Boeing’s 777X Fuselage Was Ripped Apart During Structural Testing

New images have surfaced of what really happened during the September structural testing of Boeing’s new 777X aircraft. September’s test was widely reported to have failed, with a cargo door being blamed for the issue.

Now, it seems that the situation was a lot more serious than that.

Boeing 777X blown apart
Damage to the 777X during the pressure test was much worse than originally thought. Photo: Boeing

Explosively ripped apart

The news that a cargo door had blown off the 777X during its stress test in September was shocking enough. However, it now appears that the situation was far worse than we could ever have imagined.


According to reporting by the Seattle Times, it wasn’t just the door that ruptured, but the entire fuselage!


Apparently, as the stress test was nearing its target level, a weakness at the keel caused the structure to fail, leading to an ‘explosive depressurization’ ripping through the fuselage. The Seattle Times has obtained photos showing the extent of the damage, something which Boeing has reportedly been keen to keep to themselves.

Earlier reports that a cargo door blew out are not entirely unfounded. Apparently the fuselage skin ripped open just behind the wing, and as such a passenger door was dislodged and fell to the factory floor. The damage is clearly far worse than originally revealed; the test aircraft is a complete write-off.

Boeing statement

Boeing spokesperson Paul Bergman was kind enough to provide Simple Flying with the following statement in regards to the incident.

“In the final load testing of the 777X static test airplane, our team conducted a test that involves bending the wings of the airplane up to a level far beyond anything expected in commercial service. A testing issue occurred during the final minutes of the test, at approximately 99 percent of the final test loads, and involved a depressurization of the aft fuselage. The test team followed all safety protocols.

“As we shared on our Oct. 23 earnings call, our root cause assessment continues, and we are pleased with the progress we are making as we complete our detailed analysis. What we’ve seen to date reinforces our prior assessment that this will not have a significant impact on the design or our preparations for first flight. We do not see any impact from the test on the overall program schedule.

“On the call, we did update our target for first delivery from late 2020 to early 2021. As we’d said for some time, there had been significant risk to the late 2020 timeline. What changed is that we now have a clearer understanding of how the GE9X engine issue has impacted the details of our flight test program. For example, the timing of engines for the remaining flight test airplanes will affect when they begin flying, which in turn affects our detailed test schedules. When we account for all these factors, we expect to fly in early 2020 deliver in 2021.

“We remain fully focused on safety as our highest priority as we subject the 777X to a rigorous test program.”

Immense amounts of stress

Airframe structural testing is an incredibly demanding process, and aims to exert some 1.5 times the normal stress that would be experienced by an airliner in use. The wings are pulled upwards some 28 feet from their normal position, the fuselage is bent downwards with millions of pounds of force on the front and aft.

Inside the plane, in this case, pressurization is raised to around 10lb per square inch, far beyond regular levels. This is not an FAA requirement but was something Boeing had opted to do voluntarily.

777X blown apart
Structural testing exerts incredible amounts of stress on the airframe. Photo: Emirates Airlines

The FAA requirement says that forces need to be piled upon the airframe up to 1.5 times the maximum load that would ever be experienced in normal flight. It then has to be held there for at least three seconds. The 777X had reached a load of 1.48 times the maximum, around 99% of the target, when the structure gave way.

The weak point was under the center fuselage, just behind where the landing gear is stowed. The extremes of stress on the fuselage caused the skin of the aircraft to rupture. Because the inside was so strongly pressurized, this led to rapid depressurization that a whistleblower described as “a loud boom, and the ground shook”.

It was this rapid depressurization that caused the extent of the damage. The fuselage skin split up the side of the aircraft, damaging an area around a passenger door that fell out of the fuselage to the ground.

Will not require a retest

Because the test was within 1% of its target levels, the Seattle Times believes that the aircraft will not have to undergo a retest. While that might sound alarming to some, it’s important to remember that these sorts of tests exert immense amounts of stress on the airframes, far more than would normally be encountered in a natural environment.

777X blown apart
Despite the scary photos, the 777X is unlikely to require a retest. Photo: Boeing

Boeing maintains that nothing has happened to delay planned delivery schedules.

According to reports, an anonymous source at the FAA said that, because the blowout happened so close to the target load, it barely counts as a failure. Although Boeing will need to look at the area of the keel where the weakness presented itself, the airframe is unlikely to be represented for this test again.

What do you think about all this? Let us know in the comments.


