Leading Edge Slats

Discussion in 'Aviation' started by wuzak, Jun 23, 2016.

  1. wuzak

    wuzak Well-Known Member

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    Here is a post from Shortround in the other thread:

    I was wondering how many aircraft of that era had powered leading edge slats?

    And how the slats would work/deploy on take-off in cases like the Bf 109 where the slats were deployed aerodynamically.
     
  2. Shortround6

    Shortround6 Well-Known Member

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    I am not sure that any did, Or perhaps a few STOL aircraft with full span slats had manually operated ones?
    [​IMG]
    [​IMG]

    The part span slats, like on the 109 and the 3 planes I posted photos of, don't do a darn thing for lift/airflow until the angle of attack exceeds 13-14 degrees and nobody tries take-off with that angle of attack on the wing. Even the Ryan Dragonfly in the photos here is going to make it's take-off ground run at an angle of attack at which the slats are pretty much useless. If the tail wheel comes up the angle of attack is really far from the slats useful angle.
    What happens after the wheels leave the ground is a different story but the large angles of attack the slats work at are also very high in drag to lift, making gaining airspeed difficult. Useful for clearing obstacles (trees, hills, buildings) near the runway but not so good otherwise.
    I hope that makes sense.
     
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  3. GregP

    GregP Well-Known Member

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    You don't happen to know the wing area of the YO-51, do you?

    Been looking for that one for years.
     
  4. wuzak

    wuzak Well-Known Member

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    Yeah, that makes sense.

    Thanks SR.
     
  5. stona

    stona Well-Known Member

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    I think most of the 'STOL' aircraft of that era had fixed slats/slots, like the 'Storch'.

    Cheers

    Steve
     
  6. Glider

    Glider Well-Known Member

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    I thought the Lysander had automatic slots, certainly could be wrong on that
     
  7. stona

    stona Well-Known Member

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    They were automatic, but quite sophisticated in operation.
    The Lysander had two sets of slats (inner and outer) which both operated automatically. Furthermore the inner set were interlinked, and linked to the flaps, all operating automatically.
    Here's part of an article from a 1938 'Flight' magazine article.

    "The best and most recent example of a machine in which
    slots and flaps have been utilised to the very best advantage
    is the Westland Lysander. This machine has a top speed
    of nearly 230 m.p.h., yet, with the slots open, the flaps
    down and the use of a fair amount of throttle, it will fly
    under full control at a speed probably lower than 55 m.p.h.
    In this machine the slotted flaps are interconnected with,
    and controlled by, the slots along the leading edge of the
    inner section of the wing. Consequently, the pilot does
    not need to worry about the operation of the flaps and is
    freed of a good deal of responsibility. He simply flies the
    machine as he wishes to fly it, and the slots and flaps do
    the rest, while the wing-tip slots serve throughout to provide
    adequate lateral control and stability at large angles
    of incidence, and, of course, at low speeds.
    Both sets of slots in the Lysander are entirely automatic,
    but those at the root, which are used to operate the flaps,
    are designed to open at a rather lower speed, and to close
    again when an adequate margin has been obtained above
    the highest normal approach speed. With varying speeds
    the root slots and flaps open in such a way that, at the
    Qorrect speeds for take-off, climb, glide-in, or landing, the
    flaps are pulled down to their most effective setting. As the
    machine is flown more slowly its characteristics change so
    that, within reason, it can fly even more slowly."

    Petter obviously liked slats as they were fitted, rather less successfully, to the Whirlwind too.

    Cheers

    Steve
     
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  8. Glider

    Glider Well-Known Member

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    Thank you for that, much appreciated
     
  9. gumbyk

    gumbyk Well-Known Member

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    Are you talking AoA or deck angle?
    With the slats as they are fitted to the 109, you will have the outboard section of the wings not stalled (due to the slats) but the inboard section of the wing will be stalled, so you won't be able to make use of that extra angle.
     
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  10. pbehn

    pbehn Well-Known Member

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    It has been pointed out here that many German LW aces said getting in a turning fight with a Spitfire was very unwise even when the Spitfire MK V was outclassed in all other fields of performance. Those were lucky men to even see a Spitfire because most crashed on takeoff,, where is my $1000. You seem to confuse normal pilots with Joachim Marseille who certainly did shoot across the chord and definitely shot down planes he could not see. That is life there are occasionally people appear who can do something with a piece of machinery that others cannot, I have two arms and ten fingers but that doesnt mean I will ever play a guitar like Clapton.
     
