JPerrone

I took a look at that down wind turn thread; it's big!!! Does seem like the answer was in there but there's a bit of "knowledge camouflage" like a lot of threads.

I did become aware of something I was doing that I will now watch out for; I reduce thrust on downwind leg to reduce apparent ground speed. I just prefer flying slowly and the airplane is going faster than I like. But it sounds like could end up going too slow if I'm not careful.

to Mr speedracertrixie: That white plane looks like a mig 3; you just don't see enough of those!!! I particularly liked the BF 109. I always liked the different color schemes on the real one and that particular color scheme isn't one I've seen yet!!! What type/brand airplane are those?


regards

Rob2160

No you don't have to do that at all you just eyeball how much drift correction is necessary, the same principle applies to flying real aircraft when flying "seat of the pants" or during circuits in cross winds, you just eyeball it.

In RC model flying, you can fly without having a clue about aerodynamics. In full size, you won't get a license unless you pass certain exams proving you have at least a basic understanding.

I know you seem to be against full size pilots offering advice in these forums but if somebody asks a question, what is the harm in getting the "technically correct" answer?

Most RC flying is eyeballing and correcting what you see happening, I never think of vectors and formula when I am flying, RC or full size . That being said, what is the harm in getting the right answer when a question is asked?

Rob2160

One thing I will agree with is that the size of models vs full size does change how they are affected by wind. IE a model plane flying at 30 Mph will be affected more by a 20 mph cross wind than a real aircraft doing 150 Mph.

However that is not a cut and dried argument either concerning many aspects of the aircraft handing.

EG take a 33% Extra and compare it the full size.

Those two aircraft will fly more alike than say an UMX aircraft vs the 33% Extra.

Or perhaps the Full size Extra compared to a Boeing 747.. They are both full size planes yet the difference will be greater than comparing the Real Extra to the 33% version.

One thing I will say, and I am basing this on almost 36 years of flying RC planes (perhaps over 300 different types) and 33 years of flying full size. (8500 hours)

RC models "in General" are infinitely more forgiving aerodynamically than full size aircraft. You can easily "ham fist" an RC plane and usually get away with it, e.g. pulling high G, cross controls, flying too slow, heavy landings etc, try some of those in a full size aircraft and you die very quickly.

I also have a full size Helicopter CPL, and over 15 CP RC helicopters, an RC Helicopter is virtually impossible to break in flight. I have tried it with mine, maximum Pitch climbs, pulling massive amounts of G, positive and negative. Nothing ever breaks unless you hit the ground.

In a real helicopter, being too harsh on the controls of some models, IE snapping full left then right cyclic, will snap the rotor mast completely and you die.

That's the real difference, and probably why full size pilots must do exams before they are allowed to fly solo but RC pilots do not.

dabigboy

If you learn how to use rudder properly in normal phases of flight (coordinating your turns, to start with), it will not be a problem on approach/landing. If there is a crosswind, I use ailerons to correct drift, and rudder to keep the plane pointed down the runway. This will result in touching down first on the upwind wheel, followed by the downwind wheel, and finally the nosewheel (or tailwheel). It works with a real airplane, and it works with our models.

*IF* you use ailerons and don't touch rudder, you will end up making a steady heading change into the wind, which will result in going off-course, naturally. If you "correct" this only with ailerons, you will end up wings-level and NOT pointed down the runway (looks like a slip from the ground, but you are actually in coordinated flight). You can get away with this with a lot of our light, tough models, but it's one reason you see guys at the field landing and immediately veering off the runway, or having other directional control problems on the ground.

If there is no wind, I still find myself adjusting my course and heading with rudder and aileron, mainly to keep the nose pointed straight ahead when making slight bank angle corrections. The rudder is also handy for quick, small corrections. Now, if you try to use ailerons for all corrections (especially heading corrections) and the rudder as an afterthought, you will find it's hard to correct quick enough, and then not over-correct. This is because using roll exclusively takes more time than just easing into the rudder a bit. With ailerons, you need time both to initiate the bank, and to get back to wings-level. Plus you will still be getting on the rudder to keep the plane coordinated (at least, you should). I find it best to correct drift with ailerons, and adjust heading with rudder (basically).

