Top_Gunn

My Feedback: (6)

No full scale pilot lands any plane by using the ailerons to keep the wings level and steering with the rudder. As another poster pointed out earlier, it's a myth that RC pilots should do this. I don't fly that way, none of my students flies that way, and I don't know anybody else who does. If it works for you, fine. But recommending this to people looking for flying tips is giving poor advice.

As for slips, I don't understand your point. It's true that forward slips and side slips are different. But each of them is uncoordinated, as I said. It's also true that you wouldn't do a Chinese pass with a 747. Nobody said you would. If you are steering with the rudder and keeping the wings level, all your turns are skidding. There's nothing to be gained by doing that.

HarryC

My Feedback: (1)

Sadly I can point to a lot of modellers (but never full-size pilots) who hold it as a God-given truth and will argue vehemently that you steer a plane with rudder, or you steer it on approach to land with rudder, that you pick up a lowered wing with rudder, or that you hold in rudder constantly into wind during any crosswind, and all sorts of other nonsense about the rudder.

Since we are all used to the idea of steering a boat or a car etc simply by yawing, the innocent trainee naturally believes that rudder is a steering control for an aircraft too. Add in a cross wind, and the myths and bad flying become terrible. When those who have really been taught to fly try to explain to them the error of this, the rudderista cult usually get rather heated about it, and cling ever harder to the myths and malpractice and abuse of the rudder.

Top_Gunn

My Feedback: (6)

Yeah, there are lots of them here. The myth about how you should hold rudder constantly into the wind to land in a crosswind is balanced by the myth that your plane will "weathervane" into the wind by itself when flying in a crosswind. I suspect that there are some people who hold both of these views, strange as that may seem. I've never met a rudder-steerer in person, though.

(I should add that on some models the ailerons become ineffective at low speed, making use of rudder on final advisable. It's not really "steering with the rudder," though, it's using the rudder plus dihedral to create bank.)

sensei

What does the rudder in an airplane do?


The rudder is used to control the airplane on the yaw axis (left and right.) It is most commonly used to keep an aircraft "coordinated" through a turn.

During a turn, the pilot first uses the ailerons to roll the aircraft towards the direction he wishes to turn. Once the desired bank-angle is achieved, the pilot will use the elevators to maintain altitude, and make minor adjustments with the ailerons to maintain the bank angle. During the turn the aircraft may have a tendency to "skid" meaning the tail of the aircraft does not follow directly behind the nose of the aircraft, just like a car skidding around an icy corner. There are many reasons that this is undesirable, not the least of which is the comfort of the passengers. The pilot will use the rudder to keep the aircraft "coordinated" through the turn. To the passengers in back, a properly coordinated turn will feel no different than straight and level flight, whereas a skidding turn will feel like zipping around a corner in a car.

The rudder is also used to counteract "adverse yaw" which is the tendency of the aircraft to yaw in the opposite direction when using the ailerons to adjust the bank angle. The reason for this is because the ailerons produce additional drag when they are being deployed, the additional drag produced is not left/right symmetrical and thus the aircraft will yaw towards the side where there is more drag.

P-factor also plays an important role with propeller-driven aircraft. When a propeller-driven aircraft is at a high power setting and in a climbing configuration (such as just after takeoff) the angle of airflow onto the prop produces thrust stronger on one side of the prop arc than on the other. The spiraling wake of the spinning propeller also contributes to P-factor. This makes the aircraft tend to yaw left requiring the pilot to activate some right-rudder to counteract it.

When a multi-engined aircraft loses one engine, the thrust of the remaining engine will of course be off-centered in relation to the aircraft. This can lead to a very dangerous situation if the pilot does not counter-act this off-center thrust with the rudder. For this reason, multi-engined aircraft almost always have a rudder trim-tab which allows the pilot to set the rudder to whatever position is needed, but without having to exhert constant pressure on the rudder pedals.

Aircraft also make use of the rudder during cross-wind landings. During a cross-wind landing, the aircraft obviously must point the nose to the upwind side slightly in order to maintain alignment with the runway. Think of rowing a canoe across a fast-moving stream. You would need to point the canoe up-stream in order to cross the stream directly, otherwise you will wind up downstream. In a cross-wind landing, the pilot must maintain this up-wind pointed angle (crab angle) all the way down the glideslope until immediately before touchdown. Right before touchdown, the pilot must use the rudder to align the aircraft heading with the runway heading.

