On Dec 3, 11:13*am, Sam Spade wrote:

Most airliners cannot use wing de-ice until after takeoff and at not
less than 400 feet; sometimes higher. *The bleed air required for wing
de-ice takes so much power that it invalidates the takeoff flight path
performance.

MD-11 must be more sophisticated than "most airliners". If icing
conditions are expected on takeoff the wing and tail anti ice are
selected ON after engine start. The valves open when the aircraft
transitions from ground to in-air. Wing and tail anti ice cannot be
used on ground as the slats/leading edges will overheat.

In flight, the CFM requires wing and tail anti ice to be ON if icing
detection system indicates icing is present, or if icing is expected.
There is no specification of how soon before entering icing conditions
the systems should be selected ON.

Andy