Scheibe SF25C, G-FLKS
The SF25C is a motorglider of tail wheel configuration. On completion of a short flight of 30 minutes duration in conditions that were clear and sunny, the aircraft was landed directly into a northerly wind of some 20 kt. After rolling to a stop, the pilot operated the tail wheel lever to disengage the tail wheel and allow it to freely castor. The pilot began to taxi the aircraft with the stick held in the fully back position, turning to the right, with the intention of returning downwind to the launch point. After the glider had turned through approximately 80 degrees, it stopped. The pilot applied more power, with the stick still held fully back. At this point, the tail rapidly lifted and the propeller struck the ground and shattered. It took the pilot two or three seconds to react and to switch off the engine, which was still running with the remains of the propeller were still turning. On exiting the aircraft, the pilot noted that the tail wheel lever was in the locked position, but this may have been disturbed when the pilot and passenger exited the aircraft. Ground manoeuvring of tail wheel aircraft in strong and gusting winds requires caution particularly as, when crosswind, there is a strong tendency for such aircraft to weathercock into wind. Under such circumstances, if rudder and power are applied in an attempt to continue the turn, particularly if differential wheel braking is applied with rudder, then a nose down pitching moment is generated and the tail may lift. Also, when crosswind in a strong wind, the propeller slipstream may be deflected to some extent from the tail surfaces, reducing the down force on the tail normally expected when the stick is held back. In this situation, a tailwind component of the wind may additionally be present and contribute to the de-stabilisation of the aircraft.
Published 10 December 2014