The FAA is considering issuing an AD applicable to STC airplanes equipped with Honeywell TPE331 series turboprop engines with a propeller pitch control (PPC) lever interface to the airplane control system for the engine. The TPE331 series engines have a known airworthiness concern in which the propeller pitch control lever can loosen and detach in flight, causing a loss of engine control.
The AD would follow SAIB NE-16-18. Honeywell issued a letter detailing how to install a secondary retention feature to prevent the PPC lever’s detachment (see photo below). The FAA recommends that all STC holders affected by SAID NE-16-18 incorporate this retention feature. According to the FAA, attaching the Honeywell letter to the engine and airplane manuals after completing the work will constitute compliance with continued airworthiness.
NAAA previously reported on this issue in October 2021 when the FAA issued an airworthiness concern sheet for G-164 aircraft that have a TPE331 series engine installed. Specific details for G-164 aircraft are available in the Airworthiness Concern Sheet (ACS).