Why does an aircraft have TWO independent ENG INTI-ICE systems?

[honesty_will]

Apologies if this has been discussed before.

I am flying Airbus. I don't know much about Boeing.

Boeing has the same system?

Anyway, my question is

Wing ANTI-ICE has just one push button,

But why two ENG ANTI-ICE push buttons?

[Wizofoz]

So that if one of the EAI system fails, it can be switched off.

In the case of WAI, in the case of a failure on one side, it is actually desirable to have the whole system off, as symmetrical icing is preferable to one side being iced up an the other not.

[Wizofoz]

Well, generally TAI uses bleed air FROM the engine itself, so if it isn't running it doesn't make much difference if the system is switched on or not.

[Cough]

Say you get a valve that is (a little stuck). Whilst cycling the sticky valve I would like the other to stay completely open and maintain full engine anti ice on the 'good' engine. For this you need two buttons...

[White Knight]

Mine's got FOUR:ok:

[vilas]

honesty will and Wizofox
Single Wing anti ice valve button controls both side anti ice valves and the bleeds air from respective side is used to de ice that side wing. Wing anti ice is used as more of De icing after ice has formed or is forming . In case of failure of one engine it is possible to de ice the other side wing through the cross bleed. In case of engine anti ice they are two independant systems so has one button for each engine. It is not possible to de ice the failed engine.
It is not preferable to have symmetrical icing but preferable to have symmetrical De icing. If wing getting iced up and one side wing anti ice has failed you do not switch off the available side, that would be ridiculous. This is what happens when one engine fails and the fire button is pushed. You keep the anti ice on and because one side is iced up Vapp goes up by 10KTS and try to avoid icing conditions.

[Wizofoz]

vilas,

You absolutely DO turn off the entire WAI system if one side fail, at least in the Boeing I fly.

Both the 777 BLEED LOSS WING (Lor R) and WING ANTI ICE checklists call for turning the WAI system from AUTO to OFF, and specifies this is to avoid asymmetrical icing.

Of course full de-ice is preferable to no deice, but no deice is preferable to asymmetric deicing, at least according to Mr Boeing.

Maybe your Airbus is different, but you write as if all aircraft are the same. Admittedly I may have done the same.

[lomapaseo]

I read the OP as having to do with the engines alone.

Makes a difference in the answer whether it's wing ice or inlet ice.

From the engine standpoint a failure in the valving control to the inlet is of minor concern to either overheat or ice build up and shed. (engine still useable)

Asymetrical performance on aircraft surfaces is an entirely different matter and is addressed in the discussion above

[Lord Spandex Masher]

If wing getting iced up and one side wing anti ice has failed you do not switch off the available side, that would be ridiculous.

:eek:
..........

[flyingchanges]

Most likely because the TAI valve is ahead of the PRSOV.

[rudderrudderrat]

Hi Vilas,
If wing getting iced up and one side wing anti ice has failed you do not switch off the available side, that would be ridiculous.

Can you then please explain your statement in the light of ABN 30 Ice & Rain Protection, Wing Anti Ice SYS Fault:

"(ONE WING VALVE REMAINS CLOSED WHEN THE WING ANTI-ICE IS TURNED ON)
WING ANTI ICE ....... Off
STATUS
AVOID ICING CONDITIONS
•IF SEVERE ICE ACCRETION:
MIN SPD VLS +10/G DOT
MANEUVER WITH CARE"
This is what happens when one engine fails and the fire button is pushed. You keep the anti ice on and because one side is iced up Vapp goes up by 10KTS and try to avoid icing conditions.
FCOM ABN & EMERG 70 Power Plant, ENG 1(2) Shut down
"If ENG FIRE pb-sw pushed:
XBLEED SHUT
WING ANTI ICE OFF
AVOID ICING CONDITIONS"

[A Squared]

You absolutely DO turn off the entire WAI system if one side fail, at least in the Boeing I fly.

Yep, if we're talking about *wing* anti ice and not *engine* anti ice, you do on my plane also (Lockheed) and on my previous airplane (Douglas). It's not "ridiculous" at all.


but you write as if all aircraft are the same.

That's sort of a common theme with him.

[vilas]

Wizofox and rudderrudderrat
My unconditional apology. I had misunderstood anti ice in the context ot engine failure with fire button pushed. Although the reason for switching of is not given still you both are right. Sorry guys.

[rudderrudderrat]

Hi Vilas,
Although the reason for switching off is not given
It has always been the case that both wings must be symmetrical (as far as possible) to prevent roll with AoA change.
e.g. see De-Icing and Anti-Icing Fluid Cautions | Air Operations | Operations and Safety (http://www.caa.co.uk/default.aspx?catid=2520&pageid=14018)
"Fluid Coverage

De-icing treatments must be symmetrical, even when only one side of the aeroplane is contaminated."

[FE Hoppy]

How do pilots get on the line with such limited basic knowledge?:confused:

[flyboyike]

One possibility, Hoppy, is that some people who post on here are not pilots, regardless of what their handles might be.

[galaxy flyer]

The other possibility is there are a whole lot of pilots with unbelieveably low knowledge of what they are doing or how their flying machine works--very scary. Then again, I had a pilot tell me the pre-charge on the accumulator could hold the parking brake. I quickly demonstrated his lack of basic hydraulic understanding.

[Wizofoz]

Steady on guys, the dude made a mistake and has admitted and learned from it.

We've ALL done that at some point.

[vilas]

RRR
Strange as it seems I never had to use WAI in decades. Got rusty or more appropriate"iced up".Thanks for the article.

[tdracer]

Back to the original question - why not one switch for Engine anti-ice?

Engine to engine isolation. A single switch can fail and take out AI to all engines. There is actually an FAA regulation that addresses engine isolation.

As others have beat to death, for Wing AI, it's desirable to have an AI failure affect both wings the same. Not so for engines.

[MarkerInbound]

Just to stir the pot, the aircraft I flew before the present ride HAD two wing anti-ice switches. Yes, there was a duct connecting the two sides and a note that if either tapped engine or it's valves failed, the remaining engine could anti-ice both wings as long as it was spooled above 70%.

[TURIN]

Engine anti-ice is dedicated to the engine. IE. L.Eng bleed supplies Left Engine anti-ice. Also, the engine anti-ice bleed is independent of the main bleed supply. Separate bleed tap from compressor. Separate bleed valve. Separate switch etc.