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Ueli Praett

If the requirement is 1.5x work load during the test, it has to be proven. Achieving 99% of test pressure and to accept any deviations from the requirements is an absolute NO-GO!!! I am too long in similar business and no authority will never ever accept that.


Maybe the FAA of yesteryear would.

Paul Proctor

But they can prove the fix through analysis, they don’t have to retest.


Airbus failed its wing in the same test. It was fully agreed that they could reinforce that area and did not repeat the test. Nothing wrong with that decision. It supports the design is solid with a small miss on the structure.

There is no reason that this does not apply to Boeing as well.

Ueli Praett

In principle this might be right. But on this object you can’t do a Finite-Element-Analysis (FEA) to cure the defect. If this would be allowed, why to perform the test at all? The FEA could show everything. I remember some occurrencies with off-shore-platforms where the FEA was good, but the platform broke into pieces and many people lost their lives. And who can guarantee that at 99,5% another part will burst? FEA is good for dimensioning but reality is in the test. I had to perform quite a lot pressure test with (simple) cylinders and no authority accepted any tiny… Read more »


@Ueli Praett 100% correct. That’s also the reason why test flights are necessary, despite the fact that all sorts of numerical simulations are done beforehand. A good example is the flutter problem on the 747-8, which only revealed itself during actual flights. Other examples occur on a daily basis with new bridges/buildings that unexpectedly “sing”/vibrate under certain wind loads, despite extensive numerical simulations of the design prior to construction; in such instances, correctional vanes often have to be applied to mitigate the undesirable effects. Yet another example: the resonances that are occurring in PW engines at certain operating revs, which… Read more »

Ueli Praett

@Bryce. Dynamic analysis of oscillating structures especially under wind load is a nightmare. You are happy if you are hitting the right order of magnitude. Static Analysis is much much simpler but it also requires a correct stress assessment of the results concerning limit stresses. From my point of view (which is limited) the vertical force has initiated the cracks only supported by the internal pressure. It seams to be a brittle fracture and I know that it is hard stuff to evaluate the behaviour of aluminum in 2-dimensional tensile stress field.


@Ueli Praett Even a static model can be a nightmare, because (as you probably know) you have to accurately model higher-order effects such as torsion and shear, in addition to first-order effects such as bending; indeed, tensor calculus (an advanced area of mathematics) was initially developed for the purpose of accurately describing stress effects in bulk materials. It also depends on having a correct model of the material(s) being tested — again, as you probably know, a brittle metal behaves very differently to a compliant one. Temperature also plays a crucial role: most people don’t know, for example, that common… Read more »

Ueli Praett

I agree 100% !

Alexander More

I, for one, find it alarming and, in the current climate surrounding Boeing, rather astonishing that they are not planning on a retest. The purpose of the test is to show that the airframe will not fail during brief exposure to outlandish but predetermined stresses. In this case it not only failed but did so in a spectacular fashion before the stresses had reached their full level. How, without retesting, can Boeing satisfy the FAA (or the public) that any design tweak they introduce will guarantee the integrity of the structure? Or perhaps they will just devise a software fix… Read more »


Until two planes fall down and people pay with their lives.

High Mile Club

Since the purpose of these tests is to literally break the aircraft, so it isn’t surprising to hear that the fuselage itself broke. I believe the 777x will have a pressurization of down to 6000ft at cruising altitude like the 787 and A350 (most jetliners pressurize to 8000ft at altitude), which (if going by the 1.48 multiplier at about 38,000ft) would probably put the aircraft at a fictional 56,000ft of altitude, which would necessitate the use of a higher operating pressure that would result in the stress test failure. As just about all commercial jets of a maximum ceiling of… Read more »


Who said the purpose is to break the aircraft? The purpose is to ensure that the aircraft doesn’t break before the test limit is reached…so it can still potentially overshoot the limit without breaking. The higher pressure may be mandated to simulate the effects of a tired fuselage: in other words, whereas a brand new fuselage might fail at pressure X, a tired fuselage with a high number of flight cycles might fail at pressure Y < X; that's probably why X is chosen to have a high value to start off with, so that Y will also be comfortably… Read more »

High Mile Club

The entire point of a stress test is to find out when an aircraft or its components will experience a point of failure that could compromise the airframe; it’s not just about just finding out if it’ll live up to its true potential. It’s a major part of that, but ultimately the end goal is the test the aircraft’s integrity well beyond normal limits. During load tests like this, they won’t use an old fuselage because metal fatigue would already guarantee a failure point that’s below a fresh airframe; and considering new aircraft are not old by any means, it’d… Read more »

A Comfortable Seat

Just to clarify, the ‘tired fuselage’ is called metal fatigue, something that naturally occurs over the lifetime of an aircraft. And the way you explained it is a little confusing. I mean, if a plane is meant to last 25-30 years, wouldn’t the test be set to a number that effectively represents how long the plane’s been in service? If it failed at 1.48, then wouldn’t that in theory give the plane a life limit of about 28 years or something?


