B777 Wing Anti-Ice

[Alpha Sierra]

Hi Guys,

Can the wing anti-ice be used with the wing slats extended or not?

It also states this in the FCOM...

Automatic wing anti–icing operation is inhibited when all the following conditions exist:
• TAKEOFF mode is selected, and
• wing icing conditions exist, and
• less than 10 minutes has elapsed after liftoff

Why is this? The second condition has me confused
Also, if the WAI is selected to on during the inhibited period, does it override the statement?

Thank you

[Green Guard]

RTFQ

why confused ?
The question is about AUTOMATIC wing A.I. Right ?
So if you really feel you need it, select it manualy.

PS
You may really need an Wing A.I. for T/O once in a life time, or twice..

in any case you loose much more power by heating that wing then by being "iced" in first 10 min

[NSEU]

• wing icing conditions exist, and

So... the Auto Anti-Ice system is not inhibited if icing conditions do not exist?

I see what you're saying. From a purely logical standpoint, any of those conditions not in effect will cause the Anti-Ice to operate.

Poorly worded. The Maintenance Manual replaces line 2 with "AUTO Mode is selected".

[Alpha Sierra]

Thanks for the replies...

why confused ?
The question is about AUTOMATIC wing A.I. Right ?
So if you really feel you need it, select it manualy.

Okay, so manual selection of WAI will override the AUTOMATIC inhibit period. Thanks

The Maintenance Manual replaces line 2 with "AUTO Mode is selected".

Thanks for that... will look into it. 'AUTO Mode' makes more sense


So.... I'll word the question slightly differently then. Should WAI be used on approach with SLATS extended? Pro/Cons?

Thank you

[Green Guard]

if you really are in icing conditions, of course use it even with slats "on"... but do not rush with slats....chack you App "clean speed"

[777fly]

1. Wing antice will NEVER operate while the aircraft is on the ground or take off roll, regardless of switch position.
2. It is only the slats that are de-iced, whether they are extended or retracted.
3. Wing antice in 'auto' will not operate after takeoff until the engines come out of thrust ref, or after 10 minutes,
4. Wing antice in 'manual' will operate immediately after lift off, with no inhibit.

[Alpha Sierra]

Thanks for the info guys... managed to get my hands on the AMM

Quote from it...

Operational Mode Inhibits
With AUTO or ON selected, any of these operational mode inhibits keeps the WAI valves closed:
- Airplane on the ground (except during an initiated or periodic BITE test)
- TAT is more than 50F and the time since takeoff is less than 5 minutes
- Takeoff mode and airplane in the air less than 10 minutes
- Auto slat operation
- Air-driven hydraulic pump operation
- Engine start
- Bleed air temperature less than 200F (93C).

[Oakape]

Automatic wing anti–icing operation is inhibited when all the following conditions exist:
• TAKEOFF mode is selected, and
• wing icing conditions exist, and
• less than 10 minutes has elapsed after liftoff

As the first word indicates, the FCOM is taking about automatic operation. In Auto, the system will only command the WAI valves to open when icing coditions are detected. If there is no icing detected the valves will not be commanded to open & therefore the system does not need to be inhibited.

A bit of a given & really doesn't need to be included in the FCOM statement. Including it as condition #2 just causes confusion, as evidenced by the original post.

[JammedStab]

My question is....why do they have this inhibit for 10 minutes. Engine failure considerations?

[Capt Quentin McHale]

Alpha Sierra,


In answer to your questions I did a little research of the AMM with one of our engineers and this is what we found...


1... Yes, wing anti-ice operates with l/e slats both retracted or extended due to a telescopic anti-ice tube in each leading edge.


2... Selecting wing anti-ice switch position to ON will operate the wing anti-ice system PROVIDING there are no operational mode inhibits as per your post #7 re "Operational mode inhibits".


3... Wing anti-ice only operates in air mode, BUT, you can do two ground tests via the MAT, one with bleed air and one without. The other way is the self test every 24hrs that the aircraft does itself provided the aircraft is on the ground, wing anti-ice switch in auto and pneumatics on.


4... Only l/e slats 3,4 and 5 on the left wing and l/e slats 10,11 and 12 on the right wing are anti-iced.


5... A bit of a head scratcher concerning FCOM item 2.


JammedStab,


That's one of those questions that make you say Hmmmm. Could not find anything to explain as to why. The engineers said bleed air is prioritised to the ADP's to assist the centre hydraulic system electric pumps for flap and gear retraction, and, yes your engine out scenario definitely has merit with bleed air loads increasing on the good engine. 10mins is a long time... but you just never know....


Hope this helps.


McHale.

[JammedStab]

Originally Posted by Capt Quentin McHale

JammedStab,


That's one of those questions that make you say Hmmmm. Could not find anything to explain as to why. The engineers said bleed air is prioritised to the ADP's to assist the centre hydraulic system electric pumps for flap and gear retraction, and, yes your engine out scenario definitely has merit with bleed air loads increasing on the good engine. 10mins is a long time... but you just never know....

Apparently 10 minutes at takeoff thrust is an option for some Boeing aircraft, typically I think for hot and high operations. So the guess is that perhaps the 10 minute inhibit would cover that option where you might not want it to come on at an innopportune while struggling to climb out with an engine failure. The 10 minute inhibit is only in auto so you still are left with the On option for that rare occasion during normal ops that you actually need it wing anti-ice. Just a guess though.

I notice that some of the other inhibits for this system while in flight that were listed earlier are at times where you may be in a situation where engine thrust would not want to be wasted for bleed use.