Andy wrote:
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

On the B-727, wing anti-ice cannot operate on the ground, but will open
up once airborne, like the MD-11. On the B-737-200, you *can* operate
the wing anti-ice on the ground, but it automatically snaps off when
takeoff power is applied, and must manually be switched back on once
airborne.

On the DC-6/7, fuel fired heaters blow hot air throughout the leading
edges, and of course there is no performance decrement. The heater
units are of the exact same type that supplies heated air to the cabin,
and circulates heated air in between the windshield panes.

Happy Flying!
Scott Skylane