– It doesn’t necessarily have to be metal fatigue (which is a bulk material effect): it can also be a failed rivet or a running crack, for example, though metal fatigue is also possible.
– I was merely explaining why a high pressure is chosen — well outside operational limits — to counter the BS argument that “those pressures will never be encountered in practice, so there’s no need to do tests at those pressures”.

A Comfortable Seat

Doesn’t that also count as metal fatigue? Rivets are what hold the fuselage together and are more likely to break than a rivet free section of the fuselage. In fact, I believe most instances of aircraft depressurizing were often cause by this.


@A Comfortable Seat
Failing rivets don’t have to be caused by metal fatigue…for example, if they have the wrong constitution, they can be brittle rather than compliant (like on the Titanic). Or they can just be inserted improperly.
Many instances of depressurization are caused by a running crack that creeps from one rivet hole to another. But this doesn’t have to correspond to bulk micro-cracking in classic metal fatigue.

A Comfortable Seat

If the rivet was improperly installed or it’s the incorrect rivet, that’s faulty maintenance. However, it makes more sense if a crack starts from the rivet holes because that’s where the metal would often at its weakest since it’s used as an entry point to hold two pieces of metal together, and subsequently have the most pressure applied. Given than sheets of aluminum are very flexible in their own right, it’d have a long life span; but rivets don’t have as much stress tolerance. And all that pressurizing and depressurizing would eventually break them if they don’t outright burst out… Read more »


If the rivet is in any way at all faulty, on a pre-production, static test aircraft, then it’s either design or build-quality that’s at fault. Maintenance has absolutely nothing to do with it.
IF Boeing has a design or build-quality issue on an entirely hand built one-off airframe,
then exactly how good will the quality-control be when they’re in full production.?

A Comfortable Seat

That is true, but we were talking about aircraft that have already clocked in thousands of flight hours.

High Mile Club

No one is saying that they SHOULDN’T do the extreme testing, I’m just stating what I believe were the values that came up when the fuselage broke short of its intended goal. It’s probably why they’re saying it’s barely a fail and considering whether a second test is needed, but I’m sure they’ll do it anyway as a recheck.


@High Mile Club
They’d better do a re-check one way or another…because EASA and Transport Canada will never accept this type of faking after the MAX fiasco.

High Mile Club

Keep in mind the article is an opinionated statement from The Seattle Times. Boeing nor the FAA had stated the aircraft wouldn’t undergo a second test. Given current events, they’re more inclined to do so than not, as not doing a second test could lose confidence in customers looking to buy the type.


They accepted the Airbus test. Boeing will strengthen the area of the break and all will be fine. The Max is a very good aircraft with a software problem. The structural aircraft is sound.


I.E., right off two aircraft !


Better to write off two on the ground than one in the air with a full load of passengers. Another crash would be the end of Boeing.


You’re right, of course. But, in the case of the 777X, since none have been ordered by US carriers, Boeing will be able to conveniently blame any crashes on “incompetent foreign pilots”…


Many if not most Airbus A320ceo are already operating at 6000ft. I checked it myself 2 months ago on a JetStar A320-200 flight from Sydney to the Gold Coast using the pressure altimeter in my iPhone. The decision is probably the airlines as it somewhat reduces the cycle life. Airbus started doing this on A319ACJ which being business jets have less cycles and so had a lot of experience before transferring this to the rest of the range.


More Boeing quality, and another Boeing cover-up.

To the FAA:
1.5 is 1.5…it’s not 1.48. The aircraft failed before it reached the mandated limit, so the test will have to be repeated…no discussion required. If the FAA goes soft on this, they might as well flush their reputation entirely down the toilet.

To Tim Clarke at Emirates:
Think carefully before you put any faith in this junk!

Paul Proctor

Learn the power and accuracy of modern computational analysis.


