Anti-ice operation

[zubart 5]

Then its off. One exception though is on the descent.........always turn the TAI on.

 

The engine TAI is only turned on when icing conditions exist or are anticipated, except during climb and cruise below -40C SAT (During climb and cuise at higher altiutudes and the OAT is below -40 SAT, not -40 TAT, turn off the Engine TAI).

 

When Engine TAI is turned on, always turn the Start switches to continuous.

 

What are icing conditions?

Icing conditions exist when the TAT on the ground and for takeoff or in flight is 10C or below, and visible moisture in any form is present (such as clouds, fog with visibility of one mile or less, rain, snow, sleet or ice crystals.

 

Icing conditions also exist when TAT on the ground for takeoff is 10C or below when operating on ramps, taxiways or runways where surface snow, ice, standing water, or slush may be ingested in the engines. Requires a ground deicing program to be in place at the airline or no flyiing.

 

 

There is a caution associated with engine and wing anti-ice use.

Caution: Do not operate engine or wing anti-ice when inflight total air temperature (TAT) is above 10C.

 

John Floyd

[zubart 5]

Since WAI will automatically trip OFF during T/O when would you normally switch it back ON considered you're flying in icing conditions...right after T/O or wait until the a/c is clean?

 

Turn on the WAI after flaps are up and if required. If de-cer with type II or IV de-icing fluid, it is usually on a urgent situiation to get the WAI on right after liftoff anyway. Normally WAI should be used as a de-icer which allows ice to build on the wing leading edge and then turning on the WAI to clear it off. YOu can use the WAI as a anti-icer but it is not the prefered Boeing method.

[WebMaximus 372]

Ok thanks!

 

I read that normally you would only use WAI as an anti-icer when flying in severe icing conditions.

[Jack_C 1]

John, dont go by TAT on the ground. The ambient air temp is used.

 

JackColwill

[zubart 5]

I read that normally you would only use WAI as an anti-icer when flying in severe icing conditions.

 

Yes you would of course. Keep in mind no airplane is certified to fly in severe icing conditons. You would always avoid severe icing in any airplane unless you accidently flew into it. Transport airplanes are certified for moderate icing condtions or less with proper anit-ice and de-ice equipement installed.

 

John, dont go by TAT on the ground. The ambient air temp is used.

 

JackColwill

 

Yes Jack, thanks for catching my typo error, I should of wrote OAT.

[nuNce 2]

Ok thanks!

 

I read that normally you would only use WAI as an anti-icer when flying in severe icing conditions.

 

Going trough FCTM (or FCOM, can't recall right now) I read you could use it as de-icer in flight, letting first enough ice build up and then turning it on, so the ice would come off all at once, instead of melting and then freezing back over the wing.

[3-2-1-Now 126]

letting first enough ice build up and then turning it on, so the ice would come off all at once, instead of melting and then freezing back over the wing.

WHAT??!

 

It is called ANTI-ICE for a reason (ANTI- is the hint). DE-ICE it is not!! If you let "enough ice build up first" then it may not work AT ALL. You'd get shot if you did this IRL!

 

ANTI-ICE is supposed to prevent the build-up of ice in the first instance. Only DE-ICE is intended to remove ice that has already accumulated. ANTI-ICE can soon be over-whelmed in icing conditions if you leave it too late to activate it. NO aircraft is certified to fly through SEVERE icing. Even HEAVY icing could cause you to have a very bad day. Moderate icing you may get away with. Ultimately, you may not exceed the certified icing conditions (and even then I'd try and avoid those conditions to start with).

 

Switch ANTI-ice ON when:

 

* TAT is +10°C or lower or the aircraft has been cold-soaked

and

* Flying through visible moisture (fog/mist/cloud/precipitation/etc..)

 

Switch Engine anti-ice on when:

 

* TAT is +10°C or lower, or when the aircraft has been cold-soaked

and

* on the ground taxiing in high humidity, mist/fog/precipitation/etc..

or

* Flying through visible moisture (fog/mist/cloud/precipitation/etc..)

 

At takeoff thrust and max climb thrust the engines are likely to remain free of ice. It is in the lower thrust regimes that you are likely to get cowling ice. Note that use of any anti-ice system degrades aircraft performance.

 

Best regards,

Robin.

[nuNce 2]

WHAT??!

 

It is called ANTI-ICE for a reason (ANTI- is the hint). DE-ICE it is not!! If you let "enough ice build up first" then it may not work AT ALL. You'd get shot if you did this IRL!

