ICE crystals
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ICE crystals
Hi
Flying through supercooled water means ICE formation...(That´s nothing new for us...)
Could we say the same for flying trough ICE crystals?
I dont mean to have ICE formation on aerodinamic surfaces while flying through ICE crystals conditions.
But what about the hot sections of the engine?
Thanks
Alejandro
Argentina
Flying through supercooled water means ICE formation...(That´s nothing new for us...)
Could we say the same for flying trough ICE crystals?
I dont mean to have ICE formation on aerodinamic surfaces while flying through ICE crystals conditions.
But what about the hot sections of the engine?
Thanks
Alejandro
Argentina
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No. Below -40 degrees C, ice does not form anywhere on the fuselage or engine. It is practice to never turn on engine or airframe anti-icing below -40 degrees C. Supercooled water cannot exist at below -40 degrees C as far as conventional wisdom says.
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well, there is
considerable research going on since quite a while..
and there have been engine problems that were presumably traced to "ice crystals"...small & large jets...
see the Boeing AERO article below..
me, still not sure whether that phenomenon just seems to pop up nowadays, because we may fly a tad too close to some convective weather at altitude at times..for whatever ill-advised reasons..
AERO - Engine Power Loss in Ice Crystal Conditions
can't help the feeling that these things have always been around, but maybe in earlier times farther away from planes....( remember the microburst debates & training and what you have in the 70's and early 80's...well CBs have produced microbursts before humankind..'s just that not so many folks had tried to land or take-off during thunderstorms before..)
but maybe I'm all wrong and it can be all attributed to "climate change"
and there have been engine problems that were presumably traced to "ice crystals"...small & large jets...
see the Boeing AERO article below..
me, still not sure whether that phenomenon just seems to pop up nowadays, because we may fly a tad too close to some convective weather at altitude at times..for whatever ill-advised reasons..
AERO - Engine Power Loss in Ice Crystal Conditions
can't help the feeling that these things have always been around, but maybe in earlier times farther away from planes....( remember the microburst debates & training and what you have in the 70's and early 80's...well CBs have produced microbursts before humankind..'s just that not so many folks had tried to land or take-off during thunderstorms before..)
but maybe I'm all wrong and it can be all attributed to "climate change"
See the links in this post http://www.pprune.org/tech-log/37634...ml#post5027449
Ice crystals will normally bounce-off both cold and heated surfaces; however, on some heated surfaces if the crystals are slowed down by airflow disturbance, closed curves, etc, then depending on several variables (particularly heat flow) then some of the ice may melt and the water traps other particles resulting in ice accumulation.
This is not normally a problem for engines except in exceptional circumstances, i.e. near large Cbs.
Ice crystals will normally bounce-off both cold and heated surfaces; however, on some heated surfaces if the crystals are slowed down by airflow disturbance, closed curves, etc, then depending on several variables (particularly heat flow) then some of the ice may melt and the water traps other particles resulting in ice accumulation.
This is not normally a problem for engines except in exceptional circumstances, i.e. near large Cbs.
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Based on IGh's post...
...the correct action would be to start a descent and turning on Engine Anti-Ice protection?
BTW, there have been lots of rumours about what happened to WCW708 in Venezuela, but no "official" response to the question "What happened to that airplane?". Although ice has always been on the table as a cause of the crash.
BTW, there have been lots of rumours about what happened to WCW708 in Venezuela, but no "official" response to the question "What happened to that airplane?". Although ice has always been on the table as a cause of the crash.
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Originally Posted by Rainboe
No. Below -40 degrees C, ice does not form anywhere on the fuselage or engine. It is practice to never turn on engine or airframe anti-icing below -40 degrees C.
The problem among our pilot community is that we actually know little about ice particle (or ice crystal) icing.
For those flying on the bus, FCTM says to turn Engine Anti Ice ON when flying near CBs even if SAT is <-40°c ! that's mainly because of ice particle icing (e.g. in an anvil).
Thalès pitot probes -AA (AF447) series seemed very sensitive to that particular phenomenon, given their ASR history.
Most Ice particle types are not detectable by Wx radar. When in it, pilots are often misleaded by the sound of melted ice particles on the windshield (if any) that is wrongly interpreted as rain or hail...
