The Daimler L15, sometimes later known as the Daimler-Klemm L15 or the Klemm-Daimler L15, was an early two-seat, low-powered light aircraft designed by Hanns Klemm and built by the Daimler Aircraft Company in Germany. It first flew in 1919 and is considered one of the world's first practical light aircraft. During its career, it also flew as a glider.
Design and Development
After World War I, the terms of the Versailles Treaty ended military aviation in Germany. Hanns Klemm, who had previously designed the Daimler L11 and L14 fighter prototypes, turned to developing a low-power light aircraft. The L15 was a high-wing cantilever monoplane with a 6 kW (7.5 hp) Indian motorcycle engine. It featured unusual rotating wingtips for roll control instead of conventional ailerons and a single-axle undercarriage. Only one example was built.
Early in the testing programme in 1919, the aircraft suffered serious propeller damage, and Daimler and Klemm temporarily abandoned aviation.
Glider Conversion (1922)
In 1922, stimulated by the Rhön glider competitions on the Wasserkuppe, Klemm proposed rebuilding the L15 as a glider. The engine was removed and replaced with a long, smooth, removable nose. The pilot sat at the wing leading edge within this nose, with a passenger cockpit between the two wing spars. The wings were rebuilt in three pieces for easier transport, and the empennage had no external bracing, making the aircraft aerodynamically very clean for its time. The fixed axle undercarriage was replaced with separately mounted wheels on faired V-struts with vertical shock absorbers. The wheels had ash-tyres, as rubber was expensive in postwar Germany.
In the summer of 1922, the L15 made glider flights of up to 13 minutes, with an estimated lift-to-drag ratio of about 16.
Return to Powered Flight (1923–1924)
Towards the end of 1923, the L15 received a second-hand 9 kW (12.5 hp) Harley-Davidson motorcycle engine with 3:1 epicyclic reduction gearing. The pilot now occupied the former passenger cockpit, with a passenger seated behind at the wing trailing edge.
During tests, the powered L15 reached an altitude of 2,150 m (7,050 ft) solo and 1,100 m (3,610 ft) with a passenger. A solo flight lasting 185 minutes was recorded, and a passenger-carrying flight lasted 122 minutes. Flights covered up to 190 km (118 mi).
In the autumn of 1924, the L15 was fitted with floats and successfully took off from water, with takeoff taking 12 seconds even with only 12.5 hp.
The aircraft also briefly tested an unusual uncowled Daimler-Versuchmotor F7506, a two-stroke, six-cylinder, air-cooled radial engine with a Roots blower producing 15 kW (20 hp), but this was soon abandoned. The final engine fitted was a 30 kW (40 hp) Salmson, and the aircraft was refined with flaps, slats, and pneumatic rubber-tyred wheels.
Legacy
The flights of the L15 attracted attention and launched Klemm on a path that led him to establish his own light aircraft company in 1926. The L15 was eventually put on display in the Deutsches Museum with the placard "The First Light Aircraft," but was destroyed during World War II.
Specifications (Harley-Davidson engine)
- Crew: Two
- Wingspan: 12.6 m (41 ft 4 in)
- Wing area: 21 m² (230 sq ft)
- Empty weight: Less than 200 kg (441 lb)
- Powerplant: 1 × Harley-Davidson two-cylinder motorcycle engine, geared down 3:1, producing 9.3 kW (12.5 hp)
- Propellers: Two-bladed
