Automating Leading Edge Flaps to reduce takeoff and landing distances

L Edge

Master member
With larger prop and EDF models, as they increase in size, usually requires a runway. One way to reduce distances is to use a Thrust Vectoring nozzle.
Another method is to use leading edge flaps(LEF) that are automated. Here is an example(watch the left tip, so every time pitch is used, the LEF travel). So, question is, can RC pilots duplicate that and be automated? So watch the left tip of the F-16.


Not having a wind tunnel, can we shorten takeoffs and slow the landings down(also tighten turning radius) to use shorter runways?) being automated.

Looking for things that don't exist, the big question is how can it be done?

So many moons ago, took my testbed (F-22) plane and made many sets of LEF supports ranging for zero to 35 degree deflection. Lots of time testing each angle to see what happened. At 35 degrees deflection, flight is getting unstable so my range was 0-30 degrees. To save time, takeoff lengths were reduced until about 20 degrees, then LEF drag of airflow increased. Automated is designed that LEF is always parallel to airflow where wing angle changes..

12 years ago tried to program(used heli section) and the best I could get is to increase throttle/lower the LEF so at 1/2, is was down 30 degrees. Over 1/2, the LEF jumps to zero. Best you can do with a radio that was old and not enough knowledge about gyros.


So again, this video is shown to explore flight stability and I am yanking and banking in a closed field with 6 -15mph wind. Notice it slides nicely and I am on the hairy edge of disaster(7:12). Now just imagine an runway approach with say a 15 degrees wing angle on a descending slope with controlled throttle. It slows those landings(boring for me) and stops sooner. So it will be up to you to pick your glide slope (by throttle and elevator) to determine your speed for landing. Same for takeoff.



Here again, is where I throw it to launch and quickly yank and bank right to set up spot landings.. Could you ever do that with a F-22 without leading edges in that short distance?


Finally, a demo with a thrust vectoring nozzle if you don't want LEF's. To me, it is the same as LEF's. Since your thrust vector has an upward(lift component) value, it will slow your t/o and landings.


Tomorrow, I will explain the layout out of my F-22 on how to set up LEF's so that it will be off, flip a switch so then it reacts to pitch changes(separate from your flying elevator control) and only go from zero LEF to what ever degree your plane needs to shorten takeoffs and landings.
 
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L Edge

Master member
Reserve
lef.JPG
 
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Piotrsko

Master member
Only gonna get so much extra lift mostly from the bottom of wing changing angle of attack. Le slats are just basically good for avoiding tip stall ot full stall at the higher angle of attack you could reach. Camber changes with big flaps work better, and retractable flaps more than 1/4 wing area work better still
 

clolsonus

Well-known member
I'm probably not saying this exactly right, but to go up, you need more lift force than load factor * weight. In straight level flight load factor is 1 and in a 60 degree bank it's about 2 ... so your effective weight is about double and you need double the lift out of your wing. And at a specific angle of attack and airspeed, a specific wing is going to make a specific amount of lift. So a lighter airframe is going to give you the most bang for your buck in terms of going up sooner (at slower speeds or requiring you to accelerate less or shorter runway, etc.) But if you can't go any lighter, then things like higher lift airfoils, flaps/slats, and thrust vectoring and vortex generators become interesting.
One thing that is fun for me is to outfit my planes with pitot/static air data system, gps and imu so I can start collecting accurate flight data. This is useful for making autonomous flight systems, but also if you are tweaking configurations you can collect and analyze real data (But this requires an aircraft large enough to carry the extra instrumentation, and also adds to the weight ... not to mention can be a pretty steep learning curve at first ... and probably not everyone wants to be an aerospace engineer or would think that is fun ...) :)
 
