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

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.

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";)

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.

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.

If I were you, I'd do my homework before spreading falsehood.
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...:rolleyes:

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.

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.

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.

It's not the Beechjet per se but its engines, JT15D's that appear susceptible to the ice crystal phenomenon. Same probably goes for the engines on the big transports, rather than the airframes they are attached to.

Very correct. But I am not sure if it is just a particular dash number of that engine that is susceptible and happens to be on the Beechjet(maybe only on the Beechjet) so I didn't want to say that engine in particular.

Thanks.

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.....

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.

hi,
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.

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.

I don't mean to pick the above quote apart, just to add on.

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.

Well said lomapaseo :ok:


Here is just another extract:

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

Hi

Thanks a lot for your helpful answers.:D
I was reading them and I found a lot of good information with good links.
More answers are welcome...:ok:

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!

Rainboe - you are confused by the meteorology you learnt all those decades ago. It is true that at temperatures below -40, the amount of water vapour that can be held in air is so small as to render super-cooled droplets irrelevant, and that is the basis for the existing guidance. HOWEVER, in conditions of strong convective or lenticular activity, sc droplets can be carried aloft into temperatures well below -40. Ice crystals are also a threat to engines at those temperatures as you should have read on these very forums. Things HAVE changed. You will do what you are used to over '40 years', of course. Others take note of new information and learn. Out of interest, what do you see as the problem in using anti-ice in relevant high-level cloud at temperatures below -40, apart from a very small fuel penalty and the fact that you will no doubt have noticed over the years that the 'bible' does not say you should not use it?

well, Rainboe...
 

would humbly suggest, you try to "get some updates" for your 40 year old SOPs..

to call a Boeing AERO article "dodgy accident connections and theoretical papers"..well, how about you contact Boeing and try to set them straight???

strange perceptions you have..

Really...? The question (and this topic in general) is actually far more complicated for anyone on this forum.
But that was a good opportunity to review/discover/share thoughts on that phenomenon and its operational impact.

As for the OP, try not to speak on his behalf, that would be a good start.

to Rainboe
 

Though your comment wasn't necessarily directed at me, I didn't make reference to a theoretical paper on my previous post but rather a direct quote from the 'Boeing Flight Crew Operations' manual and said 'Bulletin' is still (IE) 'In Effect' so as far as conventional wisdom suggests perhaps a buzz to Tech Pilot or Tech Dept of one's largest airline to ask for Boeing's latest bulletin updates is in order.

Furthermore, I don't think that ice crystals have the ability to distinguish between aircraft or engine types.

Blue skies,

MC

I'm sure that Rainboe has big enough shoulders to withstand a little critical comment. However, I would ask that we keep criticism to objective comment and not allow it to move into subjective pejorative .. ie "play the ball .. not the player"

Quote:

---

For those flying on the bus, FCTM says to turn Engine Anti Ice ON when flying near CBs even if TAT is <-40°c ! that's mainly because of ice particle icing (e.g. in an anvil).

---

Is there are more current version of the FCTM, or was that a Typo?

FCTM 04.010... (A320) July 2008 Version
FCTM 5.10.5... (A330, A340) 2006 Version


In climb or cruise, when the SAT decreases to lower than -40 °C, engine anti-ice should be turned off, unless flying near CBs..."

Also.....

FCOM 3.4.30 (Rev 39)

"...icing conditions may be expected when the OAT (on ground and for take-off), or when the TAT (in flight) is at or below 10 c, and there is visible moisture in the air (such as clouds, fog with low visibility of one mile or less, rain, snow, sleet, ice crystals) or standing water..."

Quote:

---

Could we say the same for flying trough ICE crystals?

---

Someone had mentioned earlier that the query related to Boeing, thus the "Boeing Bulletin" would apply. But, it's interesting to note that Airbus seems to agree (...Ice Crystals...).

Like some other examples between the two, Airbus says "do this, don't do that," Boeing tells you why.

Let's try again,
Some of you are quoting Airbus procedures and some are quoting from theoretical papers, not official documents. All I see are up-to-date procedures from my OMB Procedures.

I have spent much of a 38 year career flogging up and down over the depths of Africa at night through Cbs, and across the ITCZ in the Indian Ocean. Once below -40C, anti-icing never went on. Even in severe turbulence and precipitation, forget 'near Cbs, this is in them. Until I see my manuals changed to reflect advice, I don't see that a problem has been proved that aeroplanes cannot handle it. Strange and weird some of you chose to respond to this with personal insults! I've spent a career there. I see no problem with current standard procedures and advice. I'm afraid I am too busy working to go reading theoretical papers and unsubstantiated and unproven theoretical possible accident causes. The advice has not let down me or BA in at least 40 years that I know of.

