This paper describes some unexpected unsteady motions exhibited in the wind tunnel by an aircraft model with thrust reversers operating in ground proximity. The cause of this oscillatory behavior was determined to be an unsteady interaction between the wall jets formed by impingement of reverser jets on the ground and the oncoming free stream. Time histories of rolling moments measured by the wind tunnel balance were analyzed. The effects of dynamics of the model balance/support system were removed and frequencies were scaled by Strouhal number to full scale. Corrected time series were used to simulate the motion of a fighter aircraft in ground effect. The simulation predicted large roll angles and nose-down attitude at touch-down. The paper also describes briefly the time-averaged stability and control changes (relative to reverser off) associated with the unsteady effects. In ground proximith, the aircraft experienced a strong pitch-up accompanied by the loss of horizontal tail and aileron effectivenesses. The magnitude of reverser-induced changes in ground effect was much larger than corresponding changes in free air. The paper points out the need for accurate transient unsteady aerodynamic data for a realistic simulation of aircraft motion during approach and landing with thrust reversers. A test concept for acquiring such data is outlined.
Unsteady thrust reverser effects in ground proximity
Transiente Effekte durch Schubumkehr in Bodennaehe
AIAA-Papers ; 1-11
1984
11 Seiten, 14 Bilder, 6 Quellen
Aufsatz (Konferenz)
Englisch