The U.S. Federal Aviation Administration (FAA) issued Emergency Airworthiness Directive (EAD) 2014-12-52 on 10 June 2014 in response to a production defect on the Honeywell TFE731 engine type.  This was prompted by reports of 2nd stage Low Pressure Turbine (LPT2) blade separations due to casting anomalies at or near the root of the LPT2 blade.

The EAD requires review of maintenance records before next flight to determine if any engine has LPT2 blades with less than 250 operating hours and not flying an aircraft with more than one engine so affected.  This action is to manage the risk of a double engine shutdown due to the same failure mode.

TFE731 (Credit: Honeywell)

Affected are the TFE731-4, -4R, -5AR, -5BR, -5R, -20R, -20AR, -20BR, -40, -40AR, -40R, -40BR, -50R, and -60 engines, which are fitted to a wide variety of corporate jets and some military trainers.

This is not the first significant production quality defect that Honeywell has suffered with TFE731 critical parts.  In 2008 the FAA issued Airworthiness Directive (AD) 2008-02-19 following production defects in TFE731 engine discs.  In that case Honeywell became aware from a manufacturing audit in June 2006 that some High Pressure Turbine (HPT) discs had received “improperly machined radii in the root of the forward and aft curvic teeth”. This increased the risk of an uncontained engine failure.  Honeywell quickly issued a Service Bulletin on in July 2006 but the FAA did not propose making that mandatory until September 2007 when they issued a Notice of Proposed Rule Making (NPRM).  The AD was finally issued in February 2008, 20 months later. This shows the importance of operator’s Continuing Airworthiness Management Organisation (CAMO) correctly classifying important Service Bulletins and promptly acting in advance of a regulator.

For more details on the earlier problem see:

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