AD/TPE 331/13 - Short Torsion Shaft Spline Wear - Inspection - CANCELLED

What this is: This document officially scraps a previous aviation safety rule (called an Airworthiness Directive or AD) that required owners of certain aircraft engines to perform a specific mechanical inspection.

What it did previously: The original rule required inspection—and potential replacement—of the short torsion shaft spline (a component that transmits power) on AlliedSignal (Garrett/AiResearch) TPE 331 series turbine engines once they had flown between 1,350 and 1,750 hours.

What it does now: The requirement is completely cancelled. Aircraft operators no longer need to carry out this inspection or keep records to prove compliance with this specific rule.

Who it affects: Owners and operators of aircraft fitted with TPE 331 turbine engines—commonly found in regional airliners, cargo planes, and agricultural aircraft.

Why it matters: This reduces maintenance costs and administrative burdens for operators because one specific repetitive inspection has been removed from their compliance obligations.