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The full-range pawl-and-ratchet clutch will permit very versatile operation of an air turbine starter. The need for a full-range pawl-and-ratchet clutch arises from various aircraft anomalies that may lead to ordinary clutch failures and therefore cause unnecessary delays for commercial as well as military aircraft. Air turbine starters containing a full-range pawl-and-ratchet clutch permit running engagement starts of aircraft jet engines at any speed from zero to above 10,000 rpm. The starter automatically disengages from the engine after completing the start and spins down to zero rpm. The concept embodied in the full-range pawl-and-ratchet clutch will provide a new generation of aircraft starters and represents a revolutionary advancement in the state of the art for air turbine starters.

The main engine air turbine start system, which typically consists of an air turbine starter and starter control valve, is a key contributor to aircraft dispatch reliability. Evolving aircraft propulsion systems have resulted in more aggressive operational environments, thus providing the impetus to improve the design of the start systems to enhance their durability and aid in improving both dispatch reliability and system responsiveness.

A ceramic turbine wheel has been designed as a retrofit for Waspaloy for a military cartridge mode air turbine starter. This results in reduced cost and weight while increasing resistance to temperature, erosion, and corrosion. Techniques used to perform ceramic turbine three-dimensional fast fracture reliability analysis were verified with spin testing of ceramic test rotors and correlated well with burst speed predictions. Reliability estimates have been made for design and proof conditions, providing guidance for selecting a ceramic supplier and for detennining proof test yield. Room temperature whirlpit burst testing is planned to verify the mechanical design and reliability of the wheel.