Thursday, July 18, 2013

AAIB confirms fire on Ethiopian 787. Fire looks to originate from ELT

The AAIB is recommending inerting (turning off) the lithium-manganese powered ELTs and is recommending a safety review of the batteries that power the ELT. The AAIB says that the aircraft was plugged into external power but the aircraft itself was not powered up. 

This means that the Honeywell supplied ELT was the source of the fire which affected the composite structure and interior insulation as well as blackened and peeling the paint externally. There was damage to the composite structure. The firefighters tried using handheld halon extinguishers which were not effective then resorted to water hoses which put out the fire. The ELT was effectively destroyed and the AAIB also said that there we no other aircraft systems in the vicinity of the ELT "which, with the aircraft unpowered, contain stored energy capable of initiating a fire in the area of the heat damage." The AAIB is not certain if the combustion was initiated by a release of energy within the batteries or an external source such as an electrical short.

There are two recommendations:
1) The FAA orders the inerting of the Honeywell ELT until it can be fixed.
2) The FAA initiates a safety review of the lithium powered ELT in other aircraft types and mandate appropriate fixes.

Essentially this clears Boeing and the electrical architecture but it would be paramount to understanding the source of the combustion.  The Honeywell ELT is used in other aircraft types and have been certified for use in commercial aircraft since 2005. 

The AAIB also said that there typically isn't any fire detection or suppression equipment in the space where the fire took place and if it had occurred during flight could have posed a "significant safety concern and raise challenges for the cabin crew in tackling the resulting fire."  The firefighters had to rip down the ceiling panels and overhead luggage bins to access the area of the fire.

With inerting the ELTs, the risk of a fire is taken away. Boeing will still have to determine if they can economically repair ZA261 and return it to safe and normal service. This will be a major challenge for Boeing's engineers. You can read the full AAIB interim report:

26 comments:

TravelingMan said...

Glad that the 787 lithium ion batteries aren't to blame. Strange nonetheless that this should happen on a 787 for the first time, since the batteries in question have been used for years on other planes.

Emile Hendrik said...

Good to hear it was not the aircraft systems itself.. since I operate the B787 and have been informed that the ELT are not decommissioned as per the FAA orders I guess i wont have to worry about that one tomorrow.. or any other day ;-)

Uresh said...

Are you a 787 pilot? Which carrier?

1coolguy1 said...

JAL flight 7 from Boston Logan turned around over Hudson Bay a few hours ago and returned to Logan due to a fuel pump indicator light.

Hope these anomalies on the 787 stop soon - They are becoming a daily "watch for" item.

nskiwi said...

Hey Uresh
Have you got any update on deliveries? Seems the chinese are taking some time to come and get them.i know some of the testing was prior to testing but there seems to be a hold up or something,may affect total deliveries for the month. I see qatar and japan flying b1 etc but not much for Hanian or china southern

Soren said...

This may mean that some of the cables to the ELT may have experienced a short circuit. All ELT has a manual start function. It may be these cables that is the culprit. It would mean a faulty installation.

What I find strange is that matriel in aircraft are used that are not fire-resistant. If a short circuit occurs, only a local glow damage should occur, not a fully developed fire. What materials have been used?

There are many questions! This ELT is found in many airplanes, but has never caused any problems.

I think you have a faulty installation of ELT, hoping it only applyes to this specific aircraft. Is it a system fault, it becomes much worse.

TravelingMan said...

http://www.reuters.com/article/2013/07/19/us-boeing-dreamliner-investigation-idUSBRE96I18020130719

thomas85225 said...

ELT's are used on commercial, military and some private aircrafts, for years
ELT's are self contain unit with a built in batteries
How does a ELT short out when it’s in the standby position and the aircraft check list has remove the aircraft power from the avionic, another first for Boeing 787
Also each life rafts, has a ELT, one per door
Honeywell has stated that early ELT model had defect antenna
The 787 is composite aircraft, was there a ground path return for the ELT, was an electrical bonded check perform when the ELT was installed, this should be callout on the Boeing installed job card.
Where are the Circuit Breakers for ELT at that are should have prevented the overload.
The ELT is already in a box it’s time to add a fire detection and build in fire bottle to all Electrical components and external fire truck pumper connecting and fire sprinkler system installed
This aircraft was line number 44 and the first 50 787-8 had to parked are reworked
Honeywell supplies the 406MHz emergency locater transmitter whose antenna is visible amidst the most serious burn marks atop the crown of the 787 fuselage see
http://bit.ly/13sf9rR
WASHINGTON (Reuters) - Ultralife Corp makes the lithium-manganese battery that powers the emergency transmitter that is being investigated as a possible cause of last week's fire on a Boeing 787 in London, a source familiar with the investigation said on Monday.
http://bit.ly/16LVIMM
http://bit.ly/16LVIMO

1coolguy1 said...

Any ideas on why Qatar and JAL are not accepting delivery? They are listed as being "ready for delivery" as of 6/28 and 7/1.

Maybe until the Ethiopian fire is resolved?

TravelingMan said...

http://www.usatoday.com/story/travel/flights/2013/07/20/faa-boeing-787-dreamliner/2571441/

agincourt said...

Looks as if LOT 41 landed at Goose Bay for a while en route Toronto July 20. Can't find out why at the moment. Will be late into YYZ

agincourt said...

Looks as if LOT 41 landed at Goose Bay for a while today July 20th. Now in the air to reach Toronto a little late. Can't find a reason at the moment.

