Boeing seeking to reduce scope, duration of some physical tests for new aircraft

[Smythe]

Given the current issues with computer modelling vs reality....(0.6 to 2.5 on modelling assumptions)
this is pretty bold by Boeing if true...

PARIS (Reuters) - Boeing Co engineers are reducing the scope and duration of certain costly physical tests used to certify the planemaker’s new aircraft, according to industry sources and regulatory officials.

For Boeing’s proposed twin-aisle jetliner, known internally as NMA, Boeing’s Test & Evaluation group is developing the technology to replace costly and labor intensive physical safety tests used for decades - such as using machines to bend the wings to extreme angles and shaking the fuselage until it cracks - with computer modeling, according to three people with knowledge of the matter, including an FAA official.

https://www.reuters.com/article/us-france-airshow-boeing-certification-e/exclusive-boeing-seeking-to-reduce-scope-duration-of-some-physical-tests-for-new-aircraft-sources-idUSKCN1TH0A3

[Less Hair]

They have a point: It creates some big mess to break CFRP-wings. I still favour real tests.

[groundbum]

since there will be lots of new materials and bonding methods in these structures, so lots of new uncharted territory, then if nothing else it would be good to conduct destructive testing just to validate the computer predictions. So if the computer says it will break after 15,000 cycles but it goes 25,000 cycles that shows an error with the computer modelling. Otherwise this is one computer checking another computer, and the first real world test is likely to be with passengers onboard. And we've seen where that suck-it-and-see approach got us...

G

[A and C]

I would suggest that composite technology is well known within aviation and related industries with gliders and light aircraft having used composites for over thirty years.

I know of one company that has a marine turbine system that is effectively three 25 ft aircraft wings that has the fatigue life assured to beyond thirty years.

While caution should always be used just because a technology has not been used in an airlines it does not follow that the data is not available to make reliable fatigue predictions.

[FrequentSLF]

MCAS was the result of computer modelling... and had to be increase from 0.6 to 2.5, because the computer modelling missed issue at low speeds...
Cars are crash tested to be certified, and there extensive computer nodellings also there, even Formula 1 cars are crash tested and are all composite materials.
IMHO this shows that Boeing has gone all the way to save money jeopardizing safety... and what is a bigger concern is that the FAA is just their rubber stamping agency

[visibility3miles]

With MCAS concerns still looming large, this seems like a really bad time to request fewer tests.

Boeing has trust issues at the moment.

[Rated De]

With MCAS concerns still looming large, this seems like a really bad time to request fewer tests.

Boeing has trust issues at the moment.

Precisely.

[infrequentflyer789]

With MCAS concerns still looming large, this seems like a really bad time to request fewer tests.


I recall reading somewhere (although can't find it now) that Boeing tried to get fewer / no physical flight tests _during_ the MAX development, arguing that the computer modelling was so good that physical testing could be dispensed with. They weren't allowed to skip physical testing, and the modelling turned out to be b:mad:cks, as a result MCAS got 4x more powerful, unlimited and at any-g, and the rest is history.

Ironically it might (accidentally) have turned out safer if they'd been allowed to do computer modelling only...

[MCDU2]

Does Boeing not have a PR department? Or a CEO with a brain.....

[Chris2303]

I find it interesting that Boeing Co is fighting for the life of at least one of it's airplanes, and possibly the company and somebody comes out with this.

Silo mentality methinks?

[tdracer]

To be fair, while CFD has much improved over the years, it's still far short of computational structural analysis - which is very highly evolved.
Sure the timing is pretty lousy, but structural testing to destruction of a completed structure is a bit archaic in this day and age. 300 meter tall skyscrapers are becoming the norm, no testing to destruction of completed structures needed. If one of those ever structurally fails, the death toll would be massive.

[FrequentSLF]

To be fair, while CFD has much improved over the years, it's still far short of computational structural analysis - which is very highly evolved.
Sure the timing is pretty lousy, but structural testing to destruction of a completed structure is a bit archaic in this day and age. 300 meter tall skyscrapers are becoming the norm, no testing to destruction of completed structures needed. If one of those ever structurally fails, the death toll would be massive.
those structures are designed with high safety margins that will take care of modelling errors, that is allowed since are standing on ground and have minimal weight issues. A failure can be detected and fixed over time, and rarely fails, however there are several cases of wrong design that costs several lifes. Furthermore each and every single building has its own modelling, an error is limited to a single building not to thousands of planes carrying million of pax...