I’m thinking that’s what they did with MCAS. How’d that work out for them?


All other aircraft models certified had pass the 1.5x pressure test but 777x failed. Doesn’t give me confidence in Boeing


@Paul Proctor
Will you give us a break, repeating the same old crap about “modern computational analysis”? We know what it is…and it isn’t the “magic wand” that you seem to think/hope. The fuselage failed the test, and demonstrated catastrophic failure of a type that would appear to point to a major design flaw. That flaw is not going to fix itself, no matter how much you’d like it to. And a Band Aid won’t work either…there’s a serious underlying weakness in that photo.


…and probably they performed the magic of ‘modern computationsl analysis’ before the test. The results speak for themselves.

Charles Bolland

Oh my word what is happening with Boeing, wouldn’t be flying the 777x when it comes out.


OK, so, in order to win the lottery, I need to have a correct sequence of 10 numbers.
Hey, I had 9 out of 10 correct, so I’m going to demand the jackpot anyway…because I’m convinced that 9 is enough.


Ultimately, this is telling us that the air frame is weaker then other aircrafts. Has anyone considered the impact of climatic conditions across many different cycles that could undermine the integrity of the airframe? To me this is indicative of a compromised attitude to safety at Boeing and the FAA. I am starting to get increasingly vary of stepping onto a Boeing aircraft.

A Comfortable Seat

Just to nitpick, but it’s…just…aircraft….

‘Aircrafts’ is not an actual word to describe multiple aircraft. You’d be better off just saying planes. Sorry, but that just…REALLY irritates me when people say that….

James Hayward

I’m guessing here, but your entire understanding of this topic is what you gained here. Also I am guessing again, but I doubt you have data from other tests and manufacturers and have a foundational (Made that word up just for the nitpickers) clue what has and has not been accepted by the regulatory bodies. After all, the FAA did accept MD’s WORD!!!!!!!!!?? that they would fix the cargo door on the DC-10 until Turkish Airways found out they lied. I’m sure Boeing has figured out if a 777x has a catastrophic structural failure a la TWA Flt 800 or… Read more »


The DC-10 cargo door problems are a bad example. After the floor collapse incident, McD were made aware of the cargo door lock problem & issued a maintenance directive.
It was a company directive, not an FAA one….. But, it isn’t the makers fault that the subsequent crashes & incidents were down to a failure of the airlines to properly implement McD’s fix.


While there were other problems besides the design flaw, the FAA forced MD to redesign the latching system. The sheet metal fix that MD originally came out with was found deficient. An accident is very rarely caused by a single issue. They call it the Swiss cheese model. That all the holes in each safety layer has to align. Yes, the Turkish crash had other issues besides the design flaw, but the original directive did not resolve the obvious flaw.


Who was supervising this test? Boeing influenced FAA personnel or only Boeing personnel who would sign it off on behalf of the FAA? European or Asian observers should have been there.


The main problem here is that boing has once again tried to cover up its failings to save its stock price. Boing is losing the respect and trust of everyone.


Have Boeing employed former British Leyland quality controllers? Whilst physics and aerodynamics aren’t precise sciences, you have deliver on testing and quality or you just lose credibility. BL learnt this the hard way – that’s why the British car industry -the vast majority of which is now under foreign ownership – is only now rivalling the best elsewhere in the world again.
Come on Boeing – you’ve been in one inquiry already; didn’t you learn anything from that??


As long as CEO Muilenburg remains in charge, profits before safety will, in my view, be the primary directive at today’s Boeing.

Paul Proctor

I know Dennis and supported him while working in Boeing HQ. He’s an incredibly hard-working, SMART and honorable guy. There’s no way he’d deliberately put profits before safety. Methinks Blais is just short on Boeing stock, making accusations.


If he was smart he wouldn’t have allowed flawed design to proceed. If he was honourable he wouldn’t have covered up evident aircraft deficiencies.


@Paul Proctor
What a load of BS! We all saw him at the hearings on Capital Hill…he did nothing but pivot, and fudge, and deny, and repeat meaningless mantras. But he wasn’t willing to surrender (part of) his remuneration…no, that had to be taken from him by a board decision a few days later.

Neil W

When the A380 wing was undergoing static tests during certification it also failed at around 98/99% of the test load.
Airbus was not required to repeat the test and the aircraft was certified successfully.


