ELT was under own power at time of Ethiopian 787 incident

Here is some more information on the Honeywell Electronic Locator Transmitter and the installation/operation on the Boeing 787.

We asked Boeing about the prospect of interface between the ELT and the 787’s electrical system. Boeing told us:

In the event of an emergency, the ELT will be activated either automatically by means of an internal acceleration sensor—or manually by one of the flight crew via the flight deck ELT control panel.

At the time of the incident, there was no power to the airplane. The ELT was powering itself via its battery. When an airplane is in flight, the ELT still powers itself with no help from the airplane. It interfaces with the airplane via wires connected to the flight deck so that the pilot can activate the transmitter, if necessary. Turning on the transmitter doesn’t transfer any power to the unit. There is a co-ax cable from the unit that connects to the antenna (located on top of the fuselage).

As we noted in a prior post, Honeywell’s ELT in a different version was subject to an airworthiness directive from Canadian and European regulators. Reuters has this additional detail, including comment from Honeywell. The AD related to improper grounding, so an obvious question is whether there is a grounding issue with the 787 ELT that led to a short that prompted the fire. Investigations are still underway.

In any event, this appears to exonerate the 787. We still reserve final judgment pending a more complete investigation.

Boeing said that the ELT can be removed within one hour by the airline.

The New York Times has this update.

  • If this news weren’t good enough for Boeing, last night it rolled out the first 787-9. The Seattle P-I has a number of photos.

 

28 Comments on “ELT was under own power at time of Ethiopian 787 incident

  1. Appearances can be deceiving …

    A sneak circuit is stil possible- for example

    Airplane ground may be above earth ground when ground power is connected but breaker/switch turned off- or if only ground connected loop problems can happen

    Coax cable external shield is grounded to airplane ground

    Rubbing or vibration can short out adjoining cables to ground, including coax

    The answers are not yet forthcoming

    relax and watch the blinking lights .

    • Which is why I think Boeing should issue a bulletin recommending that the wiring harnesses associated with the ELT be inspected for defects or damage. ANA and JAL have already done this.

  2. A close reading of the accident report tells us that combustion of the ELT battery resulted in structural damage to the aircraft. As a similar fire on a787 in flight would bring the aircraft down, you can remove a hazard simply by getting rid of the ELT battery. (obviously that approach wouldn’t work with an equivalent problem in the engine).

    The AAIB also claim that the ELT battery is capable of self igniting. We probably infer that the ELT did cause the fire, but I don’t think the AAIB quite say that.

  3. A key sentence in the Reuters article:

    – The directive involves an earlier model from the beacon available for the 787 that entered service in October 2011.

    This is a four year old SB. Since then a new model was developed and installed on the 787. But it does not mean they had completely solved that problem, whatever that problem was. We need more info to settle the case. For the time being I guess it can remain part of the internal-short theory that says an internal short might have triggered a thermal runaway. The other theory being that a thermal runaway ignited spontaneously; or, as I think, was induced by excessive heat that had accumulated in the crown.

  4. Some seem to be keen to jump to a quick conclusion. May be just to avoid evade a more thorough look at the electrical system?

  5. kc135topboom :
    The question still remains; Is this airplane repairable by Boeing?

    Sure its repairable- but at what cost ? What PR value ?

    does not need an autoclave- many composite repair and inspection techniques available.

    may just replace whole aft section at production joint about 2-4 feet front of obvious damage

  6. Japan issuing temporary rule changes for ELTs.

    191436 RJAAYNYX
    (J3652/13 NOTAMN
    Q) RJJJ/QXXXX/IV/M/EW/000/999/3310N14118E999
    A) RJJJ B) 1307191435 C) UFN
    E) EXEMPTION FM EQUIPPING AUTOMATIC ELT ACTIVATED BY IMPACT
    THE ACFT UNA TO EQUIP AN AUTOMATIC ELT ACTIVATED BY IMPACT OTHER
    THAN HONEYWELL MODEL 1152682-2 OR 1152682-3 ARE EXEMPTED FM
    EQUIPPING AN AUTOMATIC ELT ACTIVATED BY IMPACT ON THE COND THAT
    THEY EQUIP AT LEAST ONE ELT OF ANY MODEL IN ACCORDANCE WITH THE
    SUPPLEMENTARY PROVISION NR 3 IN THE ORDINANCE NR 56 IN 2008 TO
    AMEND A PART OF CIVIL AERONAUTICS REGULATION.

    • I’m curious why there would be increased humidity or likelihood of condensation. Surely an unheated airliner parked up for the day on a grey winter day in the UK, when outside RH is 80-90% and the interior temperature delta is unlikely to lower this by much is going to have a higher RH inside than this 787, which was parked in an outside RH of 40-60% (probably 50ish) and would have had lower still RH inside due to baking in the sun. Plus no cold surfaces on a summer day for condensation to form on (except around A/C perhaps), again unliked a cold, often wet, winters day at LHR.

