EAI in a climb and descent

[seifly]

In my 737 FCTM it is recomended to have EAI on in the climb and descent if there is a chance of icing but not in cruise. Would someone enlighten me on why no EAI in cruise?. Even in the 10 to -40c spread.:cool:

[de facto]

Read your fctm again and slooowwwly:ok:

[PantLoad]

Rule number one is to strictly follow your company's SOP. This is a legal requirement.

Generally, the rules are:

On the ground, when icing conditions may be encountered ("anticipated")or are encountered, use the engine anti-ice.

In flight, again, the use of engine anti-ice is required whenever icing conditions are encountered or are anticipated.

Usually, most manuals include the caveat to not wait until you actually begin to accrue ice before turning on the engine anti-ice. In fact, there is usually a specific procedure for turning on the engine anti-ice when it is realized that you already have ice.

So, what criteria constitute 'icing conditions'?

Again, read your company's SOP...read your flight manuals...for this definition.

But, generally, when on the ground, if you have precipitation of any kind and the temperature on the ground is +10 or less (not "below ten", but plus ten or less), you should use engine anti-ice. Or, if in low visibility and the temperature on the ground is +10 or less. For the purpose of using engine anti-ice on the ground, low visibility, in the U.S, is defined as one statute mile or less. So, foggy conditions would be one example of this.

Keep in mind that, puddles of water, snow patches, wet or damp surfaces...all...constitute an icing hazard to engines when the temperature is +10 or less. So, it may be a pretty, sunny day, but if you're taxiing over water puddles, snow patches, wet or damp surfaces and the temperature is +10 or less, the engines may pick up ice.

In flight, we look at both the TAT and SAT. Again, +10 or less is the magic number. There are exceptions!!!! Let me explain....

Normally, "during climb or cruise", if in moisture, if the SAT is colder than minus 40, we don't have to use engine anti-ice. However, during descent, we would use engine anti-ice, if in moisture, regardless of the SAT (as long as the TAT is +10 or less).

The exception to the above is, if operating in or near CBs (TRW), we would use engine anti-ice, assuming the TAT is +10 or less, regardless of phase of flight, regardless of SAT.

All of the above is delineated in both my former company's SOPs (I'm retired.) and the Airbus manuals (FCTM and FCOM). It's been many years since I've flown a Boeing, but, if my memory serves me correctly, the above general rules apply to Boeing, as well.

A common error and misconception occurs when, during cruise, pilots are hesitant to turn on the engine anti-ice. Their interpretation of the rules is that use of engine anti-ice is expressly prohibited during cruise if the SAT is below minus 40.

Not quite the case.... The problem with turning on anti-ice at cruise is that, under certain circumstances, turning on the engine anit-ice reduces the amount of thrust available....thrust that may be needed to keep the thing flying at high weights, high altitudes, etc. We generally try to fly at the 'optimum altutude' for fuel economy, and under certain circumstances, total thrust available may be an issue. Add turbulence due to flying in and around CBs and TRWs (which you shouldn't do, anyway, but we all have at one point or another in our careers)...speed decays...thrust comes up to compensate....not enough thrust available with the engine anti-ice on....well, you get the picture. But, on the other hand, the thrust becomes greatly limited when all engines flame out....:rolleyes:.

Many problems occur when flying in or near CBs and TRWs in tropical climates. There have been several incidents where engines have flamed out....most have involved the CF6 engine, most were during descent (thrust idle or close to idle), visible moisture, and SAT colder than minus 40. In almost all cases, the crew followed the SOP and had the engine anti-ice on. Despite this, there were still problems.

In tropical climates, where the tropopause is very high, CBs and TRWs grow very tall. In these climates, there is a lot of moisture. That is to say, the clouds are relatively wet. (as opposed to a TRW over Minnesota in March) In these cases, there is a lot of 'wet' packets of moisture at high altitudes and at low temperatures. Again, during descent, when the thrust settings are low...when flying in these conditions...be sure to have the anti-ice on. Or, as the Airbus FCTM suggests, even during cruise, in these conditions, run the engine anti-ice.

Hope this helps...hope this answers some of your questions.


Fly safe,

PantLoad

[seifly]

Tanx for the answer.However my confusion arose from reading the FCTM and the limitation from vol.1.The FCTM states under a note in the climb,cruse...section "The EAI system should be turned on whenever icing conditions exist or are anticipated. Failure to follow the recommended anti ice procedures can result in engine stall, over temp or engine damage".And from the limitations page "Engine TAI must be on when icing conditions exist or are anticipated,EXCEPT DURING CLIMB AND CRUISE below -40C SAT".:ugh:

[de facto]

So?
What is it you dont understand?its clear.:suspect:

[ImbracableCrunk]

I think he's got it now.

[JABBARA]

Seifly,

I will try to explain with my poor English:

Contrary to what is known, suspended water in the air does not turn to form of ice at 0C or below. It needs a surface to change into ice format. In another word, a water droplet at -20C is still in liquid form until it hits to aircraft surface, sticks and freezes: Icing.

However around -40C, the water does not need to find a surface to freeze, it freezes on its own. Then, when it hits to an airplane it cannot stick but bounces away: No icing

While climbing, once you see -40C, no more TAI is needed becuse as you climb OAT will be even colder. While cruising, as long as OAT -40C or below no TAI is needed too.

While you are descending the things are different, even the OAT is -45C now (no icing possible), it will be warmer than -40 C soon as you keep descending (icing is anticipated). So TAI is needed now, as you are starting to descent even OAT is colder then -40C

Regards

[PantLoad]

Please refer to the Airbus FCTM SI-010 P 4/16 dated 15 JUN 10.



