JPerrone

Another thread got me interested in the turn skill, and I looked up "how to turn" on youtube, came across a video by alishanmao. Wow, I now think I never knew anything about how to turn a plane!!! Practiced the technique/s in RealFlight and made large improvements in control in just two days.

The combination of rudder + aileron was different between planes. On the Albatros, you almost have to use both aileron & rudder in same direction. Switch, Electristar, you need opposite rudder & aileron to successfully turn. I would expect this to be true for physical models as well.

A common problem I've been having is keeping the plane close in. With a tighter turn, it is easier to do that! Looking forward to practicing this in real life

Regards

Top_Gunn

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I doubt that there is any plane that needs opposite rudder and aileron to turn. Perhaps one of your servos is reversed. Most planes turn by banking, which you do with the ailerons. The rudder is used in turns to keep the plane from yawing in the direction away from the turn.

jetmech05

I will start the turn with ailerons but as I add rudder I usually have to reduce ailerons. Now to make a flat turn its rudder with opposite ailerons

Top_Gunn

My Feedback: (6)

Yes, you can make flat turns that way, and it's kind of fun. But it's not the way beginners should be learning to turn. And there are no planes I know of that "need" opposite rudder to turn, which is what the OP was claiming.

jester_s1

It sounded to me like he meant that the trainers required some opposite aileron when he uses the rudder to turn. That's true if you initiate the turn with the ailerons and then feed in rudder, since those planes have such a strong roll coupling with the rudder. A rudder only turn will work fine with those planes, but if you roll into them and then input rudder it will make them roll too much.

JPerrone

I practiced this with 7-8 planes. The effect using this method was
- turns are much flatter. You could even make them completely flat; but that doesn't seem to work as well as "sort of flat but with some bank"
- turns are slower;
- tighter turn

Enough opposite aileron to make a completely flat turn did not seem to work as well as allowing some amount of banking.

My initial exploration into this topic was to learn how to use rudder, as I have mostly (100%) been using aileron only for turns, and only using rudder for take-off. I think rudder is better for landing; banking at low altitude sometimes doesn't work very well (for example, scrape round with one wing!). As I am practicing this maneuver, I am finding that my fingers are becoming better at coordinating between rudder and aileron, which was the original desire.

For some of the planes, starting the turn with aileron only doesn't work as well as starting with rudder, and then introduce aileron. Each plane seems to have its own unique combination of how much rudder vs aileron, and when to apply it, that results in a flat, tight turn. The Albatros didn't like reverse rudder/aileron at all, and just about wouldn't turn with rudder only

But maybe my RealFlight works differently than others!!

When I said "need opposite rudder/aileron to turn successfully", I meant "need opposite rudder/aileron to flatten the turn and turn tighter than by using aileron only".

Regards

buzzard bait

Good experimentation! Flat turns are fun to do because they look different, but they are not aerodynamically efficient. In a flat turn the plane is skidding and air flow over the wing is somewhat span wise. There is a myth that had currency for awhile about making flat turns with gliders in order to lose less altitude in a turn, but in fact, it doesn't work.

Jim

Top_Gunn

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Exactly right. Fun aside, there's no reason to try to make your turns flat. On some trainers, the ailerons aren't very effective at low speeds, so using rudder to turn when landing is a useful habit to develop. But of course that's rudder in the direction of the turn. I find it hard to believe that you get "tighter" turns by using opposite aileron and rudder. For a really tight turn you can lay it on its side and give it a lot of up elevator. If using rudder in a turn causes you to bank too much because of roll coupling, the best technique is to add less rudder, not to use opposite aileron.

Some day, when the OP is beyond trainers, using opposite rudder in a turn is going to cause his plane to spin. A stall won't make you spin if you're coordinated when the stall occurs, even in a turn, but if you're not coordinated, it can get exciting.

AMA 74894

My Feedback: (1)

yup, I was going to chime in for exactly this reason, one of the main reasons for having a turn and bank indicator in a full scale airplane... cross control stalling.

a cub, Sopwith, really any model big enough to NEED rudder in a turn is a thing of beauty in a forward slip, but ooooo boy it gets ugly quickly if you forget the first commandment:
"maintainest thou airspeed lest the ground smite thee"

anytime you're feeding in opposite ailerons and rudder, KEEP THE AIRSPEED UP

speedracerntrixie

My Feedback: (29)

Jim, as someone who has competed in a US soaring team selection finals, this was a technique I used frequently to expose as much wing to a thermal as possible. It's very useful when the thermal is quite small and would otherwise require more then 40 degree bank angle to stay in the thermal. During a dead air/sink situation you would be correct that it would lessen the sailplanes efficiency.

eddieC

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This works, since the heading change (yaw) occurs quicker. Just use a small amount tho: all things in moderation! Top Gunn is correct in all he's written.

