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Engine icing problems on 747-8 and 787.

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Engine icing problems on 747-8 and 787.

Old 23rd Nov 2013, 11:24
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Boeing, GE notify airlines about engine icing risk on 747-8, Dreamliners

Boeing warns of engine icing risk on 747-8s, Dreamliners

TOKYO (Reuters) - Boeing and General Electric have notified airlines about engine icing risk on 747-8 airplanes and 787 Dreamliners with some GE engines, urging carries to avoid flying them near thunderstorms, a Boeing official said.

The issue affects 15 airlines, including Lufthansa , United Airlines, an arm of United Continental , Japan Airlines and Cathay Pacific Airlines .
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Old 23rd Nov 2013, 15:10
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Engine icing problems on 747-8 and 787.

BBC News - Boeing: 15 airlines warned over high-altitude ice
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Old 23rd Nov 2013, 15:18
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from article ....

Fifteen airlines have been warned about the risk of ice forming on Boeing's new 747-8 and 787 Dreamliner planes.

The issue - affecting some types of engines made by General Electric when planes fly near high-level thunderstorms - prompted Japan Airlines to cancel two international routes.

There have been six incidents since April when aircraft powered by GE engines lost power at high altitude.
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Old 23rd Nov 2013, 15:42
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http://www.pprune.org/tech-log/52843...eamliners.html
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Old 23rd Nov 2013, 15:52
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Japan Airlines said on Saturday it will replace Dreamliners on its Tokyo-Delhi and Tokyo-Singapore flights with other types of aircraft while also dropping a plan to use 787s for its Tokyo-Sydney route from December.
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Old 23rd Nov 2013, 16:21
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It would be nice if future posts on this topic could get into informed speculative, or knowledgeable discussion, about why this high altitude icing is affecting only the GE engines and not the Rollers, just for once, please?.
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Old 23rd Nov 2013, 16:25
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787 Engine icing warning - GEnx engines affected

BBC News - Boeing: 15 airlines warned over high-altitude ice



Fifteen airlines have been warned about the risk of ice forming on Boeing's new 747-8 and 787 Dreamliner planes.


The issue - affecting some types of engines made by General Electric when planes fly near high-level thunderstorms - prompted Japan Airlines to cancel two international routes.


There have been six incidents since April when aircraft powered by GE engines lost power at high altitude.


The Boeing 747-8 series and the new 787 Dreamliner and the only types of aircraft affected by the high-altitude icing issue.

The new warning was given to airlines including Lufthansa, United Airlines and Japan Airlines.



It says aircraft with the affected engines - GE's GEnx - must not be flown within 50 nautical miles of thunderstorms that may contain ice crystals.
As a result, Japan Airlines (JAL) has decided to withdraw Dreamliners from service on the Tokyo-Delhi and Tokyo-Singapore routes.



"Boeing and JAL share a commitment to the safety of passengers and crews on board our airplanes. We respect JAL's decision to suspend some 787 services on specific routes," a Boeing spokesman said, according to Reuters news agency.


A GE spokesman told the agency the aviation industry was experiencing "a growing number of ice-crystal icing encounters in recent years as the population of large commercial airliners has grown, particularly in tropical regions of the world".


He said GE and Boeing were hoping to eliminate the problem by modifying the engine control system software.
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Old 23rd Nov 2013, 16:25
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Er, isn't it a bit late in the development cycle of an engine to discover this sort of problem?
Engines and airacrft are not developed at the far ends of an icing envelop. Now that it is realized that the operation intends to use this envelop as often as they do, the engine needs to have a work-around for such an encounter.

Lots of other examples in-service where recommendations were not followed to avoid encounters and where extraordinary action need be taken at the product level
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Old 23rd Nov 2013, 17:19
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............

Last edited by Radix; 18th Mar 2016 at 01:01.
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Old 23rd Nov 2013, 17:28
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Is the title on this thread accurate?

