|Quoting tdscanuck (Reply 6):|
That doesn't determine design service life...design life is a target established at the beginning. The requirement is that the fatigue test article has to go (at least) to double the design life but it doesn't have to do that before certification. According to the flight global article, they just need to stay 10,000 cycles ahead of the fleet leader.
That may be way Boeing is doing it now but, when the Aging Aircraft Task Force was established, and all commercial aircraft with a MGTO weight of over 75,000 lbs had to provide a Design Life Goal what I stated was the criteria used. Additionally if the OEM did not provide a DLG the FAA would establish one for them using that basic criteria.
I must use my experience on the L-1011. If you have seen pictures of the L-1011 fatigue test airframe it did not have a flight station. Instead it had had a metal fitting that was used to pressurize the fuselage, which meant the flight station had to be tested separately. So while the entire airframe, less the flight station, was tested to 84,000 flight cycles. The separate flight station test stopped at 72,000 flights. One half of 72,000 is 36,000 the design life goal of the L-1011.