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Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: SAN20010046
Date issued: 27 March 2001
Safety action status: Closed
Background: Why this Recommendation was developed

Output text

The Civil Aviation Safety Authority should note the safety deficiency identified during this investigation and consider introducing methods to identify and record time in service of piston engine cylinder heads particularly for those cylinder heads utilised in passenger carrying operations.

Initial response
Date issued: 01 May 2001
Response from: Civil Aviation Safety Authority
Response text:

I refer to your Safety Advisory Notice SAN20010046 resulting from Air Safety Occurrence Report 199804715, forwarded under your BO/199804715 dated 27th March 2001.

SAN20010046 states:

The Civil Aviation Safety Authority should note the safety deficiency identified during this investigation and consider introducing methods to identify and record time in service of piston engine cylinder heads particularly for those utilised in passenger carrying operations.

The essential corollary of recording cylinder life is that some maintenance action is placed on the cylinders.

The problem of heat-induced fatigue in engine cylinders is acknowledged. The comment in the ATSB report by the engine manufacturer, Teledyne Continental Motors, that; past two engine overhaul cycles it is difficult to project future life, indicates that a safe replacement life is about two overhaul cycles. This would likely result in the replacement of cylinders at every second overhaul. As the cost of new cylinders greatly exceeds the cost of reconditioned/overhauled cylinders, the cost of implementing the proposal would be very high.

If the proposal were limited to passenger carrying operations only, the cost would not be reduced significantly. VH-XAJ was conducting charter operations and most aircraft are available for charter operations.

The Bureau of Transport Economics report Cost of Civil Aviation Accidents and Incidents, October 1998, estimates that the cost to society of each major injury is about $545,000 and the cost of each minor injury $205,000. The two incidents between start of 1990 and end 1999 that resulted in five serious and two minor personal injuries would therefore cost society about $3,135,000. It is estimated that the cost of implementing the proposal would be about 10 times the cost of the injuries avoided. There would also be a number of practical issues that make it difficult to implement the recommendation, including the number of engines overhauled/repaired overseas, where the organisation performing the work is often the engine manufacturer working to the requirements of the local regulatory authority. New engines would have a similar problem. A unique Australian requirement would not be easy to implement during overseas manufacture/maintenance and would be a substantial and unknown impost after the engines arrived in Australia.

Implementing the SAN for cylinders currently in service would require cylinder installation and time-in-service to be recorded. Aircraft maintenance release records, aircraft logbooks, engine logbooks and component release documents would assist the development of the new record. However, establishing the record trail would often be costly, and may not be successful, resulting in situations where cylinder changes are required because the history of existing cylinders could not be determined.

A number of older aircraft are fitted with engines that do not have replacement cylinders available. To life these cylinders would limit continued operation of these aircraft, adding to the cost of implementing SAN20010046.

The aircraft subject to ASOR 199804715, VH-XAJ was shown in the A TSB report to be in a condition conducive to engine overheating. The engine baffles were in poor condition. The six point CHT indication system was unserviceable, the single point CHT pick-up was incorrectly installed and the CHT gauge was unreliable. These aspects may lead to cylinder failure before any reasonable cylinder replacement life.

The recommendation is therefore considered to have technical merit, but it is difficult to justify on economic grounds. Furthermore, had the recommendation already been implemented, it may not have prevented this unfortunate accident. CASA has therefore considered SAN20010046 as requested, but the Authority does not intend to adopt the proposal.

 
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Last update 01 April 2011