Investigation of F/A-18A Engine Throttle Usage and Parametric Sensitivities

Projection of realistic engine usage is essential for advanced tactical fighter aircraft to avoid significant durability problems and associated high weapon system costs. Previous engines such as the TF41 and F100 experienced durability deficiencies because actual field usage was more severe than initial projections. Thus, MCAIR developed systematic prediction procedures to provide improved usage estimates for preliminary design. These procedures based on digital flight simulation models were used to investigate throttle usage for peacetime training flights of the Navy F/A-18A aircraft with F404-GE-400 engines. The purpose was to identify major contributors to engine damaging usage and provide an early assessment of anticipated F/A-18A field utilization. Data are presented for individual mission throttle cycles and time histories as well as composite engine duty cycles. The prediction procedures were validated demonstrating excellent agreement by comparing results with flight data from the contractor phase of the Navy’s Accelerated Service Test (AST) at Patuxent River Naval Air Station (NAS). Engine usage was projected for F/A-18A transitional training at Lemoore NAS, the first deployment site. Results indicate that the severity of cycles and hot time at Lemoore will be comparable to that for AST. The ground attack, air combat, and air intercept missions were found to contribute the most to usage. Sensitivities were also evaluated parametrically for F/A-18A aircraft performance and mission parameter variations. Usage was found to be most sensitive to aircraft thrust to weight, and insensitive to store drags. The results provide valuable insight into how missions, maneuvers, and aircraft performance parameters affect usage which is important for cost effective design of durable, high-performance engines.