737 Wing Anti Ice and Bleeds Off?
 

Maybe I´m supposed to know this but I´ve been unable to find it in the books...

If you need to take off with Anti Ice on and at the same time need Bleeds Off for performance reasons - do you then have to fly it as an unpressurized takeoff?

Wing antice does not work on the ground, so you can't take off with it on. On a B737 there is an air/ground sense input.
During take off you are using the deicing fluid to provide antice protection.

WAI does work on the ground. Check your manual.

Some (older?) 737s had ground inhibited WAI. Non ground inhibited WAI trips off when TO thrust is set. Engine AI is sourced on the engine side of the bleed air valves so it makes no difference what power source is supplying the packs.

so the short answer is 'no'.

APU is used to run pressurization. WAI is available on ground, except with T/O thrust. At least, on our B737s...

Whats wrong with doing your bleeds off take off and after you reach 1500ft reconfigure it back according to the checklist at SP.2.11. Select WAI ON when your done?

The 737NG will allow WAI on the ground.

When t/o power is set, the WAI valves close automatically.

At liftoff, the WAI switch on P5 overhead will auto off.

From then on, it's up to you!

Cheers, FD :E

Well you made me look it up.
B737-200 inhibited on the ground.
B757
B767
B747-400
B777 all inhibited on the ground.
But B737-300 onwards works on the ground as FD says.
Why is that? Why should the B737 need WAI on ground, but no other Boeings?

Swedish Steve,

It's been a couple of years, but I seem to remember the Classic B747 had the capability to use the WAI on the ground!

Cheers FD :hmm: