Tristarsteve
Posts: 3374
Joined: Tue Nov 22, 2005 11:04 pm

Wing Antice On Boeing Aircraft.

Sat Dec 09, 2006 6:19 am

Boeing 737 from 300 onwards have a WAI system that can operate on the ground. It has temp sensors in the leading edge that open and close the valves. When the throttles are advanced, the valves are closed (for performance reasons, WAI uses a lot of air), and when the aircraft lifts off the system closes the valves and trips to OFF.
The B737-200 ( and some early -300s)
B747-400
B757
B767
B777
all have WAI that is inhibited on the ground, in fact the B747-400 is inhibited with the leading edge flaps not UP.

Why?

p.s. A320 also inhibited on the ground.
 
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HAWK21M
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Joined: Fri Jan 05, 2001 10:05 pm

RE: Wing Antice On Boeing Aircraft.

Sat Dec 09, 2006 6:05 pm

Quoting TristarSteve (Thread starter):
all have WAI that is inhibited on the ground,

Not normally needed & to avoid overheat.Remember its WTAI & not De-Icing.
Also the Test sw presnt with Bleeds available can be used to momentary use WTAI on grd until thermal sw activates Valve to close to prevent ovht.
regds
MEL
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MX757
Posts: 495
Joined: Wed Aug 17, 2005 5:38 pm

RE: Wing Antice On Boeing Aircraft.

Sat Dec 09, 2006 9:25 pm

Without any airflow going across the wings to keep the leading edges cool not only will they overheat they will start to warp and wrinkle too. I saw this happen once on DC-9-10. We had to replace all the leading edges on both wings! Not a fun job at all!  crazy 
Is it broke...? Yeah I'll fix it.
 
Tristarsteve
Posts: 3374
Joined: Tue Nov 22, 2005 11:04 pm

RE: Wing Antice On Boeing Aircraft.

Sat Dec 09, 2006 10:14 pm

Quoting MX757 (Reply 2):
Without any airflow going across the wings to keep the leading edges cool not only will they overheat

Yes I fully understand why aircraft don't have WAI on the ground.
What I dont understand is why the B737 (except-200) does.
And why it switches off on rotation.
 
troubleshooter
Posts: 420
Joined: Mon Feb 07, 2005 5:22 am

RE: Wing Antice On Boeing Aircraft.

Sun Dec 10, 2006 6:36 am

Quoting MX757 (Reply 2):
Without any airflow going across the wings to keep the leading edges cool not only will they overheat they will start to warp and wrinkle too

Thats why the B737 wing anti-ice system uses overheat switches (one per wing) to control the system on the ground. They close the valves at a set temperature or if the thrust levers are advanced and they open the valves again after temperature drop or thrust reduction.

Quoting TristarSteve (Reply 3):
And why it switches off on rotation.

The switch trips off at lift off due to performance considerations as the bleed demand for wing anti-ice is a lot. By setting the switch manually to on again, the crew takes the decision to use the big amount of air from the engines or not.

[Edited 2006-12-09 22:37:03]
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SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

RE: Wing Antice On Boeing Aircraft.

Sun Dec 10, 2006 6:41 am

Quoting MX757 (Reply 2):
I saw this happen once on DC-9-10.

Quite a few of the old baby-nines had patches at the very least at the point where the hot air duct comes up into the leading edge spaces, inboard of the porkchop, IIRC.
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