Engine Anti-Ice, "ON" at what temp?

[quid]

Making the assumption that you are at cruise levels in IMC, do you at some point turn the engine anti-ice "OFF"?

Some SOPs call for it Off at temps colder than -10C RAT, others leave it ON no matter how cold.

What does your company do?

[18-Wheeler]

In visible moisture, on at temps between +10°C TAT and -40°C SAT. Not required outside that range.

[pilotusa]

In addition to 18-Wheeler's response, some carriers require that engine anti-ice be turned on during any descent where the TAT is below +10C, regardless of how cold the SAT is.

[320DRIVER]

Interesting to note that take-off perf corrections for wing-/engine anti-ice are only valid for temps. of +10 and below. Technically, if you switch ON the anti-ice for take-off for higher temps. you are not covered by the take-off perf. calcs. This is for A320 family.

[catpinsan]

off for SAT of -40C and below in climb or cruise

that goes for both boeing and airbus

beware of rapid changes in temp - on entering patches,banks of (sometimes embeded) cloud - the temp sometimes rises rapidly, atleast in the tropics

[quid]

320Driver-

Many a/c have a +10C limitation for use of Anti Ice. In any event, you wouldn't need it ON any warmer, right?

[False Capture]

A few years ago, Engine Anti-ice on the BAe 146/Avro RJ was OFF during climb and cruise when the SAT was below -40C.

We now have it on whenever we're in icing conditions (TAT 10C or below and visible moisture is present) - even if we're sitting in the cruise with a SAT of -56.5C!!:confused:

[Blip]

May I ask the question that has been bugging me for years. It relates to this discussion.

Fair enough that you must turn the Engine Anti-ice ON when the TAT drops below +10C. But why is it so important that it be turned OFF when the temperature is +11C ?

This drives me nuts sometimes when the temperature is fluctuating around those figures!!

Also I can think of many situations where you know that you will be needing Anti-ice shortly as you are either climbing in cloud or you're clear of cloud but approaching some. You check the TAT and it's +13C. Then something distracts you or whatever. Next time you look it's +6C. AAAARGH!!:{

Why can't there be some overlap? For example, sure make it a requirement to have engine anti-ice on at +10C or below but allow the engine anti-ice to be on up to +15C. That way in the situation above where it's +13C and expected to decrease, you can turn it on in anticipation and then turn your attention to something else.

Can someone with engineering knowledge tell us why this couldn't be done??

Thankyou.

[411A]

It can be done, of course...and usually is, with pilots (and by companies) with common sense, sadly missing with some...:mad: :mad: :uhoh:

[Blip]

Well then if it's no big deal, let Boeing apply some "common sense" and put it in the book!

This would remove that awkward feeling in the flight deck where one pilot is comfortable with applying "common sense" and the other is comfortable with "complying with the Operations Manual."

There's plenty of other examples of common sense vs what's published but that would hijack this thread.

[oldebloke]

The Industry uses oat below +10 since pal
mnair 737 accident at Washington.At that time My Co' used to use below+8 on the DC8/9's.After the accident the industry and FAA directed the use below +10 with visable Moisture present.
As capsiar says keep an eye on temp changes on descent especially when one 'slows' up at FL100(10000 in north Amer')the reduced airflow allows the wing to cool off into the required heat range.
The danger of using it above +10,on the ground was the lack of airflow cooling could poss' lead to o'temp warping of the plumbing around the engine nacelle leading edge.. :O

[BlueEagle]

I was told that the reason it should be turned off in temps above +10C was because the hot air would alter the temper of the metal that comprises the cowl lip or the leading edge and if you then encountered hail it could lead to bad denting of said metal.

If that is a load of old 'tosh' I've no doubt that there is an engineer out there who will tell me!:D

[BOAC]

I have always interpreted the +10 quite flexibly, as long as common-sense is applied (hey! - am I agreeing with 411A?:eek: ).
I would not propose the use of it on take-off around +10 because of the high temperatures of the bleed air. It really is no trouble, if pre-briefed, to put it on at any stage. From personal experience (737), a little care when putting it off is a bonus:D

Engines do not suddenly start icing-up like a Christmas cake at +9.99. I am also fairly certain they are unlikely to accumulate ice at 10.01.

[catpinsan]

i would think +10 already has some margin built in

744 SOP says off above 10C and the system gives us an eicas reminder at +12

i agree about the nacelle damage

[Willit Run]

When I was on the DC-8 with Pratt engines and the 747 classic,also pratt engines, it was a limitation out of the manual not to use engine anti -ice above 10 TAT. The L-1011, rollers obviously and the A-300, GE's, had no such limitation. There was always conflict between the pratt guys and everyone else about the 10 degree limit. There is no magical phenominon(sp) about 10 degrees, just good common sense.

