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Wing Antice On Boeing Aircraft.  
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4036 posts, RR: 33
Posted (7 years 10 months 4 weeks 6 hours ago) and read 3612 times:

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.

5 replies: All unread, jump to last
 
User currently offlineHAWK21M From India, joined Jan 2001, 31692 posts, RR: 56
Reply 1, posted (7 years 10 months 3 weeks 6 days 18 hours ago) and read 3537 times:

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



Think of the brighter side!
User currently offlineMX757 From United States of America, joined Aug 2005, 628 posts, RR: 12
Reply 2, posted (7 years 10 months 3 weeks 6 days 15 hours ago) and read 3512 times:

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.
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4036 posts, RR: 33
Reply 3, posted (7 years 10 months 3 weeks 6 days 14 hours ago) and read 3501 times:

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.


User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 5
Reply 4, posted (7 years 10 months 3 weeks 6 days 6 hours ago) and read 3439 times:

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]


This job sucks!!! I love this job!!!
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 5, posted (7 years 10 months 3 weeks 6 days 6 hours ago) and read 3434 times:

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.



Happiness is not seeing another trite Ste. Maarten photo all week long.
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