by Horst Zoeller, 1996 - 2020, 67th Edition, 22 Nov 2020

Junkers Fo3

Five Cylinder, two strokes, diesel oil driven

A major disadvantage of the carburetor engines was the small operating range. In the mid 20s Junkers therefore returned to the diesel- and oil-engine designs, which offered good performances as ship engines.

While Junkers gathered a lot of experience about the construction of oil and diesel aircraft engines from the Junkers Fo2, his first real aircraft engines still were carburator engines, like the L2 and L5. Nevertheless, Junkers was sure, that just diesel engines would offer an economic aeronautical power unit. Therefore he continued his studies about diesel engines parallel to the carburetor engines.

In 1926 the Junkers Fo3 resulted from these studies. This was Junkers first real diesel driven engine. While the cylinders of the Fo2 were laying, the Fo3 cyclinders were in an upright, vertical position.

The Fo3 was an experimental engine, which should allow to gather expierence about the two stroke mechanism. It was never used on an aircraft

Technical Data:

Engine Designator year Cyl. Bore
in mm
in mm
in litres
in %
in m
in m
in m
in kg
T/O Power
in kW
Cruise Power
in kW
Fo 3 1926 5 140 n.a. n.a. n.a. n.a. n.a. n.a. na. 610 n.a. n.a. n.a.

Aircraft Types equipped with Fo 3:

None used in aircraft.



  • National Advisory Committee for Aeronautics
    Development of the Junkers Diesel Aircraft Engine
    Washington, May 1930, Download PDF here


introduced Nov 1996, transfered Aug 2017
contents last updated 13 Aug 2004