Roller Coaster (Pullup/Pushover) Maneuver

The Roller coaster (RC) maneuver is used to determine the aircraft drag polars. Starting from a trimmed level flight (this condition is not really necessary), the pitch stick is first pulled to slowly increase the normal acceleration from 1g to 2g (at the rate of roughly 0.1g/s) and then returned slowly to level flight in the same fashion, i. e., to 1g. Then the stick is pushed slowly, causing the acceleration to change from 1g to 0g at a slow rate and then returned slowly to trimmed level flight. This is a dynamic maneuver in the vertical plane with load factor varying from 0g to 2g or up to 4g as the case may be. The thrust should be kept constant and the speed variation should be minimal. The data are recorded at least for about 25-30 s in this slow maneuver, which covers low angle of attack range (0°-10°) and Mach number from 0.4 to -0.9. The speed should be kept constant in the beginning. This maneuver can also be performed up to 4g if found necessary. Typical RC maneuver flight-time histories are shown in Figure 7.9.

7.7.1 SD Maneuver

The purpose of SD maneuver is to determine the drag polars in the high AOA range. The maneuver is performed in the vertical plane and the Mach number range is 0.4 to low speed range. The aircraft is trimmed for level flight at the chosen flight condition. Then the elevator stick is pulled slowly to maximum AOA and then recovery is made from the stall entry. The data are recorded for 25-30 s. The thrust must be kept constant. Typical SD maneuver flight-time histories are shown in Figure 7.10.