When does one most often use the rudder?

If you fly powerful enough planes, the takeoff roll might need some rudder input. For cross wind landings, you will want to use rudder to keep the plane from drifting. For aerobatics, you will find the rudder to be your paint brush.

Outstanding!

When I hit some rudder to help me turn, it puts the nose down. . . in the sims , too. Explanation?

You might want to check out this thread:

http://www.rcuniverse.com/forum/m_65...tm.htm#6577280

The video is pretty neat, but not very practical for beginners. It shows the rudder in use for 3D flying and many new people are way to immature in their flying to even attempt this sort of thing.

I would practice using the rudder for take offs and landings to position the aircraft where you want it to be on the runway. Then use it for coordinated turns while flying regular orbits and figure eights.

Once more advanced stuff is desired, do hammerheads (stall turns) that require rudder to do properly as do many other maneuvers to get the plane lined up and going straight. A well done loop needs to be approached straight from left to right or right to left, and that is done by using the rudder to get the nose pointed perpendicular to the maneuver. Then pulling on the elevator, with NO aileron leakage is a difficult process. Using the rudder in the process straightens out the nose should it tend to yaw to the left or right while in the maneuver. This is all pretty advanced stuff and takes some time to even begin to see the action of the rudder.

The mussle memory thing is the process that takes long. You begin to do things automatically. Practice using the rudder is the best way to get used to using it and learning how to use it properly. The proper amount of input using the rudder at certain times becomes an art. As someone said, it's the paintbrush.. and that's a great analogy.

Practice..practice..practice.. burn fuel...lots of fuel. The more you do, the more things become automatic and you can add to your capabilities.

We have a guy in our club who is FAI level pattern. He is good. I watched him do a horizontal rolling loop then at the end of that, he converted it to a vertical rolling loop. I watched his hands and fingers. He burns an awful lot of fuel throughout the year, that's all I can say.

CGr.

With an airplane in a banked condition, applying rudder with the turn, actually will cause the nose to pitch down as the rudder sorta becomes an elevator in this condition. You will always need up elevator input in a turn. The sharper the turn, the steeper the bank and the more elevator will be needed.

As for the use of the rudder, many airplanes will exhibit adverse yaw. This is when rolling an airplane with the ailerons, the down aileron, because it is creating more lift, also creates more drag. The rudder is used to force the draggy wing forward, overcoming adverse yaw and making a coordinated turn. You steer with the rudder on the ground. The rudder is really put to use, once you start doing advanced maneuvers. So, it's not the useless appendage some would think it is. Get the basics down and your understanding of the use of the use of the rudder will slowly come to you.

Yup. That's absolutely correct. Experience = burn fuel It differs with each plane, as to how much rudder and elevator to use in a turn, and what your turn rate is to be. Slow purposeful maneuvers, watching the plane as you input controls, and understanding what's happening is the key. The understanding thing usually lags the learning the control inputs, but comes with time and of course, the more you fly (burn fuel) the more you become more in control of what's going on and the more you understand how it works.

CGr.

It's called a couple. It happens with some layouts more than others and with different surfaces. It happens in every scale of airplane.

With a rudder, you can have two different couples. One is a pitch couple, the other a roll couple.

If the rudder movement also changes the pitch, it's called a rudder/elevator couple. And some call it a rudder/pitch couple. When rudder movement causes a roll, it can be called rudder/aileron couple or rudder/roll couple.

If you'd like to experience them both in an example that would be hard to miss, fly a CAP sometime. I've built a couple. Did one for a buddy who's somewhat new at the hobby, and his reaction was, "HOLY S*******!!!!!!!!! WHAT'S WRONG WITH THIS &$^#@&*%$#@(&^%$ !!!!!!!!!!!!!!! " He thought somebody had turned on, on his frequency. Lots of CAPs do both pitch and roll couples quite strongly with even a little rudder.

In your case, you're seeing a rudder/pitch couple.

