AD 2020-19-06 Rompted By Reports Of An Unapproved Variant McCauley Idler Gear Bearing

The FAA is adopting a new airworthiness directive (AD) for certain model McCauley Propeller Systems (McCauley) governors installed on airplanes.

This 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 AD requires replacing the governor with a governor that is eligible for installation. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective November 3, 2020.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain model McCauley Propeller Systems (McCauley) governors installed on airplanes. The NPRM published in the Federal Register on April 7, 2020 (85 FR 19399). The NPRM was prompted by reports from McCauley that an unapproved variant idler gear bearing, 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 nonconforming 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.

The NPRM proposed to require replacing an affected governor with a governor eligible for installation. The FAA is issuing this AD to prevent failure of the idler gear bearing, which could result in failure of the governor, loss of propeller pitch control, engine and propeller over speed, engine oil contamination, and loss of airplane control.

FMI: www.regulations.gov