Flight 611 Probe Finds Likely Rear Fuselage Fatigue Cracks
By Michael A. Dornheim/Aviation Week & Space Technology
06-Aug-2002 10:16 AM U.S. EDT
The following is an excerpt from the above article.
Quote:
There were flat fracture cracks likely caused by fatigue in about three places on stringers around the aftmost No. 5 left exit door. A repair doubler there was made of stainless steel, not aluminum. The current structural repair manual forbids stainless steel, Yong said.
Mechanics have to be careful about blending a repair in with surrounding structure. It is possible to have a repair that is strong in itself but alters stress paths and overloads surrounding structure.
The No. 4 left exit door had a puncture hole about the size of an orange at about fuselage station 1694. The hole has sharp teeth and appears to be caused by a high-energy impact, but there are conflicting indications of the direction of the impact, Yong said. The No. 4 right door has not been found. Unquote.
The largest cracks so far, have been found around the doubler repair of the tailskid repair damage, which is aft of the bulk cargo compartment on the underside of the fuselage. That doubler incidentally appears to have been an approved repair with approved material in contradiction to some reports here, that it was stainless steel. The stainless steel doubler repair was around the stringers of L5 door, which is on the left hand side of section 46 at station 2261. The aft cargo door is on the right hand side of the fuselage at station 1865. The L4 door was found to have a puncture hole the size of an orange due to undetermined impact damage. I shall leave it to Barry to pontificate on the possible reasons for this but it would be interesting to see how this particular damage could be attributed to an aft cargo door latch failure from the opposite side of the fuselage?