Aviation safety issues and actions

Advantage 70 engine modification

Issue number: AO-2018-007-SI-01
Who it affects: All operators of Airbus A330 aircraft fitted with Pratt & Whitney PW4170 engines or Advantage 70™ engine modification.
Issue owner: Pratt & Whitney
Transport function: Aviation: Air transport
Background: Investigation Report AO-2018-007
Issue release date: 06 November 2019
Current issue status: Safety action pending

Safety issue description

There were a total of 16 engine malfunction events globally over a 4-year period attributed to modification of the Advantage 70™ engine. The modification increased the engine outer duct gas path temperature, which led to distortion and liberation of the outer transition duct segments.

Proactive Action

Action number: AO-2018-005-NSA-01
Action organisation: Pratt & Whitney
Date: 21 March 2019
Action status: Released

Safety action taken

As a result of this occurrence and other similar incidents, the engine manufacturer Pratt & Whitney have advised the ATSB that they are taking the following proactive safety actions:

P&W has processed an engineering change that revises OTD material with higher temperature capability. The redesigned hardware will be available from November 2019 and will be recommended for incorporation when the LPT [Low Pressure Turbine] module is disassembled at a minimum.

All engines are planned to incorporate redesigned OTDs at the next shop visit when a major engine flange is separated for the purposes of performing maintenance regardless of planned LPT maintenance. This interval is approximately 3000 cycles on average, but can vary depending on the specifics of each carriers’ operating characteristics. This recommendation will be made with P&W Service Bulletin numbered PW4G-100-A72-261, which is pending release at this time.

New production PW4000 100” Advantage70 engines are no longer being produced.  At overhaul, engines that are re-built prior to November 2019 will not receive the redesigned OTD. However, every engine shop visit prior to November 2019 where the LPT is disassembled will be recommended for installation of a full set of non-engine run, current design OTDs.  This practice will provide a benefit to the fleet by removing OTDs that were potentially exposed to elevated temperatures.

ATSB comment:

The ATSB welcomes the proactive safety action taken by Pratt & Whitney to develop an improved outer transition duct. However, the ATSB believes that Service Bulletin PW4G‑100‑A72‑261 should hold a mandatory compliance status due to the significant number of OTD failures in a relatively short space of time. This will also ensure a fleet-wide compliance with the service bulletin. Additionally, as the installation of the redesigned components is at the operators’ cost, this has the potential to hamper incorporation of the improved components.

As a result, the ATSB issues the following safety recommendation.

 

Recommendation

Action number: AO-2018-007-SR-021
Action organisation: Pratt & Whitney
Date: 06 November 2019
Action status: Released

The ATSB recommends that Pratt & Whitney, together with the United States Federal Aviation Administration, take action to maximise incorporation of the redesigned outer transition duct as detailed in Service Bulletin PW4G-100-A72-261.

Response to the safety issue by the United States Federal Aviation Administration

At the time of writing, the Federal Aviation Administration advised that they are considering the implementation of an airworthiness directive to mandate the corrective action proposed by the engine manufacturer.

 

ATSB comment:

The ATSB supports action that will increase fitment of the redesigned outer duct transition and therefore issues the following safety recommendation.


 

Recommendation

Action number: AO-2018-007-SR-022
Action organisation: United States Federal Aviation Administration
Date: 06 November 2019
Action status: Released

The ATSB recommends that the United States Federal Aviation Administration, together with Pratt & Whitney, take action to maximise incorporation of the redesigned outer transition duct as detailed in Service Bulletin PW4G-100-A72-261.

Last update 06 November 2019