrawal. After repairs and the fitting of a Genet Major engine the D-18 went on to set three world records in 1930. For the 1930 Europa-Rundflug the D-18 was fitted with an enclosed canopy, but engine problems forced Rudolf Neininger, the pilot, to ditch in the Mediterranean Sea. Akaflieg Darmstadt D-19 Darmstadt II. Designed by F. Gross. First flight 1928. Construction: Wood, plywood and fabric. Aerofoil: Joukowski 15% to Joukowski 8%, root to tip 18 m (59 ft), Wing area 16.9 m2 (182 sq ft), Empty wt. 162 kg (357 lb) No. of seats 1. 1 built. The D-19 utilised elliptical wings with ailerons on the outer sections, mounted on a pylon aft of the cockpit and a tail section similar to the D-17. Akaflieg Darmstadt D-20 Starkenburg. Designed by H. Hoffmann. First flight 1929. Construction: Wood, plywood and fabric 16 m (52 ft 6 in), Wing area 17.5 m2 (188 sq ft), Empty wt. 145 kg (320 lb) No. of seats 1. 1 built. The D-15 Westpreussen rebuilt and improved after its crash at "Würzburg", piloted by A. Endres. Rudder and aileron interconnection was fitted similar to the system used on the D-9. Akaflieg Darmstadt D-21. Designed by F. Fecher. First flight 1930 7.9 m (25 ft 11 in), Wing area 13.9 m2 (150 sq ft), Empty wt. 540 kg (1,190 lb) No. of seats 1. 0 built. A projected single-seat powered aircraft for aerobatics. Akaflieg Darmstadt D-22. Designed by F. Fecher. First flight 1931. Construction: Wood, plywood and fabric. Powered by 1x 150 hp (110 kW) Argus As8R 7.4 m (24 ft 3 in), Wing area 13 m2 (140 sq ft), Empty wt. 345 kg (761 lb) No. of seats 2. 3 built. An improved D-18 with a German engine, retaining the heavily staggered cantilever, open cockpit, biplane configuration. Three aircraft were built, of which the first was sold in England, crashing in January 1932. The second aircraft was delivered to the Reichsverkehrsministerium for evaluation and the third was retained at Akaflieg Darmstadt. Akaflieg Darmstadt D-23. Designed by V. Caspar. First flight 1930. Powered by 1x 60 kW (80 hp). Aerofoil: NACA M12 6.5 m (21 ft 4 in), Wing area 10.8 m2 (116 sq ft), Empty wt. 305 kg (672 lb) No. of seats. 0 built. The D-23 remained a project. Akaflieg Darmstadt D-24. Designed by G.Horn. First flight 1930. Powered by 1x 80 kW (110 hp). Aerofoil: NACA M12 11.7 m (38 ft 5 in), Wing area 16.7 m2 (180 sq ft), Empty wt. 400 kg (880 lb) No. of seats 2. 0 built. The D-23 high wing, cantilever monoplane, cabin two-seater remained a project. Akaflieg Darmstadt D-28 Windspiel. Designed by R. Kosin, R. Schomerus. First flight (D-28a 1933) (D-28b1933). Construction: Wood, plywood and fabric. Aerofoil: Göttingen 535 12 m (39 ft 4 in), Wing area 11.4 m2 (123 sq ft), Empty wt. (D-28a 54 kg (119 lb)), (D-28b 72 kg (159 lb)) No. of seats 1. 2 built. Built to realise all potential performance gains using available theory and construction techniques. The D-28a was very light for its size and required very careful ground handling to avoid damaging the structure. The relatively high performance achieved allowed the D-28a to break the world record cross-country flight at 240 km and a 140 km goal flight, from Darmstadt to Saarbrücken, on 8 March 1935. A second modified heavier aircraft was built as the D-28b. Akaflieg Darmstadt D-29. Designed by H.J.Biedermann, H. Voigt. First flight 1937. Construction: Wood, plywood, steel tubing and fabric. Powered by 1x 119 kW (160 hp) Bramo Sh 14 A. Aerofoil: M6 12 m (39 ft 4 in), Wing area 11.4 m2 (123 sq ft), Empty wt. 560 kg (1,230 lb) No. of seats 2. 1 built. The sole D-29, (D-EILE), was built as a flying test-bed for high-lift devices on the wings, with a fixed, spatted, undercarriage, two seats under a long greenhouse canopy and a T-tail. The T-tail was intended to alleviate down-wash effects from the wings and high-lift devices during measurements. Testing was carried out on slats following the G. V. Lachmann patent and split flaps. Akaflieg Darmstadt D-30 Cirrus. Designed by R. Schomerus, H. Alt, H.J. Puffert. First flight 1938. Construction: Wood, plywood, Duralumin and Elektron. Aerofoil: NACA 24xx and Göttingen 600 laminar profiles 20.1 m (65 ft 11 in), Wing area 12 m2 (130 sq ft), Empty wt. 190 kg (420 lb) No. of seats 1. 1 built. The D-30 was built for high performance as well as, reputedly, aerobatics and cloud flying. The long span, high aspect ratio wings with newly devised laminar flow sections, combined with new construction techniques and materials, such as Duralumin and Elektron, gave the D-30 the desired performance. The D-30 went on to break the world record out and return distance on 7 July 1938 with a flight from Lübeck to Bremen and return. First place was also awarded to the D-30 in the Students competitions. Akaflieg Darmstadt D-31. Designed by H. Friedmann. First flight 1937. Aerofoil: NACA 4415 to NACA 4412 20 m (65 ft 7 in), Wing area 20 m2 (220 sq ft), Empty wt. 180 kg (400 lb) No. of seats 2. 0 built. A projected two-seater similar to the D-30 Cirrus, with a pod and boom fuselage and wings of lower aspect ratio. The second cockpit was to have been under the wing centre-section accessed by a cartype door on the starboard side. Akaflieg Darmstadt D-32. Designed by R. Nusslein and H. Zacher. First flight 1938. Construction: Wood and plywood. Powered by 1x 120 kW (160 hp). Aerofoil: NACA 2415 to NACA 2409 7.9 m (25 ft 11 in), Wing area 9 m2 (97 sq ft), Empty wt. 310 kg (680 lb) No. of seats 1. 0 built. A project for an aerobatic aircraft. Akaflieg Darmstadt D-33 a.k.a. Lippisch DM-1. Designed by Alexander Lippisch and W. Heinemann. First flight ca 1942. Construction: Wood and plywood. Aerofoil: Ringleb 15% thick elliptic and symmetric 6 m (19 ft 8 in), Wing area 19.9 m2 (214 sq ft), Empty wt. 375 kg (827 lb) No. of seats 1. 1 built. Design was started by Lippisch to carry out aerodynamic research for his P.13a interceptor design, with detail design and construction passed to Heinemann at Darmstadt. Part way through the airframe was transferred to a combined team at Akaflieg München and renamed the DM-1. It was almost complete at the end of hostilities in 1945 and created a lot of interest. The team of engineers at Munich were ordered to complete the DM-1 which was then shipped to the US for wind tunnel testing. The DM-1 survives to this day at the National Air and Space Museum storage facility. Akaflieg Darmstadt D-34a. Designed by W.Sarnes, H.J.Merklein. First flight 1955. Construction: Wood, plywood and foam. Aerofoil: NACA 644-621 12.65 m (41 ft 6 in), Wing area 8 m2 (86 sq ft), Empty wt. 128 kg (282 lb) No. of seats 1. 1 built. Built as a study project for the design and construction of high-performance sail-planes, the first of the series used wooden structure with plywood skin bonded to foam inners which gave a very smooth surface finish. The genesis of the modern glider is evident in the large canopy over a semi-reclining seat, T-tail and slender rear fuselage. Despite being a research aircraft the D-34s had some success in competitions. Akaflieg Darmstadt D-34b. Designed by G.Jacoby. First flight 1957. Construction: Wood, plywood and foam. Aerofoil: NACA 644-621 12.65 m (41 ft 6 in), Wing area 8 m2 (86 sq ft), Empty wt. 141 kg (311 lb) No. of seats 1. 1 built. Similar to the D-34a but with a higher empty weight. Akaflieg Darmstadt D-34c. Designed by M.Rade. First flight 1958. Construction: Wood, plywood, foam and steel tube. Aerofoil: NACA 644-621 12.65 m (41 ft 6 in), Wing area 8 m2 (86 sq ft), Empty wt. 145 kg (320 lb) No. of seats 1. 1 built. The D-34c introduced welded steel tubing to high stress areas, such as the fuselage/wing intersection. Akaflieg Darmstadt D-34d. Designed by A.Puck, K.Weise, H.Wurtinger. First flight 1961. Construction: Wood, plywood, glass-fibre reinforced plastic and paper honeycomb. Aerofoil: NACA 644-621 12.65 m (41 ft 6 in), Wing area 9.18 m2 (98.8 sq ft), Empty wt. 155 kg (342 lb) No. of seats 1. 1 built. Construction techniques for glass-fibre and paper honeycomb sandwich were researched with the construction of the D-34d. Akaflieg Darmstadt D-35. Designed by A.Puck, H.Wurtinger. First flight 1959. Construction: Glass-fibre reinforced plastic, paper honeycomb and steel tube 19 m (62 ft 4 in), Wing area 18.05 m2 (194.3 sq ft), Empty wt. 240 kg (530 lb) No. of seats 2. 