Brake failures

Does anyone know if the default KEY_TOGGLE_ brake failure methods actually work? If I try the following:-

	if (event==KEY_BRAKES || event==KEY_BRAKES_LEFT || event==KEY_AXIS_LEFT_BRAKE_SET)	{		lookup_var(&left_brake);		if(left_brake.var_value.n>0)send_key_event(KEY_TOGGLE_LEFT_BRAKE_FAILURE,0);/etc.

-the aircraft tracks quite happily in a straight line whereas I would expect a sudden swerve to the right.-Dai