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FAA Directive on PW4000 Turbine Due To Design Flaw

Last updated Fri, 03 Aug 2018 21:34:40 GMT
Originally posted on Thu, 12 Apr 2012 05:00:00 GMT

On 23rd March 2012, the US Federal Aviation Administration (FAA) adopted a new airworthiness directive (AD) that requires operators of 954 Pratt & Whitney PW4000-series turbofan engines on US-registered wide body aircraft to retire the engines' first stage high pressure turbine (HPT) hubs prematurely. 

PW4000 Jet Engine.

PW4000 Jet Engine.

This comes after Pratt & Whitney re-evaluated the low-cycle fatigue analysis of the Boeing 757 engine, as well as for other "similar" engine designs including the PW4000.

FAA said, "Pratt & Whitney's updated analysis indicated that the original grain size requirement specified on the HPT stage 1 front hub design drawing was too large, and may not be sufficient to meet published life limits." FAA farther said, "Although we have not received any reports of cracks, parts with the larger grain size may initiate a crack prior to the published life limits."

According to FAA, if cracks develop, this will lead to failure of the hub, causing engine failure and aircraft damage.

If the FAA directive is approved, the affected parts that had lifetimes of either 15,000 cycles since new (CSN) or 20,000 CSN will need to be retired at 13,700 or 18,000 CSN, respectively. This will cost about $23 million in "lost life value" for the fleet.

FAA said there are 605 PW4000 engines on the US registry that use a 20,000 CSN life limit for the part, and 349 engines with a 15,000 CSN limit. 

Video of a PW4090 engine

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Ian Stephens

Ian Stephens

Ian Stephens is a flight simulation industry expert with over 20 years of experience and also has a keen interest in aviation and technology.  Ian spends a lot of his time experimenting with various simulator packages but has a love for Microsoft Flight Simulator X because of the huge selection of add-ons available.  However, Ian also has copies of Prepar3D and X-Plane installed. 

Ian has been writing for Fly Away Simulation for over 9 years.  Should you wish, you can contact Ian via email at


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