The FAA on July 28 issued a supplemental notice of proposed rulemaking (SNPRM) to expand the scope of a 2018 proposal to require the tail rotor (T/R) drive shaft yoke assembly be replaced and inspected for sealant on certain Robinson R66 helicopters.
The 2018 notice of proposed rulemaking was prompted by reports of two failures of the T/R drive shaft forward hanger bearing because the bearing was “undersized for its housing,” the proposal states. “Consequently, the bearing was spinning at a speed that caused excessive heating of the bearing during operation and led to the breakdown of the bearing’s grease and ultimately seizure of the C647-16 bearing.”
Failure of the T/R drive shaft forward hanger bearing could lead to loss of helicopter control, the proposal states.
The SNPRM proposes “either installing Robinson field kit P/N KI-235 or replacing an affected T/R drive shaft assembly with T/R drive shaft assembly P/N D224-4” and “prohibiting installing an affected T/R drive shaft assembly on any helicopter.” The T/R drive shaft assembly would have to be replaced or the kit installed within 100 hours’ time in service.
The number of helicopters affected by the proposal has expanded from 249 helicopters to 290. The FAA estimates that it could cost about $1,460 or $4,835 per helicopter, depending on the method of compliance used.