Summary: | Airworthiness certification of commercial transport aircraft requires a
safety analysis of the propulsion system to establish that the probability of a
failure jeopardising the safety of the aeroplane is acceptably low. The
needs and desired features of such a propulsion system safety analysis are
discussed, and current techniques and assumptions employed in such
analyses are evaluated. It is concluded that current assumptions and
techniques are not well suited to predicting behaviour of the propulsion
system in service. The propulsion accident history of the high bypass ratio
commercial transport fleet is reviewed and an alternate approach to
propulsion system safety analysis is developed, based on this accident
history. Features of the alternate approach include quantified prediction of
propulsion related crew error, engine-level reliability growth modelling to
realistically predict engine failure rates, and quantified credit for design
features which mitigate the effects of propulsion system failures. The
alternate approach is validated by applying it to two existing propulsion
systems. It is found to produce forecasts in good agreement with service
experience. Use of the alternate approach to propulsion system safety
analysis during design and development will enable accurate prediction of
the expected propulsion related accident rate and identification of
opportunities to reduce the accident rate by incorporating mitigating
features into the propulsion system/ aeroplane design.
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