Junkers L1

Hugo Junkers' early engineering experience was with stationary opposed-piston two-stroke diesel engines for industrial applications and this arrangement was eventually adapted for aircraft use. Nonetheless, his company's first aero engine was a petrol-fuelled four-stroke, the six-cylinder inline air-cooled L1. L was Junkers' notation for petrol engines from the L1 to the L10, which became the Jumo 210 in 1931.[1] It first ran in 1921[2] and was the subject of much static testing, but the intention was always to produce a flight engine. The first aircraft to test fly the L1 was the Junkers T 19; this aircraft first flew in 1922, but the date of its first flight with the L1 is uncertain.[1]

Notable features were the four large valves per cylinder, two inlet and two exhaust; the ball race main bearings; and the double ignition system, with twin magnetos and two sparking plugs per cylinder.[1]

The L1 was largely an experimental engine, but a small production line was set up in 1925. Reliability was not high, however and only a few aircraft, themselves built only in small numbers, used the L1 and its variants.[1] The large diameter, circular blower fitted to the L1a resulted in a flat fronted, circular cross section cowling, particularly noticeable on the Junkers T 19 and 26.[3]

• L1 Original version.
• L1a Larger bore diameter and a large circular blower, gear driven, mounted at the front of the engine to enhance high altitude power.
• L1b

• Focke-Wulf A 16b
• Junkers T 19
• Junkers T 26
• Junkers J 29

Data from Kay (2004) p. 263