Back in the good old days, before computer radios, the precision aerobatics guys dealt with that kind of couple by sawing the model apart and glueing it back together a bit differently. They'd move the stab up or down depending on which way the rudder pitched the airplane. And how much they moved it was based on a WAG as to how strongly it was pitched. Today, all you have to do is punch in a rudder/elevator mix into your computer radio. It's easy and contratry to many opinions, it's not cheating or disreputable behavior. It's called "making your airplane fly true" or "trueing the response". And it's fairly easy to do.

The idea about "true response" is simple. You want the rudder to only control yaw. You want the elevator to only change pitch, and the ailerons to only affect roll. And when the airplane does that, it's called many different things, all of the terms being complementary. And there are a number of schools of thought about this deal. Lots of people think you should learn to live with it. They've got a good argument for that until the new model YOU just maidened turns out to be evil. Then it's worth considering doing some TX mixes.

Consider this.............

It's very worthwhile to control your model's takeoff direction with the rudder. A vast majority of modelers will agree with this. Even the "you oughta learn to fly the pig and you'll be a better man for it" crowd.

So what do you think happens when you've got your model blasting down the runway, it's a tail dragger and the tail has come up, and a bump turns it towards the pits, and you hit the rudder stick to turn it away from the mother with twins in the stroller who has just brought hubby a sandwich for lunch and walked right past the sign that says "Only flyers in the Pits" ???????????? Hooo Hahahaaaaaaa, it's time to turn, right? or left? And what happens?

The rudder tries to pitch the nose down with that rudder movement. And it's doing the pitching as fast as the yawing. And the gear is keeping the nose from pitching down, so the airplane does what it can do and the tail goes up some. And then the nose does sorta pitch down. The gear spreads out, the prop starts eating dirt, and the mother has to throw her body in front of the stroller and.......... Man, some days at the field just go SO wrong.......

whatever..............

It's usually worthwhile to have a rudder that only makes the plane yaw.

And it's also nice to have an airplane that when it's on the landing approach, if you decide to keep it from landing in the bushes along the side of the runway and give it a little rudder correction, that it doesn't also decide to nose down into the dirt while turning back onto the runway.

Ya know, Rock, I've been doing this for several years now and STILL don't have the concept of coupling down. I can't figure out when I need it and when I don't. So, I probably put up with some of the behaviors of my airplanes thinking that 'that's the way it is'.

Perhaps a little tutorial on what happens when, and what to do about it (ie, what coupling is needed, and just how much a WAG becomes) would be a good thing. I don't want to re-invent the wheel, here, if someone has done it already, then a link would be nice for those of us that don't know where to look.

And of course, thanks in advance!!!!

CGr.

When is it appropriate to use rudder? Well let me count the ways.

1. During the takeoff roll, it is the only way you can hold the model straight.
2. Whenever you use aileron to make a turn you should also use some rudder to keep the turn coordinated. On full size airplanes you always want to keep the ball centered in a turn. If you do the plane is not likely to do something that will surprise you. (Read that, snap spin)
3. Any time you pull the nose up at greater than 45 degrees a little right rudder will counteract the yaw to the left.
4. Of course there is always knife-edge flight. That’s a given.
5. To fly a perfect roll, either slow or four point, you should use a bit of rudder when at knife-edge.
6. Any aerobatic maneuvers that require snap or spin inputs.
7. On final for landing with a crosswind. Use the rudder to hold the nose into the wind and maintain alignment with the centerline.
8. Last but not least, taxi back to the pits.

Other than the situations listed above, I never use the rudder. Just fly with the right stick.

Like I said, mussle memory. Try to remember all this all at once when first trying it. Do it one thing at a time, for sure, gain some proficiency (read mussle memory or reaction to the maneuver becoming automatic) then follow that up with some practice and then move on the the next step.

CGr.

yetti831,

While I certainly find myself in agreement with nearly everything said here, I'm going to go a different direction:

When does one use the rudder? EXCLUSIVELY, for one flight a day. Meaning this:

Head out to the field for a day. For one flight (first, last, middle, whenever..just pick one) fly the entire flight with Rudder and Elevator only. Don't use the ailerons.

When you reach the point that the rudder/elev flight looks indistinguishable from one with ailerons, and you complete the entire thing, from takeoff to landing, never touching the ailerons...trust me...you'll know when and how to use the rudder.


