Question NPRM: McCauley propeller governors

  • Jen D
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28 Apr 2020 16:43 #2373 by Jen D
NPRM: McCauley propeller governors was created by Jen D
Hi Piper Flyer members,
We are assisting AOPA with gathering comments on another NPRM. If you comment directly to the FAA (which we recommend) please also send a copy to me. If you don't want to use the formal comment system through the FAA, please post your comments here, or email me directly.
Comments are needed before May 22, 2020
ACTION: Notice of proposed rulemaking (NPRM).
The FAA proposes to adopt a new airworthiness directive (AD) for certain model McCauley Propeller Systems (McCauley) governors installed on airplanes. This proposed AD was prompted by reports of an unapproved variant McCauley idler gear bearing, part number (P/N) A-20028, that could be installed in the affected governors. This proposed AD would require replacing the governor with a governor that is eligible for installation. The FAA is proposing this AD to address the unsafe condition on these products.

The FAA has received reports from McCauley that an unapproved variant idler gear bearing, part number (P/N) A-20028, was installed on certain governors during production between January 31, 2017, and September 27, 2018, and may have been installed on governors in service after January 31, 2017. The unapproved variant of the idler gear bearing does not conform to McCauley drawing requirements.
All models of McCauley governors have an idler gear bearing with P/N A-20028 installed; however, the unapproved variant of the bearing can be identified by part marking “BA-59.” The non-conforming idler gear bearing could have also been included in the idler gear assembly (idler gear and bearing), P/N A-20107, or the governor overhaul kit, P/N PL-20233 or PL-20234.
The non-conformity of the bearing may cause premature failure of the idler gear bearing. Early symptoms that the idler gear bearing may fail include inability of the governor to hold the selected RPM, hunting, surging, etc. An investigation identified 23 occurrences of airplane operation problems related to erratic governor behavior that may have resulted from the unapproved idler gear bearing.
This condition, if not addressed, could cause the idler gear bearing to fail. This failure could result in failure of the governor, loss of propeller pitch control, engine and propeller over speed, engine oil contamination, and loss of control.

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