ESTIMATION OF DRAG POLAR IN WIDE MACH RANGE FROM A SINGLE CONTINUOUS DYNAMIC MANEUVER

摘要

This work proposes a new flight test technique and data reduction method in order to estimate the drag polar parameters of a high performance aircraft, by following a single continuous dynamic maneuver through transonic and subsonic flight regimes. The technique consists of a sequence of pushovers and pullups in a range of Mach numbers, covering a relatively wide area in the Mach number and lift coefficient domain. A new procedure for data reduction based on the least squares method using pseudo inputs is also proposed. The pseudo inputs were conceived in a way that allowed the simultaneous estimation of the drag polar parameters at the complete set of breakpoint Mach numbers, considering a continuous linear variation of the parameters between them. The technique was flight tested using an instrumented Northrop F-5FM of the Brazilian Air Force, leading to 54% reduction of flight test time, compared to the classical pushover-pullup and windup turn maneuvers, in order to explore the same portion of the flight envelope. For being a natural extension of the pushover-pullup technique, the maneuver was named multi-pushover-pullup. The execution of the maneuver resulted in a minor pilot workload, because a tight control of Mach number tolerances was not necessary, and required no prior training. The newly proposed approach led to the same accuracy level of the classical dynamic maneuvers.