Must agree with HighPlains...what an OUTSTANDING metaphor.

Hi CGRetired
After years of ignoring the rudder I decided to learn to use it after I had two instances of aileron failures on student planes. I managed to land both planes OK, but I was surprised how difficult it was. Now I frequently do the landing pattern with rudder and elevator only, in both directions. When I fly my Flying Lawnmower I chuckle when I note I'm using rudder input during turns. The mower does not have a rudder! My rudder input now seems to be on automatic pilot. It is intersting that when inverted, the rudder is reversed.

Oh, I absolutely agree. Only problem is that many of us, including me don't often use the rudder. We get into a 'rut' and just fly what we are comfortable with. The suggestion above by gboulton is a good way to get that much needed practice in And it will show up in flying because it makes one more proficient in every aspect of the flying not just the elevator/aileron flyers like me.. although I do use the rudder, I still don't have it down like I should. Practice... is the key, and as soon as I fix my Protege.. grrrr.. darned wind... and stupid me... (a couple hours of work, a little epoxy and CA and it will be good as new) I will get up and do that very thing.

CGr.

gboulton .... when making a turn with the rudder only... the nose seems to drop, and I revert back to the ailerons for safety sake. What's going on there? CG? Trim? What??

CGr.

I learned to fly RC with A two channel plane and radio, A little HOB Cub. Right away I learned rudder. Teaching my students at one point I had A little three channel Cub that was A great teacher, wish I still had it.
I teach landings using elevator, throttle and rudder only, that teaches both rudder and throttle management and the students never know what they are learning so they don't freeze up when they start learning rudder, they have been using it for A long time.

Nose drops when you use ailerons too. For a bunch of reasons...our planes tend to have roll rates that, in a full scale aircraft, would be downright lethal, you compensate without realizing it after years of experience, etc...it's just not as obvious or dramatic.

Specifically, however, it's really nothing more than a function of drag, and the airplane doing what it can to offset the effects. Consider this:

The key to EVERYTHING an airplane does (I'm paraphrasing Wolfgang Langewiesche here) is understanding that at any given angle of attack the airplane will fly at a constant airspeed of X....regardless of power (we'll come back to that in a minute).

Apply rudder, change the drag, airplane tries to re-find the SAME AIRSPEED because it seeks to maintain the SAME ANGLE OF ATTACK (all other things being equal).

There's only one way it can do this...point the nose down.

Now, our problem here is a couple of things. First, the drag isn't equal along the sides of the airplane. That is to say, you roll with ailerons, and for most practical purposes (this isn't technically accurate, but it'll work for this conversation) you've applied the same increased drag to each side as one aileron deflects up, the other down. As such, the application of elevator (and thus the change in the angle of attack of the aircraft) is "consistent" along the length of the aircraft. (Again...something of a gross oversimplification, but it'll work for now).

With rudder, the induced drag is greater on the side the elevator was deflected to. Here's where the real "difference" is from the airplane's point of view. Since it yawed its nose, say, left in this case, it has changed not only the angle of attack of the wings, but also changed THE AMOUNT OF AIR THEY'RE SEEING. In a very real sense, you just gave the airplane one wing that's smaller than the other.

The only option the aircraft has, in its constant, unchangeable, and inarguable effort to ALWAYS maintain its current AoA/Airspeed is to make life easier for itself...point the nose down.

If you REALLY want to "prove" this to yourself...that it is ENTIRELY a function of the aircraft trying to maintain AoA and thus airspeed....try this. When you're out flying rudder/elevator only, give the aircraft a couple clicks of throttle in the turn. Watch the "nose drop" flatten out considerably.

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Now for the boring "more on this later" stuff *heh* This will seem off topic, but really it isn't...it's a long winded pet peeve that directly applies to what airplanes do when you change their attitude, and thus...it applies to how and why the rudder behaves in certain ways. The reader is cautioned that if he/she does not wish to spend the next 5-6 hours reading boring drivel, he/she should probably move on to the next thread

At risk of starting another of RCU's famous "You're wrong, I'm right aerodynamics arguments" the whole "at any given angle of attack the airplane will fly at a constant airspeed of X" has been, for me at least, THE single biggest key to understanding why an airplane does what it does in ANY situation. My maneuvers got cleaner and smoother in full scale aircraft, my full scale landings improved dramatically, my precision RC flying took huge strides, and I even figured out how to fly a heli...ALL nearly "overnight", simply by grasping this.

