Ethiopean 787 fire at Heathrow

[phiggsbroadband]

Hi, to make (or repair) any carbon fibre component, am I correct in saying that you need a Big Oven, to cure the material. Where are they going to find an Oven that is 787 size?

So it looks as if carbon composites will not be used for the repair.

[A and C]

Big oven

The industry has gone away from autoclaved composites for the very reason that they need a big oven to cure, the trend is now for resins that cure at room temp and get their strength from a post cure cycle IRO 80C.

The suggestion that this will be a non composite repair is unlikely, but as I said above I suspect that it will be a metalcentric repair that fails to take advantage of the bentfits that composite construction offers.

[blakmax]

causing deep damage to aft bh and rudder/elevator system

I don't think this will be covered by the tech log. Even a really big heater blanket just won't do. Heaven forbid trying to get a vacuum bag to seal!

I am aware that the FAA and EASA are struggling to establish size limits for composite repairs, but I suggest that by the above description, this damage would exceed even their wildest ideas.

So it looks as if carbon composites will not be used for the repair.

Not quite true, but the material type may be of less concern than the manner of joining the repair to the structure. Fasteners in composites in areas where they were not designed into the structure can be quite tricky because of the low bearing strength of composites in the structure. Adhesive bonding is far more efficient but the size of the bond may be prohibitive to achieve. I am sure there are a number of customers who are watching eagerly to see how/if Boeing undertake a repair of this size in composite structure.

I am also concerned about any evidence of release of carbon fibres due to combustion. Hopefully only resin was consumed and no fibres were released. If not, then the smallest particles of carbon will cause havoc with not only the aircraft electronics but those of any surrounding electrical or electronic equipment in adjacent aircraft or GSE. This would be an ideal time to determine just what the risk of fire in a composite aircraft really is.

[wings1011]

Battery life for towing

For those who are interested the batteries are suppose to last for about 30 min for towing- maybe more depending if the main battery switch is set to on or not - on ovhd panel there is a batt test switch besides main batt switch - high/med/low . If high then about 15 min with main batt switch to on- if medium or low its mot recommended to tow without apu on.

[Hi_Tech]

Power distribution panels

There are 17 Remote power dist panels all over the aircraft. One is located exactly in the fire damaged area. But if you are saying the aircraft had no GPU and APU was also not running, then there is no power at these panels. The panels have 115V AC and 28V DC power supply.
This info about APU/GPU may not be correct. Some one mentioned the aircraft was getting ready for a tow to Departure area from remote parking. In which case the aircraft will be powered, most probably from the APU.

[Lemain]

No smoke detection or fire alarm?

Is there no fire alarm system on these aircraft when they are left empty?

[A and C]

Blakmax

A bonded repair is the only way to go ! I agree about the heat blankets but we have a solution to address this problem but to talk about it hear would compromise my company's competitive position.

Any use of metal fasteners in this repair would be giving into the metal bashers who don't understand composites.

[superq7]

A&C metal bahers

If this was a conventional a/c it wouldn't have melted saying that feel very sorry for boeing ( am ex BAC BAe )

[MilktrayUK]

Ground power connected

According to the Boeing documents, the ground power receptacles are below the 1L door. The ground service locations can be found on the Boeing web site http://www.boeing.com/assets/pdf/com...ps/787sec5.pdf This is used by airport designers for setting out the service points on the apron. The distributed design on the 787 electrical system can also be found on-line. A photo on BBC news clearly shows that both sides are physically connected.
The access panels can be seen to be open on both sides, with the ground power cables hanging down. This would seem to be a fixed installation. behind the nose gear appears to be a cart, with an articulated cable system. The ground power converters appear to be at the base of the apron flood light masts. These would be fixed regulated solid state systems converting from 415V 50Hz to 110V 400Hz. Clearly from the photos, it is not possible to see if they are energized. There does not appear to be a tow tug or tow bar in the photo, so either they got out sharpish, or discussion about towing is not relevant.

The ground power requirement is rated at a nominal 90kVA at 110V 400Hz. Each connection can provide up to 1100 Ampere. For a typical turn around, both sockets at the nose will be connected. On a stand, they would normally be used until the APU is started. If there are any activities on the aircraft, such as cleaning or maintenance on board, it is likely that cabin lighting would be on as a minimum.

I think the concern for the industry and passengers would be if it is normal and acceptable for an overheating water heater / failing cabin air fan / discarded cigarette / overheating phone on charge / overloaded panel board to burn through the skin so quickly. Hopefully there will be a recording of voltage and electrical load conditions leading up to and during the event for analysis. This may show an event which can be used to time stamp the time of the failure. Clearly there will be no black box (FDR) recording, without the engines running, however the power system has limited data logging. One of the concerns of the NTSB in the previous battery investigation, was a lack of confidence in recorded voltage values.