I too don't understand why the OP is using opposite rudder. In modern trainers, just a touch of rudder in the direction of turn is needed for coordinated turns due to the generous amount of dihedral. In earlier aircraft with little/no dihedral (WW1, Cubs with 'barn-door' ailerons), a fair amount of rudder is needed in the direction of turn for coordinated flight. In fact, I find it best in a Cub to lead the turn a bit with rudder, then add aileron. Each aircraft type responds differently of course.

Rob2160

I agree with this.

When you apply aileron the down going aileron produces more lift and the penalty is more drag.

The opposite wing has an aileron that moves up, resulting in less lift and less drag.

If one wing has more drag than the other it causes yaw. In this case it is called 'adverse yaw'

The rudder can be used to compensate for this adverse yaw. By applying rudder in the same direction as the aileron application.

Note that adverse yaw is a function of aileron deflection, not angle of bank. IE you only need to apply rudder while your ailerons are deflected.

This will produce a 'coordinated turn'. If you were in a real aircraft. You would see the balance ball is centred if you apply the correct amount of rudder to compensate adverse yaw.

There are many factors affecting the amount of adverse yaw in a given aircraft design, wing span, wing profile, use of differential or Frise ailerons.

I agree there are many situations where you may want to fly out of balance to achieve a specific objective, eg, thermalling, turning with minimal bank, or side slipping in a crosswind, or aerobatics.

For normal flight, use of rudder will improve your turns by eliminating adverse yaw.

Plenty of good reading if you google 'secondary effect of flight controls'

http://youtu.be/NXMwvEx56Gs

bikerbc

That is right . My flight instructor used to tell me to " Step on the ball " It co-ordinated the turns . Same thing when we fly RC . we need to co-ordinate our turns with the rudder . I agree with Eddie C I like to use both rudder and ailerons to turn my cubs . I find if I don't they will drag their tails especially if your speed is down . If your speed is up its not so bad . I like to fly fairly slow though . Not to point of stalling but slow enough that you are flying on the wing .

JPerrone

Actually, I'm not using opposite rudder. I'm starting the turn with the rudder; the plane banks; I reduce the bank with opposite aileron.
For a left turn, push the rudder to the left. After it starts banking, reduce the bank by pushing the aileron stick to the right.

If the plane is only banking a little bit, this isn't necessary.
If it's banking a bit more than I care for, and one indication of this is that it's losing altitude, then flatten the turn using opposite aileron
If it's losing altitude, dial in a bit of elevator as well.

So this has got lots of fingers going and coordination!!!! Mind you, I'm doing all this experimentation in RealFlight; I don't think I'll just jump into this with the physical model. At least, start with just little corrections and if they don't work-discontinue.

That's not really any different than what I am finding by trying out the different planes. Some of them like opposite aileron; some of them want aileron in the same direction. So, I try a little, if it works fine. If not, think about what it's doing and adjust accordingly.

Regards

Rob2160

Good to experiment in a sim before trying in the real aircraft.

Just letting you know, if you are holding opposite aileron in a turn, it means you have more rudder than necessary to coordinate the turn, and by cross controlling, your aircraft is now in a "skidding turn"

This configuration is setting your aircraft up for a sharp spin entry if you stall.

There is a saying in the full size aerobatic world.

Watch him spin, watch him burn
He held off bank in a skidding turn.

http://www.youtube.com/watch?v=PMhoPJYCvXA http://www.youtube.com/watch?v=swk25weGyYo Here is another good video of an aircraft stalling in a skidding turn (and in slipping turns) you can see a big difference in what happens at the stall.

In a skidding turn the aircraft will drop "into" turn, in a slipping turn it will stall "out of" the turn.

http://www.youtube.com/watch?v=wioGN2SPGps

bikerbc

You do need to correct your bank and bring it back to horizontal flight with the ailerons . This is not so pronounced with a trainer because of the dihedral but when you have little or no dihedral you need to correct your bank with opposite aileron .

SrTelemaster150

I always set up my ailerons W/the servo arm @ 5 O'clock (forward) @ neutral. That achieves mechanical aileron differential, less down than up aileron deflection. That reduced drag on the high wing & also reduces the need for a lot of rudder imput for a coordinated turn.

JPerrone

The skidded turn video is amazing!!! Thanks for sharing!

looks like simulator may be more forgiving than a real plane; maybe more than a model plane. Although I actually find a real model to be easier than RealFlight for some reason.

HarryC

My Feedback: (1)

Some contributors seem to have a fundamental mis-understanding of what the rudder is for.
If you want to steer with rudder, get a boat!
An aircraft is NOT turned with its rudder, if anything the rudder is there to assist the fin to keep it straight on into the airflow, not turn it out of the airflow. Aerobatics such as flat turns, knife edge etc are a different thing - normal balanced flight and proper turns which is what beginners should be doing, use the rudder to keep straight on into the airflow and not to turn or to hold the nose up etc.

