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787 Lightning strike issues v FAA

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787 Lightning strike issues v FAA

Old 11th Dec 2019, 05:03
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787 Lightning strike issues v FAA

Looks like another cost-schedule win over safety .Sure glad FAA management backs their people - WAYYYYY back ..

https://www.seattletimes.com/busines...tion-measures/


FAA engineers objected to Boeing’s removal of some 787 lightning protection measures

Dec. 10, 2019 at 5:00 pm Updated Dec. 10, 2019 at 8:00 pm


By
Dominic Gates
Seattle Times aerospace reporterLast spring, Federal Aviation Administration (FAA) managers approved removing a key feature of the 787 Dreamliner wing that aimed to protect it in the event of a lightning strike.

Boeing’s design change, which reduces costs for the company and its airline customers, sped through despite firm objections raised by the agency’s own technical experts, who saw an increased risk of an explosion in the fuel tank inside the wing.

That clash will come under scrutiny Wednesday as FAA Administrator Steve Dickson appears before a House committee examining the agency’s regulatory performance in the wake of the two Boeing 737 MAX crashes.

Lightning protection on an airplane like the 787 that’s fabricated largely from carbon composites is more elaborate than on a metal aircraft. When Boeing developed the Dreamliner, it included special measures to protect the wing fuel tank. It sealed each metal fastener in the wing with an insulating cap and embedded copper foil in strips across the carbon wing skin to disperse the current from any lightning strike.

..... goes on with a few good diagrams
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Old 11th Dec 2019, 08:13
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The FAA initially rejected the removal of the foil from the wing on February 22, when its certification office ruled that Boeing had not shown, as regulations required, that the ignition of fuel tank vapor by a lightning strike would be “extremely improbable,” defined in this case as likely to occur no more than three times in a billion flight hours.

By then Boeing had already built about 40 sets of wings without the foil.
This last sentence is also revealing on how some in Boeing view the FAA ...
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Old 11th Dec 2019, 11:26
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Without wishing to start Boeing versus Airbus debate, does the A350 have the foil in the wings?

The question is only because, if the wing construction is broadly similar and EASA / Airbus require it, that is strong evidence that the FAA should have insisted.
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Old 11th Dec 2019, 11:56
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With respect to FAA Administrator Steve Dickson ...

I followed two congressional hearings with him, including his confirmation hearing in congress at the time. My take from that was that he said to have a strong 'flying' CV. But responding to congress members' questions (relating to the MAX) he answered that he had no 'design engineering' and no '(design engineering) certification' experience. Possible manufacturing engineering experience was not discussed but it appears he may not have any. The other 'MAX' witnesses did not have any either by the way.

Will be interesting in that light to follow the MAX certification hearing. He will surely have to lean heavily on the knowledge and experience of others.

Boeing has a 'history' with fuel tank explosions. Discussions about those are still going after many years. So 'surprising' that an issue like this, either static or lightning related, is added to that. And would be 'amazing' indeed, from not only a design engineering but also a manufacturing engineering point of view, if they have indeed proceeded to build wings without solid FAA authorisation.
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Old 11th Dec 2019, 12:22
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Having just said that ... taking a look at the Hearing Agenda (thanks by the way @Grebe & Seattle Times for referring to that)

Start Quote

Stephen Dickson, Administrator, Federal Aviation Administration, Testimony
Accompanied by
Earl Lawrence, Executive Director, Aircraft Certification Service, FAA,
Matthew Kiefer, Member of the FAA’s Technical Advisory Board,

End quote

Last edited by A0283; 11th Dec 2019 at 12:50.
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Old 11th Dec 2019, 18:16
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William E Boeing must be spinning in his grave!
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Old 11th Dec 2019, 19:11
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Originally Posted by Chris2303 View Post
William E Boeing must be spinning in his grave!
Yep - and if you wired up his grave, Bill allens grave and t wilson grave, you could power all of Seattle - or generate enough to fire up ole sparky for a few recent types . .