Ice particle phenomenon is quite a new study field (less than 5 years). Those MET conditions being very difficult to recreate in a lab, thus modeling.
In flight, as said by safetypee, it's usually around deep convective cells.
I suggest these readings:
Ice particle threat to engines in flight
FSF article about Ice Crystal Icing
PPS by Jeanne Mason, a (the?) specialist of ice particle icing
Correct course of action...
I would say it depends on the icing severity. Sometimes it could as subtle as an anomalous TAT reading that you won't even notice in cruise.
In a case of powerloss, with EPR engines, it could be difficult to discriminate between an actual icing of compressor stage(s) or just a severe TAT cloging.
I would say, (E/AI ON, disconnect A/THR) get out of those conditions first (descend most probably), see after.
But I am not Mr Airbus or Boeing, so...
Last edited by shortfuel; 19th Jul 2009 at 09:55. Reason: TAT corrected to SAT in the text
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The Wall Street Journal had published an article in its April 7,2008 edition titled "Airline Regulators Grapple With Engine-Shutdown Peril." It's about the ice in the engine. I think these may of been the cause of an engine flameout in a Lear 25 years ago in a flight from the Bahammas to Boston for a company I had once worked for.
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The problem with Pprune is there are so many people here that if you say white is white, some smart Alec will prove that in certain circumstances, white is, actually, black, don't you know? We now get Airbus advice, and me told to do my homework, when such advice does not appear in the Boeing handbook. We are given unproven evidence from 2 crashes where icing may have been a factor, but it is unproven, and anybody quoting that as support for a wider definition is skating on thin ice! If you pardon the expression.
The OP asked a simple question which has been overcomplicated by numerous 'experts' here, quoting a totally different type. A little research about the OP would reveal he is evidently learning from a Boeing POV, not Airbus, and that was where my answer was based. There is no need to needlessly complicate for a foreign speaking poster- he was asking from an inexperienced learner working from a Boeing perspective, not Airbus, and that was the perspective my answer. So thanks for the lesson, but not needed, or desired, in this thread.
Now how does Antonov and Ilyushin play it then? Any advance on Tristars and Embraer? It's getting frightening to answer any queries here because there are always pedants who will prove your answer wrong for a type that is not even being asked about.
The OP asked a simple question which has been overcomplicated by numerous 'experts' here, quoting a totally different type. A little research about the OP would reveal he is evidently learning from a Boeing POV, not Airbus, and that was where my answer was based. There is no need to needlessly complicate for a foreign speaking poster- he was asking from an inexperienced learner working from a Boeing perspective, not Airbus, and that was the perspective my answer. So thanks for the lesson, but not needed, or desired, in this thread.
Now how does Antonov and Ilyushin play it then? Any advance on Tristars and Embraer? It's getting frightening to answer any queries here because there are always pedants who will prove your answer wrong for a type that is not even being asked about.
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I think perhaps the problem is with you. I believe you said "Below -40 degrees C, ice does not form anywhere on the fuselage or engine". Someone could misinterpret with unfortunate consequences.
The first line in the Boeing Aero magazine says "Since 1990, there have been at least 100 jet engine power-loss events on both commuter and large transport airplanes, mostly at altitudes higher than 22,000 feet, the highest altitude where airframe icing is expected to exist.". Some have been below -40. Then it goes on to explain the ice crystal phenomenon.
The Beechjet appears to be particularly susceptible.
I suggest you read and then realize that it is a strength to be able to admit when you are wrong.
The first line in the Boeing Aero magazine says "Since 1990, there have been at least 100 jet engine power-loss events on both commuter and large transport airplanes, mostly at altitudes higher than 22,000 feet, the highest altitude where airframe icing is expected to exist.". Some have been below -40. Then it goes on to explain the ice crystal phenomenon.
The Beechjet appears to be particularly susceptible.
I suggest you read and then realize that it is a strength to be able to admit when you are wrong.
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The Beechjet appears to be particularly susceptible.
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Thanks.
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Not quite correct....
Not quite correct: Ice cannot form when temps are below -40c.
Please read the Airbus FCTM with regard to this. You will find that
the procedure is to NOT use anti-ice systems during climb or cruise
when the OAT is below -40C except when flying in areas of CBs.
