Abstract: A control system for controlling the flight of a free flight model aeroplane having an electrically powered drive unit and a tail unit comprising a thermal air current brake comprises a time switch for releasing the thermal air current brake and for interrupting the supply of power to the drive unit. The time switch comprises a spring mechanism, means for winding up the spring mechanism, the spring mechanism including a shaft, a control disc provided on the shaft, a peripheral recess and a cam surface being provided on the control disc or on a disc which is fast therewith in use. The peripheral recess is associated with and engageable with one arm of a two arm release lever such that when engaged by the one arm and rotated through a prescribed angle, the one arm will be released to undergo swivelling motion. The other arm of the release lever is connectable through tensioning means to the tail assembly of the aeroplane such that swivelling of the first arm causes actuation of the thermal air current brake.