0 built. This large high performance, V-tailed, two-seater, project was cancelled because the individual parts were too big to be built in the available space. Akaflieg Darmstadt D-36 Circe. First flight 1964. Construction: Glass-fibre reinforced plastic, Balsa wood. Aerofoil: Wortmann FX62-K-131, Wortmann FX 60-126 17.8 m (58 ft 5 in), Wing area 12.8 m2 (138 sq ft), Empty wt. 285 kg (628 lb) No. of seats 1. 2 built. "The D-36 was designed to incorporate all the latest improvements in aerodynamics and construction techniques to produce a high performance glider better than its contemporaries. Competition successes included:- 1st place Open Class German National Championship 1964 2nd place Open Class Gliding World Cup 1965 3rd place pen Class German National Championship 1966." Akaflieg Darmstadt D-37 Artemis. Designed by F.Sator (D-37a), W.Dirks (D-37b). First flight 1967. Construction: Glass-fibre reinforced plastic, plasticell foam. Powered by 1x retractable sustainer motor. Aerofoil: Wortmann FX 66-S-196, Wortmann FX 66-S-160 18 m (59 ft), Wing area 13 m2 (140 sq ft), Empty wt. 325 kg (717 lb) No. of seats 1. 1 built. A high performance single seater, fitted with a retractable sustainer motor (incapable of take-off), the initial D-37a was modified to the D-37b. Akaflieg Darmstadt D-38. Designed by W.Dirks. First flight 1972. Construction: Glass-fibre reinforced plastic, Balsa wood. Aerofoil: Wortmann FX 61-184, Wortmann FX 60-126 15 m (49 ft 3 in), Wing area 11 m2 (120 sq ft), Empty wt. 210 kg (460 lb) No. of seats 1. 1 built. The D-38 was in effect the prototype of the DG-100, built by Glaser-Dirks. Built almost exclusively of GRP with Balsa wood filler the D-38 was a Standard class sailplane with 15m span wings no flaps, retractable undercarriage and provision for water ballast. Akaflieg Darmstadt D-39. Designed by G. Neubauer, B.Hügel. First flight 1979. Construction: Glass-fibre reinforced plastic, Balsa wood. Powered by (D-39) 2x Sachs KM 914 Wankel rotary engines, (D-39 HKW/McHinz/D-39b) 1x 48.5 kW (65.0 hp) Limbach engines. Aerofoil: (D-39) 15 m (49 ft 3 in), (D-39b / McHinz) 17.5 m (57 ft 5 in), (D-39 HKW) 20m (65f 7in), Wing area 11 m2 (120 sq ft), Empty wt. 370 kg (820 lb) No. of seats 1. 2 built. The D-39 was originally designed as a single-seat touring motor-glider with 15m wings and paired Sachs rotary engines driving a folding propeller. Unsatisfactory performance from the airframe and the engines led to the re-design and rebuild into the D-39b McHinz and the privately built D-39 HKW by Heinrich Konrad Weinerth, using 17.5m / 20m wings respectively, a Limbach engine, and Wölbklappenflügel - automatic flaps. Akaflieg Darmstadt D-40. Designed by K.J.Heer, D.Teves. First flight 1981. Construction: Glasfibre-epoxy, Carbonfibre-epoxy, Aramid-epoxy, with Balsa, Conticell and Rohacell fillers.. Aerofoil: FX 67-VG170 - FX 60-126, root to tip 15 m (49 ft 3 in), Wing area 11.5 m2 (124 sq ft), Empty wt. 260 kg (570 lb) No. of seats 1. 1 built. Designed and built to comply with Federation Aeronautique Internationale (FAI) 15m class rukes, the D-40 includes area-increasing flaps which extend rearwards, hinged at the outboard end of the inner trailing edge at about ¾ span, similar in fashion to a pocket knife. Akaflieg Darmstadt D-41. Designed by. First flight 1993. Construction: Carbonfibre-Epoxy. Aerofoil: Wortmann FX 81-K-130/17, Wortmann FX 81-K-148/17modified 20m (65f 7in), Wing area 14 m2 (150 sq ft), Empty wt. 431 kg (950 lb) No. of seats 2 side by side. 1 built. This two-seater, with side-by-side seating follows contemporaries like the Akaflieg Berlin B13 and Stemme S10 motor-gliders, but is a pure glider with no engine. The wing is derived from that of the Rolladen-Schneider LS-6, extended to 20m at the roots. Akaflieg Darmstadt D-42. Designed by M.Schröder, J.Scholz, P.Erb. First flight 1996. Construction: Glassfibre-epoxy, Carbonfibre-epoxy. Aerofoil: Wortmann FX 82-L-168 Wortmann FX 82-L-145 18 m (59 ft), Wing area 13.2 m2 (142 sq ft), Empty wt. 340 kg (750 lb) No. of seats 1. 0 built. A projected 18m solar-powered sailplane with retractable engine/propeller. The solar cell and battery combinations required were considered too expensive and further work was abandoned. Akaflieg Darmstadt D-43. The D-43 is an ongoing project for a two-seater trainer to replace the Schleicher ASK 13. The initial stages in progress include the definition of a specification and market analysis, with decisions on prototype production and further work dependent on the results of the market survey. Akaflieg Darmstadt D-44 Soteira. The D-44 is a proposed rocket-powered glider pilot escape system, under development. Full-scale tests with dummies from static cockpits have been carried out, and a production system is proposed for fitment to the nascent D-43 trainer. Model Photo Lippisch DM-1 and P13a Akaflieg Darmstadt D-6 Geheimrat D-6 Geheimrat Role - Single seat glider National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - L. Hoffmann and F. Nicolaus First flight - 1922 Number built - 1 The Akaflieg Darmstadt D-6 Geheimrat, often shortened to Darmstadt D-6 Geheimrat, was an early competition glider with a single seat and high cantilever wing, designed and built by German University students in 1922. Development The Akademische Fliegergruppe of the Technical University of Darmstadt was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. One of the first of these students was the son of a Privy Councillor (Geheimrat) and the group's sixth design, the D-6, was named in his honour. The Geheimrat was a wood-framed aircraft with a rectangular cross section, flat sided, plywood covered fuselage. In plan it tapered only slightly but the depth decreased rapidly towards the tail, making the fuselage behind the wing strongly wedge shaped. The wing was mounted on two extensions at the highest point, with an open, unscreened cockpit below its leading edge behind a more rounded nose. A pair short skids attached directly to the edges of the fuselage underside acted as the undercarriage, aided by a short tailskid at the rear. The thick section wing was a cantilever structure with ply covering from the spar to the leading edge and fabric covered aft. The centre section, about half the total span, was straight edged and with a constant 1.41 m (4 ft 7.5 in) chord. The outer panels were straight tapered, mostly on the trailing edge which carried the roll control surfaces. Unusually, the pilot did not alter pitch with elevators but by varying the angle of incidence in flight. The contemporary Harth-Messerschmitt S.10 glider used the same method. As a result, the fabric covered, rectangular tailplane, mounted by its leading edge at the extreme tail, was without elevators. The similarly covered fin and rudder together almost formed a square, its trailing edge over the tailplane's front spar. Operational history The D-6 Geheimrat first flew in 1922 and competed in the Rhön (Wasserkuppe) glider meeting that August. It gained second place in the sink rate section, though overall a contemporary observer judged the earlier Darmstadt D-4 Edith, a braced monoplane, more successful. Having seen the Akaflieg Hannover Vampyr slope soaring for up to three hours, the Darmstadt students were soon making similar long flights in both their aircraft. Specifications (Data from Sailplanes 1920-1945) General characteristics Crew: 1 Length: 5.50 m (18 ft 1 in) Wingspan: 12.10 m (39 ft 8 in) Wing area: 14.8 m2 (159 sq ft) Aspect ratio: 9.9 Airfoil: Göttingen 387 Empty weight: 98 kg (216 lb) structure Gross weight: 175 kg (386 lb) in flight Performance Wing loading: 11.8 kg/m2 (2.4 lb/sq ft) Akaflieg Darmstadt D-7 Margarete D-7 Margarete Role - Two seat glider National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - Fritz Hoppe, R. Kercher and E.Schatzki First flight - 1923 Number built - 1 The Akaflieg Darmstadt D-7 Margarete, often shortened to Darmstadt D-7 Margarete, was one of the earliest two seat monoplane gliders, designed and built by German university students in 1923. Development The Akademische Fliegergruppe of the Technical University of Darmstadt was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. The 1923 D-7 monoplane was their first two-seat design and one of the first of its kind, though the Fokker FG-2 two seat biplane glider flew the previous year; the D-7 was named after