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Old 11th Dec 2019, 23:40
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William E Boeing must be spinning in his grave!
Exactly!

I forefronted technology and innovation...Why are we still using cables to control surfaces?!?!?!?!
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Old 12th Dec 2019, 04:54
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Originally Posted by turbidus View Post
Exactly!

I forefronted technology and innovation...Why are we still using cables to control surfaces?!?!?!?!
Because when all electric goes fubar, it will still fly

And when a special EMP warhead goes off within maybe 100 miles- it will still fly



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Old 12th Dec 2019, 07:56
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So does the A350 have lightning protection for the wings?
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Old 12th Dec 2019, 08:09
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It has metallic foils embedded in the CFRP-structure.
https://www.airbus.com/newsroom/news...aluations.html
page 21:
https://www.fzt.haw-hamburg.de/pers/...20_A350XWB.pdf
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Old 12th Dec 2019, 21:20
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The sky is black with pigeons coming home to roost.
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Old 13th Dec 2019, 19:30
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Originally Posted by SLF3 View Post
The sky is black with pigeons coming home to roost.
The sky is falling.
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Old 13th Dec 2019, 21:39
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Originally Posted by GlobalNav View Post
The sky is falling.
That's just pigeon poop.

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Old 13th Dec 2019, 23:18
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The 787 has a copper mesh embedded in the carbon fiber matrix - the wing, fuselage, pretty much everywhere. In addition - due in part to the uncertainties in the lightning characteristics of carbon fiber - they added a metallic copper foil to the inside of the wing skin. Once they had real aircraft structure to test and analyze they were better able to quantify the lightning threat. Then:
In December 2018, SAE revised the zones based on data from reports of more than 1,000 lightning strikes on aircraft. It found that the area aft of the engines — designated Zone 2 when the 787 was certified — was rarely hit, and so changed its classification to Zone 3.
Combined with the zone change around the engine pylon, it was determined the foil was no longer needed, that the copper mesh along with the nitrogen inerting system provided adequate protection against lightning strike.
I worked with Tom Thorson - the FAA specialist quoted in the linked article - and he's reasonably sharp. But he's a Propulsion specialist, not a lightning specialist. I worked some aspects of lightning protection for 20 years, but my lightning knowledge was a small fraction of that what the Boeing (and FAA) lightning experts knew.
I used to say - somewhat joking - that I knew enough about lightning and lightning protection to be dangerous. Based on some of the posts on this thread, it appears ignorance is even more dangerous.
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Old 13th Dec 2019, 23:35
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Originally Posted by tdracer View Post
The 787 has a copper mesh embedded in the carbon fiber matrix - the wing, fuselage, pretty much everywhere. In addition - due in part to the uncertainties in the lightning characteristics of carbon fiber - they added a metallic copper foil to the inside of the wing skin. Once they had real aircraft structure to test and analyze they were better able to quantify the lightning threat. Then:

Combined with the zone change around the engine pylon, it was determined the foil was no longer needed, that the copper mesh along with the nitrogen inerting system provided adequate protection against lightning strike.
I worked with Tom Thorson - the FAA specialist quoted in the linked article - and he's reasonably sharp. But he's a Propulsion specialist, not a lightning specialist. I worked some aspects of lightning protection for 20 years, but my lightning knowledge was a small fraction of that what the Boeing (and FAA) lightning experts knew.
I used to say - somewhat joking - that I knew enough about lightning and lightning protection to be dangerous. Based on some of the posts on this thread, it appears ignorance is even more dangerous.
Good points- but the penetrations of front and rear spars for various metal parts is also a problem, when immersed in fuel and having possible electrical gaps due to not so obvious ground paths. Walt Gillette was very much aware of that kind of issue while working on one of the programs not listed in his bio. . .wuz there
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Old 13th Dec 2019, 23:41
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Originally Posted by tdracer View Post
The 787 has a copper mesh embedded in the carbon fiber matrix - the wing, fuselage, pretty much everywhere. In addition - due in part to the uncertainties in the lightning characteristics of carbon fiber - they added a metallic copper foil to the inside of the wing skin. Once they had real aircraft structure to test and analyze they were better able to quantify the lightning threat. Then:

