BA 777 on fire in Las Vegas

[D Bru]

2nd NTSB update confirms it was the HPCR 8-10 spool covered in two FAA AD's

See my post #188. HPCR 8-10 spool already covered by AD 2002-04-11 and by AD 2011-15-06 and subject to additional inspections for years. Both GE and Boeing tried to convince the FAA in 2011 that the condition covered in the latest AD could not lead to uncontained engine failure and damage to the airplane. FAA denied their argument but despite the two AD's this seems now to be the first uncontained engine failure of the type.

Boeing and GE comments on FAA's 2011 "unsafe condition" qualification of GE80-85B
From FAA AD 2011-15-06 concerning "unsafe condition" of GE90-76B; GE90-77B; GE90-85B; GE90- 90B; and GE90-94B Turbofan Engines
––––––––––––––––––––––––––––––––––
"This AD was prompted by cracks discovered on one HPCR 8-10 spool between the 9-10 stages in the weld joint. We are issuing this AD to prevent failure of the HPCR 8-10 stage spool, uncontained engine failure, and damage to the airplane".

"Request
Two commenters, General Electric Company and The Boeing Company, requested that we remove the ''Unsafe Condition'' paragraph from the AD, and reword the Summary section to resemble the Summary section of AD 2002-04-11. The commenters stated that, by their analyses, cracks in the weld joint would not develop into an uncontained failure. The commenters stated that HPCR 8-10 stage spools, P/Ns 1844M90G01 and 1844M90G02, be inspected by an enhanced inspection, similar to those parts covered in AD 2002-04-11.

Answer
We do not agree. AD 2002-04-11 was issued because of additional focused inspection procedures that had been developed by the manufacturer. Because cracks were discovered on one HPCR 8-10 spool between the 9-10 stages in the weld joint, this unsafe condition is likely to exist or develop in other products of the same type design. The unsafe condition could result in failure of the HPCR 8-10 stage spool, uncontained engine failure, and damage to the airplane. We determined that this unsafe condition requires mandatory repetitive inspections for cracks. We did not change the AD."

[Global_Global]

Thanks D Bru, very interesting reading!

[philbky]

Something that has come up in discussion with both professionals and enthusiasts over the last few weeks has been the total destruction of the composite areas of the structure.

Coming after the A400M accident at Seville where little of the structure remained, the question arises about the survivability of post accident fires in an otherwise survivable accident/incident in an aircraft with a high degree of composite construction.

Also, how much more difficult will accident investigation be where structural failure/damage causes an accident but the structure has all but disappeared?

Perhaps someone with knowledge of this area may wish to comment.

[wanabee777]

Combustiblity of Composites

Originally Posted by philbky

...the question arises about the survivability of post accident fires in an otherwise survivable accident/incident in an aircraft with a high degree of composite construction.

Very good question!

Had it not been for an alert mechanic, that JAL 787 which caught fire in BOS could have been a total loss.

[D Bru]

On the question whether G-VIIO’s failed engine was covered FAA AD ‘s concerning the G

According to GE, quoted by AP on 6/10, the spool in question was amongst the first made for the specific engine type (GE90-85B) in 1995.

Now, AD 2002-04-11 not only states that it is applicable to GE90-85B engines, but specifically “to each engine of the type, regardless of whether is has been modified, altered or repaired in the area subject to the requirements of this AD.” See page 4 of this document:
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/c38ae8b2dcfa515f86256bb3006c362a/$FILE/020411.pdf

GE is also quoted to have stated yesterday about the engine fitted to G-VIIO that “this was the first engine failure of its kind, as spools could be similar in design but were not built identically.” This last part is very important, not only because it distinguishes between an earlier uncontained engine failure, which concerned a different (and btw later) version of the GE90, but also because that is exactly where in my opinion part numbers become relevant, if one talks GE90-85B.

The table on page 6 of the document referred to above, mentions the HPCR Spool stage 8-10 and indicates that “all” partnumbers are covered. So, any HPCR Spool stage 8-10 on a GE90-85B.

