Structural Problems More Difficult To Repair Than Originally Thought

Two engineers with knowledge of the situation say that the structural issues with the B787 Dreamliner are more complex than originally described by Boeing, and the maiden flight of the aircraft could still be months or more in the future.

The engineers told The Seattle Times that the issue involves an area where the wing joins the fuselage, caused by high stress loads at the ends of the stringers in the upper skin of the wing. As the wings flex during flight, the stress loads could cause the composite stringers to delaminate from the skin. This condition occurred during wing flex tests.  The engineers said while this is not likely to lead to a catastrophic failure of the wing, it would require constant and expensive monitoring and repair over the aircraft's life.

The repair as described to the paper by the engineers is extensive, and involves someone inside the wing of the aircraft first relieving and then reinforcing the stress points. They said the repair would need to be completed on the non-flying test aircraft before proceeding on to the flight-test models.

The delamination showed up during the maximum load test of the wing, which the engineers said is 50 percent higher that is expected in normal operation, though it is unknown if it began at lower stresses and was masked by titanium components in the wing. The repair will have to be monitored at every stress level during subsequent tests.

The engineers told the Times that Boeing's focus now is on repairing the current Dreamliners so testing can resume, and that it has not been determined at what point in the production process a permanent fix would be implemented.

FMI: www.boeing.com