Many engineering problems are unsuitable for either pure digital or pure analogue computation. An example is provided by the helicopter. Owing to the size of the problem, a digital solution takes too long, and far more equipment is required than is generally available on analogue computers. In addition, there is the difficulty of including important non-linear effects.

A hybrid computer is a combined digital and analogue computer and can be used to advantage in these circumstances. I shall mainly be concerned with the integration difficulties which arise when applying this form of computation to helicopter simulations. The concepts developed are not restricted to the helicopter problem and an integration technique will be explained which has wide application in the study of other engineering systems.