air safety

Aug 22, 2015

That tail fire in an Ethiopian 787 was more serious than thought

The aviation world quickly lost interest in a tail fire in a parked Ethiopian Airlines 787 at London Heathrow in 2013 when it was found to have been caused by a pinched wire in an e

Ben Sandilands — Editor of Plane Talking

Ben Sandilands

Editor of Plane Talking

The Ethiopian 787 at London Heathrow after the tail fire was suppressed

The aviation world quickly lost interest in a tail fire in a parked Ethiopian Airlines 787 at London Heathrow in 2013 when it was found to have been caused by a pinched wire in an emergency locator transmitter and not its then controversial underfloor lithium ion batteries .

However this last week’s release of the UK incident investigation by the AAIB has changed that.

It found that the fire that spread from the crash locator device into the crown of the aft cabin was fueled by the epoxy resin that glues together those layers of composite tape that comprise much of the fuselage of the Dreamliner, and would have been very difficult to locate and extinguish had the fire broken out in flight.

The AAIB report said that “the resin in the composite material provided fuel for the fire, allowing a slow-burning fire to become established in the fuselage crown, which continued to propagate”.

This was a fire that proved very difficult to control even with heavy duty emergency ground equipment at London’s largest airport. America’s safety regulator the FAA, which also certified the Dreamliner as safe, is now reevaluating the current flammability and toxicity testing of composite aircraft materials and studying new certification procedures for future use of resin bonded composites in airliners.

While the implications of the AAIB report might not make for comfortable reading if aboard a 787 flying a long and remote route it is important to keep a perspective on this otherwise troubling document. Airlines that use 787s would have no reason not be be aware of the need to ensure the safe installation of the emergency locator transmitter that suffered the unlikely fault that set fire to the fortunately parked not flying Ethiopian jet.

The report tells us that once a fire breaks out in a Dreamliner it can be fed by the glue within the layers of the composite structure, and we can surmise, destroy the integrity of the hull and cause a disaster in a fairly short period of time.

But the dangers of deep seated structural fires on metal alloy airliners are no less daunting, and are the reason why  the drill in such emergencies is a rapid descent and an emergency landing or crash landing. It’s been that way since the early days of enclosed cabins in propeller aircraft, and perhaps much longer.

The literature on airborne fires suggests that they can destroy airliners within 18 minutes, if not sooner. The biggest risk that figures in airliner concerns these days is from shipments of lithium ion batteries in cargo holds (now all but banned world wide), or checked in passenger luggage contrary to specific and clearly communicated airline warnings to customers to keep such devices with them in the cabin.

Cabin crew have well rehearsed procedures to deal with the small number of spontaneous combustions of lithium-ion batteries now occurring on scheduled flights, and also in recent times, in airport waiting lounges.

The Ethiopian incident is a very very lucky break for air travel. It happened on the ground, and revealed risks in such composite structures not envisaged when they were designed into airliners.  What doesn’t kill us makes us safer.

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21 comments

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21 thoughts on “That tail fire in an Ethiopian 787 was more serious than thought

  1. Fred

    Sobering news. Structural fires are impossible to extinguish in-flight and are extremely dangerous. As Ben said, a fire can cause structural failure in less time than it takes to make an emergency landing or ditch the aircraft. Nevertheless, we still have idiots who insist on smoking in aircraft toilets…

  2. comet

    Inflammable resins.

    It reminds me of certain trees, like the eucalyptus tree, that contain inflammable resins in their structures, which add fuel to wildfires.

    But are these resins specific to the Dreamliner’s baked barrels? Does the Airbus A350 not use such resins?

  3. comet

    The AAIB report said:

    “The resin in the composite material provided fuel for the fire”

    I don’t remember anything like this being said about metal structures of modern airliners.

  4. Tango

    Ben: Well done level report, serious issue, do not panic, though maybe a bit understated in some respects. ETOPS flight with no handy airport would be a extremely serious issue if not fatal (We frequently see 777 flying on one engine 3 hours to get to our North Pacific airports, ie. Anchorage, Cold Bay, Shimya)

    I have not forgotten this incident (many reasons) but the battery issue is one of two top ones.

    Comet: Please read the following, it was the final incident or a trail that said, if there is a fire, put it down even if you have to ditch.

    https://en.wikipedia.org/wiki/Swissair_Flight_111

    ELTS: As noted, it looks like the same energy release and cell failure propagation as the 787 batteries cascading.

    So why do we have these and not Nicads?

    Major restrictions and not allowed to carry bulk shipments of Li Ion batts on freighters and passenger aircraft with a number of laptops going hot on pax flights.

    Add in that ELTs have played no role I can remember in finding commercial jet crash. Tubo props?

    It seem they are a hazard and maint item that has no return in at least larger commercial aircraft application (and costly to design in) and should be taken off the MEL.