Not entirely correct: “…Garcia says that the failure of the wing below the 1.5 target will require “essentially no modifications” to production aircraft: “This static test airframe has the first set of wings built, and we have refined the structural design for subsequent aircraft due to increased weights etc. We will use this calibration of the FEM to prove the adequacy of the structure on production aircraft.” “Airbus structural engineers had stated that it planned to carry out “a residual strength and margin research test” in 2006 after completing ultimate load trials.” The equivalent situation here would be: –… Read more »

High Mile Club

One thing that has puzzled me with the A380 is the complete lack of a center fuel tank; it’s all carried in the wings and the trim tanks. This may be due to the fact it has 6 wing tanks so it wouldn’t necessitate the need for a center one, but it is a little baffling when you figure the 747 has one. In fact, the A340 and A330 also don’t have one either; but the A350 does.

It’s weird…


Maybe it was felt that having a central fuel tank would eat up too much potential cargo hold space? There’s already enough space lost in the A380 due to having to carry twice as much passenger luggage.
From the illustration, you can see that there’s some room for cargo between the wings…

comment image

High Mile Club

Likely, though given how the fuel tank would sit below the cargo deck on most twin jets, I don’t see how exactly it would eat up space. I tried digging around online for a technical answer or at least to find out what led to that design, but I keep coming up short.


Minor correction Bryce; ‘… in the affected area and similar design areas,’ Yes there are going to be long delays.

James Hayward

The wing didn’t fail on the 777x test. The fuselage failed the pressure test. Boeing has a reputation for very strong wings.


Yes, we know that. This sub-discussion was about failing elements during the pressure test.


This stirs a distant memory. Didn’t Boeing say the 737MAX would be fine on the night as well?? From the PR point of view I would think that saying “what we’ve seen to date reinforces our prior assessment that this will not have a significant impact on the design or our preparations for first flight” is a disaster. Some of you will remember how Boeing and the FAA got the 747 approved with warping engine casings which meant that the engines were not able to deliver full power, and lumps of depleted uranium deployed to “cure” wing flutter and problems… Read more »

Dave Richardson

Frightening! And no further test?



Boeing carved out few inches of the original B777 interior fuselage to make the interior room wider to accommodate wider seats. They are promising 18″ seat width and 1.5″ arm rest, the same as A350. Although the aisle would be smaller.

This is why B777X have one of the thinnest fuselage compared to other aircraft. I believe it’s the thinnest one out there today.

Could this be one of the reason why the fuselage ripped apart?


Maybe this catastrophic failure is the reason why Boeing announced two weeks ago that it was going to abandon plans to use robotic fuselage assembly on the 777X, and revert to assembly by hand:

Anthony Usoro

AI/ROBOTICS far more efficient than hand like reverting to stone age medieval tech. However may boost employment figures.


It’s just like modern day Boeing to say ‘no planned delays’ in an aircraft that clearly needs more scrutiny. Profits before safety, right Mr. Muilenburg?

Paul Proctor

See my previous response.


“No planned delays” is another way of saying “we think we’ll get away with it, but if we don’t, then the ensuing delays will of course be unplanned”.!

Doron Kabilio

Here come the Boeing Haters, who claim they won’t fly it (as if they fly anywhere other than their simulators)

The Anti Boeing Bias here is emblematic of the US Main Stream Media and Anti-American as well.

How many comments were posted about Airbus reliability under the A380 Quantas story of 3/4 of the fleet out of service….


It was 1/4 of the Qantas A380 fleet out of service (not 3/4), which amounts to 3 planes. If you had read the article, you’d have seen that 2 of those are having routine D-checks, and the other has an engine problem.

What kind of contorted nationalism equates criticism of a US company to criticism of the US itself?

Another Boeing cronie that can’t deal with the fact that Boeing is flushing itself down the toilet…

Paul Proctor

Please address why the Pratt-engined A320neo isn’t grounded after dozens of inflight engine failures. Sure looks like a red flag to me.


Maybe it’s the same reason that the 787 isn’t grounded, after repeated issues with the Trent 1000. Exercise your right as a tax payer, call the FAA and ask them 😉


Bryce, do you for Airbus ? or is an Airbus website ?


…was that English…?

Gerry Stumpe

Bryce makes great points. I don’t think he’s working from a biased viewpoint. What do you have to offer Max? What is YOUR point?