Given these specifics mentioned in the AD and the year of manufacture (1995) of the G-VIIO engine, it seems therefore pretty clear at least to me that this particular engine was covered by AD2002.

Now whether it was also covered by AD 2011-15-06 depends on the specific partnumbers of the failed engine of G-VIIO. This AD also applies to GE90-85B engines, but concerning the HPCR 8-10 spool, only if it would involve partnumber 1844M90G01 and 1844M90G02 (but not other builds, although of the same design). GE has denied that these parts were involved in the G-VIIO engine, so that AD 2011-15-06 would not seem applicable.

[lomapaseo]

There are two parts to a safety assessment involving engines. One is the consequences to the engine itself e.g. should not catch fire, burst its cases damage its mounts or lose the ability to be shutdown (sic).

The other equally important aspect is the assessment at the aircraft level. Any AD actions need consider both and address the need to minimize either or both by corrective actions.

At this time with so little facts published it is not obvious to me what such AD update is warranted.

[Spooky 2]

Actually the RP did play a significant role in the outcome of this event. The Commander asked him to go back into the cabin to check on what was happening. The RTO was at around <70kts and they had shutdown and firing of the bottles was complete. They were running the checklist and starting the APU when the RP came back up say there was a significant fire outside the aircraft and this is when the evacuation was ordered. The fire was caused by a ruptured 2" fuel line and it had spilled about 40 Gal of fuel. Both the spar valve and engine firewall shut off worked as designed. There will be more news regarding this event over the next week or so.

[olasek]

. Coming after the A400M accident at Seville where little of the structure remained,

Look up other such accidents where little structure remined and aircraft had traditional aluminium fuselage. It is a myth that composite aircraft enhances flammability, research has settled this question long time ago, you can google relevant scientific papers.

[lomapaseo]

The Commander asked him to go back into the cabin to check on what was happening. The RTO was at around <70kts and they had shutdown and firing of the bottles was complete. They were running the checklist and starting the APU when the RP came back up say there was a significant fire outside the aircraft and this is when the evacuation was ordered. The fire was caused by a ruptured 2" fuel line and it had spilled about 40 Gal of fuel. Both the spar valve and engine firewall shut off worked as designed.

Is there any kind of time line whether the fuel valves were closed while the aircraft was moving or only after it had come to a stop?

[Volume]

Something that has come up in discussion with both professionals and enthusiasts over the last few weeks has been the total destruction of the composite areas of the structure.

No way to compare those, thin walled sandwich composite parts behave totally different from thick walled, monolithic composites. Compare the burn through time of a 3 layer plywood panel with that of a 10 ply panel, it will be a factor of 100 between. Every destroyed layer acts as a protection for the ones underneath, from a certain thickness it basically becomes fireproof. While melting metal runs away immediately exposing the one behind, burned layers will stay in place and protect the remaining ones. Heat transfer through aluminum and composites is totally different. Aluminum is destroyed by external fire, composies burns by itself once a fire started.
Finally both wreaks will not be a pretty sight...

The only thing we may learn from this accident is the fire scenario which should be used for tests. The scale of samples we should use for the tests, the type of flame we should use. Maybe one standard test does not give all the answers. And again (since british airtours) streched acrylic windows should get a second thought.

[wanabee777]

Fuel Valves

Originally Posted by lomapaseo

Is there any kind of time line whether the fuel valves were closed while the aircraft was moving or only after it had come to a stop?

Almost certainly, the fire handle(s) would not have been pulled until the aircraft was stopped.

[Wirbelsturm]

RTO,

Bring the aircraft to a stop, apply the parking brake, ensure forward idle on the thrust levers and .......... wait.

Check the reason for the stop call, confirm it between ALL flight crew and then commence memory items/communication as appropriate.

For engine fire and emergency shut down the fuel cutoff switches must be selected to cutoff before the fire handle is pulled.

