A leading analyst has played down the impact of the failure during testing of a cargo door on the 777X.
According to New York-based Bernstein, a Boeing spokesperson said that that failure took place at “conditions well beyond any load expected in commercial service”.
Bernstein in a special report, “Initial perspective on 777X stress test failure”, said: “We find this failure surprising given the relatively small changes in the fuselage for the 777X. The biggest issue for stress tests is typically on the wing, which is all-new for this airplane.”
“We do not yet know details on what caused this failure. This could have been a latch failing, which would be relatively minor, or a structural issue, which could be more significant. Because of the similarity of the fuselage to the 777-300ER, we would be surprised to find a serious issue here.”
It added: “We also do not know how far out in the test envelope (up to 150% of limit load) this failure occurred. The Boeing statement suggests it was toward the 150% value, but we do not yet know.”
Bernstein noted that when the A380 was in stress testing, the wing failed at 145% of the limit load (below the 150% required). This issue did not result in significant delays for the airplane (other factors later did, particularly wire harnesses), as the structural fixes were relatively straightforward to implement.
The 777 has been in service for almost 25 years and there have been no cargo door design issues.
First flight of the 777X has been delayed till January 2020 due to issues with the GE9X engine which requires replacement blades.