The aircraft I mentioned that has leading edge DROOPS is the North American FJ4 or FJ4B ( AF1E ). They were electrically operated when the trailing edge flaps were lowered ( electrically operated ) .

There are different kinds of LE flaps. Some are simply hinged at the lower edge of the wing ( F 104 ), and some use offset hinges that form the lower part of the leading edge when retracted ( B 707- 707's don't have slats). Boeing calls this type a Krueger flap. It has an articulating feature that deploys a rounded tip as the flap extends. Some airplanes use both LE flaps and LE slats on the same wing ( 727 ). The 747 uses LE flaps which are unique. They are flexible and actually change shape when they deploy. I believe they are made of fiberglass (at least the old ones) and are known as variable camber LE devices. There is even variation in how they are deployed. The 727 slats come out in pairs, the inboards first then the outboards together with the LE flaps. Most newer planes deploy them all together but have different positions. Some are just up or down, and some has as many as 4 positions. My point is that there are many different types, you just have to know what your subject airplane uses.
I don't know of any large airplanes with aerodynamically actuated slats. In fact the only ones that I'm aware of are the F 86, F100, the Sabreliner, and I believe the ME262. Maybe someone knows of others.
It would be nice to hear from more of those builders who have fitted these to their models to see if they consider the effort worthwhile on our models.
Paul

Ramprat,
I don't care if your impressed or not. First of all, please read the messages right It was the F-4 not the F-104 that I was talking about with the bleed air. THE POINT THAT I HAVE BEEN TRYING TO MAKE TO YOU IS THAT ALL THES DEVICES LOWER THE STALL SPEED AT HIGH AOA WHETHER IT AT LANDING OR DURING MANUEVERS. Which is what the bleed air over the wing does. You seem to be stuck on proving that you are right and I am wrong that youn miss the whole point. Just keep on with that attitude and someday it will get you when it hurts the most!

This is from the B-707 flight manual. The leading edge flaps are located as follows:

1 set outboard of the outboard engine pylons ( 4 on each wing)

1 set between the pylons ( 2 flaps )

1 set inboard of the inboard pylon ( 2 flaps )

PURPOSE: To increase the lift capability of the wing for takeoff and landing.

Remarks: The leading edge flaps are hinged at the leading edge and are driven forward approx. 100* from the chord line by hyraulic cylinders. There is no intermediate position; they are fully extended or retracted. The leading edge flaps will extend when the outboard trailing edge flaps extend beyond 9-1/2*.

..and i pointet out that the F-104 was the first to use that system, and that it was irrelevant to the discussion...

Quote:

THE POINT THAT I HAVE BEEN TRYING TO MAKE TO YOU IS THAT ALL THES DEVICES LOWER THE STALL SPEED AT HIGH AOA WHETHER IT AT LANDING OR DURING MANUEVERS.

..and i don't question this at all..



I'd like to see you install a bleed-air high-lift device on a model...


The fact is that you made a statement that has no basis in fact what so ever:

"as an adendum, L. E flaps are powered up and down either hydraulicaly or electrically where slats are designed to be extended and retracted by airloads depending on the airspeed and the angle of attack."


I'd rather keep my attitude and keep informing people when they are wrong, rather than letting it slide so people can spread misinformation....

We all know who is spreading the misinformation. What tech school did you get your traing at?

all a slat is, is a retractable slot. it does not matter whether it's operated aerodynamically, hydraulically, electrically, automatically, by e.s.p. or whatever.
......no attitude, just correct info....
virus.

Thank you Virus!

Larry

Thank you...

Obviously not one where they teach you that slats are L.E. flaps that are operated by aerodynamic forces...

Show me in that quote where I say le flaps are operated by aerodynamic forces? and you still didn't answer where you got your training!

Darryl Usher,

Thank you for answering the question. Don't put them on your model unless you're willing to do the work/add the weight (and an additional opportunity for a failure) just for looks.

I remember many "Moons" ago when Ivan Minninghoff (SP) built his F-16 XL with leading edge flaps. He said he almost crashed it on the first flight he put them down........ He said he put 'em back up as fast as he could, and never used 'em again!!!!!!

I have to say I respectfully disagree that LE slats, in model scale, will not lift their own weight.

I have attached a graph of Coefficient of Lift, of an airfoil, with slats, and with slats and flaps.

Now the lift equation is

L = Cl * A * .5 * r * V^2

Flaps alone increase CL (and therefore lift) , AT THE SAME ANGLE OF ATTACK.

Slats increase CL (and therefore lift) by allowing a greater angle of attack

Both of these statements assume enough power is available to overcome the extra drag created by these devices.

Therefore it looks to me like slats can double the lift, and that would easily accommodate their extra weight.

It will also allow you to fly slower at the same lift, but not as much as the velocity term is a square law.

come on guys, lets put our egos away

SLOTS or SLATS, all I'm seeing is mouths that FLAP.

It appears that they indeed may work-if built properly. Since other 'air disturbing' devices, spoilers, airbrakes, flaps,elevons, etc. work when placed on a miniature aircraft, why not L.E. devices? The question, I think, then becomes-how to design and build them. In the case of the F16, what exactly did the plane do? I'm guessing if they're not exactly even, it would be no different then uneven flaps or ailerons out of trim-or built crooked.
I found some good stuff on Mike James site, think I'll give 'em a try!







.

Hi Guys
Interesting threads ! What about the A-4's ,didn't the leading edge slats deploy when the airspeed dropped off and gravity takes over ? I tried lifting one once,when a A-4 was parked on the ramp,it had some weight to it.Seemed to be a simple devise,just a couple of hinges,not much to go wrong.

Charlie H

I think one reason people may have a problem with LE flaps (NOT slat) is that they are divergent (kinda the wrong term here but close enough) under some sort of load.

So if a normal trailing edge flap bobbles a bit in the breeze, the air loads tend to blow it back up, decreasing the load on the servo.

If a leading edge flap bobbles, the breeze tends to blow it farther down, which increases the load on the servo.

I think this is part of the problem people have had. When the LE flaps are up, they gotta STAY up, at high speed. Cause if they go down even a bit, I think it will be bad.

All just my opinion. I don't thing slats have this problem, or if they do it is to a much lesser degree.

Matt,

I agree with you because LE Flaps are intended to be used at lower speeds. I think the problem with models is probably that a servo won't lock it into position securely enough.

Aha! Good point, the l.e. devices are getting the full force of the air flow; therefore, perhaps a heavy duty servo is required. A better choice would be a locking device-but how? I'm also building a Douglas Skyray F4D which had spring operated l.e. SLATS, for high AoA carrier landings, they were problematic in a dogfight, supposedly. The issue here is, I think, how can one calculate, duplicate or measure the force of the airflow against these devices, a home built windtunnel?

I think Bob Fiorenze had locking pins in the LE flaps of his big F-18

The MIG 29 kit I have does not have any locking devices however, but they are so stiff and have so little travel I don't think it matters

If you get that wind tunnel working I got some stuff I need tested.

Make sure it will get up to about 310 mph or so !

Locking pins would probably work if you want to add the extra weight and go thru the process of rigging of them. They would probably be the best solution or you could try adding some movable hooks with latch points but you still have the extra weight and rigging problems. Just some thoughts.....

By the way, Matt you mentioned a Mig 28 kit.
Who is the maker and does it use one or two engines?

It is a is now Composite ARF kit.

It uses 2 turbines. It is 1/6 scale and about 103" long.

Meanwhile I am sanding on a stingray :-(