Jozef said...

B-1 for LN 115? http://flightaware.com/live/flight/BOE561

nskiwi said...

Anyone know the reason for the hold up with deliveries?they seem to have come to a hault. Qatar amd runway japan have been sitting ready for awhile,the chinese arnt moving and seems that boeing is starting to run out of space apart from parking them back on the runway, new issue perhaps?

Uresh said...

If there was a new issue they wouldn't be flying any 787s. The delays are all customer driven I believe.

Kevin Flanagan said...

Any comments on the RAT deploying on Ethiopian ET-AOO? Matt Cawby is reporting it on twitter.

nskiwi said...

China southern will start flying daily GUangzhou to Auckland from oct 28 with the 787,sure hope they will have sorted out the delays and have a few more in their fleet by then.

Steven Lau said...

Why can Boeing repair the melt composite skin by replacing the damage area with composite panels or aluminum sheet?

Alumino said...

In general, there are two types of plastics/polymers used in polymer composites: thermoplastics and thermosets. A thermoplastic (think milkjugs) can be heated up, melted, and then recooled into a solid. A thermoset (think epoxy) cannot -- once it hardens/cures, that's it.

Epoxy in the damaged area of the 787 did not "melt" but rather it chemically/thermally degraded. It is no longer useful. It no longer effectively transfers load between fibers. Since it is a thermoset, it cannot be melted, repaired and recooled.

The damaged area must be cut out. But can a new piece be simply bonded to the fuselage? How to do that is the difficulty. You can't just rivet on aluminum sheet. Ideally, you'd like to interweave new carbon composit cloth into the existing, but that can't really be done. So you are left with bonding a patch. But bonded repair is tricky and non-optimal in many ways. For large damage, the only way to regain structural integrity may be to replace the whole fuselage barrel... that way you know the fibers are doing what they should be doing.

Steven Lau said...

Thanks for your explanation.

I agree the melted composite skin should be removed for repair. But why can composite panels or aluminum sheets be attached/riveted to the frame if it is still intact? Of course the better solution is to replace the section of the spun composite barrel and restore to its original construct.

Alumino said...

Some more info... hopefully helpful. Not the fully story, but a simplified one. Sorry for the length.

Rivets are useful in metal structures because they are ductile. If you rivet one panel to another, all the load carried in one panel transfers through the rivets and into the next panel. Where the rivet contacts the panel, where there is a stress concentration, both the rivet and the panel can deform slightly and sort of blunt that stress concentration. Composites don't work that way. Stress concentrations cause separation of fiber from the epoxy matrix and these small cracks hurt structural integrity. If you want to use metal rivets/bolts with composites, you can thicken up the material in the area of the fastener. But it is best to design that in from scratch. On the 787, the skin is not really designed to be thick enough for rivets. You could "thicken up" the material by bonding on layers of repair material, then rivet on a repair, but it would be better to just bond on the repair panel and skip the rivets.

Bonded repair -- gluing on a repair panel -- can work, but it is not optimal. Interlace your fingers like you are praying, but then open up your hands so you can see both palms in front of you. Try to pull your hands apart (each finger is sandwiched between other fingers and they will slide across each other). Kind of hard to do. Now unlace your fingers. make your hands flat like you are saluting, and overlap your hands so the back of your right fingers touch the front of your left. (Still look at both palms, all your left fingers are together, all your right fingers are together, and one hand is just lapped on top of the other) Hands are each to pull apart. Even before they pull apart, they can move back and forth easy as skin flexes.

Your finger bones are like fibers, your skin and flesh is like epoxy matrix, and when you can get the fibers to intermesh really well, you get a strong joint. When you just glue a panel on top of another panel, and fibers don't intermesh, then you get a weak bonded joint. If you increase the contact area of the bonded section, you can make it stronger (e.g. overlap your whole hand, not just the fingers.)

So bonding on a repair panel over the "hole" is possible, you just may have to have a WHOLE LOT of overlap, and you would like to have a panel on inside of plane and outside. But now as you pressurize the plane and it expands, the repair patched area want to expand less (it's thicker) and... well... the stresses get complicated.

Alumino said...

One more thing you probably already know, but just to be thorough: In the fuselage, the "skin" carries a huge amount of the load. Stiffeners and frames are there largely to prevent buckling and to allow things to be fastened to the skin. If the skin were just put on for aerodynamics and cosmetics, it would be much easier to repair.

Steven Lau said...

Alumino, thank you for your clear explanation of the difficulties Boeing faces in repairing the composite skin. It will be interesting to watch how Boeing actually solves this large area composite repair problem.

At least they can patch up the damaged plane and ferry it to the nearest repair hangar capable of composite barrel replacement.

Alumino said...

I'm sure Boeing already has repair protocols in place to address structural damage from errant k-loaders, mobile stairs/jetways, catering trucks, Canadian geese, etc. Curious to see how the engineers decide to approach this one. I'd go with JB Weld and Duct Tape....

1coolguy1 said...

I suspect they will replace the affected fuselage barrels in whole. Relatively quick to do and returns the plane to 100%.

agincourt said...

The aircraft that flew as JAL 7 from Boston and returned to Boston on July 18th is now flying as JAL 8007 back to Narita. Never read the outcome of the problem that caused the turn back. Flightaware for JAL 7 on July 18th is interesting. Took a while sort that out.