A vane motor starter, driven either by compressed air from a storage tank or by hot gas from a solid propellant cartridge, improves starting reliability in two ways: 1. When the air supply is depleted, either by leaks or by unsuccessful starting attempts, a cartridge provides the gas power to meet the emergency. 2. When the weather is cold and engine starting is difficult, a cartridge offers higher torques and higher cranking speeds than can normally be obtained from a compressed air system.This system, initially designed for trucks, has been tested in the laboratory and in the field and is now in production. Performance curves for air and hot gas are presented. Cartridge performance and safety are discussed. Reliability figures from aircraft starter cartridges which have been in production for 15 years provide a statistical reliability background for this new starting system.