Results of an Advanced Research Projects Agency (ARPA) sponsored project to demonstrate the operational benefits of incorporating advanced structural ceramic ball elements into the F117-PW-100 aircraft gas turbine engine high rotor thrust bearings is described. This program consists of design, fabrication, and experimental evaluation of candidate hybrid ball bearing designs in Pratt & Whitney and MRC Bearings test facilities. The bearing design criteria and development test conditions utilized for the project are compatible with the requirements of the F117-PW-100 engine system application. Two hybrid bearing designs were produced by analytically varying internal geometry features such as M-50 race curvatures and contact angles to optimize for the modulus of elasticity of the ceramic balls. CERBEC grade NBD 200 silicon nitride ceramic balls (1 1/8 in. size) demonstrated integrity and a quadruple rolling contact fatigue life improvement versus state-of-the-art M-50 steel balls in single ball test rigs. Thermal performance data obtained in full-scale bearing rig performance testing with 178 mm size hybrid and all-steel baseline bearings shows comparable characteristics. The hybrid bearing displayed a distinct survivability benefit in bearing liquid lubricant starvation testing. Two dozen hybrid bearings will be fabricated for full-scale bearing rig endurance tests to be conducted in 1995–1996 as a prerequisite to validation in operating F117-PW-100 engines in 1996–1997.

ARPA BAA91-10, “Advanced Ceramic Technology Insertion Program Solicitation,” 1999.
Contract F33615-92-C-2200; “Ceramic Bearing Technology Insertion,” 1992.
Cundill, R. T., Galbato, A. T., Harris, T. A., “Fatigue Life of Silicon Nitride Balls,” STLE 92-AM-8A-2, 1992.
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