Abstract: Apparatus for controlling the pitch of the blades of a variable pitch, governor controlled, aerial propeller of which the pitch of the blades is variable between a coarse pitch limit and a fine pitch limit to match the torque of its prime mover has holding means (A) to maintain a forward thrust-generating blade pitch angle greater than the fine pitch limit with the prime mover idling as when an aircraft propelled by the propeller is taxi-ing whereby the propeller rotates more slowly, and hence more quietly, than it would otherwise. Preferably the holding means is effective by actuating a lock pitch solenoid valve (21) and an autofeather valve (18).

Abstract: An economical method of, and apparatus for, de-icing the skin panels (25) of aircraft employs electromagnetic solenoid actuators (1) which use normal supply voltages (43) available on aircraft to flex the skin panels slowly and rely upon abrupt termination (S) of the flexing pressure and the consequent fast natural elastic relaxation of the panels to break the bond between the panels and the ice accreted thereon, to shrug off the ice from the panels.