[Eric Janson]

I find it interesting that Boeing Co is fighting for the life of at least one of it's airplanes, and possibly the company and somebody comes out with this.

Silo mentality methinks?

Part of a broken Company Culture. It's right there on the Boeing website.

​​​​​​https://jobs.boeing.com/diversity (https://jobs.boeing.com/diversity)

Building aircraft means hiring the most qualified people. There's no place for Diversity imho.

Virtue Signalling CEO Dennis Muilenburg needs to be fired along with everyone who allowed this to happen imho.

[tdracer]

those structures are designed with high safety margins that will take care of modelling errors, that is allowed since are standing on ground and have minimal weight issues. A failure can be detected and fixed over time, and rarely fails, however there are several cases of wrong design that costs several lifes. Furthermore each and every single building has its own modelling, an error is limited to a single building not to thousands of planes carrying million of pax...

Aircraft structures are also designed with large safety margins. The validation testing requirements for aircraft structure date back to when aircraft structure was designed with pencils and sliderules. Do you honestly believe there isn't justification for a re-think of those requirements based on current design practices? What other major industry does structural design validation the same way they did it 60 years ago?

The worst aircraft crash in history killed 583 people (Tenerife). The catastrophic collapse of a single large building could kill tens of thousands.

[RickNRoll]

Part of a broken Company Culture. It's right there on the Boeing website.

​​​​​​https://jobs.boeing.com/diversity (https://jobs.boeing.com/diversity)

Building aircraft means hiring the most qualified people. There's no place for Diversity imho.

Virtue Signalling CEO Dennis Muilenburg needs to be fired along with everyone who allowed this to happen imho.

That probably has more to do with a noose being hung over an employees desk because he wasn't white.

[Bend alot]

Aircraft structures are also designed with large safety margins. The validation testing requirements for aircraft structure date back to when aircraft structure was designed with pencils and sliderules. Do you honestly believe there isn't justification for a re-think of those requirements based on current design practices? What other major industry does structural design validation the same way they did it 60 years ago?

The worst aircraft crash in history killed 583 people (Tenerife). The catastrophic collapse of a single large building could kill tens of thousands.
Currently it is only 2,977 deaths - just the modelling is not consistent with that, under most modelling outcomes - they still stand.

[GlobalNav]

Why not just do the “flight” tests in the simulator? Heck, you could use a model pilot instead of a real one and not even use a simulator, just run the “tests” on a mainframe. I think Microsoft makes one. Wonder what it would cost to buy a fare for a simulated passenger? It’s the only way I would fly.

[Water pilot]

To be fair, while CFD has much improved over the years, it's still far short of computational structural analysis - which is very highly evolved.
Sure the timing is pretty lousy, but structural testing to destruction of a completed structure is a bit archaic in this day and age. 300 meter tall skyscrapers are becoming the norm, no testing to destruction of completed structures needed. If one of those ever structurally fails, the death toll would be massive.
The materials that they are composed of are indeed tested to destruction, and the designs are (generally) tested the same way. Whenever there is a hurricane or earthquake, engineers look at the buildings and make recommendations for any needed changes to building codes. If I were to propose some super-duper polymer glue that replaces foundation bolts , you better believe there would be some pretty significant testing to destruction before that technique was accepted by national and local building code societies, and it probably would not get widely accepted until an actual earthquake happened and it was proven.

Breaking stuff is the fun part! The process that engineers use to validate building materials is really worth a TV show, especially for earthquakes and hurricanes. I would have loved to have been part of a wing breaking team. Seriously, though, that is one of our few defenses against Murphy; when something fails in a different way than you expected it can lead to a whole bunch of the original assumptions being challenged, which ultimately improves the final design. By definition, computer modeling can't really challenge assumptions since what is in the computer are the assumptions.

Not to say that building science is anywhere near perfect, the Grenfell Tower fire is a pretty good example of what happens when you don't test the materials that you apply on a large scale.

Edit: I think that is where the engineers and the finance guys differ. Engineers love surprises (during the design phase), the stock market hates them. If you test the plane for real, you might find something wrong and that would impact the schedule, which could really move the stock price. If you test the plane using the same program that you used to design the plane, nothing unpleasant will have to be reported to the shareholders.

