Airplane Pre-Delivery Test Policies and System Reliability

The results of a study of pre-delivery reflight practices and subsequent airplane system reliability are presented and discussed. Since the airplane comprises the most complex single end item of hardware in the airplane pilot training system, the paper deals solely with the airplane. The study encompassed records of 33 airplanes delivered over a four month period. It was found that, for the corrective action policy in effect, the number of failures observed during the delivery flight was independent of the number of flights before delivery as well as of the number of failures experienced on the last flight prior to delivery. In addition, the failure rate of these aircraft in the field during the first 50 flight hours after delivery was found to be independent of the number of pre-delivery flights. As an extension of this study, the statistical distribution of airplane failure rates during the second 50 hours of post-delivery service was determined, and is presented. The overall MTBF for the group of aircraft studied was 7.46 hours during these second 50 hour periods.