Vibrations in Aircraft: A Series of Articles covering the General Principles for Aeronautical Engineers

THE majority of troublesome vibrations in aircraft arc forced vibrations, due to periodically varying forces originating in or around the power plant; the only important type which is not due to such a cause is flutter. Flutter is a vibration in a part of the aircraft structure set‐up by turbulence in the slipstream passing over the part, and has been the subject of a good deal of investigation from the early days of flying up to the present time. Control surfaces appear to be particularly susceptible to flutter, but a really spectacular example of mechanical failure from this cause is to be found in another branch of engineering—the failure of the Tacoma Bridge in America. In this case a suspension bridge, with a half‐mile central span, was completely wrecked by the effects of turbulent flow. The methods whereby aircraft designers avoid.the occurrence of similar failures are too specialized and intricate to be considered in this elementary study, and the reader is referred to the many reports on flutter included in the Air Ministry publication list.