[safetypee]

Engine anti ice ON whenever the AFM requires; normally +10C in visible moisture etc, and/or before / when descending. And don’t forget to select it early, well before entering potential icing conditions allowing the engine components to warm up; airmanship / common sense.

BAe146 / Avro RJ AFM changed to include temps below -40 as the result of flight trials. The industry standard for ignoring temps below -40 was based on some fairly old research indicating that icing would not be encountered at temps below -40C as the water content was low and any moisture would be all ice crystals. However due to 146 engine problems where ice crystals ‘stuck’ / froze within the engine, and following flight trials, the AFM was revised. N.B. All engines should now be modded thus the specific problem no longer applies. Similarly for the 146 and RJ aircraft, airframe icing in extreme / very rare conditions could cause an elevator oscillation; again all aircraft should now be modded to reduce the effects, but not completely eliminate them; hence the AFM limit to use anti ice at all temps below +10C.

Just remember that we (humans) don’t yet fully understand the weather / atmosphere; who said that hurricanes never form in the South Atlantic – so where did “Catarina” come from - it hit Brazil earlier this year. And then there wasn’t / was the hurricane in the UK…..

[BizJetJock]

On the Challengers the flight manual says that above 22,000ft you can just wait for the "ICE" lights to come on, regardless of temp - unless of course you suspect that the lights aren't working;)

[DDG]

BlueEagle,
You are correct in regards to the effect of over stressing aluminium alloys as used on leading slats/flap and engine inlet cowls on large commerical aircraft.As temperature is increased the coating of pure aluminium(used as it is more corrosion resistant than a blended alloy) begins to react as it has a lower melting point than a blended alloys.The pure aluminium`s strength rapidly reduces as does its resistance to corrosion with an increase in surface tempertaure.
Most Boeing aircraft( i will use the B737NG as an example) have a thermal overheat switch that will shut off wing anti-ice on the ground to prevent thermal distress to the surfaces that have anti-ice protection.Engine Nose Cowl Anti ice has pressure and temperature protection that functions during all phases of operation.
In flight however, the wing anti-ice thermal switches are isolated as this gives the flight crew the facility to anti-ice in all flight conditions as ice has been known to form in many differing atmospheric conditions and it is more of a priority to de/anti-ice than worry about thermal stress of metals.
The requirement to select wing anti-ice off at +11 degrees is to protect the metals from overheating as the airflow at this OAT will not have enough cooling effect to prevent this stress to the metals.

Regards DDG

[411A]

DDG...

The thermal qualities of the aluminum used is not so sensitive that a degree or two make a difference...10-15 degrees yes, otherwise, forget it.

A few younger guys want to make a federal case out of this, oh gosh...a degree or two, OFF, then as the TAT cools, ON again.
You exercise the switch/valve too much, next time (when you really need it), it fails...closed.
Then, bad news.:mad:

Much better to keep your powder dry, for when it really counts.

Tto make the job harder than it needs to be is, in my opinion, to distract the crew from the job that really matters...flying the aeroplane.
Yes, limitations need to be regarded, but to split hairs never got the job done properly...and indeed may lead to distractions, which cause incidents/accidents.

And these, are absolutely to be avoided, if possible!:ooh:

Edited to add..
Have personally noticed ice on the inlet cowl at temps at +12C TAT in TriStar aircraft...better leave it ON to be sure.

411A, I trust you read the comments on the other (now closed) thread. I have edited out the more objectionable parts of this post and you know what? All the information is still there. The difference is it is now presented in a professional, informative, polite way. I hope I shall not have to remind you again. You are sailing a little too close to the wind.

[Scallywag]

DDG, thank you for that excellent explanation :ok: . I presume that's why if wing anti-ice is tested on the ground it only remains on for 30 seconds and then wing anti-ice valves close until weight off wheels (on a320/321/330 ) whereas when engine anti-ice is switched on it remains on. There's nothing mentioned in FCOM's so it's nice to learn something new that is very pertinent. Cheers

[DDG]

SCALLYWAG,

It has been a few years since i touched an A320 but my rusty memory of it is that it is very similar to the boeing and as you stated.

411a,
It is not so much a case of 1 degree of change in oat is insignificant.It is the cooling effect of high speed airflow has on a heated (internally using bleed air)aluminium surface and core temperature changes rapidly with every degree of change of OAT.

However i agree the most important thing is to prevent/rid the surface of ice and therefore ensure safety .

Regards DDG