NTSB issues urgent recommendation for 777s with RR engines (BA crash at LHR)

[JF Mezei]

This has to do with the BA 777 crash allegedly due to having flown in
very cold weather on Roll Royce engines and Delta airlines having
recently had a similar occurance (but was able to recover).

This is the result of an NTSB urgent safey recommendation:
http://www.ntsb.gov/Pressrel/2009/090311.html

##
Washington, DC - Following two engine thrust rollback events on Boeing
777 aircraft powered by Rolls-Royce engines, the National Transportation
Safety Board issued an urgent safety recommendation today calling for
the redesign of a Rolls- Royce engine component. The Safety Board also
recommended that, after the redesign is completed, the new system be
installed on all affected B-777 airplanes at the next maintenance check
or within six months.

These recommendations are being issued in response to the findings in
two investigations - an accident and an incident - involving engine
thrust rollbacks on Boeing 777-200ER airplanes powered by Rolls-Royce
RB211 Trent 800 Series engines. In both cases a build-up of ice (from
water normally present in all jet fuel) on the fuel/oil heat exchanger
(FOHE) restricted the flow of fuel to the engine, resulting in an
uncommanded engine rollback.
##

The Delta event happened in Nov 2008. Only one engine experienced
"rollback" of thurst and crews were able to recover power and continue
to Atlanta (from Shanghai)
.
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[Roland Perry]

Post by JF Mezei
These recommendations are being issued in response to the findings in
two investigations - an accident and an incident - involving engine
thrust rollbacks on Boeing 777-200ER airplanes powered by Rolls-Royce
RB211 Trent 800 Series engines. In both cases a build-up of ice (from
water normally present in all jet fuel) on the fuel/oil heat exchanger
(FOHE) restricted the flow of fuel to the engine, resulting in an
uncommanded engine rollback.

If there have only ever been two such events in the 12 years that the
777-200ER has been flying, then it's especially bad luck that the first
(BA) incident affected both engines.

[JF Mezei]

Post by Roland Perry
If there have only ever been two such events in the 12 years that the
777-200ER has been flying, then it's especially bad luck that the first
(BA) incident affected both engines.

How long has RR equipped 777s been flying polar routes ?

Delta is a newbie to the 777. And they are newbies to longrange routes
between atlanta and asia.

How long had BA been operating their 777s to china from London ?

If that engine variant has been operating long haul polar routes for
many years already, then yeah, it is odd that this would start to happen
now.

But you need specific conditions for this to happen, namely very cold
during cruise, and warm enough to start melting ice on pipes during descent.

If you are landing in winter, then ice accumulated on pipe walls won't
melt during descent, so it won't get dislodged to clog the filter-like
surface of the heat exchanger.
.
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[A Guy Called Tyketto]

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Post by JF Mezei

Post by Roland Perry
If there have only ever been two such events in the 12 years that the
777-200ER has been flying, then it's especially bad luck that the first
(BA) incident affected both engines.

How long has RR equipped 777s been flying polar routes ?

Depends. Does SIA run some of their B772s over the poles in
lieu of the kangaroo route? I know they would at least head over the
Aleutians to SIN from the West Coast. IIRC, they have the biggest
number of Trent-powered B777s around.

If you count west coast operations going to Japan/Asia via
Alaska as polar, there would be quite a bit between 1997 and now.

Post by JF Mezei
If that engine variant has been operating long haul polar routes for
many years already, then yeah, it is odd that this would start to happen
now.
But you need specific conditions for this to happen, namely very cold
during cruise, and warm enough to start melting ice on pipes during descent.
If you are landing in winter, then ice accumulated on pipe walls won't
melt during descent, so it won't get dislodged to clog the filter-like
surface of the heat exchanger.

Well, the FAA also put out the AD on it, so that may give a bit
better insight:

http://tinyurl.com/dza94s

FlightGlobal has more on the exchanger issue as well.

http://tinyurl.com/dzvn4p

BL.
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[Roland Perry]

Post by JF Mezei
But you need specific conditions for this to happen, namely very cold
during cruise, and warm enough to start melting ice on pipes during descent.

As my colleagues in the southern hemisphere keep telling me, it's their
Autumn at the moment, and talking about having a meeting "in the Summer"
doesn't show much respect for their timezone. I expect there are routes
with certain combinations of temperatures somewhere in the world much
more often than we might suppose, from sitting in London or Los Angeles
in the middle of March.

[Jeff Hacker]

Post by JF Mezei

Post by Roland Perry
If there have only ever been two such events in the 12 years that the
777-200ER has been flying, then it's especially bad luck that the first
(BA) incident affected both engines.

How long has RR equipped 777s been flying polar routes ?
Delta is a newbie to the 777. And they are newbies to longrange routes
between atlanta and asia.

Not that new. They have been flying to Asia for well over 10 years.
Started with MD11's and replaced them with 777's.

Post by JF Mezei
How long had BA been operating their 777s to china from London ?
If that engine variant has been operating long haul polar routes for
many years already, then yeah, it is odd that this would start to happen
now.
But you need specific conditions for this to happen, namely very cold
during cruise, and warm enough to start melting ice on pipes during descent.
If you are landing in winter, then ice accumulated on pipe walls won't
melt during descent, so it won't get dislodged to clog the filter-like
surface of the heat exchanger.
.
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[JF Mezei]

Post by Jeff Hacker
Not that new. They have been flying to Asia for well over 10 years.
Started with MD11's and replaced them with 777's.

But MD11s weren't exactly very long range. They were able to do west
coast to asia. But the 777 ERs can do east coast to asia and the route
keeps the aircraft in very cold regions for much longer. And Delta
hasn't had 777s for that long.

The 777 is also the first truly long range twin being used on polar
routes. Since a GE90 class engine drinks roughly twice as fast as that
of a CFM56 for 340s, it means that when pilot increases thrust, you have
far greater fuel flow to the big engine. This might result in all of the
"ready to fall" ice on the pipes to dislodge at once and clog the heat
exchanger, whereas smaller engines might see more gradual ice flow.

Evidently, the GE90 class engines haven't experienced this and folks
like Continental have used 777s on polar routes for quite some time.

I assume the NTSB will have looked at differences between GE and RR
engines. Anyone know if there are significant dfferences between the two
in terms of fuel inlet and heat exchanger ?

Is it possible that the RR engines have a more instantaneous fuel flow
increase compared to the GE ones ?

.
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