Anthony Usoro

Those dual genocide in Ethiopia and Indonesia angered d whole world cos Boeing told us the appropriate safety feature was extra and those airlines didn’t pay for it so their passengers have to die to serve as a lesson to others. Cos of a few bucks??? Ridiculous. Safety shouldn’t be compromised. They told us a safety feature was repaired overnite without d knowledge of the crew.


Is anyone going to mention the US import/export taxes on non-Boeing aircraft. You see, it’s the Dems. 😉

Arne R J Bengtsson

Sorry I do not understand. Why go to such extremes if reality is much different ? There is something fishy on this.

Andy Richards

Sorry but 99% is NOT 100%. I would expect it to at least make 110% or even 120%. After the MAX debacle, the 777X has to be absolutely bullet-proof. Retest is absolutely essential. Anything less is a total dereliction of duty and responsibility.

Paul Proctor

Learn the power of modern-day computational analysis.


One would think Boeing had done thorough structural analysis prior to the live test. And then there could be manufacturing quality coming into play.


So here's a question. Boeing only failed by one percent but the FAA still wants to certify the aircraft. If I took the FAA knowledge test and got a 69 percent, 70 is passing for those who don't know, would the FAA pass me? After all, I was only off by one percent. I think not. Boeing and the FAA need to quit lowering the standards and pull it together.

Paul Proctor

You are confused. If you got 99 out of 100 n an FAA knowledge test you’d pass.


I understood Booker’s comment perfectly.
It seems that you’re the one who’s confused 😉

Hint: Booker has normed his example to 70, rather than 100…

James Hayward

Welcome back, Joanna Bailey! Please set your sights on making sure news is confirmed by more than an “unnamed source close to the situation said”, or a “a whistle blower, said” who might just have an ax-to-grind”.
Again, Welcome back. Think of writing a book; I’ll read it!


What the hell are you on about? Apart from being in the Seattle Times (in Boeing’s original home town), the same story was on CNN’s Quest Means Business last night, and the story is currently online on Reuters for you to read.
You Boeing cronies just can’t stand reality, can you?


Tim Clark, President of Emirates said, that the B777X plans to Test the aircraft in Dubai, and emphasized the fact that Emirates will an “Assiduously” Test, and added “ I want one aircraft to go through Hell On Earth” to make sure it all works…This is going to be a proper certification process”. I believe, that Emirates must have been aware of the latest Test Calamity on the B777X that happened during September2019, and the Dubai Airshow was in mid November/19. Take Trump’s suggestion to change the B737 MAX name, but suggest BOEING start changing their brand name to Whatever,… Read more »

Paul Proctor

Was there any original reporting in this story?


Why ask? Are you upset because it put your Darling Dennis in a bad light?
It was on CNN last night, and it was on Reuters just after it appeared here. The purpose of news media is to spread news…even if that’s inconvenient for Boeing.


The test was to get to 1.5 of the maximum load – and hold it for three seconds. It not only failed slightly before the 1.5 target – but didn’t maintain the required loading for the requisite time. Clearly the Boeing engineers’ computer modeling had indicated it would work – or they wouldn’t have attempted it. It was designed with this test in mind from the outset. So – if it’s failed – then the modeling was flawed. Or – the manufacturing was flawed. Or a combo of the two. I doubt this is the first time an airframe or… Read more »


This may seem off topic and irrelevant and this will rub a lot of folks up the wrong way, but to what extent is excellence in all sorts of spheres such as production, engineering, education, manufacturing, new development, etc. compromised in the US for its unwillingness in certain cases to adopt new methods (often not developed in the US) such as the metric system for instance? There is often a silent mentality of “good enough will do” instead of “only the best will do”.


It’s part of an Engineering process. Don’t be a scare monger! Some of your recent reporting are unfortunately headed in that direction.


Boeing was happy to let the story circulate that the test failure was due to a cargo door blowing off. Honesty is also part of the engineering process. Reporting the true story isn’t scare mongering.


1.48 out 1.5 times Stress (Proof Stress aka Factor of Safety) is almost at the touch line! Boeing is being professionally honest in circulating the story. It’s a need to know information. Even a true and honest story can monger scare in these days of viral culture.


How are they being professionally honest in circulating the story that it was just a cargo door when the fuselage ripped open? Because we live in an age of ‘viral culture’ we should suppress the truth in case it scares someone?


