AD/TPE 331/4 - Propeller Pitch Control - Modification - CANCELLED

This document cancels a 42-year-old aviation safety rule that required owners of specific aircraft engines to modify their propeller pitch control systems.

What it does:

• Removes the mandatory requirement for owners of AlliedSignal (Garrett/AiResearch) TPE 331 series turbine engines to comply with a 1967 modification order
• Stops requiring adherence to "Airesearch Service Bulletin No. 7" (the manufacturer's technical instructions)
• Takes effect on 24 September 2009

Who it affects:

• Owners and operators of aircraft fitted with TPE 331 series engines (typically commuter aircraft and agricultural planes)

Why it matters: The original directive was issued in 1967 as an emergency measure requiring immediate modifications to prevent propeller control failures. After more than four decades, the Civil Aviation Safety Authority has determined this specific safety fix is no longer required—likely because the affected engines have been retired, redesigned, or the original safety risk has been eliminated through other means.