I took you to mean that if your model wasn't flying parallel to the runway, you used rudder alone to change the line and avoid being easily seen to be making a turn. Are you actually saying that you hold on into wind rudder all the way along a "straight line"?

Differential is used for two reasons. One to reduce adverse yaw created by the downward aileron producing more drag then the aileron moving up. The second is to counteract the the aileron moving down will result in more gained lift then the wing with the aileron moving up has lost. So by introducing differential you fix both situations. I do agree that for full scale it's not an issue as one can feel the slip and simply lean on the rudder. Our models are a little different as for competition aerobatic pilots we strive to get our airplanes to fly as pure as possible. This means getting rid of as much control cross coupling as possible. Everything is a compromise, while aileron differential will help rolls on the verticals and upright it does do the opposite while inverted. Most guys find that more manageable then having the nose wander on up line rolls. Imagine trying to do 1/2 of an 8 point roll followed by an opposite 3/4 roll on an up line and pulling to an outbound cross box travel 90 degrees to the runway when the airplane is not rolling axially. This can be farther proven by different setups required when ailerons are hinged at center Vs. top hinged on some all composite models. The center hinged requires that through the TX you set positive differential. On a top skin hinge aileron your TX would be set to negative differential because the mechanics of the top hinge actually has you ending up with too much differential.

Correct, when trying to fly a parallel line to the runway in a cross wind blowing inbound I would be holding rudder outbound.

Harry,

A lot of these pattern people think they do that. I think what they're really doing, possibly without being consciously aware of it, is crabbing, and entering the crab by making a skidding turn, which makes the judges happy because the plane doesn't bank. They may even be keeping the plane cross-controlled all the way along. Sort of a Chinese pass, but with the wrong wing down, and then a crab the other way to keep the sideslip from taking them off line. Either that or they aren't really "holding" rudder, they are just using enough rudder to keep the plane where they want it to be (which turns out to be none, but with your mind on other things they may not notice that).

There may be some pattern fliers who are also full-scale pilots, but I've never met one. No full-scale pilot could possibly believe that holding rudder can either cause you to yaw or keep you going straight, depending on what you want it to do.

Al this may be quite true however I think it's because full scale airplanes have roll and pitch coupling when rudder is applied. On a high end pattern or IMAC airplane we strive to eliminate these tenancies. On a well set up aerobatic airplane when you give a rudder command you get yaw and nothing else. This is why when you look at an Extra 300L competition model you will notice some scale deviations. Most have the engine lowered, all have the stab lowered and it's usually on the thrust line, the rudder has more cord on the bottom and the wing has been raised. All these things contribute to the goal of having no control cross coupling. As far as not holding rudder but thinking we do, not buying it. There have been times when the wind is strong enough I can see my airplane 15 degrees off from path of flight. If one does not hold rudder in a cross wind then with each pass he would be getting blown inward or outward. Some can be corrected in the turn around maneuvers, but eventually you would either have the judges looking strait up or squinting to try to figure out what the dot 200 yards out is doing.

If you get yaw and nothing else when you apply rudder, then applying rudder and holding it would cause you to keep yawing, and you'd be making a flat turn. That would not keep you flying in a straight line.

Sure it would, we are only holding enough rudder to counteract the force of the wind. Imagine driving in a strong cross wind. You have to hold the wheel slightly towards the wind but your not doing a constant turn. Sailboats also do the same thing. If it were under clam conditions you would be correct.

The wind doesn't make a plane yaw. It just carries it in the direction the wind is blowing, without changing its heading at all. The car and sailboat analogies don't work, because they are not moving in a mass of air. The better analogy with a boat is a boat moving in a stream with a current. say you point the boat due east on a north-south stream with the water flowing south. If you row without turning, the bow of the boat will keep pointing east, but the boat will move sideways (relative to the ground) at tem miles an hour. It doesn't turn. A plane flying in a mass of moving air behaves the same way.

An airplane in coordinated flight "sees" wind only from straight ahead. Once off the ground, a plane in a steady wind handles absolutely the same way as a plane on a calm day. (For much, much more on this see the "downwind turn myth" thread in the Jets forum.)

