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Old Nov 03, 2008, 08:23 PM
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USA, CA, Oakley
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Using rudder with ailerons in turns

While I was out flying the other day, a friend (and more experienced pilot) made a comment before leaving about using some rudder in my turns for more realistic scale flight (this is on my PZ Corsair).

I've tried incorporating rudder in the air and on the simulator and just can't seem to get the gist of which direction and how to do it. I always end up with a very sloppy maneuver which doesn't resemble a turn at all. any pointers would be appreciated.

-Eric
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Old Nov 03, 2008, 09:08 PM
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United States, KY, Hopkinsville
Joined Feb 2008
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Adding rudder will keep the tail from sagging in a turn. Use left rudder for left turns and right rudder for right turns. It will take some practice because in a full coordinated turn you will be using ailerons to keep the plane tilted at the correct angle, elevator to keep from losing altitude and rudder to keep the tail from sagging all at the same time. But when you get it down the turn will look a lot better.

Freddy
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Old Nov 03, 2008, 09:22 PM
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Rudder is used with ailerons to keep the flight coordinated. Without rudder input the plane will sideslip while banking. Sideslip relates to the displacement of the aircraft centerline from the relative wind and is generally avoided because it creates drag and increases the risk of a plane entering a spin.
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Old Nov 03, 2008, 09:29 PM
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Just keep the ball between the lines. Oh...wait...

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Old Nov 03, 2008, 09:38 PM
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Quote:
Originally Posted by hackdroot
just can't seem to get the gist of which direction and how to do it.

Move the rudder stick in the same direction as the aileron stick. How long and how much will depend on your plane and flying style.
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Old Nov 03, 2008, 11:45 PM
raz
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A lot of computerized radios allows you to program in some rudder with ailerons so you don't have to mess with it.
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Old Nov 04, 2008, 12:02 AM
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Etnering the turn, apply appx 1/3 as much rudder as aileron. (Thats usually a good starting point.)

While in the bank and pulling for the turn, you may want to hold a small amount of rudder into the turn (shallow bank) or apply rudder opposed to the turn to keep the nose from dropping (steep bank with light pull... extreme case = knife-edge)

Comming out of the turn you may want more or less than when entering... it depends on the plane. But you will still move both sticks the same direction.
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Old Nov 04, 2008, 02:06 AM
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Awesome, thanks for the help guys. Off to the sim to practice.
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Old Nov 04, 2008, 07:15 PM
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Good planes to practice using rudder with are 3D aircraft with lots of fuselage area. They pretty much force you to use the rudder, so you end up learning how to use it.
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Old Nov 05, 2008, 05:02 AM
Account closed
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Quote:
Originally Posted by hackdroot
While I was out flying the other day, a friend (and more experienced pilot) made a comment before leaving about using some rudder in my turns for more realistic scale flight (this is on my PZ Corsair).

I've tried incorporating rudder in the air and on the simulator and just can't seem to get the gist of which direction and how to do it. I always end up with a very sloppy maneuver which doesn't resemble a turn at all. any pointers would be appreciated.

-Eric
Eric,

I do not own nor ever have had any simulator as I started RC back in September 2003 and back then, there were perhaps none and if so, they were extremely expensive.

However, in discussion here with the actual model, I have been able to turn my Park Zone F4U Corsair with just rudder and a little UP Elevator during the turns. Yes, just like a 3-Channel trainer!

It is just amazing how well Park Zone (Horizon Hobby) has designed this RC Airplane Warbird, a True Park Flyer to it's definition!

In the following video about 2:25 into the video I was turning my PZ Corsair with just rudder as I made her fly nice and slow so I would not disturb wing lift by using ailerons.
ParkZone F4U Corsair Maiden Flight (7 min 5 sec)
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Old Nov 05, 2008, 10:09 AM
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Don't worry about it too much until you're flying scale airplanes or doing aerobatics. Almost all trainers have aileron differential which drastically reduces the need for rudder. A lot of scale planes need rudder, because they fly like their full-size counterparts. Sailplanes often need rudder because of the long moment arm their ailerons operate on. It seems like scale Cubs are notorious for needing a lot of rudder (just like the big ones).

Rudder's primary use is to counteract the adverse yaw caused by the downward deflected aileron. Once the bank is established in the turn, the ailerons are neutral and rudder is no longer needed until opposite aileron is applied to roll back to straight and level flight.

Unless your plane appears to be wallowing into and out of the turns, you can leave the rudder alone. If you want to practice using it, it's as simple as moving the rudder the same way as the ailerons. If the ailerons are neutral, the rudder is neutral. Just remember, you'll probably need to keep the rudder movements much smaller than the aileron movements (unless you program in a lot of rudder exponential).
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Old Nov 05, 2008, 10:52 AM
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Actually there is more to it than adverse yaw, indeed it is to compensate for that but there is yet another effect at work.
If ya'll will refer to the image of that turn coordinator that Boidster posted, and on the ball in the curved glass tube, and note that it rests at the center between two lines.
When a plane goes into a bank, that ball will fall to the inside of the turn and then the pilot will apply rudder in the direction of the turn to swing the ball back to center and hold it there. And you do have to hold rudder to keep the ball centered, and the steeper the bank the more rudder is required.
So once banked the ailerons are relaxed but the rudder is still held througout the turn. It's not much mind you, even just pressure applied I'd say.

