Use of wing anti ice (Airbus)

[Bearcat]

Can someone post the definitive on the correct use of wing anti ice on airbus aircraft. Does it have to be on at all times in icing conditions? The use of same as a deicer or an anti icer? Everyday's a school day................

[mcdhu]

FCOM 3.4.30 P1 says it can be used either to prevent or to remove ice.

[Neupielot]

i was just gonna ask the same question;).
Thanks for the reference.
:ok:

[Mad (Flt) Scientist]

Just because it says it CAN be used to do two things doesn't mean you necessarily have the choice though. What do the Limitations say? - that's where it would be mandated.

caveat - non AB. But on the type I'm familiar with, our AI systems can also be used either to remove or prevent (any pneumatically heated system will be capable of both, basically). But we have an absolutely crystal clear Limitation that says it MUST be on in icing conditions. In our case the "can be used for removal" statement is somewhat superfluous.

[STBYRUD]

Again, not a bus driver, but Wing Anti-Ice is ill-named on my type since Boeing recommends not to use it continuously as anti-ice due to the extremely high bleed air demand but instead to use it in cycles to break off accumulated ice. I'd be interested to know about the airbus though.

[Wizzaird]

From Airbus Flight Crew Training Manual

"Wing Anti-Ice should be turned on, if either severe ice accretion is expected, or if there is any indication of icing on the airframe"


Seems a pretty straighforward statement.

[Mad (Flt) Scientist]

@Wizzaird.

Problem with that statement is there's no "must" in the sentence, and it's not in the Airplane Flight Manual but rather a "training" manual. So it reads as "advice" not "instruction" or "requirement". A true Limitation would be worded more strongly, I think. (Ours are)

[Wizzaird]

True, but nevertheless the FCTM was written to help in the interpretation of the AFM (A320) which simply states:


 When icing conditions are encountered:
Turn on engine anti-ice.
Set wing anti-ice as required.

[Neupielot]

I always thought wing anti ice are used to remove not to prevent but Airbus fcom says otherwise. Fcom 3.4.30-
WING ANTI ICE may either be used to prevent ice formation, or to remove ice accumulation from the wing leading edges

Question: If ice accumulation noticed on visual ice indicator or wipers, how long do u keep the WING ANTI ICE on?:confused:

[Meikleour]

Neupielot: In my experience of the A320 series, if you watch the leading edge after having selected the wing antice on, you can see the ice being shed from the leading edge. Once the flaps are selected to F1 an air gap opens up therefore the wing antice hot air is lost and the system is not effective and may therefore be switched off.

Incidently, the A330 & A340 seem to be much less prone to the build up of ice on the leading edge.

(return to bunker ready to accept incoming ............... )

[shortfuel]

Once the flaps are selected to F1 an air gap opens up therefore the wing antice hot air is lost and the system is not effective and may therefore be switched off

From where did you get this? Own experience only?
I disagree. Even with slats extended, WAI is still going to heat outboard slats, and that, in severe icing can save your day.

[red 5]

The wing Leading edges are De-iced if selected on regardless of slat position.

[FlightDetent]

Why not start with reading manufacturer's FCOM 3 Supplementary Procedures Ice & Rain Protection? ... whenever airframe icing is observed by accumulation on the icing indicator, etc ... ?

Sincerely
FD (the un-real)

[Meikleour]

Shortfuel: Many contributors here have referred to FCOM 3.04.30 P1 Suppl. Procedures. Under the advice given, in bold outline, Airbus have always said to avoid
"extended flight in icing conditions with slats extended"
Why do you think that is?

Once the gap in the leading edge is created by slat deployment you are not going to get the same heat transfer to the leading edge hence much less protection than when the leading edge is `closed`. This is Airbus admitting to you (warning you perhaps) that you should be aware of the lesser protection. Which now applies to the whole leading edge and not just the non heated areas.

All the types that I have flown with slats had similar considerations.

[shortfuel]

Meikleour,

Your second last post has nothing to do with the last one.
The one I referred to contains two wrong statements:

an air gap opens up therefore the wing antice hot air is lost
No hot air is lost whatsoever, same amount of hot air goes through outboard slats, thermal exchange is altered at most because of an increased heat exchange surface ("the gap").

system is not effective and may therefore be switched off
That is the shocking part. Since when do you switch off a system because it is less effective?
Believing that WAI is not effective at all with slats extended is incorrect. WAI has its limitation, that's it.


