Leading Edge Slats

[wuzak]

Here is a post from Shortround in the other thread:

Yep, the British should have persevered with this design instead.

At least it had slats.
Or for a bomber prototype

Or fit heavy nose guns to this as a bomber destroyer. Just think of the angle of attack this could pull

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.

 

[Shortround6]

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

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.

 

[GregP]

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

Been looking for that one for years.

 

[wuzak]

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

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.

Yeah, that makes sense.

Thanks SR.

 

[stona]

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

Cheers

Steve

 

[Glider]

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

 

[stona]

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

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

 

[Glider]

Thank you for that, much appreciated

 

[gumbyk]

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.

 

[pbehn]

Absolutely correct, and not in dispute!!!
What is in question is what happens to the 109 after it has gone past 13-14, or even 15 Degrees Angle of Attack?
Can it make use of that extra 10-12 Degrees AoA that the Leading edge slats give it in combat, not necessarily to evade, but to pull extra G to make the pointing adjustment to fire his guns at a target that other planes with AoA's in the 12-15 Degree range can not even shoot at?

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.

 

[Shortround6]

Absolutely correct, and not in dispute!!!
What is in question is what happens to the 109 after it has gone past 13-14, or even 15 Degrees Angle of Attack?
Can it make use of that extra 10-12 Degrees AoA that the Leading edge slats give it in combat, not necessarily to evade, but to pull extra G to make the pointing adjustment to fire his guns at a target that other planes with AoA's in the 12-15 Degree range can not even shoot at?

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.

 

[stona]

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

 

[BiffF15]

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

 

[Shortround6]

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??

 

[wuzak]

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??

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....

 

[GrauGeist]

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??

Because the TBF guys didn't want to make the SBD guys look bad!

 

[wuzak]

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.

 

[GrauGeist]

You have seen the light! If you take the top 100 to 150 Me-109 Ace pilots who scored over 100 kills, and add up their scores, they shot down more planes than the Entire RAF, ALL of the USAAF Fighter commands, the Russians, or any other single Air Force. Maybe the second and third scoring AFs above combined?
As to the second point about the bit in Yellow above, you are terribly uninformed. Why would you shoot at a plane you can not see?

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.

 

[pbehn]

As to the second point about the bit in Yellow above, you are terribly uninformed. Why would you shoot at a plane you can not see? The simple fact is that the inverted engine gave the 109 pilot's a better view over the nose than a Mustang, or Spit. But that is not even remotely relevant!
When the Ace pulls the extra Gs to make the shot, he still has a clear LoS to the target.
Make the diagram I explained before and the see how far ahead the target has to be to still fall under the 109's guns which are pointed some 7 Degrees above the lowest possible Line of Sight.

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.

 

[Shortround6]

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.