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L Edge

Master member
I'm probably not saying this exactly right, but to go up, you need more lift force than load factor * weight. In straight level flight load factor is 1 and in a 60 degree bank it's about 2 ... so your effective weight is about double and you need double the lift out of your wing. And at a specific angle of attack and airspeed, a specific wing is going to make a specific amount of lift. So a lighter airframe is going to give you the most bang for your buck in terms of going up sooner (at slower speeds or requiring you to accelerate less or shorter runway, etc.) But if you can't go any lighter, then things like higher lift airfoils, flaps/slats, and thrust vectoring and vortex generators become interesting.
One thing that is fun for me is to outfit my planes with pitot/static air data system, gps and imu so I can start collecting accurate flight data. This is useful for making autonomous flight systems, but also if you are tweaking configurations you can collect and analyze real data (But this requires an aircraft large enough to carry the extra instrumentation, and also adds to the weight ... not to mention can be a pretty steep learning curve at first ... and probably not everyone wants to be an aerospace engineer or would think that is fun ...) :)

Agree with you whole heartily. Way I do it is search for the college or NACA reports. That is how I found the "Stabilizer" and it kicks butt to meet flying stability for foamys. I design things that don't exist. In this thread, you can use a gyro to help you conduct experiments that allow to duplicate what the actual plane does. See next entry.
 

L Edge

Master member
Let me explain how it works. Exploring changing wing angles on a transport was the result of seeing a F-8U (wing up 7 degrees coming in for a landing to lower the landing speed) and seeing the fuse horizontal.

The answer to conduct wing angle changes was solved by a gyro. So, first of all, used a servo and variable pot to hooked to a hinge to change angles of the wing. next, set up elevons on the wing with a fence to keep the flow across the elevons. Yaw was present by differential thrust, so now I could fly the transport with a horizontal fuse.

Next, we need to keep the plane horizontal at all times, as a reference point in respect to determine the wing angle which I could set with the pot. So a gyro was mounted on the fuse and power and a switch(emergency) to turn on/off and then from the pitch gyro to the elevator servo in the tail. So when you pitch the fuse up/down, the rear elevator servo responded to make it level.
Watch the distance and speed to take/off/land as wing angles increase.


When flying EDF jets, some use long takeoffs/landings due to design. One way to shorten those distances is to add automated leading edge flaps just like the F-16 so we have scale characteristics. Mine max out somewhere between 30-35 degrees down on a F-22 testing every 5 degrees down.

After getting a gyro and a internal program for a computer, I learned that you can manipulate settings that control gain, limit deflection of the servo, even shutting it off. The gyros center is like your servo, tip up, it goes one way, tip down, the other way and returns to neutral when level. So with LEFlaps, you don't want any movement above the wing.
So my gyro is set up so 1500 is the neutral point and end travel down is 1000 and end up travel is 2000.

So my concept is to use only pitch so that when the nose of plane goes up, the gyro sends the servo for the LEF's down. Since I want only 30 degrees max, I set 1336 units. To prevent up LEF movement above the wing, I set the travel to zero by changing 2000 to 1500.
You could set roll and yaw ends from 1000 or 2000 to both 1500 so you would have no movement from them. Your not hooking up to them. I just do that so if you plug the pitch into wrong axis on the gyro.

Setup:
1) Just hook up your servos to the plane as usual for the Rx.
2) Now you have the gyro(eagle tree, your might be slightly different) which need power, so plug gyro 3 wire lead from gyro to Rx.
3) Now assign a three position or 2 position switch to the aux channel. Take the yellow lead(signal and 1 wire) and plug from the gyro into aux and setup your on/off switch. Now turn on tx and rx battery, and set direction of switch the way you like.
4) Since there are 2 LEF flaps, you need a "Y" coming out of the gyro pitch output.
5) Point-with 2 servos on a "Y", you need trim on each to get zero deflection as well as the deflection end.
a. Make sure you set up servos so both go down(pitch up plane).
b. With power on, level with gyro, set one servo(glue?) when LEF is even with wing and if I set 1336 it is say 30 degrees. If not, trims are changed from 1500 say to 1497 (zero degrees)and 1339 for the 30 degrees.
6) Make sure the second wire is the same length and find some way ( threaded end so it can be adjusted if needed ) so it is flush with wing and deflects to 30. Then glue the servo.

In my F-22 setup, I used a 1 1/2" flap. If you noticed in the F-22 above, I added some rear end flaps. Hope this spring to do further testing with that.

Any question on way I approach it to get it to deflect automatically?

Notice I added my "UDDER RUDDER" design which allows me to yaw an any high angle of attack even with gusty winds due to prop wash..