So, with this, there is to be noted exceptions to this "minus 40 rule".
First, this applies only to climb and cruise. Second, this applies only
if not in the vicinity of convective activity.
Other posts, so far, list the reasons why......
Fly safe,
PantLoad
post script.....It was SOP at my former company (I've retired several years ago.) to follow the above-mentioned rule. And, we flew the Boeing
(with JT8D, CFM 56, and CF6) as well as Airbus (with CFM and Pratts on the 330).
By the way, there was an excellent article from Airbus....will try to find it...about flameouts at high-altitudes on CF6s. What was happening
was, during initial descent, at temps well below -40C, the engines were
flaming out. If I recall the article, it mentioned that most of the events
occurred in tropical climates where CBs were present. In every case,
engine anti-ice was not selected at top-of-descent....when in visible
moisture...but OAT less than -40c.
Interesting.....
Please read the Airbus FCTM with regard to this. You will find that
the procedure is to NOT use anti-ice systems during climb or cruise
when the OAT is below -40C except when flying in areas of CBs.
So, with this, there is to be noted exceptions to this "minus 40 rule".
First, this applies only to climb and cruise. Second, this applies only
if not in the vicinity of convective activity.
Other posts, so far, list the reasons why......
Fly safe,
PantLoad
post script.....It was SOP at my former company (I've retired several years ago.) to follow the above-mentioned rule. And, we flew the Boeing
(with JT8D, CFM 56, and CF6) as well as Airbus (with CFM and Pratts on the 330).
By the way, there was an excellent article from Airbus....will try to find it...about flameouts at high-altitudes on CF6s. What was happening
was, during initial descent, at temps well below -40C, the engines were
flaming out. If I recall the article, it mentioned that most of the events
occurred in tropical climates where CBs were present. In every case,
engine anti-ice was not selected at top-of-descent....when in visible
moisture...but OAT less than -40c.
Interesting.....
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I've been flying 737, 747 and 757 for 32 years, and procedure in one of the worlds largest airlines has always been, 'below -40C, anti-icing is not needed, unless you are in a descent, where it may be switched on in anticipation of entering icing conditions'. That, is standard procedure. I don't recall it ever failing in all that time.
I really have no idea about special Airbus definitions or requirements. I still don't understand thottles that don't move. The OP is asking about Boeings as evidently that is what he is studying. If you are going to take the trouble to answer his query, it is worth seeing where he is coming from and not confuse him with other types' special procedures.
I really have no idea about special Airbus definitions or requirements. I still don't understand thottles that don't move. The OP is asking about Boeings as evidently that is what he is studying. If you are going to take the trouble to answer his query, it is worth seeing where he is coming from and not confuse him with other types' special procedures.
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I've been flying 737, 747 and 757 for 32 years, and procedure in one of the worlds largest airlines has always been, 'below -40C, anti-icing is not needed, unless you are in a descent, where it may be switched on in anticipation of entering icing conditions'. That, is standard procedure. I don't recall it ever failing in all that time.
you might have followed a wrong SOP during 32 years as I did until now on both Boeing & Airbus. Same with wrong check-list amended after accidents. By the way, what I teach to my experienced trainees is to follow the SOPs unless you know or have a well founfed reason to think that it is unsafe. Some pilots write the books and others have to cope with bad literature in the air.
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Originally Posted by Rainboe
The OP is asking about Boeings as evidently that is what he is studying
Question was about possible crystal icing on hot sections of engine.
And don't worry, your SOP will be amended soon by Boeing (if not already), you might even get a tech bulletin on crystal icing.
I didn't know that Boeing was an engine manufacturer, as you really insist that is a type related question...
Question was about possible crystal icing on hot sections of engine.
And don't worry, your SOP will be amended soon by Boeing (if not already), you might even get a tech bulletin on crystal icing.
Question was about possible crystal icing on hot sections of engine.
And don't worry, your SOP will be amended soon by Boeing (if not already), you might even get a tech bulletin on crystal icing.
Boeing and Airbus etc. both have the advantage of knowing all the ins and outs of engine icing just simply due to their oversight of the various engine manufacturers products.
