Evaluating the Dynamic Response of In-Flight Thrust Calculation Techniques During Throttle Transients EVALUATING THE DYNAMIC RESPONSE OF IN-FLIGHT THRUST CALCULATION TECHNIQUES DURING THROTTLE TRANSIENTS

New flight test maneuvers and analysis techniques for evaluating the dynamic response of in-flight thrust models during throttle transients have been developed and validated. The approach is based on the aircraft and engine performance relationship between thrust and drag. Two flight test maneuvers, a throttle step and a throttle frequency sweep, were developed and used in the study. Graphical analysis techniques, including a frequency domain analysis method, were also developed and evaluated. They provide quantitative and qualitative results. Four thrust calculation methods were used to demonstrate and validate the test technique. Flight test applications on two high-performance aircraft confirmed the test methods as valid and accurate. These maneuvers and analysis techniques were easy to implement and use. Flight test results indicate the analysis techniques can identify the combined effects of model error and instrumentation response limitations on the calculated thrust value. The methods developed in this report provide an accurate approach for evaluating, validating, or comparing thrust calculation methods for dynamic flight applications. Nomenclature A/B afterburner AJ nozzle throat area, in 2 AP area pressure (thrust correlation method) Axw aircraft acceleration along its flightpath, ft/sec 2 Azw aircraft normal acceleration relative to its flightpath, ft/sec 2 A8 nozzle throat area, in 2 or ft 2 C D vehicle drag coefficient CIVV compressor variable guide vane, deg D vehicle total drag, lb excess thrust, lb EGT exhaust gas temperature, ° C EMD engine model derivative EPR engine pressure ratio g acceleration caused by gravity FG gross thrust, lb FN net thrust, lb FNP net propulsive force, lb error in net propulsive force term, lb nozzle exterior drag, lb FR engine ram drag, lb inlet spillage drag, lb FTIT fan turbine inlet temperature, ° F FVG fan variable guide vanes, deg HIDEC Highly Integrated Digital Electronic Control HPVG high-pressure (rotor) variable guide vanes, deg IFT in-flight thrust L lift, lb Mil military power (maximum dry power) Max maximum power NZ normal load factor, g N1 fan rotor speed, rpm N2 compressor rotor speed, rpm PLA power lever angle, deg PLF power required for level flight, deg PS0 ambient static pressure, lb/in 2 PS2 engine inlet static pressure, lb/in 2 PS6 afterburner inlet static pressure, lb/in 2 PS7 exhaust nozzle inlet static pressure, lb/in 2 PT4 combustor pressure, lb/in 2 Fex