    CFRP Burn Risk: I thought that was glossed over in certification and now we have two aircraft that are allowed now (787 A350) The rest have CFRP in areas not likely or impossible for a fire.

    This also gets into an area that Anchorage was the final trigger for when a DC8 went off one of our runways 30 or 40 years ago.

    Military y charter, disciplined evacuation, those that died were smoke inhalation victims from the toxic fumes of the cabin materials not impact.

    That triggered the movement to get rid of toxic cabin materials.

    Have we replaced it with toxic CRFPO that can do the same thing? You do have to ask if its the same risk as cabin interior, how likely etc but a question that should be answered and then corrected in next generation use.

  5. Tango

    Badly stated on 777 frequently on one engine.

    I meant to say that in the pretty rare cases (maybe once a year) that it happens, they are 2 to 3 hours out from an Airport they can land on, i.e. run on one engine for that long which in a fire case is a lifetime.

  6. Tango

    Commet:

    I don’t know for a fact A350 is the same mix, I don’t know who supplies it even (Torre or some such in Japan for the 787.

    If not the same mix and mfg probably same type but that’s a guess.

  7. comet

    The Seattle Times story, ‘FAA reviewing flammability of composites in wake of Heathrow 787 fire’, quotes an FAA official.

    He says the accident clearly demonstrates that if an intense fire starts on an aircraft, the resin in the composites will burn and create a self-sustaining fire.

    Repeat: resins create self-sustaining fire.

    He says the incident “taught people something they weren’t aware of.” Hence the total review of FAA testing of plastic composites.

  8. Tango

    I got that part, what I don’t get is what the testing standard/method was when they certified the 787 (and the A350 would follow that as the standards are cross recognized between US, Europe, Canada and Japan- I assume reconciled if not)

    What I don’t know is what the A350 mix is. Probably the same or similar to not make any difference.

    A crash tends to self sustain fuel fires which then in turn ……….

    So again, what was the standard? Whatever it was it was not to the point they “became aware of it.

    When the 787 batt was certified it was driving a nail through it! Now that is downright scientific.

    Pretty amazing in this day and age to have that occur this late in the game.

    Now they are certified they will not take it away. Like the MD11 wiring they may force a change, if that can’t be done then?

    Make em change the mix down the road, opens up a lot of things and then what risk is and worth it and all that.

    Stay tuned. As Ben said, its a fortuitous accident that no one got even hurt in let alone an airframe came falling gout of the air.

    When was the last time a structural issue not induced by pilot mistake took out an aircraft structure?

    Or put another way, this is what they should have been looking for and coming up with testing standards with all the known issues with Li ion batteries seems amazingly lame, let alone other ignition sources.

    that’s one reason I said that the 787 main batt was an issue, once it got going (sustained) and in the air it would have taken out rear control surfaces and the aircraft. It should have been grounded on the first incident. I think we were very lucky there as well.

  9. Confirmed Sceptic

    There have been several whistleblowers on the 787 project. Google Vince Weldon. The epoxy resin has a very low ignition temperature, and self sustains a fire. As pointed out already, aluminium does not do that, but the rest of the materials that make up a conventional aircraft supply ample fuel for a fire anyway. The spectre of a burning structure is a sobering one, but, as a practical matter such a fire in an earlier aircraft is going to be equally fatal.

    You guys want comfortable seats and safety too? Where’s your sense of adventure if not stoicism?

  10. comet

    Confirmed Sceptic: You brought up the subject of Vince Weldon, which has now become highly relevant.

    Weldon is the guy who designed the high-lift features of the 727 wing. He is one of America’s greatest aeronautical engineers.

    Of particular note, Weldon warned that the 787’s composite barrels would burn. He also criticised the FAA’s certification procedures for composite materials.

    He knew something like this incident would happen.

    Now, a decade later, the FAA is finally admitting its certification procedures are ‘wrong’. It should now apologise to Vince Weldon

    The question is, how did the FAA allow itself to press on regardless, ignoring experts like Weldon?

    How on earth can this problem be rectified? It is inherent on every Dreamliner, including the -9 series. It can’t be rectified.

    It’s pure fluke that the Ethiopian airliner was on the ground when this happened, when the aircraft was spending more time in the air than on the ground.

    What if that 787 had crashed, which was the more likely scenario? Would we now be seeing criminal investigations against Boeing and the FAA for approving it?

    If the certification was ‘wrong’, then the Dreamliner’s approval was wrong. Building an aircraft with a structure that propagates a self-sustaining fire is like building a house out of gingerbread. Think about that next time you’re booking a ticket on a plastic plane.

  11. Confirmed Sceptic

    Comet, just to be clear, I think the entire 787 programme has been a travesty from the get-go.

    The composite structure will burn readily…but that has been an obvious and well understood characteristic of that resin, like most plastics. But again, its not like any other plane will withstand an inflight fire, so the 787 may or may not have an inherently higher risk in that regard. (It may on a statistical likelihood basis, especially when you factor in lithium batteries…but that judgement requires, I think, more data than is presently at hand.)