the wife of an Akaflieg Darmstadt student killed at the first Rhön (Wasserkuppe) glider meeting in 1920. The Margarete was a wood-framed aircraft with a high, braced, two spar wing with ply covering from the front spar to the leading edge and fabric covered aft. The wing had a thick and cambered profile inboard of the tips, which had a thinner and more symmetric profile. Initially the wing plan was rectangular, with triangular ailerons mounted on straight hinges which were attached to the front spar at the tips, reaching the trailing edge inboard. Later, the aileron area was reduced, partly by cropping them inboard and also by tapering their trailing edges and rounding their tips. Each wing was braced from the lower fuselage with an asymmetric, V-form, streamlined strut to the two spars at about one-third span. The fuselage was plywood covered with a flat top, deep, slightly curved sides and a V-shaped bottom. The nose was blunt and the open, unscreened cockpit used for solo flying was well forward of the wing leading edge. The separate second cockpit was under the wing, close to the centre of gravity so that its occupation did not seriously affect the trim. The wing centre section was supported above this cockpit on an extension of the upper rear fuselage, which dropped away aft to become slender at the tail. There was a short undercarriage skid attached directly to the fuselage underside, aided by a small tailskid. A narrow, triangular, ply covered fin carried a fabric covered, trapezoidal rudder which extended to the bottom of the fuselage. The fabric covered tailplane was mounted on the top of the fuselage; in plan, tailplane and elevators were straight edged, only slightly tapered and with angled tips. A small elevator cut-out allowed rudder movement. Operational history The D-7 Margarete first flew in 1923 and took part in both the 1923 and 1924 Rhön events, setting an unofficial record at the latter with a passenger-carrying flight of 21 minutes. It was later used for passenger flights, though not for basic training, until it was written off in 1927 when an aileron cable broke during landing. Specifications (Data from Sailplanes 1920-1945) General characteristics Crew: 2 Length: 7.65 m (25 ft 1 in) Wingspan: 15.30 m (50 ft 2 in) Wing area: 25 m2 (270 sq ft) Aspect ratio: 9.36 Airfoil: Göttingen 533 at root, more symmetrical at tip Empty weight: 180 kg (397 lb) structure Gross weight: 320 kg (705 lb) in flight Performance Wing loading: 12.8 kg/m2 (2.6 lb/sq ft) Akaflieg Darmstadt D-9 Konsul D-9 Konsul Role - Single seat glider National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - Albert Botsch,Fritz Hoppe and Rudolf Spies First flight - 1923 Number built - 1 The Akaflieg Darmstadt D-9 Konsul, often shortened to Darmstadt D-9 Konsul, was a high performance, single seat, cantilever monoplane sailplane, designed and built by a German University student group in 1923 for hill soaring. Development The Akademische Fliegergruppe of the Technical University of Darmstadt was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. The 1923 D-9 monoplane was named in honour of Karl Kotzenberg, sometime Consul General to Norway, who had provided financial support for the project. It was the most advanced glider of its day and had the highest aspect ratio (initially 16.66) of any existing aircraft. The Konsul was a wood-framed aircraft with a high, cantilever, single spar wing with stressed 3-ply covering from the spar to the leading edge and fabric covered aft. It was built in three parts, an 8 m (26 ft 3 in) inner section with a box spar and outer panels with an I-section one. The wing had a thick and strongly cambered profile, using the then new Göttingen 535 airfoil with its high lift to drag ratio that attracted many pre-World War II sailplane designers. The long wings had constant chord except for tapered tips, where the wing decreased in thickness. There was no dihedral. Half span, large area ailerons had angled hinges attached to the spar at its tip and, in the early flight tests, projected well beyond the fixed wing tip. These proved both heavy in flight and vulnerable on the ground, so were soon tapered and rounded off, slightly reducing the span and aspect ratio. The ailerons operated differentially, upward deflections being smaller than downward ones; this was a relatively new way of reducing adverse yaw but in addition the rudder and ailerons were interconnected. Small rudder deflections did not affect the ailerons but larger ones moved them appropriately. No flaps, airbrakes or spoilers were fitted, normal for the time. The fuselage of the Konsul was a 3-ply skinned, oval cross sectioned semi-monocoque, with a blunt nose and slightly tapered and more rounded towards the tail. The open, unscreened cockpit was well ahead of the wing, which was mounted directly on top of the fuselage. A short undercarriage skid was attached to the fuselage underside via rubber blocks, aided by a small tailskid. The empennage was fabric covered, straight edged with angled tips; the fin and tailplane had narrower chord than the generous control surfaces and slight sweep on their leading edges. The rudder, which reached down to the bottom of the fuselage, moved within a cut-out in the elevators. Operational history The D-9 Konsul first flew in 1923 and took part in both the 1923 and 1924 Rhön events. In 1923 the Konsul, flown by Albert Botsch, one of its designers, won the distance prize with a record breaking flight of 18.7 km (11.6 mi). In 1925 it won the distance prize again, piloted by Johannes Nehring. Nehring set another distance record that year with a flight of 24.4 km (15.2 mi) during a visit to the Crimea, hill soaring as before. The Konsul remained active until 1927 when it was destroyed in an accident. Specifications (after ailerons reduced) (Data from Sailplanes 1920-1945) General characteristics Crew: 1 Length: 6.35 m (20 ft 10 in) Wingspan: 18.20 m (59 ft 9 in) Wing area: 21 m2 (230 sq ft) Aspect ratio: 15.8 Airfoil: Göttingen 535 Empty weight: 185 kg (408 lb) structure Gross weight: 270 kg (595 lb) in flight Performance Maximum glide ratio: 1:24.4 at 53 km/h (33 mph) Wing loading: 9.1 kg/m2 (1.9 lb/sq ft) Darmstadt D-18 (Akaflieg Darmstadt D-16) Darmstadt D-18 Role - Sportsplane Manufacturer - Akaflieg Darmstadt First flight - 1929 Status - Prototype Primary user - Germany Produced - 1929 Number built - 1 Variants - Darmstadt D-22 The Darmstadt D-18 was a German light sports aircraft that was designed and built in the late-1920s by the Akaflieg Darmstadt of the Technische Universität Darmstadt. Design and development The aircraft was designed by F. Fecher and students in the aeronautical engineering department of the Technische Universität Darmstadt. It was a development of the D-16 project, that was designed for a sports aircraft contest organized by Idaflieg in 1926. The D-16 design with a 40-horsepower (hp) engine won the first prize, but was not built as the designer decided to strengthen the construction and fit a more powerful 88 hp Armstrong Siddeley Genet radial engine. The result was the D-18, a single aircraft was built in 1929. The aircraft was a cantilever biplane, with an upper wing placed low above a fuselage and ahead of a lower wing. Particular thought was given to aerodynamics and lightness and the aircraft was small, with a streamlined profile. Initially the D-18 had two open cockpits, but by 1930 it had been modified and fitted with a closed canopy covering both cockpits. Operational history The aircraft carried the registration of D-1561. It took part in the Challenge 1929 international tourist plane contest, piloted by Johannes Nehring, being one of the fastest planes in the contest. It was the best aircraft in the fuel consumption trial and, along with two other aircraft, won the first part of the contest - the technical trials. However, the D-18 dropped out due to a forced landing near Września before Poznań on 11 August 1929, during a rally around Europe, because of a fuel pipe clogging. The aircraft turned over and suffered damage; its passenger was injured. The aircraft was repaired and, now fitted with an enclosed cabin, it took part in another contest, Challenge 1930, again piloted by Rudolf Neininger. On 26 July 1930, during a rally around Europe the D-18 was