I can only agree with the first part of your last post (first 3 lines).

Why do you think that is?

IMHO, it is an aerodynamic consideration here: when slats are extended, wing curvature/AoA are increased, ice accretion is made easier because it's function of the wing curvature. I think this is why we try to avoid such a situation.
Having said that, it is not because WAI has not been designed(/certified?) to cope with extended flight in icing conditions w/ slats out that I would switch it off as you kindly suggested!


Anyway, Wizzaird answered the OP.

[HundredPercentPlease]

Using it as anti ice should be done with caution, as you run the risk (in the right conditions) of making the situation a lot worse by collecting a load of runback ice.

[aterpster]

HundredPercentPlease:

Using it as anti ice should be done with caution, as you run the risk (in the right conditions) of making the situation a lot worse by collecting a load of runback ice.

With wings that use bleed air or with boots or both?

The wings can't even be seen from the flight deck on some transport airplanes.

[BOAC]

Well, it is extremely unwise to use boots as 'anti-ice'? I cannot imagine anyone doing that.

'Run-back' ice is an age-old caution on all types I have flown with bleed de-icing and is, in my opinion, valid.

[Meikleour]

Shortfuel: you posted some time back:~ 2007

............................................................ ............................................................

I can only imagine that your company decided to associate WAI deselection during final with L/G extension.

Airbus proc extract:
-FLAPS FULL SELECT
Select FLAPS FULL below VFE.

-CONFIRM/ANNOUNCE "FLAPS FULL"

Check deceleration towards VAPP.
-A/THR CHECK IN SPEED MODE OR OFF

-WING ANTI ICE OFF
Only switch the WING ANTI ICE to ON, in severe icing conditions.

For Airbus, it comes after Flaps extension.

I don't think that it's related to OEI condition as you quote FCOM 3.03.18, normal procedures.
............................................................ ..................................................

Please explain to me how the above relates to the WAI efficiency being maintained when the slats are extended. Surely if full protection was given then Airbus would recommend it`s use until after landing ( like with the Engine AI ) My contention has always been that the WAI efficiency is much less with slats extended. Your reference to greater wing camber with slats out leading to greater ice accretion would not matter if the slats continued to be totally protected.

[aterpster]

BOAC:

'Run-back' ice is an age-old caution on all types I have flown with bleed de-icing and is, in my opinion, valid.

Never heard of it with respect to "hot" wings. Certainly have, though, with boots. My impression was that "hot" wings converted the ice to water, which did not reform as ice further back on the wing.

My former employer spend a lot of ground school time explaining the policy and critical nature of engine anti-ice. They spent very little time, however, on wing heat other than when not to use it (and reference to the OEM's AFM statements on use of wing heat). Nothing was ever mentioned about run-back ice. I don't believe I've heard of run-back ice stated as an issue with "hot wing" aircraft before this thread.

Ground deicing was a different matter, of course.

[Mansfield]

Consider that there are two ways to construct a thermal ice protection system: one is known as fully evaporative, the other is called running wet. Some designs are intended as a running wet system...my old Convair 240 comes to mind...but most jet designs begin with the intention of a fully evaporative system. That said, you can probably guess which one requires the most energy (read: fuel consumption), so it would seem that more contemporary designs are limiting the energy output rather more than they used to.

A running wet system, or a fully evaporative system being operated in a running wet state (perhaps because of reduced power during a descent) will likely generate some runback. This is due to the supercooled liquid water droplets being temporarily un-supercooled, so-to-speak, and then quickly freezing once the water mass has "run back" off the heated surface. The fully evaporative system is supposed to sizzle the little buggers into steam, so that by the time they get around to freezing again, the wing has left the building.

It takes anywhere up to five or six minutes to thoroughly heat the wing protected surface after you activate the thermal ice protection system, depending on the SAT, mass of water impinging, size of the wing and actual bleed output. During that time, the system will necessarily run wet at least briefly.

Boeing's current spin on this is to operate the system in a de-ice mode in order to preclude a runback ridge. Their boilerplate language looks something like this:

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 select the WING ANTI–ICE switch ON
when wing icing is possible and use the system as an anti–icer.

