DAL rollback update/Trent895
 

SUBJECT: 777-200/Trent 895 N862DA Thrust Rollback During Cruise - 26
November 2008


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UPDATE 1 UPDATE 1 UPDATE 1 UPDATE 1
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Reference a) provides Boeing's previous fleet communication of a 777-200
with Trent 895 engines that experienced an uncommanded thrust rollback on
one engine while in level flight cruise at FL 390. The thrust rolled back
to a level above idle on that engine, approximately 40 minutes after a VNAV
step climb. The flight crew performed the Engine Response non-normal
checklist, which restored full capability to the engine for the remainder of
the flight. The other engine operated normally throughout the flight.

Based on the FDR data and the characteristics of the roll-back, it is
suspected that accumulation of water ice in the fuel path of the Fuel Oil
Heat Exchanger is the cause of the subject incident. Although the
circumstances are slightly different, the subject incident is believed to
have been caused by similar factors as those experienced in the 777-200ER
G-YMMM accident at London, Heathrow airport on 17 January 2008 as described
by Reference b).

Investigation Status
It should be emphasized that the investigations into both events are not yet
complete, with the G-YMMM accident under an open investigation by the UK
AAIB and the subject roll-back incident under an open investigation by the
US NTSB. Boeing, Rolls-Royce, the operators and other organizations are
supporting both investigations.

Recommended Operator Action
The circumstances of the subject thrust roll-back incident have led Boeing
to review the cold fuel operations procedures released by Reference c).
Based on this review, it is believed to be prudent to revise the interim
mitigating procedures to account for what was learned in the subject
roll-back incident. Changes to the interim procedures include:

Reduce the window at top of descent from 3 to 2 hours;
Assure the crossfeed valves are closed;
Assure minimum idle thrust for 30 seconds during initial descent, and;
Clarify the Condition statement in Engine Response Non-Normal Checklist
(NNC).

Reference d) provides a list of publications from Boeing that give the full
definition of the revised interim mitigating procedures. The FAA and EASA
are expected to release regulatory action to mandate use of the revised
procedures. These procedures are interim measures that will remain in place
until a permanent solution can be defined, tested, certified, and deployed
to the fleet.

Other Airframe/Engine Combinations
These interim mitigation procedures only apply to 777s powered by
Rolls-Royce Trent 800 engines and do not apply to other airframe/engine
combinations. Based on our knowledge of the system configurations, scenario
studies, and laboratory test results, we do not believe that immediate
action is necessary or warranted for 777s powered by other engine types or
non-777 airframes regardless of engine type.

Studies of the applicability of the thrust roll back circumstances to other
engine types and airframes are in work and will continue. Boeing will
notify operators of the results of those studies as appropriate.


Tom Dodt
Chief Engineer - Air Safety Investigation
The Boeing Company
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'The newest 777s built by Boeing, the best-selling 777-300ER and the ultra-long-range 777-200LR, are only powered with GE engines.'

I wonder why that is then? Is there an inherent issue with the trent? Perhaps more experienced posters would care to answer.

Thanks

Yes, absolutely, there's an inherent issue with the Trent... (drum roll)...but sorry to disappoint you, the issue is simply that the most powerful Trent version is not powerful enough for the 777-300ER/-200LR. As a couple of minutes on Wikipedia reading about the longer range 777 models and the Trent would tell you, the -300ER/-200LR use a 115,000lb thrust version of the GE90, whereas the most powerful available Trent is "only" 95,000lb.

Easy
 

GE got exclusivity on the 777 ER/LR in exchange for them developing the 115k lb engine Boeing needed.

A purely commercial deal, nothing to do with technical features of the Trent.

"In 1998 Boeing proposed new longer range variants of the 777X; taking advantage of the Trent 800's growth capability, Rolls-Royce designed and built an improved engine designated Trent 8104 which was later scaled upwards to the even larger 8115. This development was the first engine to break through 100,000 lbf (440 kN) thrust and subsequently the the first to reach 110,000 lbf (490 kN). However, Boeing required that the participating engine developer assume a risk-sharing role on the overall 777X project. Rolls-Royce was unwilling to do so, and in July 1999 Boeing announced that it had chosen the development of the GE90, the GE90-110B and GE90-115B to be the sole engines on the long-range 777s. This resulted in the 8104 becoming just a demonstrator programme, despite setting further industry firsts for thrust levels achieved and the first to demonstrate the use of a fully swept wide chord fan."

