This post is one in a series on the development of the F-35. Click here for a Flash graphic with system cutaways. Click on Read More to read the entire post on that system and check out next week's special coverage of the program in the Dec 12 edition of AW&ST.
Weighing less than 100lb and spinning at 8,000rpm as it transmits almost 29.000shp from the engine to the lift fan, the driveshaft met the orginal specification but had to be redesigned because of greater than predicted variations in length caused by airframe and engine build tolerances, thermal and pressure growth and maneuver deflection.
Graphic: Pratt & Whitney
A redesigned driveshaft with a more-flexible bellows coupling will be fitted to production aircraft beginning early in 2014. Driveshafts in aircraft already produced, including the test jets, are being fitted with tailored shims, or steel spacers, to ensure they can accommodate the length variations in operation.
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