Prolonging safely service life of old-age aircraft

In our opinion, much of the very valuable service life of old-age aircraft has been and is being wasted due to conservative estimation of safe service life leading to the unduly early retirement of old-age aircraft. We aim to prolong safely service life of old age aircraft through proposing a new concept in estimating the safe service life of old-age aircraft. We start with the conservative estimate of safe service life, which is 60000 h for a group of 30 aircraft of the same type. When their service lives reached 57000 h to 58000 h, we could quite reliably estimate the safe residual life of each aircraft. We found only 3 out of 30 aircraft had safe estimated residual lives in the range of 9000-18000 h. These 3 aircraft should be retired according to the conservative estimate or should continue to fly only under very favorable conditions. 7 of the 30 aircraft had safe estimated residual lives in the range of 22000-51000 h. As many as 20 out of 30 aircraft had estimated safe residual lives in the range of 63000-320000 h. Our new concept is essentially that safe residual life of each aircraft should be estimated when it is near the end of its conservatively estimated life.