Trying to Understand
 

The point of the posts related to engine choice. Time marches on, things happen, technology evolves. Is a commercial decision somehow uhm... disrepectful? To be specific, the Trent located its HE in a different place and went with no recirc. It also has an extra spool. I'm a "fan" of RR;

I think no defence needed.

AF

CAPTDOUG, the first thread you started about this incident is still open and available. Don't get greedy!
http://www.pprune.org/rumours-news/3...-trent895.html

Quite.

Threads merged.

Lets be honest, all this is just part of the evolution of airplanes.
As long as this problem is controlled by the knowledge that has been gained until a rectification is made, then we are all happy.

But, on the other hand, if another frame comes down there will be hell breaking loose!! :uhoh:

Although the triple seven would never be grounded if it did happen again, because its american!!:mad:

Cyrano/Dysag - thanks for pointing that out, however my point is were RR unable to provide a higher thrust engine to boeing, or did they not want to because they new they already had issues. As Lord b states they had developed upto 110k but then pulled out, doesn't sound very commercial to me. I would imagine a lot of RR donk operators who were looking at the 777 LR variants would have been uhappy with that decision.

EASY 69

from my undertsanding Boeing wanted to enter into a risk sharing agreement with RR on the larger variants. RR did want to do that so pulled out. Essentially if the 777 larger variant failed commercially RR would have lost out badly

Apart from Emirates who were initially unhappy with RR on the base 777s, and were very happy to see GE as suppliers to 777 growth varients.

'Essentially if the 777 larger variant failed commercially RR would have lost out badly.' - conversley if the 777 larger variant suceeded commercially RR would have done very well, or would they. Seems to me that they knew something was adrift with the engine and pulled out of further development. As it stands,two rollbacks, as of yet not fully explained by the investigators, on an aircraft that it WAS designed for seems a little bit of a concern.

EASY

Do you honestly think RR would not have fixed a minor problem such as plate heat exchange unit if they knew it was faulty or they thought the engine was inherentley flawed!!! come on!!!! Saudi airlines had to change a number of their GE engines in 02 on the 777 because of a failure of some bearings, by your own summary does that make the GE unsafe?? UTTER DRIBBLE. the trent has been flying for years and up until recently was very succesful and reliable.. (and for me 2 incidents don't make a bad engine) I wouldn't hesitate stepping onto a RR powered 777... Personally i would rather fly on a plane with power from RR than GE or PW....

waits for abuse.....:mad:

boeing boeing.. gone no, not at all, but there again they didn't and a minor problem becomes a big issue. Me personally, I love them all.

Easy 69, you seem to be very ignorant of the facts while keen to voice an opinion. It might be better (for your own credibility) to read more and post less.

What facts would those be then sky 9?

I believe having spent 35 plus years in aviation that I have at least some knowledge,and like most people I like to voice an opinion on something that I have an interest in or a concern about.

Windsheer
 

Last year all 777's (UAL) had to deplane their pax and deadhead to MOC to check a firing mechanism on #5 fire bottle. This item was actually deferable, but the line recalled anyway.

Sometimes methinks the messenger takes flack when partisans are frustrated at events.

I don't see this as any thing other than the unfolding of commerce, and an opportunity to progress.

AF

If we're talking rollbacks , there was a software issue that meant an extended period of TOGA takeoffs on the GE powered ER/LR until the problem was fixed . Not the same as a suspected icing issue but still just as scary . Think if you look at all the types/engines at some time in their development there are issues which eventually get resolved , just more gets in the public domain now!!

bvcu

you have said exactly what i was trying to, but far more elequently:ok:

at the end of the day all the engines types that are hooked on to the 777 airframe must be good otherwise they wouldn't be there!!!:cool: