Abstract: A flight deck and cabin heater for rotary and fixed wing aircraft driven by a gas turbine engine, including an air heating chamber located above the exhaust section of the engine and having ram air intake to the air chamber and heated air discharge from the air heating chamber to the flight deck and cabin together with valve means to control the intake of air to the air heating chamber, valve means to control the flow of heated air to the flight deck and cabin and recirculation of cabin air, and further valve means to dump heated air, all under the control of the aircraft operator taking into account the temperature of the air outside the aircraft.