HarryC

My Feedback: (1)

Shall we hold a sweepstake on how long until someone claims the Piper Cub has to be steered with rudder on approach?

Model fliers constantly misunderstand what proper pilots are doing with the rudder. They will often see rudder being applied with the turn and believe it is the rudder making the turn. Actually it is quite the opposite. The rudder is being used to prevent a turn. The rudder assists the fin. The fin is there to keep the plane pointing straight ahead. Sometimes it can't do it, due to things like adverse yaw from ailerons, spiralling flow from the prop and so on, and the plane starts pointing off to one side. Then the fin needs a bit of help and it gets it from the rudder. The rudder is used to help the fin to keep the plane straight. To use the rudder to point the plane out to one side breaks the primary point of having the fin and rudder in the first place.

When pilots correctly apply rudder with a turn it is not to make the plane turn inwards but to stop it turning outward due to e.g adverse yaw. The pilot is using the rudder to keep the plane "straight". The pilot is bringing the slip-ball or yaw string back into the middle, not pushing it out to one side. But non-pilots don't see that, they see turn left, rudder left, therefore rudder is doing the turn, they don't see it is just enough left rudder to prevent a right turn.

At low speeds, adverse yaw becomes more pronounced, so more rudder is required to stop it and keep the plane straight, hence some model fliers thinking even more strongly that rudder is the steering.

HarryC

My Feedback: (1)

You don't make it explicit so it may be misunderstood by the rudder abusers, I am sure what you meant to say is that the pilot makes the upwind pointed angle by turning the plane in the normal manner with ailerons, and not by holding on rudder into the wind.

john josey

I'm going to make a determined effort to master this move this year bob, i will invest in a sim and even just spend 30min a day from now till march when the weather gets a bit better here. I'll try and post some video of my progress as we go.

sensei

Sounds like a good plan, I wish you the best.

Bob

bogbeagle

Guys ... I've never heard of a "forward slip" can someone explain it to me?

Oh, and how does it differ from a sideslip?

sensei

All I can really say is that if I am landing in a cross wind, I will carry rudder into the wind and use cross control ailerons impute leveling the wings until just before touchdown, then I neutral the controls and settle in. I really never try to over analyze stuff, I just kinda feel what the airplane is doing. But that just me...

Here is another windy day flight with my scratch built 52% Extra w/s 150" The video shows allot of rudder action but to tell you the truth, it is just a motor reaction, I for the most part do not even think about what I am doing, it just happens now days. Double clicking on the video will give you full screen viewing.

http://vimeo.com/22211697

Bob

Top_Gunn

My Feedback: (6)

Interesting, because this is the exact opposite of one way of landing in a crosswind. The easiest way to deal with a crosswind is just to crab into the wind enough to keep the plane flying straight down the runway (but with the nose pointed somewhat toward the wind direction, because you're crabbing). When you do this with a full-scale plane you'd use rudder (yawing away from the wind direction) to straighten the plane just before touchdown. You can use the rudder this way with a model, too, but it's really not necessary except maybe with a very large model and a strong crosswind. The harder way to deal with a crosswind is to slip: use the ailerons to hold the upwind wing down a little and use opposite rudder (i.e. away from the wind direction) to keep the plane flying straight. This is sometimes called a "Chinese pass," though it probably shouldn't be.

Interestingly, with both these techniques the rudder is turned in a direction that would make the plane yaw away from the wind if there were no other inputs. I know of no full-scale landing technique that calls for using rudder to yaw toward the wind.

I have no desire to change the way you fly. But people looking for tips shouldn't be given bad advice.

HarryC

My Feedback: (1)

Top Gunn is correct. Sensei, what you are doing is totally wrong. You do not hold on rudder into wind.

There are two ways to land in a cross wind. Either crabbing by slightly turning in the normal way into wind then levelling up and not touching thrudder until a blip of away from wind rudder at touchdown, or bank into wind to let the power of the wing oppose the wind then apply rudder away from the wind to prevent the plane from turning.