A number of people have suggested that 98% is ‘close enough’ & I understand what they’re getting at, BUT they’re not grasping the actual nature of the test. The FAA process REQUIRES the airframe to reach 150% of it anticipated maximum design stress & maintain its integrity for 3 seconds. It REQUIRES this. It’s not a ‘desirable’.! Ideally, the airframe would sustain 5-10% above this figure.! If the brand new airframe has failed so dramatically & catastrophically at under the 150% mark, it is effectively telling Boeing & the FAA, that the aircraft is NOT meeting the structural Requirements. When… Read more »


Sure thing, ruptured fuselage is nothing to worry about unless you’re seating in it 40k feet up.


why are they so frightened to do a retest? Are they scared they’ll wreck another airframe? If they are confident enough of the fix to put people in their plane, then they should do a retest. Oh wait a minute . . .

Ueli Praett

Oh man! It costs. And money is more important than safety. Upps, here is the point where all the comments are repeated……


And, in view of your excellent comment on FEA / computational analysis above, maybe they’re afraid it will fail again…in a different region and/or at a different pressure.


Interesting (and worrying) if you look at the photo of the ruptured fuselage is the fact that most of the rupture (on either side of the gaping dark hole) has not occurred along a seam: if you look at the jagged profile of the left edge of the dark hole, it matches to that of the right edge, like interconnecting (but displaced) pieces of a jigsaw puzzle. So this appears to be a bulk material failure rather than a seam integrity issue. Not an easy issue to fix! The fuselage skin is going to have to be made thicker and/or… Read more »


I think that despite the technology that we have today airliners are building less reliable aircrafts than those we had before. Engine and instrumentl problem, pressurization, softwares…. All this for maximum profit and production at the cost of safety

Gerry Stumpe

Biggest problems we have with new airplanes are the engines. At present they seem to be the root of all evil……just a perception. But new tech ALWAYS has a few glitches, it’s how we learn. This problem will pass, Elie. Welcome the future.

Moaz Abid

Yeah it is the same thing with the uber driverless cars. Mistake help you learn, and I have full faith in boeing to fix the MAX and the 777x

Aidan Corish

Are airframes that have reached the end of their operational lives ever tested to see if they still comply with the requirements under which they were originally certified?


Nearly 100 comments but everyone failed to realise one key point. This is a static pressurisation test and the test requirement isn’t test to failure. In other words even if they pass the test a second time, it does not fully guarantee the failure is out of the window. Firstly static test means you only have a limited number of factors or variables applied to the test object. In actual operations, the airframe undergo a dynamic stresses. Not knowing the ultimate failure strength in this case becomes a problem. Past B777 fuselage may have been able to handle 10x the… Read more »

Morris Reddic

Where are the pictures?

Giovanni Iannuzzi

Why don’t retest? Otherwise what was the need for reaching a load of 1.5 times the maximum load ?

Ueli Praett

These static tests will cover all uncertaincies concerning any defects in the material used, residual stresses due to manufacturing processes, tolerance problems during manufacturing, any unexpected peak loads during flight operation, degeneration of material due to fatigue and many other things. The wind load is supposed to be in unexpected magnitude. Additionally it is said that (for steel) 15% more stress will cut down the fatigue lifetime by 50%. For aluminum or other material different factors apply. The liftetime shall be 5x the design lifetime of the aircraft. This sort of overload test is very common to most safety related… Read more »

Ueli Praett

Upps. I forgot the biggest uncertaincy : Unexperienced design engineers with limited capabilities to perform a correct computational stress analysis and to interpret the results in a qualified manner.


Another imperfection of analytical techniques: they always introduce simplifications, e.g. by at least partially discounting higher-order effects. As the need for more sophistication arises, more and more higher orders have to be included. For example, I know an engineering company that does ultra-high-precision modelling of vibrations using equations that go as far as the sixth derivative of position w.r.t. time; most models wouldn’t go further than the second derivative…maybe the third.

Based on the catastrophic failure evident from the photo in this article, one can ask oneself if Boeing’s pre-test modelling used any higher-order effects at all 😉


If, for this load simulation test, the wings were being pulled upwards and the fuselage was being held down at the front and rear ends as seems reportedly to have been the case, one would have expected the rupture to have occured somewhere along the top of the fuselage and not on the underside of the fuselage (just behind the wing). The rupture in the photo does not show signs of failure under compression, rather it certainly looks like the failure occured under tension. Just an observation. Or did the failure perhaps occur with the loading simulation the other way… Read more »