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  11. Shortround6

    Shortround6 Well-Known Member

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    [​IMG]
    The inner 593.4mm appears to be the "area" of the wing "inside" the fuselage, or inside the wing root fairing.
    In any case the "area" of the wing affected by the slats is going to be about 37-40% of the area from the radiator flaps outwards. With the inboard section/area of the wing stalled (and the tips stalled) the ability of the 109 (or any plane with partial span slats ) to sustain an angle of attack beyond 13-15 degrees is going to be minimal to nonexistent. Think roughly triple the "normal" wing loading while
    having 16 sq m of wing at angle of 13-15 degrees (or more) to the direction of travel of the aircraft. Basically a massive airbrake.
    You cannot pull extra Gs. Even if you can hold the "attitude" of the aircraft the aircraft will be "mushing" out of the turn even if the pilot can maintain enough control not to "drop" a wing.
     
  12. stona

    stona Well-Known Member

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    A Bf 109 could never turn with a Spitfire, both flown to the limit, as I've explained before. I will try in simpler terms. The Spitfire wing gave cleaner and more efficient lift, with lower induced and parasitic drag and the lift stayed attached long after the Bf 109 wing had stalled. The Bf 109's wing also bled off energy faster than the Spitfire's.There was nothing that leading edge slats could do to overcome these essential differences in design. The slats were never designed as an aid to turning in combat, they were designed to make the aircraft more manageable for landing, the same applies to just about every other aircraft fitted with the devices, with the addition of take off to landing, depending on how the slats were fitted and operated.
    Cheers
    Steve
     
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  13. BiffF15

    BiffF15 Well-Known Member

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    Gents,

    Having flown the Eagle against both the F-16 and F/A-18 (slat equipped planes), it's been my experience that they help in some regimes and hurt in others. My first sortie against the Viper had us merge in such a place that his slats hindered his performance and the end result was my being able to employ the gun against him (my IP railed on me in the debrief because I shot him with both a radar and heat missile prior to our merge, but hey I wanted to turn with him...). The Hornet has the exact same weakness and a much lower thrust to weight ratio.

    Slats out mean a large increase in drag. Tomcat had slats and variable sweep wings and was the least capable threat I trained against.

    Sun Tzu said know your enemy and know yourself and you will know the outcome of every battle. Translation know your and your opponents strengths and weaknesses, and apply your strengths against his weaknesses without allowing him to do that to you.

    I will not put any info on this forum that might be exploited, but realize I would fight a Me-109 in the same manner / considerations I use with more modern threats until I became more familiar with the nuances of such an endeavor.

    Cheers,
    Biff
     
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  14. Shortround6

    Shortround6 Well-Known Member

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    I am wondering, If slats/slots worked the way Shooter claims, why slot equipped TBF Avengers didn't turn inside Zeros and shoot them down?? :)
     
  15. wuzak

    wuzak Well-Known Member

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    Because they were turret equipped and didn't need to.

    The main USAAF turret fighters (the B-17 and B-24) accounted for more enemy aircraft than the Spitfire, P-38 and P-51 you see....:p
     
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  16. GrauGeist

    GrauGeist Well-Known Member

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    Because the TBF guys didn't want to make the SBD guys look bad! :lol:
     
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  17. wuzak

    wuzak Well-Known Member

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    Shooter, you are the one with the theory. So you should do the diagram.

    But, if both the attacking and target aircraft are in level turns, the position where the attacker's shells hit the target will be below his sight line.
     
  18. GrauGeist

    GrauGeist Well-Known Member

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    Because in a tight turn, you're adversary will disappear below your cowling, that's why.

    Several aces, particularly Marsailles, knew EXACTLY where his high-deflection shots would be landing as he entered into into his high-degree turn.

    It's alot like trap shooting, knowing how much lead to put on the target...and he did that exceptionally well.
     
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  19. pbehn

    pbehn Well-Known Member

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    Marseille could fly into a Lufberry circle and shoot planes out of it, this sometimes involved flying with flaps lowered, no one knew how he hit the target but he did. Maybe he had a three dimensional picture in his mind or estimated from the plane in front, what is certin he shot at such massive deflection the target was below the nose of his plane.

    Look at the front windscreen of a 109, now tell me about the pilots massive field of view.
     
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  20. Shortround6

    Shortround6 Well-Known Member

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    [​IMG]

    Oh, yeah. I can see how looking down past the side of inverted V engine gave the German pilots such a good view that they could aim their guns without using the gunsight. ...........NOT.
     
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