Either way, the rudder is only ever applied away from, and not into wind.

Crabbing is vastly easier and safer than sideslipping. Why so many modellers think that sideslipping is the way to land beats me, it's just another modellers myth.


So, here is my tip to make any of you a better pilot - book into a full-size flying school for some proper pilot training. Too many modellers have had extremely poor "training" and carry out some really bad practices. Proper pilot training would destroy lots of myths, greatly increase understanding, and result in much better piloting.

MajorTomski

But then again in a 1:1 DC-3 if you did that you'd be exhausted by the end of the flight. Contrary to your experiance a DC-3 is a rudder airplane. You initiate a turn by pressing in a bunch of rudder in the direction you want to go followed by aileron to increase the bank angle.

The model flyer MUST remember that much of what you are reading from the 1:1 guys is airframe specific. To actually know how your airplane flys you must just go fly your own plane and learn what is correct for that plane.

sensei

OK if you guys say so, as I stated in my last post, that is just me and the videos I posted show how it works for me in 20 to 30 mph cross wind landings. Can you guys post some video of your way for us to see in similar environmental landing conditions.

Thanks in advance,

Bob

sensei

The model flyer MUST remember that much of what you are reading from the 1:1 guys is airframe specific. To actually know how your airplane flies you must just go fly your own plane and learn what is correct for that plane.


I agree.

Bob

HighPlains

My Feedback: (1)

A forward slip and side slip are two different maneuvers, though both are cross controlled with respect to rudder and aileron inputs.

The forward slip maintains the same ground path, with the heading of the airplane off axis to that path. These are great fun in full sized airplanes, especially when the wind is to the right side of the nose. Mostly used to drop a great deal of altitude without the use of flaps

The side slip is using aileron to bank into a cross wind, and the rudder is used to hold the heading of the aircraft the same direction as the flight path. With a GA high wing airplane, you can do this right down to the runway, touching down on the up wind wheel first. If you are really skilled, you can add power and stay on just that wheel for some distance.

speedracerntrixie

My Feedback: (29)

Bob, My comments are sure to break this into a debate of the full scale pilots on one side and the model pilots on the other but what the heck. The guys that are coming in here on these forums and telling us the " Proper " way to fly our MODELS need to keep more of an open mind. Our models operate differently then a full scale airplane that has far less power to weight and far more wing loading. Bob is correct in the way he describes cross wind landings with a lightly loaded aerobatic model. Appliying rudder into the wind is simply to hold position and has little to do with attitude. Just before touch down the rudder is nuetralized as to not rip the gear off the airplane. Simple as that. Bob and I have done literally thousands of landings that way. For the life of me I just can't understand why someone who has most likely never flown either a full scale Extra or a 40% Extra feel they are qualified to give landing lessons to those who have. I'm quite sure that before any full scale pilot climbs into an Extra alone he first has to be checked out with an instructor for a certain amout of hours so wouldn't the same hold true?

HighPlains

My Feedback: (1)

Most flight is done while crabbing. Unless your heading exactly into the wind or away from it, you are crabbing if you are flying from point A to point B. Full size pilots pull out their E6B to determine how many degrees off their intended ground track they must fly at to reach their destination - well that was the way it worked when everything was done with dead reckening. Later radio aids and now GPS remove much of the calculations and the work load.

So now about the only time people are greatly aware of crab angles is when they are looking at roads or runways. Yes, you can crab all the way down to contact with the runway, it doesn't matter if it is full size or model. But unless you are flying a B-52 there are these things call landing gear that would prefer to be aligned with runway when they touch. So what to do?

Stay in the crab, then straighten out with rudder at the last moment. Works fine

Slide slip to compensate for the cross wind, touch down on one wheel then slow down to align on all three. Also works fine. But you generally crab until you go into the side slip.

Now for example if the wind is from the right side of the runway, a side slip uses right aileron and left rudder. If you are crabbing, the ailerons are neutral and you kick in rudder at the end to align with the runway, but you also add aileron into the wind to hold the windtip down as you slow down.