In the real planes, I also find myself making a lot of small, quick corrections with rudder and aileron on approach. It's more intense and precise than RC, probably because I have a better view of my approach course and heading in the real plane (slip indicator, runway centerline, seat of the pants, etc). As I do not fly paying passengers (pleasure and personal transportation only), I don't have to much worry about passenger comfort on approach/avoiding side loads, so on final approach, I focus on correcting drift and pointing straight down the runway. Again, I tend to use ailerons to initiate drift corrections, and rudder to keep the plane pointed the right way.

On takeoff, you really don't want to try to use rudder into the wind, as some have suggested. Reason #1: in this phase of flight, you are at high power, low speed, and high angle-of-attack. Any deviation from coordinated flight will reduce lift on one wing, and increase chances of a stall/spin. It's true that if you are rolling straight along the runway with a crosswind, you are basically in a slip. However, as soon as you lift off, the aircraft will begin to weathervane into the wind AND begin to drift in the direction of wind. Typically, I find the plane stabilizes in the air pretty quickly on takeoff: weathervaning is very slight (if even detectable at all), the plane starts drifting in the direction of the crosswind pretty quickly. So, I focus on keeping the ball centered. If you really want to stay on a course straight off the end of the runway, simply turn into the wind (a normal, coordinated turn) until you have a crab angle that puts you on the ground track you desire. There is no reason whatsoever to put the plane into uncoordinated flight just so you can point the nose on the same heading as the departure runway, and using rudder into-the-wind to correct drift is basically the same as making a rudder-only turn (no good reason to do it, except for your own amusement).

With my RC heli, I REALLY notice the effect of bank angle and yaw angle...I can see very clearly when I need to roll for drift correction, and when I need yaw to correct my heading. Everything related to coordinated flight and "rudder" use is amplified with helis. Fixed-wing planes let us cheat on a lot of stuff.

Matt

cymaz

Agree, the laws of physics, aerodynamics etc don't care how big the aircraft is. They still act upon it.

speedracerntrixie

My Feedback: (29)

It looks like we may be making some progress here. I do agree with most of what is in the past few posts. Statements like "we can get away with more flying a model" And " Can't break a R/C helicopter while in the air " and " we fly our models by sight" all true statements. My thing was to point out that according to some of the verb-age here it would seem that the " Correct " way to counter a cross wind is establish a crab angle at one end of the field and then neutralize rudder and ride the strait line from one end to the other. Mathematically that may work But not in reality where the wind is not a constant and because we fly close to the ground there is more turbulence. From a competition pilot standpoint coming out of a maneuver yawed 5 degrees one way or another is going to be a downgrade. As far as teaching the " Correct " way to do things as we do it in full scale IMO is limiting that your students potential. Simply put, when we are talking about models there just aren't any rules or at least shouldn't be. IMO we should be encouraging each other to push the envelope and think outside the box not start a post with " That's not correct " or " That's just wrong " Again my opinion but to me that just implies an absolute and I just don't believe in absolutes when it comes to R/C. There are multiple ways to do the same things in just about every case, I don't think I have accused you guys of flying incorrectly can you guys say the same?

Now one of the examples given was slope soaring and being able to not have the wind slam you into the slope by always flying with the nose pointed away from the slope. Yes this is correct and yes you can accomplish this by making your turns less then 180 degrees but again this requires constant maintenance, its not a one shot deal and it's not the only way to do it. Most of my time on the slope had been slope racing or just practicing speed flying with an F3B sailplane. Again I would correct for drift with rudder. Even on my pylon airplanes id I happen to be out of position and need to move in or out on the course I do so with rudder. My point throughout this whole thread is that because we are flying models we need not confine ourselves with hard full scale principals, nobody is going to die or get sick if we are flying our models differently then full scale.

Jperrone, The airplane I pictured is a stand a mile off scale of an Italian Macchi 202 Folgore. It is of my own design and scratch built. if you would like more information I have a build thread of sorts in the Scale Racing forum titled: 2014 race season. Thought I would post another pic so you can better see the planform.

