The purpose of my contribution is to explain the need for dynamic testing in terms of defining the design problems where testing is required to assist or substantiate decisions made in the light of mainly theoretical evidence in the initial stages of design before hardware becomes available for testing.

I have interpreted the title in the broadest sense of the word vibration so as not to restrict the presentation only to testing associated with assessing or minimising the vibration of helicopters, but to include problem areas which result in dynamic testing requirements.