forced to ditch in the Mediterranean Sea between Barcelona and Nîmes due to breaking a piston. The crew was rescued by a passing ship that also recovered the wreckage. Specifications Description Wooden construction cantilever biplane of extreme stagger. Fuselage oval in cross-section, plywood covered. Single-spar wings, plywood and canvas covered. Aileron on lower wing only Wings were dismounted and folded. Two crew cockpits in tandem, later covered with a common multi-part canopy. Fixed landing gear with a rear skid. Five-cylinder radial engine in the cowled nose with its cylinders projecting for cooling. Two-blade propeller. (Data from Les Ailes, March 1929) General characteristics Crew: Two Length: 6.14 m (20 ft 2 in) Wingspan: 7.20 m (23 ft 7 in) Height: 2.62 m (8 ft 7 in) Wing area: 12.10 m2 (130.2 sq ft) Empty weight: 400 kg (882 lb) approximately Powerplant: 1 × Armstrong-Siddeley Genet 5-cylinder radial, 60 kW (80 hp) Propellers: 2-bladed Performance Maximum speed: 200 km/h (120 mph, 110 kn) Range: 800 km (500 mi, 430 nmi) Time to altitude: 3 min to 1,000 m (3,300 ft) Rudolf Neininger (left) with his crewman in front of the D-18 during Challenge 1930 Darmstadt D-18 3-view drawing from L'Aéronautique August, 1929 Akaflieg Darmstadt D-17 Darmstadt D-17 Darmstadt Role - Single seat glider National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - H. Völker First flight - 1927 The Akaflieg Darmstadt D-17 Darmstadt, also called the Darmstadt D-17 and Darmstadt I, was a high performance, single seat, cantilever monoplane sailplane, designed and built by a German University student design group in 1927. It was followed in 1928 by the Akaflieg Darmstadt D-19 Darmstadt 2, a similar aircraft with a new profile, longer span wing. Development The Akademische Fliegergruppe of the Technical University of Darmstadt was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. By 1927 the group were producing a range of designs traceable back to their 1923 Konsul and some of these were professionally built outside the University. The D-17, originally known simply as the Darmstadt and later as the Darmstadt 1, was one such. The D-17 was a wood framed aircraft with a high, cantilever, single spar wing with stressed plywood covering from the spar to the leading edge and fabric covered aft. Its 16 m (52 ft 6 in) was built in three parts, a 6 m (19 ft 9 in) inner section with constant chord and thickness and outer panels which tapered in both chord and thickness to elliptical tips. The D-17 had the thick, high lift to drag ratio Göttingen 535 profile that Akaflieg had first used on the Konsul. Ailerons mounted on slightly angled hinges occupied the whole trailing edges of the outer panels. No flaps, airbrakes or spoilers were fitted, normal for the time. The fuselage of the Darmstadt was a plywood skinned, oval cross sectioned semi-monocoque, slightly tapered and more rounded towards the tail. The open, unscreened cockpit was placed immediately ahead of the wing leading edge with the pilot's head against the front of a low, long chord, faired pylon which supported the wing. A short undercarriage skid was attached to the fuselage underside, aided by a small tailskid. The D-17 had all moving tail surfaces with straight edges, rounded tips and tapered by forward sweep on their trailing edges. The large rudder extended to the keel, moving in a cut-out in the one piece elevator. In 1928 a close relative of the D-17, the D-19 Darmstadt 2, was flown. Designed by F. Gross, the main difference between it and the D-17 was the wing which had a 2 m (6 ft 7 in) greater span, making the D-19 an 18 m (59 ft 1 in) sailplane. The central panel span was increased to 7.62 m (25 ft). The D-19's wing area was only slightly higher, with the result that the aspect ratio was increased from 15.4 to 19.4. The D-19 used a more symmetric Joukowsky profile in place of the strongly cambered Göttingen 535, so decreasing the pitching moment; over the outer panels the thickness/chord ratio reduced continuously from 15% to 8. There were also smaller refinements around the cockpit and pylon and a deeper, less rounded fuselage profile. Operational history The D-17 took part in the 1927 Rhön (Wasserkuppe) gliding competitions. Piloted by Johannes Nehring, it set a new hill soaring distance record at 51.8 km (36.1 mi). In early 1928 it went to the United States where Peter Hesselbach flew it over the dunes of Cape Cod, one flight lasting four hours. The flights attracted much publicity and caught the attention of the young Schweizer brothers who later became important glider designers. The Darmstadt was damaged in a collision with a flagpole at the Cape, then was sold and rebuilt with improvements to the cockpit including its enclosure under smooth glazing which merged into the upper pylon line. Renamed the Chanute in honour of the aviation pioneer Octave Chanute, it was mostly flown by Jack O'Meara. Flight reported that a Darmstadt, as well as a Darmstadt 2, flew at the Rhön meeting in August 1930. The quoted span suggests this Darmstadt, which won the junior endurance prize with a flight of 3 hr 19 min, was another Akaflieg Darmstadt model, but if It was the D-17, then two of the latter were built. The D-19 appeared at least three consecutive Rhön meetings (1928-30), setting a record of 71.2 km (44.3 mi) in 1928 then bettering it with 72.3 km (44.9 mi) the following year. It appeared there for the last time in 1934, after which it was lost during a Scandinavian tour. Variants D-17 Darmstadt 16 m span. D-17 Chanute The D-17 with an enclosed cockpit. D-19 Darmstadt 2 New 18 m, Joukowski profile wing. Specifications (D-17 Darmstadt 1) (Data from Sailplanes 1920-1945) General characteristics Crew: 1 Length: 6.37 m (20 ft 11 in) Wingspan: 16.00 m (52 ft 6 in) Wing area: 16.6 m2 (179 sq ft) Aspect ratio: 15.4 Airfoil: Göttingen 535 Empty weight: 170 kg (375 lb) structure Gross weight: 250 kg (551 lb) in flight Performance Wing loading: 15.1 kg/m2 (3.1 lb/sq ft) Darmstadt D-22 (Akaflieg Darmstadt D-22) Darmstadt D-22 Role - Sportsplane Manufacturer - Akaflieg Darmstadt First flight - 1931 Primary user - Germany Produced - 1931 Number built - 2 The Darmstadt D-22 was a sports-plane of Germany, designed and built by Akaflieg of Technische Universität Darmstadt. Design and development The aircraft was designed by F. Fecher in the Akaflieg (academic group of flyers) of Technische Universität Darmstadt. It was a development of Darmstadt D-18, slightly enlarged, more streamlined and fitted with an inline engine. Thanks to strengthening it was better fit to aerobatics. Two were built in 1931. Just like the D-18, the D-22 was a cantilever biplane, with an upper wing placed low above a fuselage and ahead of a lower wing. Aerodynamic cleanliness and low weight were emphasisedin the design, resulting in a small aircraft with clean lines. Description The D-22 was of wooden construction with cantilever biplane and oval cross-section fuselage skinned with plywood and fabric on parts of the single-spar wings, which could be dismounted and folded rearwards. The two crew sat in open cockpits in tandem, with windshields. The landing gear was fixed with a rear fuselage skid. The engine was mounted in the fuselage nose and drove a two-bladed fixed-pitch propeller. Fuel was supplied from a 100 L (26 US gal; 22 imp gal) tank in the fuselage. Operational history The second aircraft, D-2222, a D-22a, took part in the Challenge 1932 international tourist aircraft contest, piloted by Walter Marienfeld. It was handicapped in technical trials, especially the short landing trial, not having flaps or slats, being relegated to 35th place, from 43 participants, after this section. It improved its score after a rally around Europe, where it took the 4th place, with a cruise speed of 205 km/h (127 mph; 111 kn). In the maximum speed trial it was beaten only by the five Heinkel He 64s, reaching 230.7 km/h (143.4 mph; 124.6 kn). As a result, it completed the contest in 17th place. Re-registered as D-EQIN from 1933, it was in use for several years after the Challenges. Specifications (D-22) General characteristics Crew: 1 Capacity: 1 / 255 kg (562 lb) payload Length: 6.6 m (21 ft 8 in) Wingspan: 7.4 m (24 ft 3 in) Height: 2.4 m (7 ft 10 in) Wing area: 13 m2 (140 sq ft) Empty weight: 345 