First, as I've done in several threads before, let me HIGHLY recommend [link=http://www.amazon.com/Stick-Rudder-Explanation-Art-Flying/dp/0070362408]Stick and Rudder: An Explanation of the Art of Flying by Wolfgang Langewiesche [/link]. It will, imo, be the best $17 you EVER spend in aviation...scale, rc, or otherwise. Pretty much everything I'm about to say comes directly from that book.

You've probably heard people say that, when landing (RC or scale), you use the THROTTLE to control altitude, not airspeed, and use the ELEVATOR to control airspeed, not altitude. That is a true statement.

Now..the airplane doesn't KNOW it's landing. It's not self aware, it doesn't say "oh, look, here comes the runway, I must be getting ready to land". So, it's not as if the airplane suddenly becomes this "throttle=altitude, elevator=airspeed" machine. If that correlation is true for landing, it must be, by definition, true for EVERY phase of flight.

And it is.

Whether we accept to believe it or not, the LEFT stick...that is, the THROTTLE...is our up/down stick. The RIGHT stick...the elevator...is our speed up/slow down stick.

Yeah, I know...bull-****. I pull back on the right stick, airplane goes up. I push the left stick forward, airplane goes faster.

Well..yeah...for a brief time. Of course, the problem is that, except for those guys who follow their airplane from the back of a truck...a "brief time" is all we RC guys have. Before we ever have a chance to see the truth of the matter, we're at the other end of the field, and making a turn.

If you have the chance, however, try the following in a scale bird:

Establish straight and level flight at airspeed X. Trim for hands off.
Now...increase power slightly.
First, the airplane will speed up a bit...
Then, for some 'unknown" reason, it starts slowing down....and climbing.
This sequence will repeat a couple times...climb, stop climbing speed up...climb again...each time the "change" becoming less dramatic.
Within a few moments (say, 15-20 seconds or so in most small trainer-type airplanes)...the airplane will have settled down. And what will it be doing?? Flying at PRECISELY the same airspeed as it was before...in a very gentle climb.

End result : You increased POWER, and airspeed stayed the same. ALTITUDE is changing.

Try the same experiment, only instead of changing power, change trim a bit. Bump in a notch or two of up trim.
Plane goes up a bit...slows down...up a bit...slows down...finally settles down. What will it be doing? Flying STRAIGHT AND LEVEL at a LOWER airspeed.

End result : You applied UP ELEVATOR, and the airspeed DROPPED, and the altitude is CONSTANT.

Elevator is a fast/slow control, throttle is up/down.

Now, clearly, we can sit here and go round and round about this "engineering stuff", and we all know that, for PRACTICAL purposes at the RC airfield, if I want my plane to go up, I haul back on that elevator, and up it goes. Quite simply, we just don't have the ROOM or TIME to see the "oscillations" happen that the airplane will go through to regain equilibrium.

But what can help us is knowing that it will do it. If we understand that at any given angle of attack, the airplane will maintain a constant airspeed, we can not HELP but understand that as we change one thing or another, the airplane will ALWAYS try to get to the airspeed it needs to fly at its current AoA. it may take it a few tries, but it'll get there.

When does this really matter? Simple:

What is the SINGLE biggest cause of RC crashes, by far? Stalls. They may have been brought on by any number of factors, but bottom line, the airplane stops flying because we got its angle of attack too high, and it falls like a rock.

And where do we see these, ESPECIALLY with new pilots? landings and takeoffs. Why? Simple:

We taught them to stall their airplanes.

We said, with all confidence, that this right stick here is the elevator. It makes the plane go up and down. Pull back, and it'll go up. Push forward, and it'll go down. And then we 'proved" this to them during flight training.

So new guy goes out, flies around, is coming in for a landing...and the airplane starts to come down "too fast". What does he do? Every "instinct" he has spent the past few months learning and demonstrating to his instructors satisfaction says "Airplane must go up...PULL BACK!"...and it "inexplicably" rolls on its side, falls to the ground, and another thread appears in the Beginners section.