Again, this is something full-scale pilots appreciate but modelers can easily get mixed up about. Full scale gliders use yaw strings (strings attached to the plane at the bottom of the center of the windshield). Whether the glider is flying upwind, downwind, or in a crosswind, the string goes straight up the center of the windshield. A string like that on a car or boat would behave very differently.

Al you are missing a couple points, one on a full scale airplane you really would not care about the ground track, the and a 15 knot wind is not going to have as much effect on a full scale airplane as it has on a model. You seem to believe that without any any type of correction that the airplane would drift with the wind direction. So let me ask this question of you. How would one control the drift while keeping wings level? And let me state once again, I have won numerous pattern and IMAC contests using this technique, I'm not just blowing smoke here.

I do agree that airplanes do not see wind, they only see airspeed but they also drift with the wind direction if in a cross wind. If your statements were true then landing in a cross wind would be the same as landing in a head wind correct?

+1

Speedracerntrixie, you do not hold on rudder into a crosswind, as Al described above there is no crosswind as far as the aerodynamics of the plane is concerned. As Al also pointed out, a lot of people think and say they are holding in rudder when they aren't, or used it just for a moment to yaw onto a different heading without doing it properly by banking and turning which comes right back to my original point about it being done as a deception to judges. If you hold on rudder all the time, no matter how little, the plane will yaw and change direction, it won't go in a straight line

If you want to follow a particular track over the ground, and normally we do (and full-size pilots care very much about ground track!), and there is a wind blowing from a side of that track, you turn the plane slightly into that wind and then put all the controls back at the centre. You do not hold on any rudder or aileron. The plane is flying head on into its headwind, it doesn't feel any wind on its side. The plane appears to be crabbing slightly across the ground, but aerodynamically the only wind it feels is its own head wind straight on. Landing in a cross wind is the same as landing in any wind or no wind, you turn the plane until its track is straight down the runway and then put all the controls in the centre. If there is a cross wind you may notice the plane appears to be crabbing slightly along the ground. You don't come down the approach with rudder or aileron held on, the controls are in exactly the same place as if there was a headwind or no wind. At the flare just an instant before touchdown you use rudder away from the wind side to yaw the plane along the runway line so that the wheels don't get a side load, but with prop planes you often have to be using rudder anyway as the throttle is brought to idle and the rudder position for balanced flight promptly swings a little due to the change in the spiral flow.

Many model fliers have been wrongly told that you side-slip down the landing approach in a crosswind, and the error is further worsened by almost always being taught to side-slip the wrong direction! There are two ways to make an approach in a side wind. Fly normally as you would for any required track with the controls at the centre, as I described in the paragraph above, or do a side-slip. Flying normally is by far the easier and safer, side-slip is more difficult and raises the stall speed and means that if you do stall it will probably flick into a spin instantly. But if you must do a side-slip, please do it properly. Model fliers apply their misunderstanding of rudder, and put rudder into the cross-wind and then bank away from the wind, e.g. cross wind from the right, they rudder right and bank left. But this is to muddle the processes that should happen. You don't yaw into the wind to compensate for it. You bank into the wind and let the huge power of the wing compensate for the wind drift. But that would make you turn, so you then apply rudder away from the turn, i.e. away from the wind, to stop the plane from turning. So with a cross wind from the right, you bank right and rudder left.

Therefore in both methods, the normal albeit crabbed approach, and the side-slip approach, the rudder when applied will be away from the wind, not into it.

The only way to keep from drifting while holding the wings level is to crab into the wind. Pattern flying consists in part of making the plane look like it's doing something different than what it's really doing. Crabbing just a little bit, so it doesn't much show from the ground. Slipping just a little bit, so it doesn't show from the ground. If you hold rudder in a crosswind, or not in a crosswind for that matter, the plane will yaw, and keep yawing. Let's take a concrete illustration. Your runway is east-west, and a wind is blowing from the north. You want to make the plane look like it is flying straight east or west, with the fuselage lined up straight east or west and the wings level. It is not possible for any airplane to do that. So you come as close as you can to making it look that way. With practice you can do this well. But I am absolutely sure that you can't do it by applying rudder, holding it, and keeping the wings level. Because doing that with the rudder will make the plane yaw, and keep yawing.

