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Recommendation issued to: Pratt & Whitney Canada

Recommendation details
Output No: R20070015
Date issued: 09 October 2007
Safety action status: Closed - Partial Action
Background: Why this Recommendation was developed

Output text

Safety Recommendation

The Australian Transport Safety Bureau recommends that Pratt & Whitney Canada, in conjunction with Transport Canada, incorporate measures to electrically isolate the starter-generator gear-shaft input coupling spline and the engine number-1 main shaft bearing of all Pratt & Whitney Canada PT6A series engines.

Initial response
Date issued:
Response from: Pratt and Whitney Canada
Response text:

Pratt and Whitney responded to this proposed safety recommendation (draft recommendation A) in the ATSB draft report by stating:

P&WC is pursuing the incorporation of a non-conductive insert in the design of our new models of PT6A engines.  As this feature requires an extensive re-design of the gear, the oil seal, and the accessory housing, it is not practicable to be incorporated into the existing fleet of engines.

In our earlier review of this issue, it was determined that the more practical solution was to incorporate a non-conductive element into the shaft of the starter-generator unit. While the Starter-Generator manufacturer proposed several designs, P&WC is not aware that any have been developed to the production stage.

ATSB comment:

The ATSB does not accept that P&WC's response to the draft recommendation is adequate and believes that P&WC should take a pro-active role and work in conjunction with Transport Canada to develop an effective method to electrically isolate starter-generators in the existing fleet of PT6A series engines in order to eliminate the possibility of engine failure due to EDD. As such the ATSB now formally issues safety recommendation R20070015.

 
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Last update 05 April 2012