Expert: Paul Ruderham - 4/15/2008

Question
QUESTION: Hi Paul,
I am an amateur aviation enthusiast and I was wondering why the pilot retracts the slats on the 747/707 upon landing and engaging reverse thrust.  Thanks.


ANSWER: Hi Brandon,

Landing checklist for the 747 would include, flaps set (probably 40 for finals), gear down, speedbrake armed, missed approach altitude set, altimeters set and checked, cabin secure. Upon landing the speedbrake spoilers would deploy, so named because they spoil all lift on the wing, reverse thrust would be engaged by the pilot.
As the aircraft slows the spoilers would retract, and during taxi to the stand the pilot will retract flaps to zero.

Regards
Paul

---------- FOLLOW-UP ----------

QUESTION: Hi Paul,
Sorry, I wasn't clear on my question.  What I meant was that upon touchdown, the pilot normally retracts the 2 most inboard sets of slats when applying reverse.  If you don't know what I mean, just type this into your address bar; it is a window view of a 747 landing.  At time 5:52, you will notice that the pilot retracts the 2 most inboard sets of slats: http://www.youtube.com/watch?v=LI1dqKGYLzg
Thanks a bunch, and sorry to bother you again.
Brandon

Answer
Hi Brandon,

I see what you mean now. The leading edge slats tuck up under the wing on touchdown to get out the way of the engines as they deploy for reverse thrust. The engine cowling slides back during this process so the slats have to get out of the way. When the reversers are no longer needed the slats go back to position.

Nice video of the Virgin 747 landing. Notice how the wing flexes!!

Regards
Paul