Congratulations on your trophies. No number of trophies changes the laws of physics.

Harry's post appeared while I was typing mind. Everything he says is true, with one small qualification. With full-scale taildraggers, some pilots prefer a sideslip on final (with the wing down on the side from which the wind is blowing) to crabbing. The reason is that slipping lets you keep the fuselage pointing straight down the runway through the whole final approach, which in turn reduces your chance of a ground loop. With models, as Harry says, crabbing is much, much easier. (It's not because models fly differently than full-sized planes, its that when you're sitting in the cockpit you can know exactly what your bank angle is and you can tell, much better than with a model, if you are lined up straight.)

As I stated, banking the wings to compensate for a cross wind will result in a down grade, that's why we use rudder. If you doubt this then go fly your model in a cross wind and hold the same box depth while keeping the wings level. I bet you can't do it.

This all reminds me of a conversation I had with Sean Tucker. He was out watching on of our IMAC contests and asked why there were no bi planes. I told him that it's because they flew poorly. The look of horror on his face was priceless and at first he couldn't wrap his head around it but as the conversation went on and he learned about the different perspectives full scale and R/C pilots deal with he got it. Bottom line is that we have to deal with the cross winds otherwise we drift with it. I think we all agree with that one. We get downgraded if we enter or exit a maneuver without wings level. Rudder is the only option. I'm not saying this is proper technique for full scale but is commonplace for R/C pattern and IMAC. This is why full scale pilots usually get to a certain level with R/C and no more. They have difficulty leaving behind what was taught to them as it applies to full scale aircraft and set up and fly their models in the same manner as they would full scale thus leaving much of the airplane's potential performance on the ground.

So do you have an explanation for how you keep the plane from continuing to yaw when you hold rudder while keeping the wings level? You seem to think that applying and holding rudder will cause your plane to move straight sideways, counteracting what the wind is doing to it, without yawing. Rudders don't do that.

Also because some of those taildraggers have engines you can't see over such as Spitfire or Pitts Special which may make a sideslip even in no crosswind just to see where they are going, and also because full size have an airspeed indicator so can be sure they have raised their speed during a sideslip, which model fliers can't be unless speed is raised quite a bit more than required just so you can see the difference from the ground.

We can do it, by using rudder to yaw into the wind direction at the start of each pass, but only holding rudder on briefly until the necessary new heading is obtained, and then promptly putting rudder back to neutral for the rest of that straight leg.
This is just a deception for the made-up rules of that particular competition. If you want to fly parallel to the runway and the wind is blowing from the right, you turn slightly right to point slightly into wind and then centre all the controls. Your comp rules won't allow you to turn properly so you have to cheat at a turn by yawing with rudder rather than banking until the same new heading is obtained as if you had done a banking turn, and then all controls to centre. No rudder, no aileron, the plane will go straight along the runway, slightly crabbing, the end effect is the same in both methods. Straight track, same heading, slightly crabbed into wind, controls at centre. The only difference is that right at the start of each pass you did a flat turn rather than a proper banked turn to set the new heading. You can not hold on the rudder, no matter how little, keep the wings level and go in a straight line, the plane will make a flat turn.

Harry, then I suggest you actually try what you are suggesting here. IMO you two guys are still talking theory and have not actually flown an R/C model with the goal of keeping a constant depth. Perhaps we should agree to disagree until one of you guys actually gives it a try with someone standing behind you letting you know if you are drifting or not and if your wings are being kept level. Trust me it would be a big eye opener. I personally find it hard to believe that you guys want to argue this point when it's obvious that neither on of you guys have pattern or IMAC experience. Personally I would not think about giving full scale pilots advise on piloting their aircraft simply because I am not a full scale pilot and am not qualified to do so. IMO you two trying to convince me that I am flying my models incorrectly is the same, you just don't have that level of experience. As I said gentlemen, agree to dis agree. At this point all 3 of us are just repeating ourselves.

since this is neither the aerobatics, aerodynamics nor any sort of full scale forum, but rather is the RC airplane beginner's forum,
I could not agree more.

