An air guiding flap of an aircraft wherein one surface thereof faces an
air duct and is exposed to a prevailing pressure in the air duct and
whose opposite surface is exposed to the pressure of the relative wind
flowing past the aircraft. The air guiding flap comprises an actuator for
automatically opening and closing the air guiding flap which actuator
cooperates with a device for controlling the position of the air guiding
flap. In order to keep the stress on the air guiding flap low a force
detecting device is provided which detects the force impinging on the
actuator base don a difference between the prevailing pressure in the air
duct and the pressure of the relative wind flowing past the aircraft. The
controlling device adjusts the position of the air guiding flap such that
the force impinging on the actuator at any one time is at least
essentially zero.