So, in loooking at this now we see that something causes that ball to fall to one side in a bank, so what is that?
Its the CG, shifting left or right from right underneath the pilot seat, to one side of it. In a full scale plane you can feel this shift, and also see it on the turn indicator. So the rudder is also keeping this CG in line, and in balance. Other wise, if none, or not enough rudder is applied the plane slips toward the inside of the turn, if too much is applied it skids toward the outside of the turn.

Its hard though, and impossible even for us ground based pilots to know just exactly how much rudder to apply, but we can only judge the best we can.
But like has been said, it takes very little. A lot less than you'd think.
And as I said, I like to think of just applying pressure to the stick rather than that of moving it.
Thats all it took on the pedals of a full scale Christen Eagle I flew in last year, mere pressure on the pedal was enough to move the ball. I was amazed at how sensitive it was and how much you could feel it.
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Old Nov 05, 2008, 04:58 PM
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Actually there is a way you can see if you have it right with a model: put a streamer on each wingtip (they need to be the same length), and fly the tail exactly halfway between.

You can NOT remove all the need for rudder with mixes. You can deal with adverse yaw from the ailerons, but that's not the whole story.
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Old Nov 05, 2008, 08:26 PM
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VHP VOR R-318/D0.6
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Quote:
Originally Posted by SabreHawk
Actually there is more to it than adverse yaw, indeed it is to compensate for that but there is yet another effect at work.
If ya'll will refer to the image of that turn coordinator that Boidster posted, and on the ball in the curved glass tube, and note that it rests at the center between two lines.
When a plane goes into a bank, that ball will fall to the inside of the turn and then the pilot will apply rudder in the direction of the turn to swing the ball back to center and hold it there. And you do have to hold rudder to keep the ball centered, and the steeper the bank the more rudder is required.
So once banked the ailerons are relaxed but the rudder is still held througout the turn. It's not much mind you, even just pressure applied I'd say.

So, in loooking at this now we see that something causes that ball to fall to one side in a bank, so what is that?
Its the CG, shifting left or right from right underneath the pilot seat, to one side of it. In a full scale plane you can feel this shift, and also see it on the turn indicator. So the rudder is also keeping this CG in line, and in balance. Other wise, if none, or not enough rudder is applied the plane slips toward the inside of the turn, if too much is applied it skids toward the outside of the turn.
Thanks for the "dual instruction" on how to coordinate a turn, but I'm a "Gold Seal" flight instructor in airplanes (single-engine, multi-engine, instrument, and glider), as well as an instructor and check airman for a regional air carrier, so I'm pretty sure I've figured out how rudder is used.

The ball in the slip indicator has nothing to do with the CG, nor can any application of an aerodynamic control surface control the CG. CG can only be moved by the shifting of weight (the "G" does stand for "Gravity"). Ask any Concorde or MD-11 pilot. Both of those aircraft could adjust thier CG by moving fuel to and from aft fuel tanks.

Once the angle of bank is established, the ailerons and rudder are neutralized The horizontal component of the lift vector turns the aircraft, not the rudder. Gravity tries to pull the ball to the low side of the inclinometer, but centrifugal force pulls it towards the high side. The combination of theses forces create a resultant vector that keeps the ball in the center of the inclinometer. The pilot perceives this as increased G-force.

If the aircraft's iherent stability requires that the pilot keep applying aileron to maintain the desired bank, then the rudder is used to once again to counteract the adverse yaw. In steep turns there is an overbanking tendency. The outside wing is travelling faster than the inside wing, gets greater lift, and tries to steepen the bank angle. Opposite aileron and coordinated rudder are required to maintain the desired angle of bank.
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Old Nov 05, 2008, 08:40 PM
John,not Zerts.JOHN, NOT Zerts
USA, AZ, Chandler
Joined Nov 2007
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I started out with programming aileron-to-rudder mixes in my Tx, but usually rudder should only be applied when you initiate the turn, then many models fly fairly decent steady turns with neutral rudder (exceptions as described in above posts). It's pretty difficult to fly perfectly coordinated turns in a model plane anyway w/o that yaw string or turn coordinator instrument, neither is it necessary unless you are flying a model sailplane. I also verified this while in Chase View on my RealFlight sim.
If you are holding steady rudder in a turn flying a model plane, it appears nose downward and loses altitude more than it normally would (assuming you are keeping the throttle at same setting and elevator neutral for purposes of comparison).
Fast and/or low-wing planes, I apply a lot of up elevator (give a bit more throttle too) - makes the turn tighter and cleaner.
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Last edited by Zerts; Nov 05, 2008 at 08:49 PM.
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