747-400 Krueger Flaps

[R2000/1830]

Can some one tell me why they are only used inboard of engines 2-3 and not across the whole wing. (they use slats)

[titi]

It is a design decision coupled with slotted slats outboard so that wingtip does not stall first. (main problem on sweep wing aircraft)

[A-FLOOR]

The whole span of every 747 has krueger flaps... the ones inboard of engines 2 and 3 just look different as they don't "curve" as much on extension like the rest. By curving I mean that the extension mechanism increases the camber of the main surface of the flap to increase its effectiveness.

But they are not slats by any definition.

[spannersatcx]

The non kreuger flaps are variable camber leading edge flaps.