The Vibration of Airscrew Blades

Extract

Airscrews are generally made of wood and owing to the relatively low Young's modulus of timber the blades of an airscrew have a large measure of flexibility. This flexibility is reflected in the comparatively low frequency of vibration of the blades with consequent undesirable effects. Firstly, there is a tendency for the blades to heat resulting in the laminations becoming unstuck, and secondly, there is considerable danger from resonance between the frequency of the blades and the firing impulses of the engine driving the airscrew. The result of this is heating and burning of the boss and ultimately failure of the airscrew. It may even result in failure of the airscrew shaft by shearing.