AD/TPE 331/29 - Combustion Section - Plenum Chamber Forward Drain Boss - Inspection - CANCELLED

This document cancels a previous aviation safety rule that required owners and operators of specific AlliedSignal (Garrett/AiResearch) TPE 331 series turbine engines to inspect the forward drain boss (a drainage fitting) on the combustion section's plenum chamber.

What this means:

• Who is affected: Anyone operating aircraft with TPE 331 series turbine engines (commonly used in regional airliners and utility aircraft).
• What changed: The requirement to perform a specific inspection within 25 hours of service time—based on an old manufacturer service bulletin—is now completely removed.
• Why it matters: This eliminates a compliance burden and maintenance cost for operators, as the safety concern that originally prompted the inspection is no longer considered a risk.

The cancellation took effect on 24 September 2009.