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Aerospace Aircraft flaps and slats

  1. Aug 11, 2009 #1
    Here's what I know from basic tech school: Flaps = trailing dge and slats = leading edge. ?Flaps and slats aid in both take-off and landing. I'm just not sure how they do so. My guess is that during takeoff, the combo increases the wing surface area thus allowing lift at lower airspeeds. During landing, the slats keep the aircraft from falling out of the sky at low airspeeds by increasing lift while the flaps create drag about the wing thus slowing the aircraft for safe landing speeds. First, is this accurate and second, what is the function of leading edge flaps?
  2. jcsd
  3. Aug 11, 2009 #2


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    In short, flaps (leading or trailing) increase the surface area and camber of the wing to increase lift. Slat allow for higher angles of attack without stall by keeping airflow attached to the wing. I'm sure wiki has in depth articles on both...
  4. Aug 12, 2009 #3
    Indeed. Here http://en.wikipedia.org/wiki/Flap_(aircraft [Broken])
    Last edited by a moderator: May 4, 2017
  5. Aug 12, 2009 #4


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    Extending a flap or slat also adjusts the angle of attack while allowing the airframe to remain in the same orientation in space. In other words, without extending a flap or slat, tho only way to adjust the AOA would be to pitch up or pitch down the aircraft.

    http://www.myaeromodelling.com/wp/wp-content/uploads/2008/01/cf1.jpg [Broken]
    Last edited by a moderator: May 4, 2017
  6. Sep 21, 2010 #5
    during take off u want high lift and low drag...only flaps are deployed moderately while during u want high lift and high drag...both are deployed to their extreme positions...hope this answers your query..
  7. Sep 21, 2010 #6
    Full flaps are not used on takeoffs - they create too much drag.
  8. Sep 21, 2010 #7
    hence the word "moderately deployed"
  9. Sep 21, 2010 #8
    I always thought slats were used on take-off due to the angles of attack involved during climb. (They are also used during landing if required.)

    It depends what type of slat you have. On light aircraft they can be automatic, deploying at high AOA situations.
  10. Sep 21, 2010 #9
    Your post is unclear and confusing, as you then went on to say: "..both are deployed to their extreme positions..." I think you should reword that post so others can understand what it is you're saying.
  11. Sep 21, 2010 #10
    m sorry i missed the word "Landing" :-)

    during take off u want high lift and low drag...only flaps are deployed moderately while during landing u want high lift and high drag...both are deployed to their extreme positions only during landing...
  12. Sep 21, 2010 #11
    There ya go, all better now :wink:.
  13. Sep 21, 2010 #12
    Yes, it might be easier to understand, but slats are still used during take off, according to parekhharsh_j, only flaps are used 'moderately' during take-off. Highest angles of attack occur during the climb out, so you need them.
  14. Sep 21, 2010 #13
    Yes, that's correct. The word 'only' should be omitted in his sentence. Anyways- this thread is now beating a dead horse.
  15. Sep 22, 2010 #14
    Slats can be used for takeoff to reduce takeoff roll and stall speed while transitioning to climb configuration (clean - slats and flaps full retracted). They're typically used only as required for short takeoff or (near-ground) obstacle clearance requirements.

    Otherwise, as parekhharsh_j stated, only flaps are used 'moderately' during take-off, and that's only to decrease stall speed and decrease AOA during rotation. The moment the aircraft is safely away from the ground, it's "Gear Up," as as the aircraft accelerates beyond a velocity where flaps are required, it's "Flaps Up."

    Climb configuration is always clean, and done at L/D9max as that produces the best angle of climb required to clear larger obstacles, such as mountains. It's a misnomer to think that either slats or flaps increase climb rate or angle. They do neither one. All they do is reduce stall speed required during slow airspeeds.

    One might ask "if that's all they do, and flaps do the same, to a lesser degree, when why not just make flaps larger?" The issue is that with while flaps reduce stall speed and AOA, slats actually increase AOA! Thus, with full flaps AOA is decreased too much. Slats are used to balance this somewhat while providing additional reductions in stall speed.

    Now the horse is dead. I'm off.
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