+1 You said it. Flying in RNP 1 airspace, ground track is critical if you want to keep your licence.

Fly an ILS with 25 Kts crosswind.. The only thing that matters is ground track. Drift is compensated for by offset heading (crabbing) but in balance.

IE no rudder input held at all until the flare when you apply rudder to straighten the nose so you don't land sideways.

Rob I 100% agree however do this in a pattern or IMAC contest and you loose at least 1 point per maneuver for not entering with wings level. 1 point per maneuver times 10 maneuvers per sequence multiplied by the K factor and 2 sequences per flight and you could easily be leaving behind 200 points per flight. It's easy to see what motivates us to find other options. As Jim pointed out this isn't really the proper place, if we want to further discuss this maybe the IMAC, pattern or aerodynamics forum would be best. I personally would like to see it addresses in the Pattern forum as there is where it applies beast and that forum has good participation.

+1 :) I really do hate to be a wet blanket...
(yup, I've got a couple thousand hours on an ILS in a crosswind :) )
The pattern forums here are still very much alive and kicking!

most of all have fun, guys.

This isn't really about aerobatics or aerodynamics. It's about the most basic piloting skills and the use/misuse of the rudder which is relevant to beginners and many experienced model fliers who have sadly been misled.

I agree. If we're really going to have a discussion about whether applying rudder makes an airplane yaw, where better than the beginners forum? This is, or ought to be, a first-day-of-school topic.

My pattern bud corrects for a crosswind as Harry C and others stated, yawing briefly with rudder into the crosswind, then neutralizing to hold the ground track with wings level. If one were to continue holding rudder, the plane would continue yawing. Consider holding an upline or downline in a crosswind; you don't continuously hold rudder, as it would change heading.


I fly full-scale also and we use the crab-n-kick method with low-wing birds like Citation biz jets that have very little wingtip clearance; wings level and crabbed to offset the crosswind (not holding rudder there), then kick the nose straight during the flare just prior to the mains touching.
I don't consider it a detriment flying FS, in fact there's transference between both RC and FS, each informs the other.

Rob, well said. Passengers in the back seat will thank you for properly using the rudder. The rudder is very important for all phases of flight ; Taxi, takeoff, climb, turns, slips, and landings. Again, very well said....Dave

Sorry but this is just wrong, no if's or but's.

Any rudder you hold in will cause you plane to fly through the airmass in an arc if your wings are level. The only exception to this is is the rudder is compensating for a bad engine thrustline or asymetrical drag.

IF you are flying inside wing low like many fliers do, and the Aussie's observations at many F3A WC's suggest, even the top guys do it, then yes you will need to hold rudder out if the wind is blowing in or calm. I've personally seen a current top US pilot flying inside wing low and an arcing baseline and it wasn't by accident as every pass (left and right) was inside wing low with an arcing baseline..

I think you master F/S and R/C pilot types that seem to flock around the beginner's forum should get back to actually flying instead of keyboarding us of all your F/S and R/C wisdom, and while you're at it, maybe you can get some video of your own R/C flying to share with us lesser talented pilots so we may learn and see for ourselves of your masterful R/C flying skills and just who is really qualified to teach us the basic 101s of flight... There seems to be a great deal of talk the talk types in these forums but not many that walk the walk. Just an observation, so carry on.:cool:

Bob

Don't get your panties in a bunch there Sensei. It doesn't take a hotshot pilot to know that applying rudder makes a plane yaw, and keeping the rudder deflected makes it keep yawing unless you do something to stop it. "I'm a better pilot than you, so everything you say is wrong" is not a persuasive argument. If memory serves, you once posted a comment saying that you handle a crosswind by dropping the wing on the downwind side and applying opposite rudder. Is thaat right, or do you have one of those magic rudders that cancels out a crosswind without doing anything else?

So you want us to leave beginners at the mercy of the likes of that dreadful video? Who are the beginners to ask, other beginners?

LOL. I see you remembered my words to you old boy... Anyway ding, ding, ding, we have our first expert talk, talk, talk, with nothing to show. Next...

