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Recommendation issued to: Transport Canada response

Recommendation details
Output No: R20070020
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 Transport Canada, as the state of design for PT6A engines, review the continued airworthiness of PT6A series engines, with regard to its susceptibility to failure of the number-1 bearing, as a result of EDD sustained from a starter-generator malfunction.

Initial response
Date issued:
Response from: Transport Canada response
Response text:

Transport Canada responded to this proposed safety recommendation (draft recommendation I) in the ATSB draft report by stating:

TC continually monitors the continuing airworthiness of the PT6A engine. According to the latest P&WC data (1Q/2007), the 12 months in-flight shut down (IFSD) rate for the PT6A series engines is 0.004 per 1000 hours (0.011 for the PT6A-114/-114A series engines), which is well within the acceptable certification requirement of 10E-5.  The IFSD rate due to EDD would be expected to be much lower than the above IFSD rate.  TC suggests that the TSB or ATSB request P&WC provide the in-flight shut down rate due to electrical discharge damage (EDD) problems.

ATSB comment:

The ATSB does not accept Transport Canada's suggestion that either the Transportation Safety Board of Canada or the ATSB should seek further EDD related IFSD rates from the engine manufacturer. As the responsible airworthiness authority, the ATSB believes that TC should actively seek any data required to review the continued airworthiness of the PT6A series engines in relation to potential failures as a result of EDD.  That review should consider not only the IFSD rate, but also the potential serious consequences of sudden engine failure in single-engine, passenger-carrying operations. As such, the ATSB now formally issues the safety recommendation as R20070020.

Further correspondence
Date issued: 15 November 2007
Response from: Transport Canada response
Response text:

Transport Canada has reviewed the continued airworthiness of PT6A series engines, with regard to its susceptibility to failure of the number-1 bearing, as a result of EDD sustained from a starter-generator malfunction. Transport Canada Civil Aviation (TCCA) has determined the failure/reliability rate to be well within the recognised industry reliability target of 10E-5. 10E-5 is only an industry target for reliability (one failure for every 100,000 hours, which roughly translates to one failure every 20 years, if an engine is utilized 5000 hours per year, or every 40 years if the engine is operated 2500 hours per year).

TCCA notes, as a result of P&WC actions related to operator awareness and inspection criteria, the previous low occurrence rate of incidents related to EDD has been further reduced to a level where, in 2007, there has only been one EDD event and no EDD-related In-Flight Shutdowns (IFSD) reported to P&WC for 450,000 hours of reported operation for PT6A-114 series engines.

Present In-Service data does not indicate any unsafe condition presented as a result of the ATSB investigation into EDD on the smaller PT6A engines. TCCA continues to review, with P&WC, all aspects of the continued airworthiness of PT6A series engines.

 
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Last update 05 April 2012