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Model Aircraft Glossary: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Aero Engines

Internal combustion engines come in many shapes and sizes. Nowadays they are designed for specific tasks although some may be simple changes such as extra cooling fins for model car compared to aircraft installation.

When choosing an engine for a model aeroplane the first thing to do is see what the manufacturer recommends. This will normally take the form of a range of engine displacements given in cu. in. (cubic inches) or c.c. (cubic centimetres). The conversion between the imperial and metric system of units is:

1 cu. in = 16.387 c.c.

It will also state whether this is for two-stroke or four-stroke engines or a displacement range for each type.



  • Good power to weight ratio - 2.5 to 5bhp/kg
  • Good power to displacement ratio
  • Cheap to buy
  • Cheap to run


  • Noisy



  • Quiet
  • Power produced at lower speed
  • Economical on fuel


  • Expensive to buy
  • Lower power to weight - 1.5 to 2.5bhp/kg

If you really want the scale look and sound then there is nothing better than a scale multi-cylinder engine such as this one.

A model Cirrus engine.


Nearly all aero engines are air-cooled, that means you need to get a good supply of air over the cooling fins around the cylinder and over the head.

If you don′t get enough cooling the engine will not develop power, not tickover very well, wear-out more rapidly and in the extreme seize.

The engines will normally arrive with instructions that will suggest the size of propeller that best suits it, this will control the engine speed range and provide enough cooling if the engine is open to the elements.

If you are putting the engine into a cowling then remember that the air has to get into the cowl and out. If you restrict or block the outlet then the air flow will be blocked.

See also: Engine Cowling, Engines, Engine Power to Weight Ratio, Propeller Sizes, Propellers.

Some further places to look:

Model Aircraft Glossary: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z