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Ethiopean 787 fire at Heathrow

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Ethiopean 787 fire at Heathrow

Old 16th Jul 2013, 00:24
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The topic of how to repair large plastic structures has been raised on here already by me, and replied to by some knowledgeable folk.

This damage would likely be a huge repair on a metal aircraft.

On this CFRP aircraft it will also be a big (or bigger?) job.

I remain worried about the use of CF reinforced plastic in aircraft structures, but hey- I'm not exactly an expert.

Thank goodness it happened while parked.

It's not exactly 'immature' technology in aviation, but could still be quite tricky as a substitute for aluminium main structure.
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Old 16th Jul 2013, 00:25
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Don't believe the diagram. It also shows AOA Vane, Pitot probe and TAT probe behind the right wing!! Obviously not all components were depicted in their actual positions.

Last edited by nitpicker330; 16th Jul 2013 at 00:26.
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Old 16th Jul 2013, 00:26
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RCav8or: I can't testify to the Honeywell 406 ELT. On the Artex they use ships power to flash a light on the flight deck if the ELT is transmitting as a warning to the pilot it is going off.

boguing: The ELT is always powered by it's internal battery. It can be set to transmit by the remote switch on the flight deck, or by impact if the G switch has been activated. (you've crashed or had a really bad landing)

We want the ELT to work, and continue transmitting even if all ships power is lost, so we can find the downed aircraft.
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Old 16th Jul 2013, 00:30
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Lithium Ion batteries have NO business inside any aircraft
Apart from the fact that most if not all pax will be carrying some type of Lithium Ion battery either in hand luggage or stowed luggage, as other posters have remarked;

There are several different types of LiIon batteries, with different chemistries.

The type most often used in consumer electronics is Lithium Cobalt or LiCo for short. This chemistry packs most performance in terms of energy density per unit volume and weight, but happens to be a bit touchy - as borne out in various incidents with laptop and mobile phone batteries catching fire.

Other chemistries such as Lithium Iron Phosphate (LiFePO4) do not have such a strong tendency to self-destruct in this manner, and in fact Lithium Iron Phosphate is now becoming the preferred solution for automotive and aerospace applications. However, energy density is somewhat inferior to Lithium Cobalt. On the other hand, Lithium Iron Phosphate cells appear to suffer less degradation with time/cycles.

Apparently (and regrettably) the B787's batteries seem to be LiCo rather than LiFePO4. The reasons for this choice are beyond me, but it might be that the choice was made some years ago when the performance penalty of LiFePO4 versus LiCo was more severe than it is now. 5 years is a long time in bleeding edge battery tech.
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Old 16th Jul 2013, 04:40
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I notice that on the pprune threads about developing stories, there is quite a bit of grasping at straws based on tidbits from the press, balanced from time to time by reminders to wait until more is known.

Of course, it's possible that the ELT spontaneously erupted into flames, presumably from its battery. I wonder, is there any precedent for that?

But it's also possible that folks investigating the 787 found the ELT with a burned-up battery, and asked Honeywell (quite appropriately) for assistance. This is not enough to say that investigators have concluded, or even deemed it likely, that the ORIGIN of the fire was in the ELT.

If I understand correctly, Li batteries can "flare up" when put in a fire -- in other words, a fire originating elsewhere could perhaps ignite the ELT battery.

It's early days yet, and we have so few facts.
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Old 16th Jul 2013, 05:07
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Composite Skin In-Flight Fire Risk Analysis

amicus,

I understand that you did your best in trying to convince the FAA etc. to require thermal insulation throughout the inner surface of the 787 fuselage.

To the extent that I understand the logic of FAA rulemaking, they refer to quantitative estimates of risk. For example, how many aircraft expected to be lost per 10,000,000 flight hours, or some such measure. Their reasoning seems to be, that risks below a certain level don't require regulatory intervention (no doubt I'm oversimplifying, but this is the crux).

To your knowledge, did anyone conduct such an analysis, and present risk estimates to the FAA? If so, is any part of that publicly accessible?