In my personal opinion, this is driven by Boeing's general attitude that their airplanes really don't need ice protection. I don't agree with that sense, but there is no doubt that larger scale airplanes have less of an issue with ice than smaller scale machines.

However, a number of us have raised the question over the years regarding how you are supposed to know when the cycle the thing if using it in a de-ice mode? Can't see the wings, wouldn't know what we were looking at even if we could (can you estimate in the fractions of an inch at a range of seventy or eighty feet...at night?)... :ugh:

At the end of the day, the thing was supposed to be a fully evaporative anti-ice system. Fuel conservation pressures, coupled with a rather barren accident record due to inflight icing, have allowed procedures to be "relaxed" as it were.

Regarding the slat issue, I'd be cautious about asserting that the TAI is less "efficient" in one configuration or another. FAR/JAR 25.1419 has a lot of detail, particularly in the advisory material, about how to get your ice protection system certificated. No where does it say anything about "the system can be less efficient" at any particular point in time. It either meets the criteria or it doesn't.

That said, the manufacturer's procedures are written in a way that will respect the certification results. If they say turn it on, then turn it on. If they say it can be turned off here or turned off there, then doing so will respect the certification. But that doesn't mean you can't be more conservative, should you be so inclined!

[Mad (Flt) Scientist]

I'm going to speculate that Airbus may be more "relaxed" about turning on WAI with slats deployed not because the system works less well - there is no reason why slat deployment should materially affect the performance of the system - but rather because the aerodynamic effects of ice with slats deployed was found more tolerable than for the slats retracted case.

It's not that it's less effective - but rather less required. As a guess.

[Bearcat]

and the definitive use of wing anti ice from airbus is????:ugh: ..............there's no definitive and that's why I asked in the question in the OP. Maybe they may add "may your own arrangements re useage thereafter" because some folk insist in having it on all the time in icing condts cause airbus says so and others use it as required which imo would be the preferred option. The useage of continously on in severe icing is I think is where airbus is coming from not ever whisp of cloud.
Thank you for your contributions, I'm still none the wiser.....no fault of yours but the lack of definitive from airbus irks me. Rgds;)

[GA Button]

Hi Meikleour

Refer to the reply to your posting of 25.02.10 - the slats are still heated due to ducting. The worry behind flight in severe icing conditions with slats extended is due to what can build up in the "slots" and the reason they reccomend turning it off on final approach (unless in severe icing conditions) is to ensure plenty of power on the go around.

[Meikleour]

Mad (Flt) Scientist: I have PM`d you.

[A37575]

Strongly recommend reading latest Business and Commercial Aviation magazine issue October 2010. Page 72 entitled "Fine-Grain Icing on Aircraft" by Richard N.Aarons. Four pages of the best informaion around on take off icing.

[C.A.]

The AFM recommends avoiding extended flight in icing conditions with extended slats
and flaps, as accreted ice may block the retraction of the high lift devices causing
mechanical damage to the slat / flap system

From Getting to Grips Icing

[redfly]

Airbus also wants you to switch WING ANTI ICE to ON if VOLCANIC ASH HAS BEEN ENCOUNTERED. Hopefully an unlikely subject for airliners, but does anyone know or has an idea why Airbus recomends this procedure?

[TopSwiss 737]

Airbus also wants you to switch WING ANTI ICE to ON if VOLCANIC ASH HAS BEEN ENCOUNTERED. Hopefully an unlikely subject for airliners, but does anyone know or has an idea why Airbus recomends this procedure?

Wing anti-ice is switched on in order to maximize bleed extraction from the engines. This increases engine stall margin.

[redfly]

Well, maybe a rather dumb question but doesn't do maximum bleed extraction calls for MORE thrust from the engines? And that's what you should try to avoid while finding yourself situated in volcanic ash clouds, no?

[TopSwiss 737]

Most, if not all, aircraft require the thrust levers to be retarded to idle as part of their volcanic ash procedure.

This reduces possible engine damage or flameout, or both, by decreasing EGT. The lower temperature in the engine at idle thrust reduces the glass build-up from molten ash in the combustor and on the turbine blades (this glass deposit blocks cooling holes in the turbine blades, which may overheat them by a considerable amount).

Extracting maximum bleed from the engines by also switching on wing and engine anti-ice reduces the pressure gradient in the compressor, thereby increasing engine stall margin.

[redfly]

Okay, that make sense. Thank you for the advice!