kg (761 lb) Gross weight: 600 kg (1,323 lb) Fuel capacity: 100 L (26 US gal; 22 imp gal) Powerplant: 1 × Argus As 8 4-cylinder inverted air-cooled in-line piston engine, 75.7 kW (101.5 hp) Propellers: 2-bladed fixed-pitch propeller Performance Maximum speed: 230 km/h (140 mph, 120 kn) Cruise speed: 200 km/h (120 mph, 110 kn) Stall speed: 82 km/h (51 mph, 44 kn) ~ Range: 800 km (500 mi, 430 nmi) Service ceiling: 6,200 m (20,300 ft) Darmstadt D-22 3-view drawing from L'Aerophile Salon 1932 Akaflieg Darmstadt D-28 Windspiel D-28 Windspiel Role - Single-seat glider National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - R. Kosin and R. Schomerus First flight - 1932-3 The Akaflieg Darmstadt D-28 Windspiel (English: Italian Greyhound) was a single-seat, high-performance sailplane designed in Germany in the early 1930s. Intended to exploit a growing understanding of thermal soaring, it was small and manoeuvrable, with a 12 m span; silk-covered for lightness, it weighed less (empty) than its pilots. It held the world straight-line distance record for a time in 1934. Design and development The Akademische Fliegergruppe of the Technical University of Darmstadt was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their university. They began with gliders optimised for hill soaring with long span, high aspect ratio wings. By the early 1930s, partly through the experiences of the Darmstadt Musterle in the US, there was a better understanding of "blue" thermals and the Darmstadt group sought to exploit these small, weak currents with a light, manoeuvrable aircraft that could stay within their rising columns. The result was the D-28 Windspiel, combining a 12 m (39 ft 4 in) span with the lowest weight achievable with the plywood and fabric materials of the time. The D-28 was a wood-framed aircraft with a high, cantilever, single-spar wing, Akaflieg's established layout. It utilised the high-lift-to-drag ratio Göttingen 535 profile that Akaflieg had used on the Konsul and Darmstadt, though thinned by 10% to reduce drag. The structure also followed Akaflieg's previous use of wooden frames and stress-bearing plywood skin on the fuselage and leading edges of flying surfaces, with fabric covering elsewhere, but with greater attention to precision, the removal of unneeded material and metering of adhesives. The wing leading edge ply was only 1 mm (0.039 in) thick, and the fuselage was constructed without longerons. Instead of the standard aircraft linen, for lightness the Windspiel was covered in silk. The empty weight of the completed Windspiel was 55.5 kg (112 lb), a good deal less than that of most of its pilots. In plan, the wing was straight-tapered with elliptical tips. The whole of the trailing edge was occupied by camber-changing flaperons, attached to selected ribs rather than to a subsidiary spar as usual, another weight-saving measure. The hinge gap was sealed with 500 μm (0.02 in) ply strips. The wing was mounted, as with several earlier Akaflieg sailplane, on a narrow, faired pylon, with the cockpit in front of it and under the leading edge. The upper fuselage from the nose to the front of the pylon was detachable in a single piece, together with the cellophane single curvature glazing, so the pilot could access the cockpit. The Windspiel's fuselage was slender and oval in cross section, with a short skid under the centre section and small tail bumper as an undercarriage. The horizontal tail was straight-tapered, with the tailplane fixed to the top of the fuselage and carrying elevators with a central cut-out for rudder movement. The tall, straight-edged rudder was an all-moving one, but of an unusual design, divided vertically into two sections, with the front part carrying the rear surface. When the front surface moved, the larger-area, deeper rear surface further deflected by the same amount again, presenting a cambered surface. As on the Konsul, the rudder and ailerons were interconnected to ease yaw correction in turns. The date of the first flight is uncertain, but building was planned to start over the winter of 1931-32, and the Windspiel was performing record flights by early 1934. As its careful construction was slow, taking some 7,000 hours, a 1933 date is plausible. In flight it achieved the tight turns required to stay within small thermals; a medium-level turn with a bank angle of 25° produced an 80 m (260 ft) radius circle. After its 1935 accident and rebuild, the Windspiel was a little heavier, but the only major alteration was the separation of the full-span flaperons into inboard flaps and outboard ailerons. Operational history On 16 June 1934 (simons dates this to March 1934) the Windspiel, piloted by Hans Fischer, set a new world glider straight-line distance record of 240 km (149 mi) with a flight from Griesheim, Darmstadt to Thonneheim, Montmédy in France. On 9 June 1935 Fischer demonstrated the manoeuvrability of the Windspiel at an aircraft display day organised by the Aero Club de Portugal at the Amadora airfield near Lisbon. Glider aerobatics were a novelty at the time. The accident which led to the rebuild as the D-28B occurred at Griesheim in 1935. The D-28 was on the ground with Fischer aboard when an aircraft landed on the glider. It was wrecked but Fischer escaped with bruising. Rebuilt about 12% heavier, it was still capable of good performance. Hans Osann flew it from Darmstadt into the Netherlands, a distance of 275 km (171 mi). At the ISTUS meeting at Salzburg in 1937, he was one of a group to fly across the Alps. Later the D-28B was one of a group of sailplanes that pioneered thermal soaring in the Sahara. Though it flew well enough, this experiment with a very light glider did not lead to a new sailplane class. Its performance was not superior to larger, long-span aircraft which were cheaper to build and more robust in the air and on the ground. Variants D-28 Original version. D-28b Result of rebuild after ground accident. About 16 kg (35 lb) heavier, flaps and aileron separated. Specifications (D-28b) (Data from Sailplanes 1920-1945, Flugzeug-Typenbuch - Handbuch der deutschen Luftfahrt- und Zubehör-Industrie 1944) General characteristics Crew: 1 Length: 5.98 m (19 ft 7 in) Wingspan: 12.00 m (39 ft 4 in) Height: 1.07 m (3 ft 6 in) Wing area: 11.4 m2 (123 sq ft) Length de-rigged: 12.5 m (41 ft) Width de-rigged (without tailplane): 1.2 m (3 ft 11 in) Height de-rigged: 1.45 m (4 ft 9 in) Aspect ratio: 12.63 Airfoil: Göttingen 535 thinned by 10% Empty weight: 72 kg (159 lb) structure Gross weight: 152 kg (335 lb) in flight Performance Maximum glide ratio: 23:1 at 56 km/h (35 mph; 30 kn) Rate of sink: 0.58 m/s (114 ft/min) at 48 km/h (30 mph; 26 kn) Wing loading: 13.3 kg/m2 (2.7 lb/sq ft) Akaflieg Darmstadt D-30 Cirrus D-30 Cirrus Role - Single seat high performance sailplane National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - H. Alt and H. J. Puffert First flight - 1938 Number built - 1 The Akaflieg Darmstadt D-30 Cirrus was an aerodynamically advanced single seat sailplane with a very high aspect ratio wing and a pod and boom fuselage. Built in Germany just before World War II, it was intended as a record breaker and duly set a new world out-and-return distance record in 1938. Design and development The Akademische Fliegergruppe of the Technical University of Darmstadt (Akaflieg Darmstadt) was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. Before the Cirrus their sailplanes designs, whilst often advanced, had all been constructed from wood and fabric. It was well known that high performance required large lift to drag ratios, and that these were obtained by using high aspect ratio wings. The 20 m (65 ft 7 in) span wings of the Cirrus had an aspect ratio of 33.6, the highest of any aircraft built at the time, and such slender structures could not be built entirely from wood. Instead, a single, wide, tapering duralumin spar was built up out of corrugated sheets, with upper and lower skins that formed about one third of each wing surface at the root and more at the tip. Ahead and aft of the spar the wing profile was shaped with wooden ribs and plywood skinned. It was straight tapered in plan, constructed from an inner 10 m (32 ft 10 in) centre section and two outer panels each 5 m (16 ft 5 in) long, with a high taper ratio of 4 and with squared