Finally, a forward slip with the wind from the right side of the runway, you use right rudder and left aileron. In a full size airplane this puts the runway between the nose of the airplane and the wingtip. This gives the pilot a really great view in two seat airplanes with side by side seating, and is really great fun. It is also draggy as all hell since you use most of the rudder to shove the side of the airplane into the airstream. But at the bottom of the barrel, you must align the fuselage with the runway and drop the other wing into the air to land.

If you are more advanced with your model flying, I highly recommend you take your side slip to the extreme and try a knife edge approach to landing. Instead of gentle bleeding off altitude and speed, make your approach to the runway at 50 to 100 feet of altitude. When you reach a point that is 30 to 60 degrees up from the end of the runway, toss the airplane into knife edge and you will just drop out of the sky without picking up speed. Then as low as you dare, roll out and flair. Works best with models with big round cowls (drag buckets, but those Russian acro airplanes with radial engines make great models), but most sport models can do it.

Top_Gunn

My Feedback: (6)

I'm puzzled. If the wings are level and the nose is pointed into the wind, you are just crabbing, which as Harry and I have been saying is the usual way to handle a crosswind. But if you are actually holding rudder into the wind, with the wings level, you would be constantly making a skidding turn toward the direction of the wind. Why would you want to do that?

Bob says he counteracts the effect of holding rudder into the wind by holding the wing away from the wind down. So he's slipping, but with the low wing on the downwind side, so that the plane's sideways motion is away from the wind. Why do that?

I don't see how having extra power and lower wing loading justifies making skidding turns the norm. It's true, as Major T says, that different planes handle differently. In some you lead the turn with rudder, in others with aileron. I've never heard of one where skidding is routine, though. The one difference between models and full scale that makes a difference here is that models don't have passengers who would likely become uncomfortable in skidding turns.

speedracerntrixie

My Feedback: (29)

The idea is to hold enough rudder and match power so that the models flight track is parallel to the runway. Then just before touch down you would ease off and maybe even go opposite rudder to adjust the models attitude as to not land in a skidding condition. I will agree that different airplanes handle this differently but what I see lots of times here on RCU is that someone like Bob or myself will give good solid advise based on 30+ years of R/C flying and then some of the full scale pilots come in and do their best to debunk our advise while having little to no first hand experience with the models we are talking about and justify it as being normal practice for full scale.

HighPlains

My Feedback: (1)

Only one airplane that I know of where the SOP is a skidding turn when on station. The RC-12 Guardrail used by the Army.

sensei

OK, here is another video, towards the end I fly in circles at full power holding rudder one direct and carrying just a tad of cross aileron, then I cross over and go the other way. Now I don't know if it is right or wrong, what I do know is I have a heck of allot of fun doing it and to me it looks kinda cool.

http://vimeo.com/22492765

Bob

wallace.tharp

Rilght on: A quick Q. What does Invertmast mean? I think of a ship with it's mast poi t ig down. Pilot books such as Private Pilots Handbook provide understanding of the basic concepts that all R/C rs need to know. It would clear up some of the mysteries of flight like; "I turned to downwind & the tailwind that it causes made me stall & crash." All aircraft fly in an ocean of air similar to how a boat traveling on a river with a current is effected. Knowledge of stalls , stall recovery, which controll surface effects what, what is P-factor, spiriling slip stream, & torque. All relevant to R/C. IMHO. It took me years in 1/1 scale to realize that I wa flying a physics prolem! wallace.tharp CFII

sensei

I think we may be getting a off track with allot of semantics now, if you want to become a better R/C pilot then reading all the literature in the world is not going to help you, it is good information to know but stick time is what you need at the field, or on the simulator, you must do the time. Burning gas, or electrons, or a lot of both, there is just no cheating it, set your goals and master them one by one. The rest of stuff to me is just allot of keyboard jiberish, I see allot of talk the talk, but not much walk the walk, So let's not confuse those wanting to actually be a better R/C pilots. Just for the record, I know plenty of full scale pilots that have all the book knowledge in the world, Some fly R/C pretty good and yet some can't fly an R/C airplane worth a crap, it's like most things I know of, we all must pay our dues to get what we want...

Bob

speedracerntrixie

My Feedback: (29)

AMENBROTHER!!!!