[infrequentflyer789]

Not to say that building science is anywhere near perfect, the Grenfell Tower fire is a pretty good example of what happens when you don't test the materials that you apply on a large scale.


To my mind the materials testing (although there are still a lot of questions in that area) wasn't the biggest issue with Grenfell. The real problem was grafting new-standard-stuff onto old-standard-design without fully understanding how the old and new interact (in this sense it is very very similar to the MAX saga). Grenfell-style cladding is, and was, known to go up like a match, proven by testing in reality, it has done multiple times in Dubai - but people don't typically die in the fire, and the buildings stay mostly intact with little internal damage, "just" a re-clad needed. Modern skyscrapers are designed with extensive internal fire suppression systems, and typically multiple exit paths, refuge floors, etc. - all stuff Grenfell didn't have. Grenfell was designed to cope with fire the old fashioned way by fire-containment-cell. Over-cladding breaches that containment (IMO) regardless of materials because there is always, always, an air gap by design, which is a chimney by any other name. Even if the actual cladding was completely non-flammable there would still be debris/rubbish/junk accumulating in the gap, fire-containment is thus breached.

We know, from testing in reality, that containment-cell design works, we know, from testing in reality, that ACM cladding design with modern fire suppression works. This does not mean we can assume that ACM cladding over containment-cell design will work, and it didn't (same goes for steel-cables and FBW on aircraft). Retrofitting cladding on the outside of buildings designed with fire-containment-cells should never ever be allowed, I cannot see how external cladding can possibly be done keeping within the cell. The only option should be to upgrade the entire building to modern standards including full internal fire suppression - because the containment is gone.

Interestingly UK building standards are written to anticipate this sort of thing. A year or so before Grenfell I looked into a loft refurb/conversion, I was told by a building control inspector that because I was adding new accommodation space I would have to meet current regs. for exit routes and fire suppression, which with a single staircase and more than four floors meant I would have to retrofit sprinkler system and firedoors throughout the house (which made the project a non-starter).

So, where, you ask, was that building control inspector, or his London brethren, when they did the Grenfell refurb (which added extra accommodation floors as well as cladding, and definitely involved more than four floors and no sprinklers)? Well he wasn't involved, because the big guys get to do "self certification" on building projects (which brings us right back on topic again)...

[Rated De]

Shock and horror, that self regulation would end up the unmitigated mess it is.

It is endemic in so much of 'society' where the incentive always generates the outcome.
When money is the incentive, the outcome is always assured to cost someone a lot.

[EEngr]

So, Boeing want to replace testing with analysis. That might work, but I'd be hard pressed to trust Boeing to maintain a design and analysis engineering staff of any experience level between new product release events. When I was there, engineering staffing cycled up and down pretty drastically between new model launches. And there was never any overhead funds available to keep skills and tools current in the interim.

[arearadar70]

Destructive testing. Developed following the Comet crashes in 1951/2. It has worked well since then. If it it ain`t broke don`t mend it, or in this case maybe you should.

[Turb]

To my mind the materials testing (although there are still a lot of questions in that area) wasn't the biggest issue with Grenfell. The real problem was grafting new-standard-stuff onto old-standard-design without fully understanding how the old and new interact ...........So, where, you ask, was that building control inspector, or his London brethren, when they did the Grenfell refurb (which added extra accommodation floors as well as cladding, and definitely involved more than four floors and no sprinklers)? Well he wasn't involved, because the big guys get to do "self certification" on building projects (which brings us right back on topic again)...
Very accurate post and very much on topic.

Old thing with safety critical new stuff grafted on top which changed fundamental characteristics
Inadequate testing (in the case of Grenfell no testing at all) and definitely no destructive testing
Pretence that the new thing is the same as the old thing, just better performance
Insufficient training ( in Grenfell's case the fire crews hadn't got a clue what they were dealing with or how to deal with it and they killed a lot of people by telling them to stay put when they should have bust a gut to get everyone out ASAP)
Insufficient or compromised or just non-existent regulatory oversight

Is any of this going to change? Is society willing to pay the cost of doing things right?

[Euclideanplane]

Very accurate post and very much on topic.

