Rudder Pedals are backwards!

[mcurcio1989]

I took my first official flight instruction last week and the trainer plane has a rudder bar and while taxiing on the ground I realized why it was such an unnatural feeling. If I want the plane to rotate clockwise about it's longitudinal axis I rotate the stick (or yoke) clockwise about its longitudinal axis (from the pilots perspective), same thing for lateral axis. This is true for all other vehicle controls like handlebars or a steering wheel. The only place where it doesn't hold true is on boats steered with a tiller (thanks to physics).

Rudder on the other hand is the opposite. Now I know in most cases you have pedals but the movement of the feet is always coordinated so that the rotation of the controls s perceived about the vertical axis which is logical given that that is what you are controlling.

Any explanation for why this makes sense? I know I am over thinking things but it is kind of bugging me now!

[CharlieTango]

I bet the early designers/builders determined this. It is simple rather than complex to have a cable pull both the tailwheel and the rudder towards that pedal.

[mcurcio1989]

yeah but what I am saying is that the control cables or linkage should just be cross. So both the tailwheel and rudder should act the opposite of how they do now. It would not be complex at all. Obviously there is no going back now but it is not an intuitive control. . . or it is and everything else isn't

[MovingOn]

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[FastEddieB]

This has come up before.

I think it may be memories of this that make a plane's pedals feel backwards.

[CharlieTango]

Handlebars on a bicycle actually work like a rudder, to turn right you push on the right.

If you attempt to make a right turn on your bicycle before first leaning your bicycle over to the right, centrifugal forces will cause you to crash by falling over to the left. (These centrifugal forces are the same ones that throw you to the left when you drive a car around a hard right turn.) Leaning the bicycle to the right allows gravity to cancel the centrifugal forces. But how do you get the get the bike to lean to the right? By countersteering, i.e. by turning the handlebars to the left.

[drseti]

Don't think so much about turning, just visualize making the aircraft yaw. To yaw right, kick the nose to the right with right rudder. To yaw left, kick the nose to the left with left rudder. (It's just like counter-steering on a motorcycle -- put pressure on the right handlebar to lean right and turn right; press on the left handlebar to lean left and turn left.)

As for coordinated turns, there are two ways to approach this. The conventional one is to imagine that the ailerons turn the airplane, so you steer right (with your hand) to turn right. If you do this, you have to use rudder to overcome adverse yaw. That's the way it's normally taught.

But, there is an alternative (and admittedly unconventional) way to approach this, which actually may be more intuitive for some. To turn right, you need to yaw right (kick the nose to the right with right rudder), and then use the ailerons to roll the wing in that direction, so as to correct for adverse roll. To turn left, yaw left with left rudder, and while doing so, apply left stick or yoke, to overcome adverse roll.

If you learn this way, you will automatically use your rudders to point the nose (whether on the ground and in the air), and then use ailerons either to keep the wings level (in level flight), or roll them for a coordinate turn. Using this approach, it's the rudder that turns the airplane, not the ailerons -- the ailerons are your bank control.

Confused yet?

[CharlieTango]

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Confused yet?

I like the argument that it is the elevator that causes the plane to turn, not ailerons or rudder.

Technically a turn is a bend in the plane's flight path and bending the plane's flight path is done with the elevator. A knife edge pass shows the ailerons only position the attitude but doesn't turn the plane. A forward slip shows the rudder doesn't turn the plane, if the elevator isn't correctly positioned there is no turn.

[Merlinspop]

I thought about that way at first and had a hard time overcoming it. Instead of rotating on the axis, think "go that way." Whichever pedal (rudder or brake) you push, the nose will go that way.

This also is a good way to think about the elevator control. Push the yoke or stick away from you and the nose will rotate away from you. Pull and the nose comes toward you. This, to me, is better than "pull (to go) up" because it works even when inverted.

[MovingOn]

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[CharlieTango]

When the plane is banked, with the ailerons, a portion of the wing's life is diverted from vertical to horizontal and pulls the airplane in that direction. The downward aileron creates more drag than the upward aileron. This is over come with rudder pressure in the direction of the turn. The reduced vertical component of lift from the wings creates a need for back pressure on the elevator. Don't make this more complicated than it is.

In a knife-edge pass manuever all of the lift is diverted from vertical to horizontal but it doesn't pull the airplane in either direction because the elevator's position.

Your scenario ceases to be true if you use enough forward stoke to change from positive to neutral lift.

[MovingOn]

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[CharlieTango]

Actually we are talking about the intuitiveness of how our controls are rigged. The OP is perceptive enough to point out that in 2-axis the rotation is consistent with the movement of the control but on the pedals whether steering on the ground or moving the nose left or right the rudder seems to be an exception.

Your explanation on how to co-ordinate a turn does little to understand this inconsistency.

When you transition from a weight shift LSA to a 3-axis control LSA you experience a reversal of control. In the weight shift LSA you push to raise the nose and pull to lower it yet somehow this reversal is intuitive. In my mind in the weight shift I am hanging below the wing and have to push up and in the 3-axis plane I am controlling from above and therefore pull up.

Both are intuitive because the results of the input confirm. Imagine getting your plane out of the shop with the ailerons reversed, would you do an aileron roll or crash into the ground? Maybe but if you had a moment to figure it out you would be able to fly and land. As I said in my first post the rigging is likely a result of the earliest designs using the simplest method to rig. Once it was established no-one would want to reverse it and cause confusion.

Bottom line is the way controls are rigged is very intuitive, the observation was a good one but not really worth worrying about.

[FastEddieB]

Trying to think back almost 40 years, I think I found the rudder pedals "backwards" at first as well.

I would think anyone who has used their feet to steer a sled in the past might have that same initial impression.

[drseti]

Not just a sled, Eddie. Same goes for a soapbox derby car. We used to use a 2x4 as a front axle, pivoting on a bolt, with wagon wheels attached to its ends, and steered by pushing on it with our feet. (but that was 60 years ago so maybe I misremember.).