faheel - I'm not sure what you suggest is correct, e.g. under JAR ( which is pretty much in-line with ICAO and the FAR's - ergo the ETOPs approval process is reasonably standard across all regulating authorities ) it is stated in '
ACJ 20X6 - Temporary Guidance Material for Extended Range Operation with Two-Engine Aeroplanes ETOPS Certification and Operation'
( which now replaces CAP513 ) :
In establishing the suitability of a type design in accordance with paragraph 8 ( of ACJ 20X6 ) and as a pre-requisite to obtaining any operational approval in accordance with the criteria of paragraph 10 ( of ACJ 20X6 ), it should be shown that an acceptable level of propulsion system and airframe systems reliability can be or has been achieved in service by the world fleet for the particular airframe-engine combination.
For this purpose, prior to the type design approval, paragraph 8, it should be shown that the world fleet of the particular airframe-engine combination for which approval is sought can achieve or has achieved, as determined by the Authority ( see Appendix 1 of AJC 20X6 ), an acceptable and reasonably stable level of single propulsion system in-flight shutdown (IFSD) rate and airframe system reliability. Engineering and operational judgement applied in accordance with the guidance outlined in Appendix 1 will then be used to determine that the IFSD rate objective for all independent causes can be or has been achieved. This assessment is an integral part of the determination in paragraph 8.b.(2) for type design approval. This determination of propulsion system reliability is derived from a world fleet data base containing, in accordance with requirements of Appendix 1, all in-flight shutdown events, all significant engine reliability problems, design and test data and available data on cases of significant loss of thrust, including those where the propulsion system failed or the engine was throttled back or shut down by the pilot. This determination will take due account of the approved maximum diversion time, proposed rectification of all identified propulsion and ETOPS significant systems problems, as well as events where in-flight starting capability may be degraded.
I'll leave it to you to read-up on what the ACJ has to say in full ( e.g. various other sections and / or the Appendix, plus '
ACJ 20X8 - Occurrence Reporting' )
phoenix son - I believe the stats to which you refer are as follows ( and as also defined in ACJ 20X6 document ):
c. Risk Management and Risk Model
Propulsion systems approved for extended range operation must be sufficiently reliable to assure that defined safety targets are achieved.
A review of information for modern fixed wing jet powered aircraft shows that the rate of fatal accidents for all causes is in the order of 0·3 x 10-6 per flying hour. The reliability of aeroplane types approved for extended range operation should be such that they achieve at least as good an accident record as equivalent technology equipment. The overall target of 0·3 x 10-6 per flying hour has therefore been chosen as the all-causes safety target.
When considering safety targets, an accepted practice is to allocate appropriate portions of the total to the various potential contributing factors. By applying this practice to the overall target of 0·3 x 10 -6 per flying hour, in the proportions previously considered appropriate, the probability of a catastrophic accident due to complete loss of thrust from independent causes must be no worse than 0·3 x 10-8 per
flying hour.
Propulsion system related accidents may result from independent cause events but, based on historical evidence, result primarily from events such as uncontained engine failure events, common cause events, engine failure plus crew error events, human error related events and other. The majority of these factors are not specifically exclusive to ETOPS.