Ice is not unique to any one engine, however the response of the engine to ice may be unique to where it does accrete and how big it is when it sheds. I use the word shed because with today's gas turbines it doesn't melt before it is blown off the surface simply by windage. In some cases the ice buildup and shed is big enough to damage the compressor blades and cause enough damage to cause an engine stall or rundown in RPM (flameouts are rare). In other cases if the ice blocks an important engine sensor the engine begins to lose its mind (FADEC is confused).
There isn't much you can do to avoid ice crystals if you are flying over the top of weather. The engine manufacturers through Boeing and Airbus can advise you on how to handle the engine once it has exhibited symptoms so forget about all these words of wisdom (including my own) and follow the updated procedures.
I will admit that I was confused about the original question and its use of the word "hot sections". I tend to associate that definition with areas in the engine behind the burner. However if the question was about metal temperatures on probes and vanes simply above the melting point of ice > 32F then this thread discussion applies.
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Well said lomapaseo 
Here is just another extract:
Here is just another extract:
Originally Posted by Mason/Strapp/Chow research
The actual mechanism for engine powerloss takes many forms, depending on the engine. Each engine’s overall
stability is a balance between compressor stability, combustor stability, and the fuel available for acceleration.
The component that is the mechanism for failure is the element with the least margin to cope with an ice ingestion, and varies by engine type. All of the following mechanisms have occurred:
• Engine surge and stall: ice shed into the compressor can drive the engine into stall due to the combined
effect of the lost inertial and heat energy to the ice, and the inefficiency of the airfoils having ice on them.
The scenario begins with a compressor surge (a sudden flow reversal) followed by stall (engine rotor
speeds decay), as airflow is reduced due the presence of one or more compressor stages with localized
airflow separation. The combustor remains lit, and due to the lack of airflow, exhaust gas temperature
(EGT) typically rises quickly.
• Flameout: quenching of the combustor following the ingestion a quantity of ice.
• Engine damage: engine blades and vanes can become damaged as shed ice impacts them. Typically minor blade tip curl is the only damage present owever, rare instances of blade release have occurred. Damage has also occurred without any other symptom.
The event data indicate that following the powerloss, all engines were restarted. Even in the rare cases where the engine was damaged, those engines were restarted and operated normally for the remainder of the flight. Typically the encounter with high concentrations of ice particles is relatively brief, as inferred from TAT anomaly data...[...]...In all cases, once the aircraft exited the ice particle conditions, and descended to the restart envelope, the engine was restarted.
stability is a balance between compressor stability, combustor stability, and the fuel available for acceleration.
The component that is the mechanism for failure is the element with the least margin to cope with an ice ingestion, and varies by engine type. All of the following mechanisms have occurred:
• Engine surge and stall: ice shed into the compressor can drive the engine into stall due to the combined
effect of the lost inertial and heat energy to the ice, and the inefficiency of the airfoils having ice on them.
The scenario begins with a compressor surge (a sudden flow reversal) followed by stall (engine rotor
speeds decay), as airflow is reduced due the presence of one or more compressor stages with localized
airflow separation. The combustor remains lit, and due to the lack of airflow, exhaust gas temperature
(EGT) typically rises quickly.
• Flameout: quenching of the combustor following the ingestion a quantity of ice.
• Engine damage: engine blades and vanes can become damaged as shed ice impacts them. Typically minor blade tip curl is the only damage present owever, rare instances of blade release have occurred. Damage has also occurred without any other symptom.
The event data indicate that following the powerloss, all engines were restarted. Even in the rare cases where the engine was damaged, those engines were restarted and operated normally for the remainder of the flight. Typically the encounter with high concentrations of ice particles is relatively brief, as inferred from TAT anomaly data...[...]...In all cases, once the aircraft exited the ice particle conditions, and descended to the restart envelope, the engine was restarted.
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Just to add on to this friendly and interesting query and not trying to be a smart Alec but 'shortfuel' is right, there has been a tech bulleting around for a 'little while'.
- Important excerpts and 'updated procedures' only, cause it would take me all week to try and reproduce it all here, hehe.
_________________________________________________
'From Boeing Ops Manual Bulletin
Number: JDE-8
Dated: June 15, 2007.