      • reply to # 14 re humidity. Its not the then local heat/humidity that is at issue. During flight test, the 787 had so much condensation due to higher cabin humidity that they used drip pans and nicknamed it the ‘ rainliner’ or similar.

        http://seattletimes.com/html/businesstechnology/2013713745_dreamliner19.html

        Among the 787’s lesser ongoing problems is “rain in the plane,” the term used for heavy condensation dripping inside the jet’s composite plastic fuselage. Yet that issue is piddling compared with the major flaws that have brought a wave of successive delays. . . . and . . . The latest delay will at least give engineers more time to test design fixes, including some for less consequential troubles, not uncommon on new jets, such as the maddening drip, drip, drip of “rain in the plane.” On 787 flight tests, drip trays padded with squares of absorbent cloth are positioned to collect the condensation.

        Fancher said “a good design fix” to dehumidify the interior is being installed and will be tested when the Dreamliners resume flying.

        Employees working on the 787 complain about insufficient oversight of suppliers and a management system that the senior engineer called “totally broken.” . . .

      • Thanks fror the info Don. Didn’t reralise in-flight condensation was that bad in a 787. Surely though, if it is that bad, an airline could simply make it standard practice to ‘air’ a plane in between flights whenever possible (8 hours on a warm, low RH day at LHR being a definite possible)?

    • I recall that condensation inside the original battery casing was a concern and this was taken into consideration when they designed the new stainless steel casing. But if the condensation is a by-product of the composite fuselage, should this not be also a concern on the A350 which uses the same material for the fuselage?

  7. Answer to #12: Probably not. When billions of electric cars and laptops and ELTs are functioning happily all over the world even in more humid and condensed places and only 787 or Honeywell has the problem, that’s where you look to.

  8. from coming av week article – this extract

    Insiders also quietly note that the
    composite structure heldup well to the
    fire. Compared to conventional aircraftthickness
    aluminum, for which FAA
    tests have shown burn-through timesof
    30-60 sec. in intense fires, Boeing flame
    tests exhibited longer burn-through
    times for sections representative of
    the 787’s composite laminate skin. The
    aircraft maker also points out that although
    the fire was severe enough to
    visibly char the exterior of the skin, the
    fire did not penetrate the surface.

    and

    “This is the largest incident that I
    have seen as far as damage from heat
    and fire,” says Paul Jonas, director of
    environmental test labs and special programs
    at the National Institute for Aviation
    Research at Wichita State University,
    “This is a significant event. It does
    look like a lot of heating.” He estimates
    that fire temperatures may have been in
    the 1,000-1,200F range to cause the type
    of paint damage seen in photographs of
    the scene. “Composites are pretty much
    self-extinguishing. If you put flame on
    and take it off, it doesn’t propagate.”

    +++

    • I think most people are waiting for info on the actual damage and the repair. Specially related to the thick heated composite structure.

  9. Don Shuper :
    Employees working on the 787 complain about insufficient oversight of suppliers and a management system that the senior engineer called “totally broken.” . . .

    To create a fiasco like the introduction of the Dreamliner was you indeed need a totally broken management system. But I expected things to get better by now. From what you say I gather that we may not be there yet. That’s what happens when your eyes are riveted to the bottom line. How long did it take to destroy this company? Well, it’s going to take twice as long to rebuild it. But if we look at the share price everything is going fine. Only a few teething problems, that’s all.

    Please move on, there is nothing to see here. 😉

    • RE # 19. Suggest you read the excellent book – survey of Boeing management and employees called ” TURBULENCE” Boeing and the state of american workers and managers.

      The same team that wrote the book and surveys is back and getting an update.

      IMHO- the book makes VERY clear what happened starting in the early 90’s but picking up Speed when MDC bought Boeing with Boeing money, and the GE wannabees and rejects took control. Add to that the drop of of research, and the strong anti union bias, and mix well with power point rangers, ethical issues and you now see the result. How long to recover- IF BA recovers , it will be well after the current top management pulls the retirement ripcord and flies off into the sunset.

  10. Woody :
    Thanks fror the info Don. Didn’t reralise in-flight condensation was that bad in a 787. Surely though, if it is that bad, an airline could simply make it standard practice to ‘air’ a plane in between flights whenever possible (8 hours on a warm, low RH day at LHR being a
    definite possible)?

    IMO there may be another subtle problem – seems to me with a higher humidity feature- over time the insulation NOT in contact and NOT sealed or otherwise protected would result in pockets of moisture being almost permanent. And if insulation could adsorb moisture- over time weight would increase. So did the power point rangers take a close look – apparently not in the beginning. And the so called fix is a better A/C ?? NO low flow spots at all, no blind air vents anywhere?

    Now with aluminum wiring- hot electronics bays . . . . one must wonder long term ..

    • Don Shuper :
      IMO there may be another subtle problem – seems to me with a higher humidity feature- over time the insulation NOT in contact and NOT sealed or otherwise protected would result in pockets of moisture being almost permanent. And if insulation could adsorb moisture- over time weight would increase.

      The Dreamliner has special dryers at key locations inside the cabin to prevent that.

  11. Question: Is it possible that some electronic timer incorporated into certain electrochemical elements will create a short circuit to cause said elements to burn, and in the process to also cause itself to burn up so that it leaves no trace or almost no trace of evidence?

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