The New York Times article says:

"The move came after six incidents from April to November involving five 747-8s and one 787 in which aircraft powered by GE’s GEnx engines suffered temporary loss of thrust while flying at high altitude."

So why isn't the title about the 747-8 problem? - 83% of the reported problems are 747-8 incidents
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Old 23rd Nov 2013, 17:46
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GEnx Engines don't fly in icing conditions

Hi, just seen an announcement that the engines fitted to some Japanese Dreamliners should not be flown within 50 miles of icing conditions...

BBC News - Boeing: 15 airlines warned over high-altitude ice

Maybe a quick swap of engines is all that is required.
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Old 23rd Nov 2013, 20:06
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this problem has been recognised for a while and has given problems on other engines at various times and sometimes causing damage. Must be more serious if this restriction has been mandated.
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Old 23rd Nov 2013, 21:06
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Lots of possibilities but the effect of this type of icing on one engine model vs another.

If it's mechanical damage then the exact location of the ice buildup and the delay time to shed may produce damage to some blading downstream. The ice buidlup location more often than not is on the probes inside the engine that feed the FAEC etc.

If it isn't permanent damage to the blading downstream, than the effect on the engine cycle might be as simple as a probe blockage and stall condition which is not programed into the recovery logic of the engine FADECs.

Perhaps somebody with knowlege of the fix can interpret what's unique about the specific engine design or recovery logic in these state of the art GE engines
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Old 23rd Nov 2013, 21:50
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Originally Posted by Radix
Atmospheric conditions on intercontinental routes are well known.
The problem is that the precise conditions that cause engine power loss (or pitot blockage) are not well known and understood.
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Old 23rd Nov 2013, 21:56
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NOT addressing the specific present icing condition -

One early turbofan (70s) had stall/surge problems in early revenue svc, associated with heavy rain. The factory had difficulty replicating the condition and the problem.

More field research brought forth the news the engine ran fine within the heavy rain, but when the a/c exited the rain the stall would occur.

So the test rig was modified to turn the H2O on and off very rapidly. Voila! the problem was now replicated!

Turns out the issue was the rapid air temperature change at the LPC discharge was the culprit; water in the LPC flowpath cooled that flow a lot, so the air temperature sensor at that point needed the be a faster-responding design to convey correct data to the engine control.

The water-ingestion tests during FAA certification were not aggressive enough!
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Old 23rd Nov 2013, 22:50
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More problems with Boeing 787 and 748's

Boeing has warned airlines to avoid flying some Dreamliner planes near high-level thunderstorms due to a risk of engine icing problems.
The warning applies to 15 carriers who have 747-8 and 787 Dreamliners with engines made by General Electric (GE).
It is the latest alert for an aircraft which has suffered a number of technical glitches since its launch, including overheating lithium-ion battery systems that caused the planes to be grounded worldwide for three months earlier this year.
The engine warning follows six incidents between April and November involving five 747-8s and one 787, all of which suffered temporary loss of thrust while flying at high altitude.
The problem was caused by a build-up of ice crystals, initially just behind the front fan, which ran through the engine, a GE spokesman said.
All of the aircraft landed at their planned destinations safely, he added.
Boeing has prohibited the affected aircraft from flying at high attitude within 50 nautical miles of thunderstorms that may contain ice crystals.
In response, Japan Airlines (JAL) pulled 787 Dreamliners from two international routes.
Other affected airlines include Lufthansa, United Airlines, an arm of United Continental Holdings and Cathay Pacific Airlines.
A spokesman for Boeing said: "Boeing and JAL share a commitment to the safety of passengers and crews on board our airplanes. We respect JAL's decision to suspend some 787 service on specific routes."
JAL said it will replace Dreamliners on its Tokyo-Delhi and Tokyo-Singapore flights with other types of aircraft.
It also dropped plans to introduce 787s to its Tokyo-Sydney route from December.
The company will continue to fly the aircraft on other international and domestic routes, which are unlikely to be affected by cumulonimbus clouds for the time being.
A spokesman for GE, which is working with Boeing on software modifications to the engine control system in a bid to eliminate the problems, said: "The aviation industry is experiencing a growing number of ice-crystal icing encounters in recent years as the population of large commercial airliners has grown, particularly in tropical regions of the world."
All 747-8s are powered by GE's GEnx engines, while 787s are powered either by GE units or the rival Trent 1000 made by Rolls-Royce.

