Originally Posted by
Safety_Helmut
Mad Scientist
You may cause some confusion with your numbers. The civil targets you discuss are to be found in EASA CS25. The target rate for hull (catastrophic) losses is no greater than 1E-7 per flying hour. The number you quote is for an individual critical system causing loss of the aircraft. EASA AMC25 explains this and makes the assumption that there are around 100 such systems onboard an aircraft. Hence the two orders of magnitude difference.
If you read JSP553, you will find the Nimrod target to be 1E-6 per flying hour. For a miltary aircaft derived from a civil airliner and used in a passenger carrying role the target should be 1E-7 per flying hour, eg VC10, Tristar.
S_H
I think we may be in violent agreement here
Since we're talking about a specific catastrophic event, rather than any of the one hundred, the key is the 10e-9 rate, not the overall airframe design 10e-7.
Interesting that Nimrod uses one order of magnitude less. I assume it's the design rate i.e. equivalent to the EASA/FAR rate?
Incidentally the civil 'all-causes' expected rate is also 10e-6 (and is borne out by recent statistics) but that includes all the non-design causes, which I'd guess in military operations, even in peace, would be expected to run at a higher rate.