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I have heard pilots talk about flaps and slats, seemingly interchangeably.

Is there a difference between a flap and a slat or they are the same thing?

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2 Answers 2

up vote 22 down vote accepted

Flaps are at the back of the wing, slats are at the front.

pic

Easy! :)

If you want it more technical: They both help to generate more lift. See these diagrams with angle of attack and lift coefficient:

enter image description here

graph

As the lift coefficient is inversely proportional to the minimum airspeed, a higher CL will allow a lower Vmin.

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1  
Both the lectures that I know and almost all sources on the internet describe a reduced stall AoA with flaps, i.e. a c_L / alpha curve that is moved both up and towards the left. This is important, because it means that an extension of the flaps alone can cause a stall without changing the AoA. Forum post with good sources: forums.x-plane.org/?showtopic=59032 –  JulianHzg Mar 18 at 9:50
    
Just wanting to point that flaps can be located both at front and back of the wing (trailing-edge or leading-edge flaps), while slats only exists at the front. Main difference between slats/flaps is not location ,but (as you pointed out) functionality –  Radu094 Jul 28 at 13:57

Slats and flaps both change the shape of the wing when they are extended and allow the wing to generate more lift so that the airplane can fly slower.

Operationally they are both retracted and flush against the wing except for takeoff and landing at which time they are extended.

Pilots tend to refer to them together because they are used for the same purpose and used at the same time. In fact, they are normally even moved by using the same control (typically the slats comes out when selecting first detent, and then the flaps come out progressively further at each detent):

Airbus Slat/Flap Handle

Slats are on the front of the wing (on the left in this picture) and the flaps on on the back of the wing (on the right). As you can see, they both tend to make the wing bigger and more curved when they are extended:

Aircraft Wing

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It's worth noting that there are also autoslats, which extend automatically at high angle-of-attack, so it's not quite true that slats are only used at take-off and landing. –  Dan Hulme Aug 25 at 18:16
    
@DanHulme "Operationally" that is the only time that they are used. My airplane also has auto slats, but they only extend during non-standard events (flying too slowly without them extended), and I don't feel that the autoslat feature adds any to the discussion of what they are for. :) –  Lnafziger Aug 25 at 18:21
    
That's fair enough. I just think alpha protection is a good enough use to merit a mention, even if only as an aside, as it's something you can't reasonably do with flaps. –  Dan Hulme Aug 25 at 18:27

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