As I tried to outline a couple of days ago, fires are Awfully Dangerous to transport planes at altitude, REGARDLESS of material. So the threshold question would be, how much greater is the quantified risk with composite vs. aluminium fuselage skins.

Further, we might attempt to classify in-flight fires inside the fuselage into three levels of severity:

III. Combination of intensity and duration (under reasonable assumptions of crew response) sufficiently small, that the plane is likely to continue to a safe landing, regardless of construction, or top-half insulation of composites.

II. Intermediate-level, in which fire performance (including inflammibility) of skin material is expected to make a difference to the likelihood of saving the plane, and in which top-half insulation of composite skins could also make a difference.

I. Sufficiently great intensity and duration that the plane would be lost, whether of aluminium or composite skin construction, even with top-half insulation of composites.

Fires falling into levels I and III don't make any difference to flight risk -- none whatsoever.

Did anyone analyze the risks associated the level II fires? For example, did anyone attempt to quantify the parameters of fires that are survivable for aluminium skinned aircraft, but non-survivable for composite skinned (with and without top-half insulation)? Did they then look at aviation safety records, to estimate their rate (for example, how many apparent level II fires have occurred in the last 250,000,000 jet airline departures?

If no such analysis was made, that perhaps doomed the efforts to argue the point with the FAA.

Of course, this London fire offers an opportunity to revisit the question. It can only help the case, to support it with a quantitative risk analysis.
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Old 16th Jul 2013, 05:38
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A and C

Quote: "Composite airframes have been around for a lot longer than that ! To the best of my knowlage the first composite repair to primary structure was carried out in the UK in 1965."

I simply gave the A300-600 fin as an EXAMPLE of a large carbon composite structural component that has been in service for a long time. I'd be interested to know what your example is in 1965.
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Old 16th Jul 2013, 08:38
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As a complete non-technical person, I have read the battery discussions with great interest. I drive a Peugeot iOn and sit on top of the 16-kilowatt-hour (58 MJ) lithium-ion battery pack, which consists of 88 cells placed under the base floor. (Scroll down that link a bit for the section on "Battery").

I'm very conscious of the assorted cooling fans and shutters that operate when charging, and when first driving off.
The battery has a forced air cooling system to prevent overheating during high charge and discharge rates and consequent damage. There is an integral fan in the battery pack. For rapid charging, the battery pack is additionally cooled with refrigerated air from the cars air conditioning system.

Last edited by MPN11; 16th Jul 2013 at 08:39.
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Old 16th Jul 2013, 08:56
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Cool

The emergency transmitter is powered by a non-rechargeable lithium-manganese battery.
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Old 16th Jul 2013, 10:26
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LiMn is very stable, LiCo will self-ignite and is bloody hard to put out
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Old 16th Jul 2013, 10:58
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Etud_lAvia

As I noted much earlier in a 787-battery thread, the FAA commissioned a university study of fire danger re the 787 fuselage material; said study concluded that it was perfectly (-enough) safe. Sorry I'm not in a position to regurgiate the information at the moment, being on travel and on a satellite link.
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Old 16th Jul 2013, 11:20
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FST testing of fuselage material is one thing. What about the adhesive/bonding material(s)?
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Old 16th Jul 2013, 11:27
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Useful background reading...

An updated learned Paper from RAeS Flight Operations Group on 'Smoke, Fire and Fumes in Transport Aircraft' -(1st download in list)

Royal Aeronautical Society | Specialist Papers

with new stuff on Lithium-ion and composites...
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Old 16th Jul 2013, 12:35
  #354 (permalink)  
 
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Composite airframes have been around for a lot longer than that ! To the best of my knowlage the first composite repair to primary structure was carried out in the UK in 1965.
Composite gliders are around since the mid 50s and composite repair to primary structure are common business since the 60s. There are companies around that repair CFRP wings completely broken in several pieces for 25 years, and there is up to now no airframe loss attributed to a faulty repair. Did it myself, and the first time you do aerobatics in a glider where once the wing was in pueces is a bit on an interesting moment. Composite repair technology is known and field proven for decades.
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Old 16th Jul 2013, 12:53
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LI Fire

Hard to believe that a small LI battery can cause this type of damage. It is possible this battery was smoldering for some time as the aircraft was unattended for several hours. Still this gives us an idea the heat generated by these LI batteries when they go off. Think about the heat from the larger LI Cobalt battery, which is considered the most volatile of all the LI batteries. This calls into question the choice of LI battery for the Main and APU location. This problem will not go away. Every time B787 meets with an incident, the question will pop 'Is it that battery again?'. This is unfortunate.

