1. The mechanical components, that is, the bearings, seals, pump, etc., are the unheralded heroes of the successful powerplant, although they are only noticed when they give trouble. Approximately a decade ago, antifriction bearings had a dubious reputation for reliability. One in ten was expected to fail prematurely, and no designs were available which would, even on paper, meet the load, speed, and temperature requirements of a modern turbofan engine. Shaft seals were similarly undeveloped, and one of the major feasibility questions of the high-compression ratio engine was the shaftsealing problem. Over the past fifteen years, great effort has been expended in this field. Over 350,000 hr of component testing have been accomplished on 80 separate bearing and seal test stands at Pratt & Whitney Aircraft alone. The improvement in the performance of antifriction bearings and carbon seals has been greater than might have been anticipated. Figure 11 shows the improvement in anti