I cannot claim expertise on aircraft structural repairs, although I do recall a very interesting documentary on National Geographic that had a film crew following the replacement of the rear pressure bulkhead in a 767. To summarise, everything behind the bulkhead was lifted off by crane. I presume that the photo previously posted was of the rear fuselage section on a transport jig. Aircraft sections are routinely shipped for bringing together at final assembly. If the rear pressure bulkhead is compromised, what is the chance that one of these is already being prepared for shipping to Heathrow?

[Wil Neverbee]

To the composites experts reading this thread could I ask the following:

Is it possible to determine if the strength of a composite structure has been affected by heat or not?

This is an easy assessment if the fire has burnt a hole which has to be repaired but how far away from the hole do you have to extend the repair before you know you are back into good structure.

[Hi_Tech]

Repair?

Why are we discussing batteries? They are not involved here. This aircraft has serious fire damage. Those who have done repair of these modern composites know very well, the bonded repair etc hold good for only minor gouges or dents etc. This aircraft will require a complete re-paneling for about 10 to 12 feet of a very highly stressed portion of the fuselage. One picture clearly shows the frames and stringers exposed. Checking for heat damage to surrounding area alone will take weeks. Then these panels that have 3 dimensional shaping and of varying thickness have to be made. Stringers and frames are also of specially formed and shaped. it is not like the older aircraft where one can use raw stock to make splice repairs.
Again we have seen only one picture of the external damage. Inside will be in shambles with wiring, tubing etc burned. Galley and seats charred. Lucky the whole aircraft did not go up - thanks to the efficient response of fire dept.
Boeing will do anything to prevent a hull loss. Aircraft will have to be on a jig and leveled for repair. Ethiopian can forget about this aircraft for 5-6 months - if Boeing is doing the job. They will be better off looking for a lease to fill the gap.

[Walnut]

On shudders to think of the internal fire/heat/smoke damage from this incident. If it had been in flight then the a/c would have depressurised for sure. I recall the NTSB lead spokesman (Deborah ??) saying a battery should never ever catch fire, so what do we have here.? Something probably much worse. This fire was extinguished by an expert fire team with all the equipment, something certainly not available for an a/c in flight.

[Cows getting bigger]

The assumption that this was a failure of a water heater trip switch again brings into light the question of quality management/control. In the (unrelated) battery farrago there was much speculation about the quality of the parts. It would appear that a circuit breaker may have been to blame here, not necessarily performing as advertised. Sure, it may just have been one of those duff, Friday afternoon parts but Boeing can ill-afford to have such events right now.

If I was one of those Boeing Board members who are probably sat around the conference table this weekend, I know what I would be concentrating on.

[Back at NH]

Reuters: via Tawitter

Ethiopian says to continue to fly 787 fleet, LHR incident "not related to flight safety"

[Lemain]

They must know 99.999% certain the cause.....

They must know 99.999% certain the cause.....presumably they are waiting to be able to answer whether type and which variants need checks/mods/grounding

[phil gollin]

IF there isn't a crew rest area above the rear galley area on ET 787s, what do they use the space for ?

Does anyone know how (and where) the structural loads from the fin are transferred to the hull structure ?

[llondel]

Euh ? If it was so safe (on the ground) why did Heathrow's finest turn out en-masse ?

I take the PR statement to mean that it was a problem caused by the fact that there was no one around, and had it happened in flight, it could have been dealt with quickly and efficiently before it got to that stage.

[MilktrayUK]

If I was one of those Boeing Board members who are probably sat around the conference table this weekend, I know what I would be concentrating on.

If the rumours about a substantial portion of the Thomson electrical system going AWOL in flight have any truth, I guess they would be looking again at which sub-contractor is liable for the electrical design.

For all those worrying about the duration of the repair, one can imagine that the Ethiopian frame could be easily repaired before the potential second grounding is lifted. If I was in the UK CAA, I would have had a sleepless night.

[VinRouge]

What would stop an oven overheating and catching light to surrounding trim if it were left on? I am guessing an oven element left on for a full crew rest period could catch before a cb popped, especially if in-flight has been left in said oven too.

Bit of a silly idea leaving power attached if that's whats happened, my undstanding was that most stands used by the internationals at lhr have integrated power at the ramp. Rather than a gpu.

I have a feeling this is systems unrelated. I'm also guessing Boeing are relieved this happened on a Friday as if it had been a weekday, there wouldn't have been the time to do a full investigation prior to press releases we can expect late tomorrow or early Monday prior to the markets re-opening.

[fenland787]

Presume that if the hull ignites @ 540 F, then.....

I don't think the the hull 'ignites' at 540F! I am not a composites person but I think the 540F number has more to do with the degradation of the material on exposure to high temperatures and there are, indeed, specifications for how hot things can be if they are in contact with the 787 composite. This material (or to be more accurate the resin within it) can self ignite given enough heat input but it takes a lot - around 31KW/sq metre with surface temps >500C or lower heat inputs if a flame is already present. See: http://www.fire.tc.faa.gov/pdf/07-57.pdf for the FAA report on 787 composite flam tests.