  12. derrida derider

    People are missing a point Ben made – yes, an intense fire on a plastic airliner is Very Bad News indeed. But an intense fire on an Al-Li airliner is not appreciably better; that stuff melts and burns too, plus anyway intense fires and jet fuel aren’t so good a mix either. The trick is never ever to have an intense fire.

    The real safety question is surely what happens with a slow smoulder – does the resin present either a flame or toxic smoke hazard then? I assume that’s what designers and certifiers thought about.

    And Fred, I really dislike smoking – but there was a time when half the passengers (and probably the crew too) lit up in flight. I don’t think people having a fag in the dunny is a big safety risk to anyone but themselves (though it is a damned nuisance to others).

  13. Fred

    derrida:

    It’s not the smoking that’s the problem, it’s what happens to the cigarette butt afterwards. Several accidents have been attributed to lavatory fires caused by the careless disposal of cigarette butts in waste paper bins. One of those accidents resulted in the loss of 123 lives. Admittedly we’ve come a long way since those days, with smoke detectors and automatic fire extinguishers in lavatory waste paper bins. Nevertheless, I’d rather not take the risk, especially since the offender is likely to have disabled the lavatory smoke detector. That in itself is a criminal offence.

  14. comet

    Sure, there have been catastrophic fires on conventional aircraft, such as Swissair.

    But name me one fire where the airframe itself propagated a self-sustaining fire without the need for other materials to be present?

    This is the sort of thing that would happen to wooden aircraft.

  15. Fred

    The point that was made previously was that ANY fire has the potential to compromise an aircraft’s structure, composite or not. Modelling done during the Ethiopian investigation indicated that: “the strong effects of external cooling, which would be present during flight conditions, in mitigating the extent and intensity of the fire in the composite structure after the initial ELT fire was exhausted. Thus the modelling suggested that these conditions would have prevented flame propagation beyond the localised ELT ignition zone, and slowed the propagation rate to a point where the composite fire might self-extinguish.”

    The AAIB concluded that “in the event of localised ignition of the composite structure in flight, the rate of convective heat loss would reduce the extent and intensity of fire propagation, and may be sufficient to cause the fire to self-extinguish.”

    Although in-flight fires are extremely serious, accidents caused by fire-related structural failure are exceedingly rare. In the past it has generally been the toxicity of the smoke from the burning materials that has resulted in fatalities.

  16. Tango

    Problem with models is that unless you set it afire in the air then the model assumptions are never proven.

    Again I am not wigged out about it, I do wonder on the toxicity of a ground crash ala the DC8 in Anchorage, you survive the interior fire and get taken out by toxic fumes outside?

    So again I would like to see the trail of tests and justifications for approval.

    I hope its more than the equivalent of a nail driven into the fuselage and saying its all right.

  17. ghostwhowalksnz

    “..generally been the toxicity of the smoke from the burning materials that has resulted in fatalities.”
    That covers any fire, house fires especially, they are dead before the flames reach them. Its of no help whatsoever knowing this.
    Surely they could have done a real test in a wind tunnel to see if the modelling is relevant. After all Im sure plenty of modelling shows Li batteries have a low probability of catching fire at all, so no need for special precautions. Ha!

  18. Fred

    “Its [sic] of no help whatsoever knowing this.”

    If the occupants are already dead from inhaling the toxic fumes, then the subsequent structural failure is a bit of a moot point…

  19. comet

    In a 2009 Leeham report titled, ‘Uncertainty exists over fighting composite airplane fires’, Boeing says:

    Among our findings in testing using FAA-approved methodologies were:
    • The composite materials used for the 787 do not propagate an in-flight fire’.

    So the obvious thing is that Boeing and the FAA had no idea at all.

  20. ghostwhowalksnz

    B-2 stealth bomber crash on Guam Feb 08 should have been a hint that composites get nasty when they burn.
    To put out flames took 6 hours, and smouldering continued for 24-48 hours.
    http://leehamnews.com/wp-content/uploads/2009/03/b2fire.pdf

  21. comet

    There are so many issues here.

    Looking at Boeing’s website today, it says:

    Composite fuselage structures do not sustain combustion and do not aid in the spread of fire.

    So Boeing is putting out false information to airports and fire crew. Therefore, fire crews are going to be completely misinformed about the methods of fighting a composite plastic aircraft fire.

    Boeing’s own Phantom Works division did computer modelling in 2005, showing the difference between a crash landing in a composite airliner compared to an aluminium 777. The 777 was found to be much safer. The confidential document was leaked. You can read more in this Chicago Tribune article:
    http://articles.chicagotribune.com/2010-07-03/business/ct-biz-0704-boeing–20100703_1_dreamliner-chicago-based-boeing-crash-landing

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