The choice of composite materials would not have changed the out come here. Aluminum also can melt in a fire situation. Only difference could be metal conduct heat faster, so fire may not make a burn through easily. This damage occurred mainly due to the unattended nature of the aircraft on ground. If this incident had taken place in flight, the fire would be detected quickly and extinguished. ELTs are located inside the overhead storage bin and easily removed. These bins have blankets and pillows stored on most aircraft. May be they contributed to propagate the initial combustion. ELTs are in use on all modern aircraft, and cannot remember having a previous fire incident on this item. Correct me if I am wrong.
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Old 16th Jul 2013, 13:05
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A word of caution

Composite gliders are around since the mid 50s and composite repair to primary structure are common business since the 60s. There are companies around that repair CFRP wings completely broken in several pieces for 25 years, and there is up to now no airframe loss attributed to a faulty repair. Did it myself, and the first time you do aerobatics in a glider where once the wing was in pueces is a bit on an interesting moment. Composite repair technology is known and field proven for decades.
There is a significant difference between glider (and surfboard) repairs involving fibre-glass materials and that is the elastic modulus of carbon is much higher. Because of the higher stiffness, load transfer through adhesive bonds is much more demanding. For low modulus fibre glass, load transfer is much more gradual and so reliance on just the repair resin system is appropriate. In carbon fibre repairs, the demands of the high stiffness caused by the higher modulus are such that the brittle nature of resin systems virtually demands that the joint is formed by a more ductile system such as an adhesive.

So it does not necessarily mean that "sufboard" repair technology is as appropriate for carbon structures.

Be careful in assuming that just because it is a fibre composite that old technology repairs can provide the same level of structural integrity.
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Old 16th Jul 2013, 13:53
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Etud_lAvia

To your knowledge, did anyone conduct such an analysis, and present risk estimates to the FAA? If so, is any part of that publicly accessible?
Risk analysis only make sense when you have data to go by and a risk vs cost basis only is done when you are updating a current rule. This of course assumes that the current rules provided adequate protection when implemented years ago but new lessons have now been learned.

If there is something novel in the implementation of a current rule leaving questions about adequacy then it's time for a special condition ruling.

It's between the applicant and the regulator to decide on the adequacy of the product to meet what's on the books (how it's met is necessarily, competitively private).

I'm not sure at this time that the current rule is not adequate, nor if something new has been learned. I still await the investigators findings before I accept a "I told you so" claim.
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Old 16th Jul 2013, 14:07
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Our aircraft have two ELTs one situated in flight deck as a portable unit ,the other above the ceiling panels (just forward of the fin),the ELT is attached to the airframe, for locating the aircraft if lost etc.This unit would be almost impossible to locate in flight let alone realise the unit was on fire and take appropriate actions.Its hard enough to get to when doing a simple 'ping' test for maintenance purposes.One things for sure the 'silence is deafening'from Boeings PR department.

Last edited by fflyingdog; 16th Jul 2013 at 14:19.
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Old 16th Jul 2013, 14:21
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ELT

fflyingdog.
You are right. There are 2 types. One is attached to fuselage forward of the Fin and another inside the cabin as a portable unit, which the Cabin crew can deploy manually also. This unit is the one located in the overhead bins. Both have LI batteries. Both used for several years. Surprising this had to wait for installation B787 to go up in flames in a dramatic way.
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Old 16th Jul 2013, 14:41
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Carbon composite repairs

Blakmax, spot on!

Repairs, metallic or composite, to commercial aircraft are treated effectively as a modification, and require the same level of approval as the original certification. Repairs that do not meet the same strength standards as the original structure may require an additional maintenance programme, e.g. regular inspections, to assure the repair's continuing integrity.
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