Hirth HM 506

The Hirth HM 506 was a six-cylinder air-cooled inverted inline engine that was developed from the earlier four-cylinder HM 504.[1] The HM 506 was a popular engine for light aircraft of the 1930s to 1940s and powered the Bücker Bü 133A model trainer. The engine featured a cast magnesium alloy crankcase.

HM 506
Type Inline piston engine
National origin Germany
Manufacturer Hirth Motoren GmbH
Major applications Bücker Bü 133


Specifications (HM 506)

Data from Grey 1972, p. 60d-61d

General characteristics

  • Type: 6-cylinder air-cooled inverted inline
  • Bore: 105 mm (4.13 in)
  • Stroke: 115 mm (4.53 in)
  • Displacement: 5.976 L (364.7 cu in)
  • Length: 1,276 mm (49.8 in)
  • Width: 490 mm (19.1 in)
  • Height: 735 mm (28.66 in)
  • Dry weight: 149 kg (328 lbs)


  • Valvetrain: 1 inlet and 1 exhaust valve per cylinder, operated by push-rods and rockers
  • Fuel system: 2 Sum down draught carburetters, automatic mixture control and suitable for inverted flight. Twin Bosch magnetos.
  • Oil system: Fresh oil, metered for each cylinder. Rockers in oil bath.
  • Cooling system: air




  1. Gunston 1989, p.77.


  • Grey, C.G. (1972). Jane's All the World's Aircraft 1938. London: David & Charles. ISBN 0-7153-5734-4.
  • Gunston, Bill. World Encyclopaedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
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