Rob, yes flying helicopters is a different ball game but I find the challenge fun. I haven't picked up a heli in a really long time but Used to be a fair pilot.

cymaz

I need to re-read A.C. kermode "Flight without Formulae". Excellent book with no maths. As he says, to an airman there is only headwind.
Also he says that " banking to correct degree, the aeroplane presents its wings at right angles to this force( inward force) so that there is no tendency to skid outwards as there would be with no banking, or to slip inwards as there would be with too much banking. "
As rc pilots we stand on the ground and therefore have no turn and bank indicators or can follow the bubble. So we are always having to correct when we see what happens and second guess rather than react instantly to the instruments. Therefore there is always a bit of catching up to take place. I first started using rudder by acting as if there was a bar attached to the rudder and aileron sticks, ( I fly mode2 )..and flying just rudder and elevator on my 4 channel trainer.

So now I can't help but use some rudder on a turn. With using aileron at low speed ,rudder helps. If the pilot turns left, port aileron comes up and starboard goes down. The down aileron will increase lift AND drag. The right wing goes up, and goes round to the left travelling faster than the left wing. As drag increases it tries to hold the right wing back - aileron drag. This yaw acts on the rudder pushing it in the wrong direction. If the outer wing stalls the plane will want to bank the other way. This is when the rc pilot uses "top rudder" or opposite rudder. I do with my big DH60.
I think I have this correct please tell me if it is incorrect.

JPerrone

I think these are Folgore 202. The one on the left is my son's he built he when he was 8. The one on the right I built.

I should have recognized that plane I think!!!

speedracerntrixie

My Feedback: (29)

Well mine's not very scale. it is just scale enough to squeeze past the rules that it has to be a WW II fighter. Lots of liberties to make the construction easier and make it fly well.

Jaybird

If you plan to fly "strait" then you must mean in a particular place, like the Strait of Gibraltar or some other phsysical landmark with simialr characteristics.
If you plan to fly "straight" then it's a matter of relationship to you and ground track.

Jaybird

HarryC

My Feedback: (1)

Normally the aileron can't make the wing stall, the alleged angle of attack formed from the leading edge to the trailing edge of the downgoing aileron doesn't work that way. The stall happens much further forward on the wing and the aileron at the back has little effect on it. Think of 3D models doing all those rolling maneuvres at and beyond the stall, the aileron keeps working as normal, it doesn't reverse its effect.
What normally happens is that adverse yaw increases at low speeds and high angles of attack, the downgoing aileron causes a much greater adverse yaw which the pilot has not countered with enough rudder, the aileron causes very little roll in the correct direction but the plane yaws strongly to the downgoing aileron, the yaw close to the stall causes an assymetric stall and down goes the outer wing. It appears that the downgoing aileron caused a stall, but it did it by causing a yaw which the pilot did not counter and the yaw caused the assymetric stall. If the pilot had been on the rudder enough to counter the adverse yaw, the plane would have rolled slowly in the correct direction.

Now we come to corrective action. many model fliers and some full size fliers think the correct action is opposite rudder to pick up the dropped wing but that is wrong and the Australian aviation authority even included this as one of the myths in an educational leaflet they did a few years ago, see myth # 7
http://www.casa.gov.au/SCRIPTS/NC.DL...Name=22_27.pdf
If all you do is apply rudder, you will more than counter the adverse yaw and yaw the plane the other way, simply reversing the flick or incipient spin! The first thing to do is unstall the wing and that means centralising the ailerons and easing forward on the elevator. That's not the same as pushing in down elevator, to unstall you just go forward enough from where you were to unstall it, as you don't want to provoke a dive into the ground from low height. Having unstalled it, the rotation will stop, it won't have developed into a flick or autorotation spin yet. Now you are unstalled and flying again, banked over to one side. How do you control bank? With aileron, not rudder. But you don't want to provoke the same assymetric stall all over again so you gain speed and then roll upright, if necessary using enough rudder just to counter the adverse yaw, but no full rudder thinking it will roll you upright as it is more likely to flick.