Fly safe,


PantLoad

[Luckyguy]

"below -40" = COLDER than -40

i.e. -41 or colder !

However, during descent (low thrust setting) the EAI must be on in icing conditions at ANY temperature regardless of the SAT. Of course, not if the TAT is greater (warmer) than +10. This is due to the much greater incidence of icing occurring at low thrust settings.

Any clearer ?

Best regards

[Checkboard]

This is due to the much greater incidence of icing occurring at low thrust settings.

Really? :hmm:

It's because, as you are descending, the chance of forgetting to turn on the ice when the temperature warms beyond the -40ºC limit is to great to worry about the tiny amount of extra fuel it takes to turn it on as you enter the cloud.

Entering the cloud is a strong trigger - the temperature warming past -40ºC is a very weak one.

[de facto]

It's because, as you are descending, the chance of forgetting to turn on the ice when the temperature warms beyond the -40ºC limit is to great to worry about the tiny amount of extra fuel it takes to turn it on as you enter the cloud.

Puuuuuure bollocks:ugh:
Have you heard of ice crystals at temps way below -40c?
During descent at low thrust,these crystals will accumulate in the compressor area and bang bang here goes your stall/engine fail.

[Checkboard]

Puuuuuure bollocks
Have you heard of ice crystals at temps way below -40c?
During descent at low thrust,these crystals will accumulate in the compressor area and bang bang here goes your stall/engine fail.

Rubbish! Microscopic ice crystals "accumulating" in a compressor! :rolleyes:

I suggest you take you "carby ice" understanding of jets, or mis-remembered understanding of volcanic ash back to the world of Cessna 172s. :rolleyes:

I don't know if you are aware - but the engine anti-ice on a jet engine only de-ices the COWL (and sometimes the spinner) :rolleyes:

It is used to prevent ice build up on the cowl, which then leaves the cowl in chunks big enough to damage the fan. It does not warm or change the air (or ice or water) entering the engine in any way.

[de facto]

Seriously?
May i suggest you educate yourself by googling BOEING (not cessna) 'the ice crystal weather,threat to engines'
Then come back here:E
I don't know if you are aware - but the engine anti-ice on a jet engine only de-ices the COWL
Its main function is not to deice but anti ice the cowl,but you know that.

Or maybe you are right,sorry i missed the fcom note:'operate the EAI at temp below --40c during descent in case your old fart of a captain forgets to switch it ON in due course':hmm:

[kellykelpie]

Must admit that I thought the same as Old Checky. Learn something new every day:8

[de facto]

Kelly,

Dont feel bad, i aint flying 172s for a living.:p
If the old fart learnt some out of it,we are all winners.

[PantLoad]

Yep, it's another Airbus publication....the one about buiding ice crystals with low thrust settings with temps colder than -40. No kidding.

Will try to locate it and cite it, but you gentlemen can do a little research yourselves.

Has nothing to do with remembering or forgetting....

And, if you'll read the above-cited Airbus FCTM page, you'll see that, even in climb and cruise, you should use engine anti-ice with temps colder than -40 (if in or around CBs/TRWs). Yep, it's all there in black and white! Again, no kidding!


Fly safe,

PantLoad

[PantLoad]

Found it!

Airbus
15th Performance and Operations Conference
Puerto Vallarta, 23-27 APR 2007
Operation in Icing Conditions in Flight
Ice Crystals: An Environmental Threat
Presented by Helele Rebel
Head of A330/A340 Operational Standard

Easily obtained by the magic of the internet.....


Fly safe,


PantLoad

[Checkboard]

May i suggest you educate yourself by googling BOEING (not cessna) 'the ice crystal weather,threat to engines'
Then come back here:E
OK - been there, done that. Have you Googled and read it yourself?

The Ice Crystal Weather Threat to Engines (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC4QFjAB&url=http%3A%2F%2Fwww.captainpilot.com%2Ffiles%2FCOLD%2520WEA THER%2FIceCrystalWeatherThreatToEngines.pdf&ei=IZmUT_KcJMWv8QPGk8z2DA&usg=AFQjCNHky368PsaBOz9twM8zzk7hK7KTbw)

The presentation concerns engine rollback and flameout occurrences from ingesting supercooled water (ice crystals) above the certification limit of 2 gm/m³. It is warning you not to overfly large convective weather systems where these concentrations may occur, even though weather radar may show little to no return.

You're right, I hadn't read it - and I found it interesting.

More importantly, relating to this discussion, it has nothing to do with engine cowl anti-ice operation. As the engine cowl anti-ice doesn't affect the ice entering the engine, operating the cowl anti-ice will not help you in the described situation, and thus isn't a reason to use anti-ice on the descent at temperatures below -40ºC.

[JABBARA]

I agree with Checkboard,

I have different PDFs and PPTs about Ice Crystal Icing. In fact, the previous company I worked had an incident of dual engine flame out near Shanghai around 5 years back. The searches about Ice Crystal Icing is around 10 years and mostly theoretical; they believe but not prooved, how it happens. However the EAI using procedure during descent was the same as now, when I started to my Airline life 20yrs ago with B 737.

From B 737 (same as A 330)
Engine anti–ice must be ON during all flight operations when icing
conditions exist or are anticipated, except during climb and cruise when
the temperature is below –40°C SAT. Engine anti–ice must be ON prior to,
and during, descent in all icing conditions, including temperatures below
–40°C SAT.

Regards