EASA AD US-2020-19-06: MCCAULEY PROPELLER SYSTEMS - Governor Idler Gear Bearings - Replacement

What to do

Affected operators must inspect McCauley governors for the unapproved idler gear bearing marked "BA 59" and replace the governor with an eligible unit by November 3, 2020. Installation of governors containing the defective bearing is prohibited. Operators can obtain service information from McCauley Propeller Systems and should coordinate with maintenance providers to comply before the effective date.

Summary

MCCAULEY PROPELLER SYSTEMS - Governor Idler Gear Bearings - Replacement is a Federal Aviation Administration (FAA) Airworthiness Directive addressing certain McCauley Propeller Systems governors installed on airplanes. It targets governors that may contain an unapproved variant of the idler gear bearing, part number A-20028, marked with "BA 59," which does not meet McCauley drawing requirements. This unsafe condition affects all models of McCauley governors produced or serviced between January 31, 2017, and September 27, 2018.

What changed

This new FAA Airworthiness Directive requires replacing affected McCauley governors containing the unapproved idler gear bearing with governors eligible for installation. It prohibits installing governors with the defective bearing variant to prevent premature bearing failure. The directive introduces mandatory compliance actions to address erratic governor behavior and potential loss of propeller pitch control.

Why it matters

This directive is critical for aviation professionals because failure of the idler gear bearing can lead to governor failure, loss of propeller pitch control, engine and propeller overspeed, engine oil contamination, and ultimately loss of airplane control. Operators, maintenance organizations, and compliance teams must ensure affected governors are identified and replaced to maintain safe flight operations and regulatory compliance.