Taken from Sky News website.
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Old 23rd Nov 2013, 23:07
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Already being discussed in Tech Log:

http://www.pprune.org/tech-log/52844...7-8-787-a.html
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Old 24th Nov 2013, 03:43
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Hazelnuts basically nailed it. The problem with Ice Crystal Icing (ICI) is that it's a relatively new phenomena and is poorly understood.
The FAA regulations don't even account for high altitude icing - I understand that EASA has an engine level regulation that's applicable, but I don't think anyone really knows how to show if they comply.

I've been "involved" in ICI issues for the last 10 years but I'm far from an expert (I probably know just enough to be dangerous ) but the threat is something like this:
Conventional icing involves super-cooled liquid hitting cold aircraft surfaces and freezing. Commercial jetliners have typically addressed this threat by heating the threatened surfaces. Conventional icing was not much of threat to the core of the engine because the surfaces were already warm.
Ice Crystal Icing is fundamentally different - it occurs where it is far too cold for super cooled liquid to exist. The ice crystals are extremely small and extremely cold. When they hit the typical cold aircraft surfaces they just bounce off (pilot reports often refer to 'rain on the windscreen' despite TAT way below freezing). However ice crystals in the core of the engine sometimes accumulate and freeze in areas of the engine that are normally far too warm for ice to form (as in 80+deg F/25+deg C). As I understand it (again, I'm not the expert ), the ice hits the warm surface, melts, then additional ice hits and cools the liquid water enough for it to refreeze.

When this ice sheds, it can quench the flame and/or cause impact damage to the compressor.

So far, we've seen ICI flameouts on the CF6-80C2, CF6-80E, PW2000, and the GEnx. The circumstances vary between the various engines (CF6 typically ices up during an idle descent, then a shed/flameout results during the accel for a level-off).

The first few GEnx-2B events resulted in short term rollbacks where the ice quenched the flame, but auto-relight got the fire back before the engine went sub-idle. However in the last couple events, there was also compressor damage, which is what got the regulators so excited. None of the affected engines (to date) have gone sub idle before they recovered, so technically they were not in-flight shutdowns, but with compressor damage there is a real threat of a common mode multiple engine power loss.

The current plan is to mitigate the risk with a software change that will open the bleed valves during ICI to dump enough of the ice overboard to prevent a problem. Time will tell if it's enough . A large part of the problem is that the conditions are nearly impossible to re-create on the ground (among other things they can't generate ice crystals that small). And even in the convective weather systems that can result in ICI issues, the actual conditions that adversely affect the engines are rare.

While it's true most of the events to date have been the GEnx-2B on the 747-8, the -2B engine has way more operational hours than the -1B on the 787. Since the -1B has also had an event, there is no reason to believe it's fundamentally different.

Now, as to why GEnx engines seem to have a problem and not RR Trent? Figure that one out and I'm sure GE has a fat paycheck waiting for you
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Old 24th Nov 2013, 07:08
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Sounds not dissimilar to the issues with the old Bristol Britannia large turboprop in the 1950s, which had engine icing issues near tropical thunderclouds that badly impacted its development. Although mainly ameliorated, it was never completely overcome in the lifetime of the engine/powerplant, and crews developed their own procedures for it. Maybe there are a few old Britannia flight engineers still around to advise GE !
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Old 24th Nov 2013, 09:56
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Or the roll-back phenomena that affected the ALF 502 engine on the BAe146 which left two aircraft gliding with all four shut down. Fortunately, on both occasions the crews managed to retrieve the situation. One of them got down to 2,500 feet (luckily out to sea) before they got a successful relight.
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