So, the shutoff valves and pylon isolation would have been completed once the aircraft was stopped.

[THR RED ACC]

For engine fire and emergency shut down the fuel cutoff switches must be selected to cutoff before the fire handle is pulled.

This procedure is relatively new as you used to be able to just pull the fire handle and the fuel valves would then be closed automatically.

Do you think the crew used this procedure correctly?

[wanabee777]

Engine Fire Handles

Originally Posted by Wilbelsturm

For engine fire and emergency shut down the fuel cutoff switches must be selected to cutoff before the fire handle is pulled.

While the above statement is procedurally correct and proper, the fire handles can still be pulled with the engine fuel control switches in RUN, by pushing the fire handle override buttons in order to release the mechanical locks. (this would be unnecessary if there was an active fire warning for the associated engine)

This is because there needs to be a separate and independent means to shutdown an engine.

[porterhouse]

.composies burns by itself once a fire started.

Not true. The 'charring' effect stops fire propagation, look up FAA docs from 787 certification.

[Wirbelsturm]

by pushing the fire handle override buttons in order to release the mechanical locks.

This is also unnecessary as moving the CUTOFF switches to cutoff also unlocks the engine fire switches hence removing the need to press the override. (which are pretty awkward to use to say the least in my opinion!). The system is there to prevent inadvertent pulling of the handle on a live engine. The associated mechanical release is also unlocked in the event of a fire indication.

The FCOM lists the actions of closing the CUTOFF switches as

Closes the fuel valves
removes ignitor power
unlocks the engine fire switch

I believe the warning in the QRH is there to prevent crew 'regularly' using the override switches to cut the engine and to follow the correct procedure.

[wanabee777]

Originally Posted by Wirbelsturm

This is also unnecessary as moving the CUTOFF switches to cutoff also unlocks the engine fire switches hence removing the need to press the override. (which are pretty awkward to use to say the least in my opinion!). The system is there to prevent inadvertent pulling of the handle on a live engine.

The FCOM lists the actions of closing the CUTOFF switches as

Closes the fuel valves
removes ignitor power
unlocks the engine fire switch

I believe the warning in the QRH is there to prevent crew 'regularly' using the override switches to cut the engine and to follow the correct procedure.

All true. However, a catastrophic failure could render the fuel control switch(es) useless. Therefore the need for redundancy.

[Volume]

Not true. The 'charring' effect stops fire propagation, look up FAA docs from 787 certification.

I may tell you an old trick from a composites repairman...
If you have to repair a glassfibre aircraft and do not know the exact layup, just cut out a piece, light it, lett it burn off, sort out the charred layers of fabric and identify their grade and orientation.
Believe me, they do burn once you light them. Completely. Al least if they are a piece, and not a large sample which you exposed to fire in a local area in the center only, in that case you are right. And that is what the FAA tests.

[Wirbelsturm]

All true. However, a catastrophic failure could render the fuel control switch(es) useless. Therefore the need for redundancy.

You are correct but it is important to differentiate what these controls do.

The cutoff switches close ONLY the fuel valves whereas the fire handles cut off the spar valves and fuel valves, trip the engine generators, closes the bleed valves, isolate the hydraulics, depressurizes the associated engine driven pump and removes power to the thrust reverser isolation valve.

So whilst a catastrophic failure might well remove the use of the cutout switches I think you would be pulling the fire switch anyway and the discussion was the correct procedure in the event of an evacuation RTO.

Boeing do not want pilots routinely over riding the fire switches as an inadvertent pull of the switch requires a massive engineering input. Hence the QRH warning is in bold and lined above and below in red.

WARNING:
Do not pull the ENGINE FIRE switches before the FUEL CONTROL switches are in the CUTOFF position.

I suppose Boeing could have put in a caveat somewhere of 'try not to land without the gear being down', it can be done but only in times of great necessity!!!!

[wanabee777]

I guess this debate centers on how you define and apply the word "must".

My company's FAA approved QRH for the 777 does not include the WARNING that your QRH has.