several tests, static load test, final load test, and ultimate load test. I seem to remember final load test was 75% of ultimate? For ultimate, they take it to the ultimate load, and hold for 3 seconds....it appears from the press, it failed under final load, and they never got to ultimate...

Then, there is the "official" word from Boeing..

New York (AFP) - Boeing has suspended testing on its new long-haul 777X aircraft, the company said Friday, a setback that comes as it battles to rebound from the crisis surrounding the 737 MAX.

The so-called "final load" tests are part of the aircraft certification process, overseen by inspectors from the Federal Aviation Administration (FAA), and meant to subject the plane to "loads and stresses well beyond normal operational loads," a Boeing spokesman told AFP in an email.

https://news.yahoo.com/boeing-suspen...013019287.html

"During final load testing on the 777X static test airplane, the team encountered an issue that required suspension of the test," the spokesman said.

"The testing conditions were well beyond any load expected in commercial service. The event is under review and the team is working to understand root cause."

They would have a lot of questions in private. How often do we see the FAA announcing failures during the construction or testing process? Probably never. They leave that up to the corporate PR folks.

The 777X wing-box is definitely not the same as the 777 design: https://www.flightglobal.com/news/ar...ncy-co-454156/

GYS was referring to the cargo door locking system. I'd be surprised if that is much different from the current 777's.

When the wing has the max +g load the fuselage has a high bending load tension at the top. A heavy landing might cause slightly higher bending moment but the sense is the same. I have never calculated the shear but I expect a heavy landing would be the worst case.

Freight doors being at the lower half of the hull would require some strange shape changes to pop off as it would be under longitudinal compression.

It depends on the test restraints. If only the wing and center wing box were to be tested there would be no reason to have the fuselage there at all. From strength calculation point of view the box is not that difficult, the fuselage part connecting to it is.

Indeed. The issue is not a single test failure - that's what tests are there for. The issue is whether Boeing is going to identify the cause of the failure and ensure that it doesn't propagate through to the airframes that get put in service. After the 737 MAX MCAS debacle, the company is now known to be a bit hurried with its fixes, while the FAA plays the role of a cheerleader for the single major US vendor.

Edmund

more likely "call us when you're ready to submit a new cert plan" meanwhile we'll shuffle some of our manpower to something else.

Testing is done to catch design mistakes and for final verification. Still a door popping off/open during wing testing sounds a bit strange.

Computer modelling and much over the years placed on it - is just not what it was expected to be.

A door popping off/open at any time sounds a bit strange ...

But possibly slightly less strange if it happens when the fuselage is pressurised to 150% of max diff, as was the case here.

From the original 777 test programme showing the wing bend causing rippling of the fuselage.

I like the last comments "Which ever way you looked at it, the test was a success" then I though about the views out my window seat

This sounds exactly like the DC-10. Cargo door blow out in pressurization test, cabin floor collapsed. Analysis showed mechanics had not completed the latching process. Convair, subcontractor for the fuselage, performed a FMEA, said this is going to happen in production because the latching mechanism is a Rube Goldberg affair. MD altered the FMEA before submitting to the FAA. Result was first AA96 incident over Windsor, Ontario, in which the pilot was able to save the partially loaded plane. Next was TH 981 over Senlis, France, in which 346 people died. Lawsuits unveiled agreement between FAA chief and MD CEO not to issue an AD after the Windsor incident so 346 people were sentenced to death. Lawsuit uncovered the true Convair FMEA prior to MD doctoring it before submission. Resulted in the beginning of the end of MD. Hopefully Boeing remembers the lessons learned that resulted in them becoming the owner of a decimated McDonnell Douglas.

Sources told Harger that the door came flying off when Boeing was testing the maximum cabin pressure, whilst the aircraft was positioned in its test rig.

"The accident happened to what’s called the “static test airplane,” one of the two airplanes in any new jet program that are built for ground testing only and will never fly. It was during the final test that must be passed as part of the airplane’s certification by the Federal Aviation Administration (FAA).

On Friday, according to Boeing employees, caution tape was attached to all the entry doors and no one was allowed into the building."


The cabin should have been tested several times before now...this was the final test, not the first. It will be interesting to see what phase of the testing the failure happened, how close to final or ultimate load it got.

Blowing your stuff up on the final cert test in front of the FAA and probably a bunch of international certification regulators....damn.

Based on what little we know so far, it's highly unlikely that any of the factors that contributed to the AA or TK accidents were present in this latest event, despite the outwardly similar (npi) outcome.

Didn't they flatten the frames inside the X-cabin in order to win some inches of cabin diameter for the 777X? And hasn't the floor structure material been modified compared to the -300ER? Methinks it's made of CFRP now. Might lead to different bending under extreme cabin pressure?