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