An improved method of heating on aircraft engine and cabin. The engine muffler (2) is used with a shroud (4) to form a combustion chamber and heat-exchanger. A burner (3) provides heat which is transferred to air flowing through the heat-exchanger (2) and into the cabin. A two-way valve (10) controls the air flow. When the valve is closed heated air is diverted into the engine compartment. Thus the engine is heated by conduction from the muffler and by direct contact with the hot air.