When the manuals change, I will be happy to amend my procedures, but I am not taking anonymous advice from posters who seem hung up on theoretical papers or private accident theories, or trying to use home-grown procedures pending what might be future procedure changes. I have yet to see anything 'official' despite the over-reaction of some of you who don't appear to understand what working to a manual and 'established' procedures means.

I don't intend discussing this further. I have given the official Boeing line. One wishes one hadn't bothered answering in the first place. The chap just need an answer to a simple query- instead of 'yes' or 'no', he gets 2 pages of unproven theories and Airbus procedures!

Touchy Subject...
 

Gentlemen,

Obviously, this has become a sensitive topic....for whatever reason.
So, I will emphasize that we all need to follow our company's SOPs,
regardless of what manufacturers say, regardless of PPrune says.
I'm sure I don't need to explain why the SOP is most important.

I'll say no more, except to answer the question of which issue of the
Airbus FCTM I reference.

It's: A-320 Airbus Flight Crew Training Manual, "Supplementary Information" Section SI-010 P4/16 Issue date: 24 JUN 09.
(This is the latest page issue from Airbus.)


Fly safe,

PantLoad

Sorry, was refering to the quote by "Shortfuel" (post #7)

Jimmy,
Definitely a typo :E (I meant SAT).



Rainboe,

Telling people that ice does not form anywhere on the engine below -40°C is a falsehood due to your ignorance on this topic (?).
Happy flying in African CBs! But interesting attitude of yours "I did it many times, nothing happened to me".
BTW, there was no personal insult on this thread.

What's odd about this, is that a group of people who are supposed to be trained in CRM, etc, have such a difficult time accepting someone elses point of view when it contradicts their own.

I recall, albeit, from a long time ago "...agree to disagree...but respect each others opinions" What ever happened to that? :confused:

-------------------------------


Figured as much. Cheers:ok:

One last time! I have never seen ice below -40C in over 20,000 hours flying, and do not accept it actually forms. Neither does both my airlines, which publish manuals telling me such and a procedure to follow which has been followed and never known to be substandard. My 'ignorance' or your dunderheaded refusal to accept current procedures?

If Airbus has a problem with pitot tubes, I would like to see proof and new procedures. But I know nothing about Airbuses, or any wish to learn!

If you can't sustain a contradictory debate, don't bother replying.

I just assumed you were ignorant on that topic (hence the "?"). Nobody called you ignorant.

As far as I know, BA does not edict the laws of physics, do they?

I dont' really care about your company procedures and I never intented to convince you. The OP asked about a MET/physics related phenomenon and you peremptorily answered with your outdated (my opinion) company procedure based on a false statement.

Icing (not supercooled water icing with Liquid Water Content but ice particle icing) can form below -40°c in particular conditions wether you like it or not and crystal icing is a potential threat for aviation ops (and that statement is not from me, it's from Boeing / GE / NASA / FSF...).

[Airbus had many problems with certain pitot tubes, as for the proof, you have google or EASA AD section ;) ]

Rainboe. I agree with you! But, if I had said it, it would have gone like this....

I have never seen ice FORM below -40C in over 20,000 hours flying. Below -40C, I've only ever flown in Clear skys, or Ice!

Sorry, I don't agree.

Then, along comes someone (Boeing) and says that we can take that ice (or water vapour) and heat it up; thus melting it within the engine(Simple summary). Okay, turn the Anti-ice on.

Is it that complicated?

Bottom line. Employer pays me $XXXXX per month to fly their airplane, their way. If they want engine anti-ice on below -40c, and they publish that requirment in an approved document (FCOM, SOP, etc), I'll do it. Just keep the paycheck coming.

Oddments:


- It's known that in the last decade or so, there have been 100ish incidents of engine rollback in conditions which are consistent with high IWC (iced water content).

- High IWC is different to icing conditions.

- Experience says that high IWC is not readily visible from a cockpit, and that the instrumentation to detect it is only fitted to a handful of specialist research aeroplanes around the world.

- NASA is currently pursuing a research programme into this. It's in several parts but will include flying one or more research aeroplanes to look into what conditions exist where. An out of date news article here suggests use of a modified S3 Viking, although I have a little inside knowledge which suggests that it'll now be something else - as yet undecided.

- NASA is working with FAA and the Australian Bureau of Meteorology of the programme. This is because they want to look at flying in the vicinity of Darwin where they've got a good combination of ground facilities and weather.