Bob

You guys just don't get it do you? If the airplane is drifting with the wind then you must counter this action somehow. Applying a LITTLE rudder to the direction of the wind will counteract this drift. Someone used the example of the sailplane with a string with the string being strait back. Well DUHHHH that is because the sailplane is drifting with the wind. Another good example is a hot air balloon, from the perspective of a person in the basket it's dead calm. As far as a top leavel pattern pilot flying inside wing down, I'm sure he was down graded for this. If I was sitting in the judges chair ( and I have judged hundreds of IMAC unlimited rounds ) I would have downgraded him. To imply that it was intentional is just ignorance. I'm with Sensi, enough with the talk, it's time for you guys to show us something other then what you read in a full scale book that was published decades ago or what your full scale instructors taught you decades ago. You all may want to check where you are while you are at it, last time I looked this is RCU as in remote control. If you want to debate FULL SCALE piloting techniques you may want to go to that forum to do so.

I'm sorry but it's you that doesn't get it, you are completely wrong. Full-size or model is irrelevant, you don't hold in rudder to counter wind drift, holding in rudder will make the plane fly in a circle.

Speed,

The idea that applying rudder make a plane yaw is not (just) something we read in a book or heard from an instructor. It's intro to flying 101. Every pilot should know this. Saying "show me a video" does not prove that it's wrong. Nobody disagrees with your claim that a pilot can counter a plane's tendency to drift with the wind. Can you show me something that tells pilots that they can do this without either crabbing or slipping (or, in a multi-engine plane, playing with thrust)? If it were true, you'd think it would have been published somewhere, wouldn't you?

Since there are an infinite number of possible wind directions compared to the direction of flight, and only two directions (head on and tailwind) that have no side wind component to the desired track, then almost every part of any flight is done with a sidewind component of some value. Do you really think for even a nano-second, that all those aircraft doing long journeys for hours on end are holding in some rudder all the way?

Top, show me any publications that deal with advanced R/C flying. There aren't any. This is the thing you guys keep getting stuck on. A 15 knot winds influence on a full scale airplane is not the same as it would be on a model. Go fly your GA airplane in a 40 knot wind and then you may get something close. You are correct that physics don't change but because of size, wing loading, power ratio ect. the way our models react to these physics is different then what the reaction of a full scale airplane. I'm sorry you don't get that. The fact that our competition models fly truer ( Less control cross coupling ) makes a difference too. I'm betting that every R/C model you have ever flown ( and full scale too ) has had a roll couple with rudder application. This is where your arc is coming from, the roll couple. I'm betting you have never flown an airplane that exhibits pure yaw control with rudder input and no roll or pitch couple. Think about this for a few minuets before you reply. I will agree that for most airplanes out there you guys are correct, the only reason I jumped on this thread is that you guys seem to be wanting to brow beat this into an absolute and it just isn't so.

Agian.............Harry try to understand this time. WE ARE TALKING ABOUT MODELS!!!!!!! What about this do you not get?

Irrelevant. Please show me the parameter in any law of physics that inputs the variable model or full size? Since some models are bigger than some of the smallest full size, please define the cross over point so that we know it is a model or a full size from the point of view of handling. Please describe the mechanism by which an aircraft knows it is a model or a full size so that it handles differently.

As I said in an earlier posts, there are model fliers who form a cult religion about the misuse of rudder and there is nothing in this universe that can show them otherwise.

Harry, the main difference is wing loading. At what point a model becomes full scale? you and I know there is no such point. This just shows that you are stuck on absolutes, black and white if you will. You also know that this question has no real defining answer.As far as the cult thing, aren't you and Top Gunn guilty of this on the opposite side of the fence? I have offered explanation of the fact that you two have no experience flying a certain type of R/C model. I suppose given the opportunity you would tell Jeff Gordon that he is driving his car incorrectly because something he did goes against what you were taught. Go fly an airplane without control cross coupling and then you might understand my perspective.

Eh, you're the one who insists that a plane handles differently depending on whether it is a model or a full size, that is the absolutism.
Wing loading is irrelevant, once again please define the cross over point, show me the equations, where it describes how below a certain wing loading needs rudder into a side wind and above that wing loading it doesn't.