At very low speed/high angles of attack, rudder can be used for turns, on some planes it has to be as ailerons are ineffective or adverse yaw is so bad, but it is very little movement of the rudder. Slip ball is moved only just off centre, any more would likely provoke a stall. In full size power planes the rudder pedals are usually very heavy which prevents over-control, to simulate this I use huge expo on the rudder in my models to prevent over-control.

I am lucky enough to have logged a few hours piloting the full size P-51 Mustang. I have done normal and high-G stalls in it. If it drops a wing the last thing you do is put on opposite rudder (if at low level it really will be the last thing you ever do!) because the enormous gyroscopic force of the prop will precess the yaw and pitch the plane inverted. Not normally a problem for our models with much smaller lighter props. Anyway, the procedure is the normal centralise aileron and be prompt at easing the stick forward to stop the stall. The rotation stops within 1/4 roll i.e. at knife edge if you are prompt with the elevator. Then, believe it or not, ease in a little down rudder, not top rudder, to help get the nose down and get back flying speed asap. Then roll upright with aileron, no rudder required unless slip ball demands it.

speedracerntrixie

My Feedback: (29)

Harry, enjoyable read concerning full scale. Not sure I'm going to agree about an aileron not being able to create a stall. Try using barn door ailerons as flaps and see what happens. As far as your comments about 3D models being able to keep the roll rate active past stall really has nothing to do with proving your point. The main reason a 3D type airplane can continue to roll is because of the prop blast moving across the ailerons. If you have ever seen an airplane doing rolling harriers and experience an engine failure you will see the roll stop immediately. I have seen some extreme 3D type electrics sitting in a stationary hover and alternate roll directions.


I am somewhat jealous as I would love to take a ride in a P-51. IMO if you can pilot one of those you have my respect as I know it is an airplane that has no forgiveness. All the model P-51's that I have flown have had very bad control cross couple. When rudder is applied the airplane has wanted to roll the same direction and pitch downward. Is the full scale P-51 the same?

bjr_93tz

No this is wrong. RC aerobatics are judged on flightpath NOT attitude. If a pilot exited a maneuver with the yaw attitude pointing straight (parallel to the strip) in a crosswind then I'd know their flightpath can't be correct and I'd expect to see them start poking the rudder in to fix it up.

However if you meant their flightpath was out in the yaw axis by 5 degree on exit (irrespective of where their nose is pointing) then we'd be in agreement regarding the downgrade, and I'd agree the least downgradable way to fix that up is to poke in the rudder.

From memory wasn't IMAC once judged on attitude in it's early days then change over to flightpath? or was that just a rumour? I think the reason being at the time the fullsize were judged on attitude?

Rob2160

I blame the iPads for my typos. some of the spell corrections/predictions they make automatically are ridiculous.

As for flying straight.. I was flying back from the USA to Sydney 2 days ago and got a great video of the flight instruments while we were flying straight in a strong crosswind (70+ Kts)

It shows the correlation between heading, drift angle and ground track very nicely.

But I had to go to Perth the following day and that vid is on my USA mobile which I accidentally left at home.. However watch this space, I'll post it in a week.

HarryC

My Feedback: (1)

Hard to answer as I don't generally apply rudder except to keep the slip ball centred. Exceptions in the P-51 were rudder with the roll in the last 1/3rd to help keep the nose up, small amount of bottom rudder in knife edge after assymetric stall to get the nose down, and tiny amount of rudder only to turn at very slow speed. I don't recall it having any pronounced rolling effect beyond what you would normally expect and I am sure it had no pitching effect, but I must emphasise i don't use lots of rudder to push the plane way out of balance unless doing flicks or spins which I didn't do in the P-51. If you work the rudder to keep the slip ball centred at the stall, it stalls very gently straight ahead, it only drops a wing if you let the slip ball go off centre, which is true for every type that I have stalled. High speed stalls in turns tended to make the P-51 sit upright though on one occasion it rolled deeper into the turn but I was looking ahead where I was going in the turn so I may have let the slip ball move off centre in the turn.

speedracerntrixie

My Feedback: (29)

Yes I believe that in 2005 or close to then that change was made. IMAC realized that pilot perspectives were different enough to require the change.

