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SIDDELEY COMPANY.
Major Green's theoretical interpretation of a new multiple air-cooled engine type. 

Aeroplanes have been fitted with two or more engines with a view to increasing the reliability of the power plant and also increasing the total horsepower by using more engines of a given size. This has been done in two ways, either by arranging for each engine to drive its own propeller as in the usual twin-engines type, or by providing gearing so that one or more engines can drive the propeller or propellers at will.

The disadvantages of the former type are well known. The chief disadvantage arises from the lack of symmetry, one engine stopped producing a tendency to turn which has to be counteracted. The resistance of the stopped propeller is also considerable. Again with an engine stopped, the power available for flight is insufficient to fly properly with full load. Apart from these disadvantages the aeroplane is apt to get rather complicated in its design and the resistance is likely to be comparatively high, due to having the two power eggs and the main body in separate units. 

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