Experiences with A-7E and the AV-8B engine monitoring systems: the good and the ugly

The A-7E engine monitoring system, (EMS), was designed as a proof of concept system to increase safety and availability, improve reliability and maintainability and to reduce flight hour costs. The system proved so effective that the entire fleet of A-7E´s was retrofitted even though it was known that they were going to be retired in seven years. The results were that the accident rate went from an average of eleven per one hundred thousand flight hours to one. The maintenance man-hour per flight hour rate was reduce by 64%. Pilots did not want to fly the airplane without it because of successful in-flight warnings of impending failure. The AV-8B EMS, although designed after the A-7E system, was much less successful. It has been cumbersome to the user and much less effective in performance. It used newer technology but to date has not shown its true potential. There are many reasons for this lack of success with the AV-8B EMS compared to the highly successful A-7E system. These reasons are explored and documented. New enhancements to the present AV-8B EMS which should very significantly improve system performance, are presented and discussed. This paper presents the design paths of both systems, explain why one worked so well (The Good) and why one provided minimum benefits and was difficult for the users (The Ugly). The lessons learned and specific examples of successes and failures from the benefit perspective are described, and recommendations are made to aid future diagnostic and prognostic systems