off tips. Strongly tapered wings have a lift distribution which falls rapidly along the span, so the angle of incidence of the wings of the Cirrus initially increased along the span (wash-in), then decreased towards the tips (wash-out), producing a better approximation of the lift distribution to that of the aerodynamically ideal elliptical wing. The outer panels had ailerons along the whole of their trailing edges, and the inner section similarly carried flaps. The ailerons were of the differential type and were interconnected to the rudder to simplify yaw correction. Mid-chord spoilers were fitted on the centre section. Apart from its span and aspect ratio, the wing had two other unusual features. A combination of the then new NACA profiles used gave the wing more camber at the tip. Since higher camber airfoils stall at greater angles of attack measured from the zero-lift line, the combination of higher camber and washout means that the stall develops inboard and that the ailerons, on the unstalled outer wing, retain lateral control and can prevent entry into a spin. This is now a standard sailplane design feature but was new in the 1930s. The other unusual and possibly unique wing feature was that the dihedral of the outer panels (there was none inboard) could be varied in flight though large angles (+8.5/-4.4). The intention was to investigate the effects of outer wing dihedral on handling. The wing was set on top of the forward fuselage or pod, which ended just aft of the trailing edge. The pilot's seat was ahead of the leading edge, with a canopy that ran back into the wing. The canopy and part of the surrounding upper fuselage was removed for access. There was a shallow landing skid under most of the pod. Take-offs were made from a four-wheeled dolly, left behind after launch. A slender, light magnesium alloy (electron metal) tube ran aft from the top of the pod, carrying the empennage, which had ply covered fixed surfaces and fabric covered control surfaces. The horizontal surfaces, set forward of the fin were straight tapered with rounded tips; the fin, which extended above and below the boom carried a large, almost semi-circular rudder. Operational history The Cirrus, flown by Bernard Flinsch, set a new world record out and return distance in 1938, flying 306 km (190 mi) from Bremen to Lübeck and back. Damaged in a launch accident, it was rebuilt with a revised pod and redesignated the D-30B. In June 1939 Flinsch flew it 406 km (252 mi). The Cirrus did not survive World War II. Variants D-30 Original version. D-30b Rebuilt after launch accident; improved pod shape. D-31 Planned, unbuilt two seat version. Specifications (D-30B) (Data from Flugzeug-Typenbuch . Handbuch der deutschen Luftfahrt- und Zubehör-Industrie 1944) General characteristics Crew: 1 Length: 6.62 m (21 ft 9 in) Wingspan: 20 m (65 ft 7 in)* Height: 1.75 m (5 ft 9 in) Wing area: 12 m2 (130 sq ft) Length de-rigged: 10.05 m (33 ft) Width de-rigged (without tailplane): 1.8 m (5 ft 11 in) Width de-rigged (with tailplane): 1.8 m (5 ft 11 in) Height de-rigged: 1 m (3 ft 3 in) Aspect ratio: 33.4 Airfoil: root: NACA 2412 ; tip:NACA 4412 Empty weight: 175 kg (386 lb) Gross weight: 265 kg (584 lb) Performance Never exceed speed: 300 km/h (190 mph, 160 kn) g limits: +8 (ultimate) Maximum glide ratio: 1:36 at 72 km/h (45 mph; 39 kn) Rate of sink: 0.52 m/s (102 ft/min) at 62 km/h (39 mph; 33 kn) Wing loading: 22.1 kg/m2 (4.5 lb/sq ft) *In Simons's 3-view, the span is incorrectly labelled as 42232 mm; as acknowledged in the Errata in Simons, Martin (2005). Sailplanes 1965-2000 (2nd revised ed.). Königswinter: EQIP Werbung & Verlag GmbH. p. 272. ISBN 3-9808838-1-7., it should be 20000 mm. Akaflieg Darmstadt D-34 D-34 Role - Experimental single seat sailplane National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - D-34a: W. Sarnes and H. J. Merklein First flight - 1955 Number built - 2 or 3 The Akaflieg Darmstadt D-34 sailplanes were a series of experimental single seat sailplanes, designed at the University of Darmstadt in the 1950s and early 1960s to explore the structural and aerodynamic advantages of the then emerging plastics and composite materials. Design and development The Akademische Fliegergruppe of the Technical University of Darmstadt (Akaflieg Darmstadt) was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. The 1955 D-34 was their first post-World War II design and formed the basis for a series of experimental sailplanes which explored new materials, airfoils and construction methods. The D-34 was a small single seat sailplane, all variants having a wingspan of only 12.65 m (41.5 ft). The first three variants shared a common, single piece, wing of straight tapered plan with a root to tip chord ratio of 2.03 and an area of 8.0 m2 (86 sq ft). There were small, cigar shaped tip fairings, termed salmons. The profile was the thick (21% thickness-to-chord ratio) NACA 644621, intended to produce laminar flow over the front 40% of the wing. It was formed around a three box spar of pine and plywood, its cells filled with plastic foam. The spar was less deep than the wing and the surface profile was shaped in ply over a small number of full chord ribs plus a carefully shaped plastic foam block filling. The wing was attached to the top of the fuselage, with cockpit immediately ahead under a removable, smooth, single piece canopy which was faired into the leading edge and extended almost to the nose. To avoid wing surface irregularities the D-34 had airbrakes mounted on the lower fuselage under the wing leading edge, opening like rear hinged car doors. A deep, faired skid served as undercarriage; there was no tail skid. The plywood skinned, oval section fuselage tapered uniformly to the rear. The D-34 had a T-tail with a straight tapered, round tipped, tabbed horizontal surface. The original fin was upright and of narrow chord, carrying a rudder much wider than the tailplane, with a straight, raked trailing edge. The D-34a first flew in 1955. Flight testing showed that the novel wing construction worked well, but that both the ailerons and vertical rear surfaces needed more area. This was addressed by extending the trailing edges of the ailerons beyond those of the wings and extending the rudder rearwards, giving it a more rounded appearance. At the same time a rudder tab was fitted, the fin chord increased and a dorsal fillet added. Various cockpit modifications were also made, including a new, longer version which reached forward over an extended forward fuselage to the small metal nose cone. The fuselage mounted airbrakes were not a success. In 1957 another group of students produced the modified D-34b Aphrodite, with G. Jacoby chiefly responsible for the redesign. It is not certain if this was a new airframe or a rebuild of the D-34a, but it used the same wing design apart from the inclusion of flaps, capable of 60° deflections and longer, lower chord ailerons which extended over the rest of the trailing edge outboard of the flaps. The flaps replaced the unsatisfactory airbrakes of the D-34a but the enlarged ailerons did not produce effective lateral control. The D-34b kept the longer forward fuselage of the modified D-34a, though with a less extended canopy, but had the original D-34 fin and rudder. The upper fuselage behind the cockpit was raised and more strongly faired over the wing, smoothing the upper fuselage line over the trailing edge. It had a retractable monowheel undercarriage and small tailskid in place of the bulky main skid of the D-34a. These changes raised the empty weight from the 128 kg (282 lb) of the D-34a to 141 kg (311 lb). By the time the performance was tested in 1960 the D-34b was showing signs of age but still returned a best glide ratio of 28.3:1, very respectable for a 12.65 m (41.5 ft) span glider. The D-34c B'phrodite was designed by M. Rade and flew in 1958. The main change was to the fuselage, with the original stressed-ply covered, wood-framed structure replaced by a fabric covered steel frame. The monowheel was non-retractable and the wingtip salmons removed. The empty weight was decreased by 4 kg (8.8 lb). The last variant was the D-34 of 1960. Designed, amongst others, by Gerhard Waibel, it kept the D-34b fuselage and tail but married it to a wing of new construction methods, different