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Aerospace Ice in fuel

  1. Sep 5, 2008 #1

    wolram

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    Heard on the radio that the aircraft that crash landed at London airport crashed because of ice in the fuel (or that is the best guess) surly this is a cop out.
     
  2. jcsd
  3. Sep 5, 2008 #2
    Why do you think it's a cop out?
     
  4. Sep 5, 2008 #3

    FredGarvin

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    Are we talking about the large craft that had the dual engine flame out about a year ago or so? I find it hard to believe myself that ice was the culprit. With icing inhibitors and heated fuel system filters, and the fact that the shutdown happened on final, at low temperatures.I just have a tough time with that. I need to get my head back around the details of that incident.

    I see a fight coming from Boeing...
     
  5. Sep 5, 2008 #4

    wolram

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    Yes that is the one Fred.
     
  6. Sep 5, 2008 #5

    wolram

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    Tests after the accident found only acceptable amounts of water in the fuel, to me it seems very remote that ice could form and block both engines fuel supply within minutes of each other.
     
  7. Sep 5, 2008 #6
  8. Sep 8, 2008 #7
    “I see a fight coming from Boeing...”

    I don’t know why Boeing would disagree, when they are part of the team investigating the cause of the accident.

    The NTSB Accredited Representative is supported by a team which includes additional investigators from the NTSB, the Federal Aviation Administration and Boeing; Rolls﷓Royce, the engine manufacturer, is also participating fully in the investigation. British Airways, the operator, is cooperating with the investigation and providing expertise as required. The Civil Aviation Authority (CAA) and the European Aviation Safety Agency (EASA) are being kept informed of developments.

    The AAIB Interim Report is available here:
    http://news.bbc.co.uk/1/hi/england/london/7598267.stm
     
  9. Sep 9, 2008 #8

    FredGarvin

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    Of course they are going to be part of the investigation. No one knows that aircraft better. Part of that investigation is to make sure the root cause is not put improperly on something they missed. They won't steer the investigation, but they'll make darned sure that they have their butts covered. A simple problem like water in the fuel and thus icing is a big screw up. There should have been preventive measures in the design to prevent a dual flame out. They are going to defend their design vigorously to say the least.
     
  10. Sep 9, 2008 #9

    Mech_Engineer

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    Reminds me of Michael Crighton's novel "Airframe." The politics and pressure involved in aircraft crash investigations are incredible to say the least.
     
  11. Sep 9, 2008 #10

    wolram

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    On small aircraft the pilot is responsible for checking for water in the fuel, i can only imagine that the people that re fuel a big aircraft check for water, is this so?
    Even then i guess with thousands of flights every day and this one being the only casualty so far the odds must be astronomical that both engines would fail within minutes of each other, unless the fuel system has a design fault.
    I would think admitting ice was the problem would be a major concern, even leading to flight environment restrictions.
     
  12. Sep 9, 2008 #11

    wolram

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  13. Sep 10, 2008 #12

    FredGarvin

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    Yes. It is the responsibility for the engineers that maintain the pumping stations and pipe lines to ensure as little water as possible makes it through to the aircraft. In a small aircraft, it's easy to walk up to a wing port and pull a sample from the bottom of a tank. As a matter of fact, if you see water, you're supposed to keep pulling samples until you stop seeing water. That's fine when you have a couple hundred gallons. We did this every flight when I was in the Army too. However, I can't imagine the time or the hassle of getting up under the wing of a 747. The fuel farm system should have a large bank of coalescing filters that sole purpose is to remove the water from the fuel.
     
  14. Sep 10, 2008 #13

    FredGarvin

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    The liquid-liquid heat exchangers you mentioned Wolly are really meant to help with fuel efficiency in that the heat required to bring the fuel to ignition temp in the burner is reduced because it pulls heat from the oil (obviously it helps the oil too). You do bring up a good point though that there should be plenty of heating to prevent ice build up prior to the injectors.
     
  15. Sep 10, 2008 #14

    wolram

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    Found the latest news clip.


    http://www.thisislondon.co.uk/stand...kely+cause+of+Heathrow+plane+crash/article.do

    First Officer John Coward was forced to glide the Boeing 777 to safety after both engines failed at 600ft on flight BA38 earlier this year.

    The inbound jet, arriving from China, dramatically missed the perimeter fence by inches before touching down on the grass. The undercarriage collapsed, but only one person from the 136 passengers and 16 crew was seriously injured.

    The Air Accident Investigations Branch (AAIB) interim report into the incident on 17 January has indicated a drop in temperature to -76C (-105F) while flying over Russia may have caused the fuel to thicken, depriving the engines of the additional thrust needed to land.

    Further tests are due to be performed to determine the exact sequence of events. Investigators are focusing on a region of particularly cold air between the Urals and eastern Scandinavia.

    Temperatures were found to have plummeted far lower than expected. But although the weather was unusually cold, it was not without precedent and has never been known to have caused problems on other flights.

    The average freezing temperature of aviation fuel is -47C, but tests have shown that fuel on airliners does not turn to ice until -57C. Investigators' initial tests on the crashed plane found the fuel temperature never dropped below -34C during the flight.

    But even if the fuel did not freeze it could have thickened enough to affect flow to the engine. Further tests will be carried out at Rolls Royce's engine plant in Derby and Boeing's factory in Seattle.

    The AAIB has not called on Boeing or Rolls Royce to implement changes or withdraw any Boeing 777s from service.
     
  16. Sep 10, 2008 #15
    In my last post I provided a link to the Air Accident Investigations Branch (AAIB) interim report. It is about half way down the page.
    In the report it tells you that the airplane already has oil/fuel heat exchangers, and they believe restriction happened upstream of it.
    That the sumps were drained the day before, what tests they have already done and not done and a whole lot more.

    In the NY Times this weekend they reported what they may use as an in-term measure

    http://www.nytimes.com/2008/09/05/world/europe/05crash.html
     
  17. Sep 11, 2008 #16

    wolram

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    Thanks nucleus i missed that post.

    I am still confused though, ice forming in fuel will only affect one aircraft type fitted with a certain engine.
     
  18. Sep 11, 2008 #17

    FredGarvin

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    Whether or not it is icing, I couldn't believe that airlines did not use FSII. It's a small ratio of the fuel and doesn't cost that much. I find it ignorant to not use it.
     
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