744 leading edge flap retraction on landing

[YBBN]

[photoid=297321]

Is this common? I have never heard of this before. What possible benefit would it serve by retracting the leading edge flaps on landing?

[mikecweb]

Not sure bout the rest of the 74s but the 400s retract there inner leading edge flaps upon application of thrust reversers.

[screaming_emu]

This is a very uneducated guess, but methinks its prevents the slats from being ripped off from reverse thrust, I've noticed this on every 747 that I've sat in front of the leading edge that as the thrust reversers are deployed the slats retract. When the reversers are stowed, they come back out.

[aquiros]

Taking about guesses..
let's remember that the flaps help create lift on the wing, at the moment of landing you do not want any lift because you need that airplane to be firmly set on the runway. During the approach they are very important because tey are needed to create the extra lift the airplane requieres to sustain flight at lower airspeeds. At the touchdown moment you really don't care anymore about lift...so...leading edg flaps...bye bye.

just my $0.02

[AJ]

On selection of reverse thrust the inboard leading edge flap groups (2,3,4 and 5) retract to prevent foreign object damage in the flap mechanisms. On the flight deck the flap position indicator changes from green to magenta as this occurs. Some Classic 747s also have this feature, although a few companies deactivate it.

[YBBN]

Thanks AJ and all.

[LH 340-600]

very interesting.
Do other planes have this technologie?

[AJ]

Hi LH, I'm not too sure. Most new build aircraft use slats in lieu of leading edge flaps as they are of simpler design, and they are less susceptable to FOD inside the devices.

Leading edge flaps are still found on new build Boeing 747-400s and inboard on 737NGs.