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Author: NedNed Date: Sep 4, 2008 06:22
FWIW - I understand that the long overdue, and anticipated (by me at
least), AD addressing the possible role of ice in this crash will be
issued in coming days.
Ned
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Author: RobRob Date: Sep 4, 2008 17:36
Ned wrote:
> FWIW - I understand that the long overdue, and anticipated (by me at
> least), AD addressing the possible role of ice in this crash will be
> issued in coming days.
>
> Ned
BA 777 crash inquiry believes icing behind fuel-flow restriction
By David Kaminski-Morrow
UK investigators believe that ice was the source of the fuel-system
restriction which led a British Airways Boeing 777-200ER to experience a
loss of engine power on approach to London Heathrow in January, and
crash just short of the runway.
In an interim report on the accident today, the Air Accidents
Investigation Branch has issued three safety recommendations, including
one directed specifically at Rolls-Royce Trent 800-powered 777s.
The AAIB is recommending that US and European regulators - in
conjunction with Rolls-Royce and Boeing - introduce "interim measures"
to reduce the risk of restriction in Trent-equipped 777 fuel-feed
systems caused by icing of water in fuel.
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Author: Sylvia ElseSylvia Else Date: Sep 4, 2008 18:12
Ned wrote:
> FWIW - I understand that the long overdue, and anticipated (by me at
> least), AD addressing the possible role of ice in this crash will be
> issued in coming days.
>
> Ned
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Author: DCDC Date: Sep 4, 2008 20:44
Ned said the following on 4/09/2008 9:22 PM:
> FWIW - I understand that the long overdue, and anticipated (by me at
> least), AD addressing the possible role of ice in this crash will be
> issued in coming days.
Another article
http://www.theregister.co.uk/2008/09/04/heathrow_777_verdict/
Ice in fuel caused Heathrow 777 crash
Nasty chill provoked reduced fuel flow
By Lester Haines
Published Thursday 4th September 2008 16:37 GMT
The Air Accidents Investigation Branch (AAIB) has concluded that the 17
January crash-landing of a Boeing 777 at Heathrow was probably caused by
"ice within the fuel feed system" which restricted flow to the engines.
BA038 (G-YMMM), after a routine flight from Beijing, suffered reduced
thrust in both engines while coming into land and fell short of the
runway. The AAIB explained earlier this year:
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Author: David LesherDavid Lesher Date: Sep 8, 2008 12:33
Paul Saccani omen.net.au> writes:
>On Fri, 05 Sep 2008 10:36:24 +1000, Rob mine.com.au> wrote:>>"The investigation has shown that the fuel flow to both engines was
>>restricted, most probably due to ice within the fuel-feed system," says
>>the AAIB. "The ice is likely to have formed from water that occurred
>>naturally in the fuel while the aircraft operated for a long period,
>>with low fuel flows, in an unusually cold environment."
On the top of page 7, Col 2, the report talks about the water scavanging
system. It says it injects the "fluid" into each boost pump. Hello? Is
this so low flow it can't alter engine performance, or they just hope it
does not alter the thrust...?
--
A host is a host from coast to coast.................wb8foz@ nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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Author: David LesherDavid Lesher Date: Sep 9, 2008 10:46
Paul Saccani omen.net.au> writes:
>>On the top of page 7, Col 2, the report talks about the water scavanging
>>system. It says it injects the "fluid" into each boost pump. Hello? Is
>>this so low flow it can't alter engine performance, or they just hope it
>>does not alter the thrust...?
>40 PPM ? I suppose it shouldn't have a great effect.
Where did that flow rate come from?
--
A host is a host from coast to coast.................wb8foz@ nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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Author: David LesherDavid Lesher Date: Sep 10, 2008 07:36
Paul Saccani omen.net.au> writes:
>I also think you may have misinterpreted the report slightly. It
>doesn't inject scavenge into the boost pumps, but rather, near their
>inlets. This entrains fuel into that flow as well, so you shouldn't
>have solid slugs of heavily water contaminated fuel entering the boost
>pump inlets. Additionally, the tendency is for gross amounts of water
>to cause icing in the scavenge pumps which stops their operation (this
>usually doesn't damage the scavenge pumps).
I found it interesting because usually the idea is to keep the water
out of combustion engines, not send it there. I agree that in very
low percentages, it won't disrupt combustion -- some engines actually
intentionally inject H2O, the HP7 and early B52's among them..
BUT fuel system icing is the topic at hand, and water+cold often equals
ice.
--
A host is a host from coast to coast.................wb8foz@ nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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Author: SnapperSnapper Date: Sep 18, 2008 00:33
David Lesher wrote...
> Is this so low flow it can't alter engine performance, or they just hope it
> does not alter the thrust...?
Eh?
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Author: SnapperSnapper Date: Sep 18, 2008 00:38
David Lesher wrote...
> I found it interesting because usually the idea is to keep the water
> out of combustion engines, not send it there. I agree that in very
> low percentages, it won't disrupt combustion -- some engines actually
> intentionally inject H2O, the HP7 and early B52's among them..
Quite a few stationary jet engines (power generation, etc.) use water injection
to control NOX emissions, and use fine sprays at the compressor inlets to
increase the air mass and hence performance on warmer to hot days. But the
introduction of water is at high loads, and given what I know about these
engines, I think that this would be occuring for an aircraft equivalent load of
"take off thrust", I think it's called.
If the engine is at low loads and water is introduced into the mix then it'd
probably do what our engines were doing when the WI system failed to shut off -
flame out somewhat spectacularly..
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