Fighter Aircraft FA1

This is a modern high-performance fighter aircraft fully instrumented for the SIPE experiments. The maneuvers conducted were short period (SP), lateral-directional (LD), roller coaster (RC), slowdown (SD), and wind-up turn (WUT). The latter three maneuvers are dynamic maneuvers for determination of drag polars from the flight test data using parameter-estimation methods. The idea behind this is that these maneuvers save flight test time compared to the steady-state methods (Chapter 7). The RC maneuver data were generated for Mach range 0.6-0.8 for 1g excursion of acceleration covering 0°-9° AOA. The SD maneuver is a low-speed maneuver at about 0.4 Mach and the AOA range covered is 9°-19°. The WUT involves a Mach range 0.6-0.8 steep turn of decreasing radius with “g” force varying from 1g to 8g. The AOA range is 8°-19°. The WUT is a combined longitudinal/lateral maneuver. The various tests were performed at 1.5, 3, and 6 km altitudes. The signals were sampled at 16/32 samples/s. Where applicable the sideslip angle correction factors with respect to altitude and Mach were used. Various math models used for the data analysis are given in Ref. [16]. Thrust data were used as input to the mathematical model. For drag polar estimation, the model-based approach was used as against the static/steady-state approach, since dynamic maneuvers were performed. This shifts the burden from flying aircraft at several AOA/Mach numbers (to obtain the static

stability and control derivatives as well as drag polars (by estimating lift and drag coefficients as a function Mach number/AOA) from the dynamic maneuvers (RC, SD, and WUT). Most of the (longitudinal and LD) flight determined derivatives (FDDs) as well as the drag polars compared well with the manufacturer’s data. The flight-determined longitudinal HQ met the Level 1 requirements. The flight-determined SP natural frequency varied from 2.3 to 3.65 rad/s and the damping ratio was 0.3. The Dutch roll (DR) frequency was determined as 2.5 to 3.4 rad/s. The neutral point was also determined from the real flight data and the results are shown in Table 9.3.