Subject: Engine Flameout Protection
__________________________________________________
BACKGROUND INFORMATION
- Boeing and GE have investigated 21 engine flameout events which have occurred on various airplane models since 1991. Investigation of weather flight data and pilot reports associated with these events suggests the flameouts occurred between 11,500 and 33,00 feet in the vicinity of thunderstorms.
- Boeing and GE investigations conclude the event airplanes most likely encountered ICE crystals lifted by convective activity prior to the engine flameout.
-At very cold temperatures near thunderstorms the airplane can encounter visible moisture made up of high concentrations of small ICE crystals.
-These ICE crystals do not cause weather returns.
-These ICE crystals do not accumulate on cold aircraft surfaces.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
OPERATING INSTRUCTIONS
ENGINE FLAMEOUT PROTECTION
Accomplish this procedure when:
- in visible moisture with TAT below -10C near convective weather systems, including thunderstorms, and
- thrust is reduced for a descent or speed reduction.
* * * THE ABOVE APPLIES EVEN WITH SAT BELOW -40C. * * *
PACK HIGH FLOW SWITCH...................................................... ....................ON
(Increases bleed air extraction to improve engine flameout margin.)
NACELLE ANTI-ICE SWITCHES ............................................................ .........ON
(Increases bleed air extraction to improve engine flameout margin.)
Return to a normal configuration when:
the above conditions no longer exist, or
the > ANTI-ICE message is displayed
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
For additional info and details, refer to Flight Operations Technical Bulletin 747-400-55,
Subject: Convective Weather Containing Ice Crystals Associated with Engine Power Loss and Damage, dated August 1, 2006.
____________________________________________________________ _______________
Happy contrails, everyone. Cheers!! =)
MC
- Important excerpts and 'updated procedures' only, cause it would take me all week to try and reproduce it all here, hehe.
_________________________________________________
'From Boeing Ops Manual Bulletin
Number: JDE-8
Dated: June 15, 2007.
Subject: Engine Flameout Protection
__________________________________________________
BACKGROUND INFORMATION
- Boeing and GE have investigated 21 engine flameout events which have occurred on various airplane models since 1991. Investigation of weather flight data and pilot reports associated with these events suggests the flameouts occurred between 11,500 and 33,00 feet in the vicinity of thunderstorms.
- Boeing and GE investigations conclude the event airplanes most likely encountered ICE crystals lifted by convective activity prior to the engine flameout.
-At very cold temperatures near thunderstorms the airplane can encounter visible moisture made up of high concentrations of small ICE crystals.
-These ICE crystals do not cause weather returns.
-These ICE crystals do not accumulate on cold aircraft surfaces.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
OPERATING INSTRUCTIONS
ENGINE FLAMEOUT PROTECTION
Accomplish this procedure when:
- in visible moisture with TAT below -10C near convective weather systems, including thunderstorms, and
- thrust is reduced for a descent or speed reduction.
* * * THE ABOVE APPLIES EVEN WITH SAT BELOW -40C. * * *
PACK HIGH FLOW SWITCH...................................................... ....................ON
(Increases bleed air extraction to improve engine flameout margin.)
NACELLE ANTI-ICE SWITCHES ............................................................ .........ON
(Increases bleed air extraction to improve engine flameout margin.)
Return to a normal configuration when:
the above conditions no longer exist, or
the > ANTI-ICE message is displayed
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
For additional info and details, refer to Flight Operations Technical Bulletin 747-400-55,
Subject: Convective Weather Containing Ice Crystals Associated with Engine Power Loss and Damage, dated August 1, 2006.
____________________________________________________________ _______________
Happy contrails, everyone. Cheers!! =)
MC
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Well I follow what is printed in my manuals, not quotations from theoretical papers, posted here by anonymous posters. What I gave to the OP was as written in my manuals and that is what I have always flown to, and they have not been amended yet (or failed me or the airline in 40 odd years)!
What you have done is to thoroughly confuse a learner after an uncomplicated answer. How hilarious I am accused of being 'wrong' by people quoting dodgy accident connections and theoretical papers!
What you have done is to thoroughly confuse a learner after an uncomplicated answer. How hilarious I am accused of being 'wrong' by people quoting dodgy accident connections and theoretical papers!