profile and larger area whilst keeping the same span as the earlier models. To achieve the latter both root and tip chords were increased by about 12%. The wings had 1° of dihedral and 2° of forward sweep. The salmons were replaced by rounded tips and the ailerons were longer and wider than those of the D-34b; just inboard of them inboard spoilers replaced the flaps. Structurally the wing was very different; there was no main spar. The front 60%, from a light, balsa filled nose to a plywood auxiliary spar, was a glass reinforced plastic (GRP) shell with a stiffening paper honeycomb filling. Ailerons and airbrakes were attached to the auxiliary spar. Behind it, the wing had ribs covered with a GRP/plastic foam sandwich. Careful construction kept the local "waviness" to less than 20 μm (0.00079 in). Though it had a lower aspect ratio (17.5) than the D-34b (20) because of the increased wing area, the D-34d had an improved best glide ratio of 35.1:1. Like the earlier variants, it was not intended as a production or competition aircraft, but as vehicle for the development of students' experience with the new materials of the time. Aircraft on display The D-34c D-4644 may be viewed with prior permission in the German Gliding Museum on the Wasserkuppe. A section of the D-34d wing is also there. Variants D-34a 1955, original version. D-34b Aphrodite 1957, revised fuselage, retractable wheeled undercarriage. D-34c B'phrodite 1958, steel framed, fabric covered fuselage, fixed wheel undercarriage. D-34d 1960, new, GRP wing of greater area, D-34 b fuselage. Specifications (D-34d) (Data from Sailplanes 1945-1965) General characteristics Crew: 1 Length: 6.40 m (21 ft 0 in) Wingspan: 12.65 m (41 ft 6 in) Wing area: 9.2 m2 (99 sq ft) Aspect ratio: 17.5 Airfoil: NACA 643618 Empty weight: 160 kg (353 lb) Gross weight: 255 kg (562 lb) Performance Stall speed: 65 km/h (40 mph, 35 kn) Maximum glide ratio: 31.6:1 at 90 km/h (56 mph; 49 kn) Rate of sink: 0.7 m/s (140 ft/min) minimum Wing loading: 29.4 kg/m2 (6.0 lb/sq ft) Akaflieg Darmstadt D-36 Circe D-36 Circe Role - High performance sailplane National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - Wolfe Lemke, Gerhard Waibel and Heiko Friess First flight - 28 March 1964 Number built - 2 Developed into - Schleicher ASW 12 The Akaflieg Darmstadt D-36 Circe is a single seat, high performance sailplane designed and built in Germany in the mid-1960s, one of the early "glass ships". It was the winner at the German National Championships in 1964 and came second in the World Championships the following year. Design and development The Akademische Fliegergruppe of the Technical University of Darmstadt (Akaflieg Darmstadt) was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. Design work on the Circe began in 1962-3 by a team of students, Wolf Lemke (responsible for the wing), Gerhard Waibel (fuselage and tail) and Heiko Friess (airbrakes). They were later joined by the younger Klaus Holighaus. Professor Franz Wortmann designed a new airfoil for the Circe. Construction began in 1963 and the aircraft flew for the first time, piloted by Wolf Lemke, on 28 March 1964 at Gelnhausen. The Circe is built from composite materials, with flying surfaces and fuselage shells made from glass-balsa-glass sandwiches. The wings have a single spar with flanges of aligned glass fibre (uni-directional rovings) and a glass-balsa sandwich web. The fuselage has GRP-balsa stiffening cross-members. The wing is tapered in two sections, with more taper on the outer 40% of the span. Such double taper plans can provide lift/drag ratios close to that of the ideal elliptical wing, and have benign stall characteristics. Ailerons occupy all the trailing edge of the outer panels, with flaps across the inner panels. Four sets of Schempp-Hirth airbrakes, two per wing, are located just behind the spar, roughly centred on the inner panels. Each set extends its surfaces, mounted like parallel rulers, above and below the wing. They were difficult to design because of the considerable flexure of the wing, the latter leading to the Circe's nickname of Gummiflügel (English: Rubberwing) at a time of stiffer structures. The fuselage of the Circe is slender and circular in cross section aft of the shoulder mounted wings. The vertical tail is tall and rather upright, with some forward sweep on the rudder trailing edge. The original horizontal T-tail was straight tapered in plan, with sweep only on the leading edge. Forward of the wing leading edge the cockpit, housing the pilot in semi-reclining position, has a long, two piece canopy which swells above the rear fuselage line. The rear part of the canopy opens for access. The Circe has a retractable monowheel undercarriage, assisted by a tail bumper. The testing that followed the first flight showed that there was a tendency to tail flutter, so a long, projecting mass balance was added at the centre of the tailplane. The whole tail was later redesigned by Holighaus who produced a shorter fin and rudder and got rid of the sweep of the original horizontal surface by adding forward swept elevators. The tailplane was also significantly reduced in size. At about the same time as the V-1 was being constructed at Darmstadt, a second Circe, the V-2, was built by Walter Schneider. It differed from the V-1 in having a parachute brake rather than the spoilers of the V-1 and turned out rather heavier. Operational history The V-1, flown by Waibel, won the German National Championships of 1964. Rolf Spärig flew it the following year in the 1965 World Championships, held at RAF South Cerney, Gloucestershire, UK, but was beaten into second place in the open class by the Polish Foka 4 flown by Jan Wroblewski, despite the Circe's better glide ratio. Most agreed the Circe was the most advanced sailplane at the Championships but that the Polish pilot's tactics were superior, not least as the Foka was a 15 m, standard class sailplane. During practice for the Championships, Spärig had flown the first-ever 500 km (311 mi) triangle in Germany. The V-1 flew for another three years before suffering an in-flight structural failure and destruction. The pilot, Heli Lasch escaped by parachute. An investigation blamed him rather than the aircraft; the then still-novel glass sailplanes accelerated quickly and speed was easily misjudged when the traditional indicators, such as attitude or sound, were used. The V-2 remained active until the mid-2000s. Variants D-36 Circe V-1 - darmstadt built, Schempp-Hirth airbrakes D-36 Circe V-2 - built by Walter Schneider, drag parachute brake, heavier Aircraft on display The Schneider built D-36 V-2, D-4686, is on display at the Deutsches Segelflugmuseum mit Modellflug, Wasserkuppe, Germany. Specifications (V-1) (Data from Sailplanes 1945-1965) General characteristics Crew: 1 Length: 7.35 m (24 ft 1 in) Wingspan: 17.80 m (58 ft 5 in) Wing area: 12.8 m2 (138 sq ft) Aspect ratio: 24.8 Airfoil: Inner panel Wortmann FX61 - 131K (the K indicating flaps); at tips, Wortmann FX60 - 126 Empty weight: 285 kg (628 lb) Gross weight: 410 kg (904 lb) Performance Maximum glide ratio: best, 44:1 Wing loading: 32.0 kg/m2 (6.6 lb/sq ft) The Schleicher ASW 12 (this production glider was based closely on the D-36 Circe) Akaflieg Darmstadt D-38 D-38 Role - Single-seat Standard Class sailplane National origin - Germany Manufacturer - Akaflieg Darmstadt First flight - 19 December 1972 Developed into - Glaser-Dirks DG-100 The Akaflieg Darmstadt D-38 is a German, single-seat, Standard Class sailplane that was designed and built by the Fliegergruppe of Darmstadt University. Design The D-38 is a cantilever, shoulder-wing monoplane with a glassfibre/balsa sandwich shell structure fuselage and wing, the wing has no flaps and has a T-tail. The pilot has a semi-reclining seat in an enclosed cockpit with a transparent canopy and the landing gear is a manual retracting monowheel gear with a tailskid. The D-38 was, in effect, the prototype of the successful Glaser-Dirks DG-100 competition Standard class glider. Specifications (Data from Jane's All the World's Aircraft 1973-74) General characteristics Crew: 1 Length: 6.96 m (22 ft 10 in) Wingspan: 15.00 m (49 ft 2.5 in) Height: 1.49 m (4 ft 7 in) Wing area: 11.00 m2 (118.4 sq ft) Empty weight: 207 kg (456 lb) Gross weight: 363 kg (800 