Boese's new widebody jet, the 777X, suffered a setback Thursday afternoon during a high-pressure stress test on the ground as one of the aircraft's doors exploded beyond.
A 777X employee working in a nearby bay at Boeing's Everett facility said he heard "a powerful boom and the ground shook."
The accident happened with what is called "static test aircraft," one of the two planes in any new jet program that is built solely for ground testing and will never fly. It was during the final test that must be passed as part of the aircraft certification by the Federal Aviation Administration (FAA).
The failure of the doors will require careful analysis to determine why this happened, and this may mean that Boeing will have to replace the door and repeat the test.
The 777X program is already delayed due to a problem with the development of the GE-9X engine that will operate it. In July, Boeing CEO Dennis Muilenburg revealed on a quarterly earnings call that the first 777X that was scheduled to fly, which rolled out of the Everett plant in March, won't air it until next year.
The static test plane is what is deliberately stressed far beyond the limits of normal service. The aircraft is surrounded by a metal frame while weights passing through pulleys are attached to the wings and other parts of the flight frame.
During the final load test, the wings are then pulled upwards. To pass the test and become certified, the wings must bend without breaking the load on them reaching at least 1
In addition, the skin panels covering both the wings and the fuselage are pressed to the maximum stress that can be expected at the edge of any extreme maneuver expected during use. The pressure is captured by pumping air into the cabin.
Sometimes this last test goes beyond the 150 percent load until a wing actually breaks. But not always. The carbon composite wings on the 787 Dreamliner are so flexible that when Boeing tested them in 2010, they bent upwards by about 25 feet, and after exceeding the target load, Boeing stopped the test without breaking them.
The massively larger wings of the 777X are also carbon composite, with a foldable tip, and during Thursday's test they must have bent in a similarly impressive manner as those of the 787. This time, but if the wings did not give way; it was one of the doors that failed – a result that is certainly not supposed to happen.
The entire area around the static aircraft is usually cleared during this test, with all measurements taken by surveillance equipment and with engineers eagerly watching a video link as the load slowly reaches the target and pressure increases.
No one was injured in Thursday's door blast, which happened just after 1:30 p.m., and everyone could leave the building.
According to Boeing employees, caution tape was attached to all the front doors on Friday and no one was allowed into the building.
After the incident was first reported Friday by KOMO News, Boeing confirmed that a serious incident had occurred, but offered few details.
"During the final load testing on the 777X static test aircraft, the team encountered a problem requiring suspension of the test," a statement said. "The event is under review and the team is working to understand the root cause."
Boeing went on to emphasize that "the test conditions were well above any load expected in commercial service" and that the aircraft used in the test "will never fly or be used in passenger service."
Because the GE engine problem has already pushed jet aircraft flight tests into next year, it is possible Boeing may have time to analyze and redo the final cargo ground test without further hits to plan.