- The concern is about core and compressor stator icing due to partial melting then congealing of iced water crystals. The mechanism isn't well understood but it's believed that where it occurs it takes some time (15 minutes has been quoted to me) to start to get an appreciable power loss. So, you'd have to stay in those conditions for some time.

- They aren't worried about airframe or intake icing - those are well understood, and all airliners have adequate information about their avoidance and treatment. This is something quite new.

G

I have never seen ice form inside an engine, period and am unlikely to ever do so. Doesn't mean I'm going to wait until I personally experience a rollback or flame out in conditions where ice should not form, or discount the ice crystal phenomenon or ignore manufacturers recommendations to counter the risk.

Alejandro - now that Rainboe has (finally?) left this thread, may I summarise?

You asked in #1 about a phenomonen (ice crystal icing) about which some posters know nothing because it is not in their 'drivers' handbook' Others do, including major engine and aircraft manufacturers. Good on you for asking. Please take note that it is thought to be a significant occurrence. Manuals will eventually be amended if it is thought necessary. There is information published by various manufacturers which obviously has not reached the third level airlines yet.

It is up to you how you progress this. Keep an open mind and keep asking questions and looking for information.

As a final thought, it is only in the last 20 years or so that the legal requirement for London Taxis ('Hackney carriages') to carry a bale of hay in the back for the horse has been dropped. Progress indeed. It is true that not a single horse ran out of hay in a motorised London taxi in the years the law was in place.

A look back at the first post shows that the original question appears to be in general and not about a specific type. Despite claims that it is only from a Boeing point of view, that original poster may go onto other aircraft. Other people reading this thread may be on different types and when they read from a supposedly experienced type that ice is NOT going to happen below -40, they may believe it.

Examples are given showing that engines have been flaming out and aircraft involved in serious incidents much more than previously thought, yet the accusation is made that they are from "dodgy accident connections and theoretical papers" even though a Boeing magazine is quoted.

Then it is said that in 38 years of flying, icing below -40 has never been experienced even though this thread is about unseen icing in engines from ice crystals that don't accumulate on the airframe. 99% of us or more have likely never seen such icing either.

I am going to post a link to perhaps another dodgy accident connection. That is the NTSB. It talks about several of these incidents. One of them, a Beechjet was at FL 380 with a static OAT of -57°C as read in the actual accident report.

http://www.ntsb.gov/recs/letters/2006/A06_56_59.pdf

I think the original poster and others have more than one thing to learn about on this thread. One from a technical point of view and another from a human factors point of view on aviation hazards. And remember, what happens on one aircraft can be much different to what the same effect does to another aircraft. Also remember remember that over the course of your career you will receive much false/misleading information from others that you talk to.

Here are some quotes.

"The Safety Board is well aware of the threat that ice crystals can pose to turbine engines. On June 4, 2002, Spirit Airlines flight 970, a Boeing MD-82 airplane,15 experienced a dual-engine flameout of its Pratt & Whitney JT8D-219 engines after high altitude ice crystals blocked the engines’ inlet pressure probes while the airplane was in cruise flight at FL 330."

"During the investigation of the dual-engine flameout events, it was learned that a general perception exists among flight crews of airplanes that fly at high altitudes that ice is not a threat at the higher altitudes because it is “too cold.” This perception is reinforced by the fact that the ice crystals that are of concern do not accrete on the usual places that pilots look for ice such as the wings, windshield wiper blade arms, or the arm retaining bolts."

"The Safety Board notes that the problem of multi-engine losses of power due to icing is not limited to the JT15D-5 engine and that General Electric CF6-80 series engines have also experienced in-flight losses of power due to internal icing.

I'm pretty certain that Rainboe, like most experienced jet pilots is aware that, when flying in the proximity of convective systems, anvils and the like, all bets re icing are off and whilst I may not (manually for some types) switch on the engine anti-icing I'd be keeping an eye on the parameters.
A lot of the published material is engine specific, e.g. FAA document which refers to <<B767 & B747 aircraft fitted with GE CF6-80C2 and CF6-80A engines >> I note punkalouver's post also refers to P&W.

p.s. Rainboe, that's a pint you owe me ;)

The NTSB report does make this reference on page 8 of their report:

"The Safety Board is aware of a June 1, 2006, dual-engine flameout that occurred on a Qatar Airways A-330 airplane equipped with General Electric CF6-80E1 engines while the airplane was descending through IMC for landing at Shanghai, Peoples Republic of China."