Old thing with safety critical new stuff grafted on top which changed fundamental characteristics
Inadequate testing (in the case of Grenfell no testing at all) and definitely no destructive testing
Pretence that the new thing is the same as the old thing, just better performance
Insufficient training ( in Grenfell's case the fire crews hadn't got a clue what they were dealing with or how to deal with it and they killed a lot of people by telling them to stay put when they should have bust a gut to get everyone out ASAP)
Insufficient or compromised or just non-existent regulatory oversight

Is any of this going to change? Is society willing to pay the cost of doing things right?
In the case of Grenfell, decades long experience, i.e. "testing" of buildings actually occupied by people, and with varying number of casualties aquired, had already documented the problems with the concept of cladding a building using flammable material.
And the "stay put" principle had apparently been "tested in situ" with similar results at those same occasions as well. www.youtube.com/watch?v=kDdO-FVNfQI

[SeenItAll]

While I can't speak to the issue of whether computer testing should replace physical testing, what about the issue of design/test specifications? For example, wings are required to handle loads that are 1.5 times their typical expected load. Who chose the 1.5 figure? The fact that it is such a round number makes it suspect by itself. Indeed, over the past 60 years, how many planes have had their wings snap off in situations and attitudes that were otherwise recoverable? I think the answer is few to none. Thus, my hypothetical question: why should the number be 1.5? Maybe 1.4361 is more appropriate and economical? And while computer modeling may be less exact than physical testing, perhaps its margin of error is less than the difference between 1.5 and 1.4361 -- so using computer modeling and keeping 1.5 still results in appropriate safety.

Just my two cents.

[futurama]

While I can't speak to the issue of whether computer testing should replace physical testing, what about the issue of design/test specifications? For example, wings are required to handle loads that are 1.5 times their typical expected load. Who chose the 1.5 figure? The fact that it is such a round number makes it suspect by itself. Indeed, over the past 60 years, how many planes have had their wings snap off in situations and attitudes that were otherwise recoverable? I think the answer is few to none. Thus, my hypothetical question: why should the number be 1.5? Maybe 1.4361 is more appropriate and economical? And while computer modeling may be less exact than physical testing, perhaps its margin of error is less than the difference between 1.5 and 1.4361 -- so using computer modeling and keeping 1.5 still results in appropriate safety.

Just my two cents.
You're right. In engineering there are lots of "rule of thumb"s based on past experience. In the early days of flying, planes with 1.5x margin seemed to survive. Those with lower margins seemed to fail. And 1.5x margin is still economical from cost/weight perspective. And yes, it's a nice round number. Thus 1.5 became the standard safety factor -- not based on strict mathematical analysis but from engineering experience / observations.

Over many decades, newer analysis using more sophisticated methods seem to support this ~ 1.5 margin, at least for airplanes. Yes you can save weight by using a lower safety factor, but there are probably other ways to save weight -- and at the end of the day, the cost difference is marginal, so the industry just sticks to 1.5. There's very little incentive to change this.

(But for spacecraft, any weight savings equal big (big!) bucks, so they tend to use lower safety margins when building rockets, etc.)

[Aihkio]

1.5 is not really a "factor of safety" it is more properly a "factor of uncertainty" that cumulatively includes all the various imprecicions in assumptions made during the design.

[futurama]

A "factor of uncertainty" that cumulatively includes all the various imprecisions in assumptions made during the design == "factor of safety".

And in FAR Part 25, it is legally defined as such:


Sec. 25.303 — Factor of safety.

Unless otherwise specified, a factor of safety of 1.5 must be applied to the prescribed limit load which are considered external loads on the structure. When a loading condition is prescribed in terms of ultimate loads, a factor of safety need not be applied unless otherwise specified.

[Aihkio]

Calling it FoS leaves out the origin. I seem to recall that in some space projects it was called FoU. Whichever, one should remember the origins.

[Smythe]

In structural engineering, the typical Factor of Safety is 1.5. You take the intended load, and design it to 1.5 times. This is a fundamental load factor for analysis.

Along those lines, when you test to ultimate (ie failure) you can then determine the actual safety factor of each part or the assembly. In ultimate, you may determine a factor of safety of 5 for the part or assembly. This is what is strived for, because in the 1.5 factor being the bare minimum, if ultimate is only 2, then you are always looking at cases where the load or conditions may be higher than your assumption. With a higher factor of safety, you know you can cover more conditions without restrictions.