Third Paper: Servo Reliability in the ‘Seacat’ Missile

The ‘Seacat’ missile has been adopted by the Royal Navy as the standard close-range ship-to-air weapon of the 1960's. When the specification was drawn up reliability requirements were nebulous in the extreme, but it was appreciated that with such a missile a ‘high’ reliability had to be achieved in spite of intense pressure to reduce weight, space, and cost to absolute minima, and in spite of some unusual operational requirements.

This paper reviews in retrospect some of the methods adopted both in the servo actuator design and in production procedures to meet these requirements. In addition the systematic reporting of tests carried out in depots of ships enables an assessment to be given of the reliability achieved in service.

It is concluded that, in the mechanical sphere, the cost of a full scale statistical exercise aimed at a prediction of reliability may well be exorbitant, and whilst assurance will be obtained, the contribution to the degrees of reliability may only be marginal. However, the systematic recording and analysis of experience in the field will enable maximum benefit to be derived for future projects.