New Blow For Boeing

About: The Boeing Company (BA), Includes: GE
by: Dhierin Bechai

Boeing 777X structural test failed as cargo door exploded.

Test failure is a setback for the program, but does not necessarily mean additional delays.

Boeing engineers now have to analyze data to determine root cause and implement modifications.

While currently many are focused on the recertification of the Boeing (BA) 737 MAX, Boeing also has been working on bringing the Boeing 777X to the market, but that process is going far from smoothly. Initially that was due to problems with the turbofans. But the latest problem now is a failed structural test.

Boeing 777X

Source: Luchtvaartnieuws

In this report, we have a look at the delays and the failed structural test as well as possible implications.

From launch to engine test

The Boeing 777X was launched during the Dubai Airshow of 2013 with 259 orders and commitments valued $95B at list prices, marking the biggest launch in the commercial aircraft industry. Production was scheduled to start in 2017, with first deliveries in 2020.

In August 2015, Boeing reached the firm configuration milestone which is an important milestone heading into the detailed design phase of the aircraft. By October 2017, Boeing started the assembly of the Boeing 777X, which as far as we could see was on schedule. In September 2018, the first static test aircraft was completed, which should have paved the way for a 2018 maiden flight and late 2019 entry into service, which is something I covered back in 2016, which was confirmed in September 2019 by Tim Clark, President of Emirates.

Boeing 777X


Instead of a maiden flight in October 2018, the Boeing 777X was plagued by problems on the engine flight testing. As GE (GE) experienced problems on its Boeing 747 testbed and a required redesign to the lever controlling stator valves, the program was delayed by two months and problems with production-run turbofans require a stator vane redesign pushing back the first flight to what was initially believe to be fall 2019 instead of June 2019, but has turned out to be early 2020. So, even before the failed structural test, Boeing already had been facing 15-18 months of delays, including Boeing’s own contingency in the planning which has already been fully exhausted.

Failed test

Previously Boeing was able to put all schedule risk on the shoulders of GE:

On 777X development, our first two flight test airplanes are now in preflight testing. Overall the airplane is performing well in preflight tests with intermediate gauntlet and initial taxi tests completed during the quarter.

Our teams are currently focused on final systems, propulsion, and airplane level tests. However, the GE9X engine remains the pacing item as we work towards first flight. As we previously mentioned, GE, our engine supplier, is working through some challenges with the engine that are putting risk on the overall test schedule.

Based on GE's latest assessment on what it will take to address these challenges, we are currently projecting that first flight will occur in early 2020 rather than in 2019 as we have previously mentioned. This scheduled flight is obviously disappointing given how well the aircraft has been performing in preflight tests and that we are on track on non-engine activities

That's no longer the case. As if the program running behind on schedule by more than a year wasn’t already bad enough, Boeing suffered a new setback in September 2019. During what was supposed to be some of the final static structural tests, a cargo door blew out of the fuselage.

The conditions used for testing are quite a bit more extreme than what an aircraft will be met with during its in-service life, but a door blowing out of the fuselage is unheard of. These structural tests serve to validate the design. The design requirement is that the aircraft should be able to withstand the Ultimate Load, where the Ultimate Load is the Limit Load multiplied by the Safety Factor (typically 1.5). The Limit Load is the load an aircraft should only encounter once over its life. Forces and moments in normal conditions already are huge, let alone the most extreme cases the aircraft should only experience once multiplied by a 1.5 safety factor. Nevertheless, that's the load level the aircraft should be designed for and engineers should demonstrate it, which happens during structural testing.

Boeing 777X Test

Source: Aviationweek

The cargo door blew off during pressurizing the skin panels to their maximum well beyond levels encountered in commercial service. However, the fact that the door fails requires further investigations to the nature of the failure. Assuming the locking mechanism for the door is fine, the best case could be a quality defect or a mistake in the assembly. It sounds odd that a quality defect or assembly issue is considered the best-case scenario, but the other scenario would be that the Boeing 777X cargo door area has not been designed sufficiently robust, something that would send engineers back to the drawing board and could mean additional delays in the service-entry for the Boeing 777X.

The timing of the failed test is a painful one for Boeing given that the US jet maker is facing big questions regarding their engineering and decision making in the wake of two crashed with the Boeing 737 MAX and mounting delays and costs on the KC-46A tanker program. Structural testing happens to validate the design, so you’d rather not have the test fail, but it should be pointed out that this is part of the process and the Airbus A380, Irkut MC-21 and if I recall correctly even the Boeing 787 initially failed the ultimate load test.

For Boeing it's key to research test data to figure out the root cause of the failure. Assuming that the cargo door locking mechanism and installation are done correctly, a local reinforcement near the cargo door area might be required. As long as the limit load test is being passed, Boeing could still put the aircraft up for flight testing in 2020, but by the time the aircraft is supposed to enter service, the ultimate load test should be passed as well.


The structural test failure is not unsurmountable, but it comes at a moment where the Boeing 777X program already is behind on schedule and days after Tim Clark, President of Emirates, who has ordered 150 Boeing 777X has openly criticized jet makers for the reliability of their product. On top of that we have the entire world watching Boeing as they struggle with the Boeing 737 MAX crisis. At best the failed test shows the system working, since test failures also can produce useful data to improve the design…. At worst, and I'm sure some people will see it that way, the failed tests shows engineering incapability. Either way, the failure is highly inconvenient for Boeing. There might be additional delays to service entry depending on the exact nature of the failure and the load at which the test failed, but additional delays are not a given. That's because the schedule already was pushed out until early 2020, giving Boeing time to analyze data and make required changes to the design.

For those interested, I have added a video of the static ground tests for the Airbus A350:

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Disclosure: I am/we are long BA, EADSF, GE. I wrote this article myself, and it expresses my own opinions. I am not receiving compensation for it (other than from Seeking Alpha). I have no business relationship with any company whose stock is mentioned in this article.