Guess what...if we'd taught him (or, for that matter, could convince ourselves) that elevator is speed control, and throttle is altitude control...his INSTINCT (and ours) would be to do EXACTLY what we'll all tell him in his "I crashed my trainer thread" ANYWAY...use power to control altitude, elevator to control airspeed, when on final approach.

==================================

So, anyway, enough of my rant. Buy Langewiesche's book, and go take your favorite trainer to the field and do some slow flight "experiments" like the ones I mentioned above. If that book...and the single realization contained therein, isn't the most important lesson you've ever learned in RC, come back and let me know, and I'll...oh...I dunno...I'll eat my copy, and post a YouTube video of me doing it.

I've been experimenting with the rudder on the sim, and a bit at the field. This morning I stood in the middle of the field and did circles around myself with just the rudder and elevator. The wind slowed it down to almost a hover at some points. I had a blast! Thanks for the advice everyone.

Wphew.. I knew I would get a handful if I asked, and you truly proved that right. Hey, that's not a complaint, it's a compliment.

One thing. As we gain experience, me included, I've noticed that I tend to fly the plane more now than I did before. Take this past Wednesday. The wind was a constant 13 - 15 mph (my wind guage was set for mph) right down the center line. The gusts were gentle but were getting up to about 18 - 19 mph.. not more than that in the three or so minutes I watched the wind guage.

Anyway, upon coming in for a landing, I kept throttle on and allowed the plane to do what it was going to do on the approach. At the point where I was comfortable with the approach, I cut the throttle. But, this happened much further into the approach than It would have during a no-wind day. Then I watched the plane coming in, and controlled the approach with the elevator with minor, and I do mean minor inputs, until it just touched down. The plane slowed down, yet maintained the altitude until I made the very slight changes in the elevator until it softly touched down. At one point, I was satisfied with the approach, but decided not to land, so I kept the elevator alone and slowly added throttle. The plane evened out, then started a gentle climb without elevator input and that was that.

Good stuff, and I thank you for taking the time. I google'd the book and am going to order it from Amazon. We take an awful lot for granted when we fly these RC aircraft and I can see that based on what you said and my observations when flying. I will take more notice of things on my next flying day.

I'll tell ya, after my trainer days, I bought a Tiger 60 ARF. What was nice about that was it was large enough to see things happen. And that taught me an awful lot once I was able to actually see it doing things and react to my inputs. Good stuff indeed. This is why I preach that people should get larger trainers or larger second planes.. to an extent.. not to the extreme.. to 35% or something, but you get my meaning, I'm sure.

CGr.

One more quick item here.. In an aileron turn, the roll begins then the elevator is pulled in a bit to control the turn rate, the nose drops. So, I add throttle (a few clicks is all that's needed) and the nose stays where it's supposed to be.. then after the turn is complete, reverse the action by starting with the removal of elevator, then the aileron reversal to get wings level, then remove throttle.. this should result in a straight and level reversal of direction (if on a race-track pattern) without a change in altitude.

I would have to presume that this is a practiced thing and will take some time to remember the steps.. but will come natural after a few tanks have been burned making boring (yet useful) race track pattern flights... which I do anyways, and tell people that after being away from this for a couple of weeks, I have to relearn how to fly..

Ok, and thanks again.

Let me just point out one quick thing, for safety purposes. Keep the plane in front of you, don't let it get behind you as 'stood in the middle and did circles around myself'. This is bad for one reason, and perhaps others.. but if you fly at a club, this would imply that you are flying over the pits and this is pretty much verboten at many fields.... and you tend to lose orientation with the field centerline after a while.

Even when you are alone, it's always best to keep it out in front of you and in an oval pattern out there in front so you are stationary and the plane is maneuvering where you have complete view without changing your position. This is the safest way to do this.

Again, this is not scolding, just a pointer to you for keeping it safe for you and others around you.

CGr.

Incidentally, gboulton, I added your reply to my favorite places.. to come back to it and re-read.. thanks again for your time and effort here.

CGr.