 

FCOM Vol.1 page SP.16.11 (267 in the PDF)

 

Wing Anti-ice Operation - In-Flight

 

Ice accumulation on the flight deck window frames, windshield center post, or on the windshield wiper arm may be used as an indication of structural icing conditions and the need to turn on wing anti-ice.The wing anti-ice system may be used as a de-icer or anti-icer in flight only. The primary method is to use it as a de-icer by allowing ice to accumulate before turning wing anti-ice on.

 

This procedure provides the cleanest airfoil surface, the least possible runback ice formation, and the least thrust and fuel penalty. Normally it is not necessary to shed ice periodically unless extended flight through icing conditions is necessary (holding).

 

The secondary method is to use wing anti-ice before ice accumulation.

Operate the wing anti-ice system as an anti-icer only during extended operations in moderate or severe icing conditions, such as holding.

[3-2-1-Now 126]

Thanks for the quote. I would not be happy waiting for ice to accumulate before removing it, even if it does use a bit more fuel.

 

This procedure provides the cleanest airfoil surface, the least possible runback ice formation

"least possible" - any definitions? What about the ice being allowed to accumulate in the meantime?

 

Note:

 

The secondary method is to use wing anti-ice before ice accumulation.

Operate the wing anti-ice system as an anti-icer only during extended operations in moderate or severe icing conditions, such as holding.

 

Best regards,

Robin.

[nuNce 2]

Thanks for the quote. I would not be happy waiting for ice to accumulate before removing it, even if it does use a bit more fuel.

 

Note:

 

 

 

Best regards,

Robin.

 

It would be logical to me if they were the opposite. So, as standard, you'd warm up your wings BEFORE going trough icing conditions and use it as de-icer only if you didn't expect it.

Although, if ice forms on your wings I guess it makes sense to let it build up a bit, as the manual states, to avoid runback ice formation which I guess (just guess, since I have no experience in actual flying :) ) would be far worse to remove.

[3-2-1-Now 126]

Yes - in that instance it would run over the unheated part of the wing. Interestingly though that doesn't appear to be an issue in "moderate or severe icing". Maybe because severe is as it states - severe? No aircraft is certified to fly into that, so..........

 

Best regards,

Robin.

[Spin737 102]

 

WHAT??!

 

It is called ANTI-ICE for a reason (ANTI- is the hint). DE-ICE it is not!! If you let "enough ice build up first" then it may not work AT ALL. You'd get shot if you did this IRL!

 

ANTI-ICE is supposed to prevent the build-up of ice in the first instance. Only DE-ICE is intended to remove ice that has already accumulated. ANTI-ICE can soon be over-whelmed in icing conditions if you leave it too late to activate it. NO aircraft is certified to fly through SEVERE icing. Even HEAVY icing could cause you to have a very bad day. Moderate icing you may get away with. Ultimately, you may not exceed the certified icing conditions (and even then I'd try and avoid those conditions to start with).

 

Switch ANTI-ice ON when:

 

* TAT is +10°C or lower or the aircraft has been cold-soaked

and

* Flying through visible moisture (fog/mist/cloud/precipitation/etc..)

 

Switch Engine anti-ice on when:

 

* TAT is +10°C or lower, or when the aircraft has been cold-soaked

and

* on the ground taxiing in high humidity, mist/fog/precipitation/etc..

or

* Flying through visible moisture (fog/mist/cloud/precipitation/etc..)

 

At takeoff thrust and max climb thrust the engines are likely to remain free of ice. It is in the lower thrust regimes that you are likely to get cowling ice. Note that use of any anti-ice system degrades aircraft performance.

 

Best regards,

Robin.

What types have you been flying, Robin? You have some strong opinions on the matter. Coming from flying turboprops to turbojets, I had to change my views a bit.

[zubart 5]

At takeoff thrust and max climb thrust the engines are likely to remain free of ice. It is in the lower thrust regimes that you are likely to get cowling ice.

 

Not true. EAI must always be turned on for takeoff if icing conditions exist or are anticipated. There is no performance penalty for using EAI during a takeoff.

[Spin737 102]

Not true. EAI must always be turned on for takeoff if icing conditions exist or are anticipated. There is no performance penalty for using EAI during a takeoff.

I wouldn't say there's no penalty, it's just that most performance charts automatically include EAI ON if the temp is +10C or less. I think it varies on model, but it's about an 1100 pound hit.

[zubart 5]

I think it varies on model, but it's about an 1100 pound hit.

 

After taking a look at a 737-700 Performance Handbook and Airport Anyalis, the biggest hit for using EAI was for a bleeds off takeoff and it was -400 lbs.

The averge hit for using EAI was - 0 to -200 lbs, depending on certain airport conditons and runway lengths.