lb) Performance Maximum speed: 250 km/h (115 mph, 100 kn) Stall speed: 66 km/h (41 mph, 36 kn) g limits: ±6.3 Maximum glide ratio: 39 Rate of sink: 0.6 m/s (120 ft/min) Akaflieg Darmstadt D-40 D-40 Role - Experimental high performance sailplane National origin - Germany Manufacturer - Akaflieg Darmstadt Designer - K. J. Heer and D. Teves First flight - 15 August 1986 Number built - 1 The Akaflieg Darmstadt D-40 is an experimental variable geometry single seat sailplane, fitted with almost full span, camber changing flaps for optimum aerodynamics in weak thermals and integrated into the wing so as to minimise flap tip drag. One flew successfully but the D-40, like other variable geometry sailplanes, was not commercialised. Design and development The Akademische Fliegergruppe of the Technical University of Darmstadt (Akaflieg Darmstadt) was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. Design work on the variable wing geometry D-40 began in 1980 but the first flight did not take place until 15 August 1986. As understanding of thermal soaring grew in the 1930s, glider pilots and designers became aware of two conflicting requirements for cross country flights. The aircraft needed good climb characteristics and low stalling speeds to enable tight turns within thermals but high speeds in the sinking air between them. These respectively called for low and high wing loadings on wings with high and low camber. Several designs, e.g. the 1938 Akaflieg Hannover AFH-4 and the later LET L-13 Blaník and Beatty-Johl BJ-2, had added large area slotted Fowler flaps on the inner part of the wing to increase camber and add area when extended. These satisfactorily reduced stall speed and with it the turn radius, but disappointed hopes of improving climb rates because of vortex generation (induced drag) at the tips of the flaps, seriously decreasing the lift to drag ratio. A solution to this problem was to extend the whole trailing edge, including the ailerons, and this route was taken by both the disappointing, heavy and complicated Operation Sigma Sigma, the more successful but still heavy and complex Akaflieg München Mü27 and the World Championship winning 15 m class Akaflieg Braunschweig SB-11. These last three designs changed the wing geometry by extending the wing rearwards at right angles to the trailing edge. Akaflieg Darmstadt took a different approach, pivoting the single piece flap near the tip and sliding it out from within the wing trailing edge, gaining the mechanism the nickname "penknife wing". As it is extended, a track in the fuselage side guides the thin flap into its high camber position at the wing root. The wing area is increased by 21% with the flaps extended. Although this arrangement avoids the vortexes at the flap tip, like any area increasing method used on a fixed span wing it results in a lower aspect ratio and hence a lower lift to drag ratio. The D-40 is constructed from a mixture of plastic-fibre composites, glass reinforced plastic (GRP), carbon fibre reinforced plastic (CRP) and aramid reinforced plastic (ARP) with some use of balsa wood. The shoulder mounted wing has a spar built from CRP rovings and GRP-balsa webs. The skin of both wing and flaps is an ARP/CRP/balsa sandwich; the flaps have CRP stringers. In plan the wings are straight tapered, with an increase in taper close to the tips; these outboard sections carry the short span ARP ailerons. The wing has 1° of dihedral and is swept forward at 2.3° at 25% chord. There are Schempp-Hirth upper surface airbrakes slightly forward of mid-chord near to mid-span. When the flaps, pivoted immediately inboard of the ailerons, are deployed the wing trailing edge becomes almost straight, making the plan almost triangular, and 12° of washout is generated by the now strongly cambered inner sections. This produces a lift distribution close to that of the ideal elliptical wing, with its minimum induced drag. The D-40 uses the fuselage and empennage of the Rolladen-Schneider LS3. This is a GRP shell, slender aft of the wings and with a T-tail with straight tapered surfaces. The rather wide cockpit occupies most of the deeper forward fuselage and has a long, one piece, front hinged canopy. A retractable monowheel undercarriage was assisted by a tail bumper. Operational history Initially the D-40 proved difficult for the relative novices of the Akaflieg to fly. In particular the short ailerons were lacking authority. The more experienced Helmut Reichmann did show, at one competition, that the D-40 outperformed the other sailplanes present under weak thermal conditions, as hoped for. The ailerons were redesigned and tall, narrow winglets added, which much improved the handling. In the end nothing became of any of the variable geometry glider designs. They were too complex for club use and significantly increased the pilot's workload. Specifications (Data from Jane's All the World's Aircraft 1987/8) General characteristics Crew: 1 Length: 6.75 m (22 ft 2 in) Wingspan: 15.00 m (49 ft 3 in) Height: 1.47 m (4 ft 10 in) Wing area: 9.50 m2 (102.3 sq ft) flap retracted; 11.5 m2 (123.7 sq ft) extended Aspect ratio: 23.7 flap retracted; 19.6 extended Airfoil: Inner Wortmann 67 - VG - 170 (the VG indicating variable geometry); at tips, Wortmann FX60 - 126 Empty weight: 284 kg (626 lb) Gross weight: 374 kg (825 lb) . Maximum 500 kg (1,102 lb) with water ballast Performance Maximum speed: 295 km/h (183 mph, 159 kn) smooth air; rough air and aero-tow 190 km/h (118 mph; 103 kn) Stall speed: 65 km/h (40 mph, 35 kn) g limits: +5.3/-2.6 Wing loading: 34.74 kg/m2 (7.12 lb/sq ft) minimum, flaps in, 52.63 kg/m2 (10.78 lb/sq ft) maximum. Flaps out, 28.70 kg/m2 (5.88 lb/sq ft) minimum, 43.48 kg/m2 (8.91 lb/sq ft) maximum. Akaflieg Darmstadt D-41 D-41 Role - Side-by-side configuration two seat sailplane National origin - Germany Manufacturer - Akaflieg Darmstadt First flight - 1993 Number built - 1 The Akaflieg Darmstadt D-41 was a two-seat, side-by-side configuration sailplane designed to perform as well as tandem seaters. It was built in Germany in the 1990s and was used by Akaflieg Darmstadt students until it was lost in a crash. Design and development The Akademische Fliegergruppe of the Technical University of Darmstadt (Akaflieg Darmstadt) was first formed in 1921. It was, and is, a group of aeronautical students who design and construct aircraft as part of their studies and with the help and encouragement of their University. The D-41 was completed in 1993. It was designed to show that a two-seat sailplane of side-by-side layout, with its better visibility for the instructor, who sits in the rear seat in a tandem configuration trainer, and easier instructor-pupil communication, could have as high performance as one with the more usual tandem seat arrangement. The D-41 was constructed from mixed composite materials, using GRP, CRP and aramid reinforced polymer. It had a mid-set wing of straight double tapered plan with a continuous straight leading edge with almost no sweep. Flaps filled the whole of the trailing edge inboard of the ailerons. The forward fuselage and cockpit region was wider than that of a tandem seater but inclined seats kept the depth down, leading to a flattened oval cross section of not much greater area. The cockpit was covered with a long, single piece canopy reaching back to the wing leading edge. Behind the wing the fuselage became slender, ending in a T-tail with straight edged, tapered surfaces. The D-41 had a retractable central undercarriage. The side-by-side configuration requires cockpit ballast for solo flying and the D-41 also had provision for 200 kg (440 lb) of water ballast for competition flying. Operational history The D-41 was used by the Akaflieg students and proved popular, but was lost in a fatal accident during an aborted launch. A spin developed which it was impossible to recover from before crashing, killing both pilots. Specifications (Data from Jane's All the World's Aircraft 1991/2) General characteristics Crew: 2 Length: 8.30 m (27 ft 3 in) Wingspan: 20.00 m (65 ft 7 in) Height: 0.85 m (2 ft 9 in) Wing area: 14.00 m2 (150.7 sq ft) Aspect ratio: 28.6 Airfoil: Wortmann AH-FX-81-K 130/17 root, Wortmann AH-FX-81-K 148/17 tip, as Rolladen-Schneider LS6 Empty weight: 350 kg (772 lb) Gross weight: 760 kg (1,676 lb) |