Combined with the zone change around the engine pylon, it was determined the foil was no longer needed, that the copper mesh along with the nitrogen inerting system provided adequate protection against lightning strike.
I worked with Tom Thorson - the FAA specialist quoted in the linked article - and he's reasonably sharp. But he's a Propulsion specialist, not a lightning specialist. I worked some aspects of lightning protection for 20 years, but my lightning knowledge was a small fraction of that what the Boeing (and FAA) lightning experts knew.
I used to say - somewhat joking - that I knew enough about lightning and lightning protection to be dangerous. Based on some of the posts on this thread, it appears ignorance is even more dangerous.
tdracer - I think the main issues are how Boeing have been getting to their determinations (how they have been classifying things - optimistically in favour of easy and cheap), that now justify review. Remember 20/20 the MAX would have been grounded, knowing what we know now.

That and the fact Boeing produced and delivered a large number of aircraft prior to having this change approved by the Regulator/s.

Personally I can see no justification for this change based on "over 1,000" lightning strikes, I would need to see a few more zeros.
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Old 13th Dec 2019, 23:48
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If metal foil external to the carbon fiber structure is so important, why isn't it needed on the A350? According to what Less Hair posted, they embed copper mesh - just like Boeing - no mention of external foil in the fuel tanks...
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Old 13th Dec 2019, 23:58
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Originally Posted by Bend alot View Post
tdracer - I think the main issues are how Boeing have been getting to their determinations (how they have been classifying things - optimistically in favour of easy and cheap), that now justify review. Remember 20/20 the MAX would have been grounded, knowing what we know now.

That and the fact Boeing produced and delivered a large number of aircraft prior to having this change approved by the Regulator/s.

Personally I can see no justification for this change based on "over 1,000" lightning strikes, I would need to see a few more zeros.
Boeing didn't do the determination - an industry group (the SAE) did.
When it comes to specialties like Lightning protection, the FAA (and EASA) have long leaned on the expertise of the airframer experts for the simple reason that the regulators lacked that same level of expertise. When I had meetings with the FAA on lightning/HIRF issues, the FAA had one person in the entire FAA who had a similar level of understanding as the Boeing experts - he was designated a 'National Resource Specialist' (I suspect he's retired by now - he was quite a bit older than me, hopefully replaced by someone of similar expertise). The FAA routinely delegated HIRF/Lightning compliance to Boeing - long before Boeing became an ODA - for the simple reason the Boeing specialist knew far more about it than the FAA people.
If the FAA lightning specialist stands up and says it's not safe, I'll take notice. Tom Thorson - as I said a reasonably bright engineer - is not an lightning specialist. He covers all aspects of Propulsion and simply cannot be expected to also be a lightning specialist.
Oh, and aircraft were produced - NOT DELIVERED - before it was approved. Incorporating a change in production before it's certified is quite common - so long as there is a reasonable expectation that it will in fact be certified.
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Old 14th Dec 2019, 01:22
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Originally Posted by tdracer View Post
If metal foil external to the carbon fiber structure is so important, why isn't it needed on the A350? According to what Less Hair posted, they embed copper mesh - just like Boeing - no mention of external foil in the fuel tanks...
RE external foil and embedded copper/composite issues in the fuel tank(s). The problem is that to ensure non spark the copper foil/plate must be electrically continuous between inside to outside AND the internal mesh. ONE way to do that involves copper plating of the composite around the penetrations such that it is similar to a internal-external " gasket " AND electrically continuous to the ' embedded " mesh or foil. A bit of searching on patents assigned to Boeing in the mid to late 80's can explain the details. June 14, 1988 # 4,750,981 is a start.
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