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alatriste
2nd Oct 2003, 17:27
HI! I would like to know about your companies SOP concerning the use of the airfoil anti-ice for take off, when icing is expected.

Do you switch it on before brake release for take off?
Do you switch it on once airbone above certain height?

First choice, your airplane is protected once airbone, but you might be severely reducing your RTOW ( runway,climb and obstacles).
Second criteria, if you switch it on above certain height you are still protecting your aircraft, but on the other hand your RTOW is not that penalized (just obstacles and maybe climb).

ANY IDEAS? THANKS A LOT

None
2nd Oct 2003, 23:20
We do not turn on Airfoil Anti-ice until climbing through 400 feet above airfield elevation. Additionally, the jets I have flown will not allow airfoil anti-ice to operate while on the ground.

DBate
3rd Oct 2003, 00:13
If (wing) icing conditions are expected which affect the wing, it's normal at our company to switch on the wing anti-ice on ground.

None is absolutely right - wing anti-ice won't work on the ground 'till you are airborne to avoid overheating of the airfoil.

Of course you penalize the RTOW on the segments, but that's taken into account when doing the T/O Data calculation.

So long, DBate

avioniker
3rd Oct 2003, 01:19
On the 737 NG's you can run the wing TAI all you want on the ground, right up until you push the throttles beyond 53degrees for takeoff. There's switches in the control stand that trip the TAI system off at that point.
The pilot has to manually reset the system after takeoff.

LEM
3rd Oct 2003, 20:48
On the 737 classic too, if you taxi with wing TAI on, upon takeoff thrust application the valve will close, despite the switch will remain on, and the disagreement light will illuminate (bright).

Upon lift off, the switch will trip off, the disagreement light will extinguish.

Then it's up to the pilots to turn it on again, and as generally Wing antiice is used as a deicer instead of an antiicer, there's no hurry to do it...

avioniker
3rd Oct 2003, 21:59
OOPS that's one other big difference in the NG's from the classics. The leading edge is composite so you don't want to try and deice with TAI. When you turn it on (on the ground) the precooler valve goes full open to try and keep the air cooler and not damage the leading edges under the slats. Also there's no TAI to the outboard slats.

alatriste
4th Oct 2003, 02:04
Thank you for your coments. It looks like NONE and LEM do not switch on airfoil anti-ice before take off run, while the rest do.
Knowing the advantanges and disadvantanges of both procedures, I would like to Know about the policy of diferent companies.
My company calls for take off with airfoil anti-ice switch on, when the level off altitude (engine failure procedure) is below cloud base and icing conditions are expected. So if level off altitude is 800 ft AGL and cloud base is 700 feet, we must switch on airfoil A/I prior to take off, in this way we are penalizing our RTOW limited by runway (8.000 pounds) while we are protecting the airplane just between lift-off and 35 feet. Above 35 feet climb requirements and obstacle clearance are compromise but both are independent of runway lenght.
In the scenario set above (Level off 800 and cloud base 700), if we switch on airfoil anti-ice at 800 AGL only RTOW limited by obstacle clearance will be reduced. When taking off from short runways, and flat surrondings, this second procedure allow us to take off much heavier and reach the destination without any stopover.
ANY OTHER VOTE FOR THE POLL? WHAT´S YOUR SOP?

When level off altitude is ABOVE cloud base, airfoil A/I is used in T.O..........

Sorry for the mistake.