An aircraft turns by using the enormous power of the wing lift to move it sideways when the wing is banked. The fin keeps it straight on into the flow thus also making the plane rotate as it changes direction. If the fin does not do the job properly then rudder is used to help it keep the plane going straight on into the airflow. In power planes the slip ball tells the pilot what to do to keep the ball centred, in gliders a yaw string is commonly used. Turns should always be made with the ball/string in the centre, using the rudder if required to keep it there. Turns are never made by pushing the rudder to make the ball/string go off centre. Bank is controlled by ailerons, not by rudder. If you have enough dihedral then a secondary, not a primary, effect of using rudder is to get bank but only after yawing out of balance. Rudder controls yaw, if you want to bank you use the ailerons. If you get adverse yaw while rolling then use rudder to stop it, but that is rudder being used to keep the plane straight to the flow, not to turn it.

You use ailerons to control bank, rudder only if required to keep the plane straight on into the airflow, and as much elevator as required to keep the nose up, even at extreme angles of bank it is the elevator not the rudder that is used to keep the nose up. Please note that a "normal" turn at 90 degrees angle of bank is impossible, by then it has become an aerobatic knife edge manoeuvre, not a normal turn. In general beginners should not be messing about with the rudder during turns as that is the way to get into a spin when turning low and slow coming in to land. Any decent trainer model will not need rudder for turns.

If the nose is dropping and the plane is losing height then it is simply a matter of pulling back further on the elevator. The amount you have to pull back goes up exponentially with the angle of bank, so as the bank gets steeper the extra that you have to pull back goes up more rapidly than the same change at small angles of bank.

Top_Gunn

My Feedback: (6)

Losing altitude in a turn is something you prevent by using up elevator, not by trying to make the turn flatter.

With a model there's no precise way to tell whether your turn is coordinated, because you have no turn-and-bank indicator and you can't feel the seat pushing on one side of your rear end. But you can be sure that if you are cross-controlled your turn isn't coordinated. I get the sense that most of your difficulties come from your apparent belief that flatter turns are desirable. They aren't, except as a way of having fun by making the plane do something that planes don't normally do. Banking is the essence of turning: it makes the lift vector point to the side, and that is what makes the plane turn. The rudder is there mostly to prevent adverse yaw, as Rob2160 explained earlier. It isn't the primary turn control. Even a plane with no ailerons normally turns by banking, because the rudder induces yaw, which, because of the dihedral, makes the plane bank.

HarryC

My Feedback: (1)

http://www.youtube.com/watch?v=uUWZ1M9BxbA
If that's the one you mean, it's a magnificent example of why the average public should not be allowed to publish anything on the internet. It is dangerously and completely wrong. PLEASE ignore what he tells you in that video.

speedracerntrixie

My Feedback: (29)

That's funny, being that we are flying models and don't need to worry about passenger comfort or max efficiency I thought we were free to use rudder as we deem fit.

SrTelemaster150

The rudder is used to keep the nose from pointing high or in other words to keep the tail from sinking. Most non-trainer type airfcraft will need the rudder to keep the axis of the fuselage poniting straight in relationship to the path of flight. As mentioned, it is not to prevent loosing altitude, that is the elevator's function. In a scale aircraft, it take ailerons, rudder & elevator for a coordinated turn.

For those that say the rudder is not for turning. Have you ever flown a 3-channel ship? A rudder that is roll coupled will also bank the aircraft when used. My Sr Tel;emaster had so much roll couple in the rudder, I used full cross control rudder/aileron for knife edge & just released the aileron & keep the (up) rudder in to roll out level.

Rob2160

I don't think anyone will disagree that you can use rudder to turn, as it will change the direction of aircraft flight.

You can also use the secondary effect of rudder very effectively to bank an aircraft. (3 channel aircraft without ailerons work this way)

As a training exercise, in real aircraft I would get the student to fly back to the airport and line up on final using nothing except rudder, elevator trim wheel and throttle. IE hands totally off the joystick (This was simulating a total loss of elevator and aileron control ). It was entirely possible to fly the aircraft that way and is easier than one might expect.

I also agree there are many applications where you deliberately would fly out of balance. But if we are talking about performing a smooth balanced 'efficient' turn in an aircraft the rudder is primarily there to balance adverse yaw and the turn is achieved by tilting the lift vector into the direction you wish to turn. IE Banking.

Yes you need more elevator to stop the nose from dropping as the lift vector is no longer vertical. The greater the bank the more elevator you need for a level turn. At 60 degrees bank you need to sustain 2 G for a level turn. That means twice the angle of attack you have in 1 G level flight assuming a constant airspeed, IE that's a lot of elevator,

DrYankum

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I know we are talking here about trainers and flat turns, but in many Imac turns, flying in the box, many aileron turns are hard banked and approach knife edge. Opposite rudder is often needed to keep the nose from dropping to prevent down grading in the maneuver