According to the rulebook you would be correct except that your examples show correction on vertical lines. With more experience or maybe even some recent experience you would know that just following the rulebook and being technically correct is not going to win you any contests. There has to be some showmanship in there with your flight. Let me throw a couple scenarios out there.


Your flight, Lets just fly through a Humpty Bump. Mostly technically correct and as I understand the way you have described how you would handle a cross wind is to slightly roll before a vertical line is pulled. First off this is a downgrade as the IMAC rulebook does state that roll being used to compensate for cross winds is a downgrade, I did not have a copy of the pattern judges guide handy last nite so was unable to check. Then you would have a very pronounced crab angle on the way up that should be corrected before you pull or push over the top because if you don't your wings will not be level over the top and that is where it will be most noticeable. Maybe you work that roll into the pull, I don't know that for sure. Over the top you go, rudder in your crab angle to hold a straight down line. Judges are going to see that initial yaw and although technically not a downgrade it is noticed. Then if you don't rudder to remove that crab angle you will exit the maneuver with one wing low and that would be a downgrade.

Now when I fly the same maneuver I am holding just a slight breath of rudder in horizontal flight to keep what would appear to the judges a straight line. I enter the pull with no real noticeable yaw or roll. On the vertical I am holding the same small amount of rudder so the judges don't see me establish a crab angle. There was no rolling prior to the entry so no downgrade there. Wings would be level as I go over the top as I would be easing off that rudder and ease in just a tad of opposite to point the nose to match the flightpath as I went over the top. Yes there would be a slight amount of drift but because the airplane is doing this smoothly with small control inputs that are applied smoothly it's almost impossible for the judges to see.On the down line I would again apply the rudder into the wind to stop the drift, not correct the drift and get back on the same line as I came up and in reality I have drifted in or out depending on cross wind direction but it's very difficult for the judges to see that small amount of drift from several hundred feet away. Then on my pull out I would be wings level and nose pointing parallel to the runway. I would start easing into the small amount of rudder again but by this time the maneuver is finished and the judges are either writing the score down or have verbally communicated the score to the scribe. Either way his attention is not 100% on the airplane and when it is I am in position for the next maneuver. In my verticals I also did not establish enough crab angle to 100% counter the cross wind and did let the airplane drift some but that drift is very difficult to see, I made up for that drift on the horizontal flight between maneuvers where it is less noticeable and not scored. However it is done smoothly and with grace as it is part of the " Show ". The reason this is done is to try to convince the judges that the wind is having a lesser effect on my airplane then it does yours.

The other thing to remember is that if you can fly as if the wind has a lesser effect it will greatly help on those occasions when there is a slight breeze at ground level but is blowing much harder a few hundred feet up. The judges only feel that slight breeze of lets say 5 mph but you are wind correcting for the actual 15 mph wind that you are flying in then from their perspective you are over correcting. Our competitions are judged by human beings. We train them as best as we can, hold judging seminars and such but they are still humans. You can't remove that aspect so you need to learn to turn it into an advantage. Give the judges what they " Think " they want to see. In my years flying IMAC I have protested scores twice siting the rulebook. Although what I did in my flight was technically correct, waving the rulebook helped me none at all.

BTW starting out a post with " Your wrong " or " That's Just not right " type statements is rude. I doubt you would walk into a live conversation like that.

bjr_93tz

Yes the slight roll is performed during the pull.

The key difference is you enter the manuver holding a bit of rudder, I enter the maneuver with no rudder because my plane is already tracking roughly parallel to the strip. The slight roll during the pull means I exit the pull wings level with the end of the box and the flightpath vertical even though the nose is still pointing out. The push over is the reverse, the rolling during the push means the wings are level over the top, the nose is still pointing out without rudder and I exit nose still out wings level with the end of the box on the downline.

Try using your stick plane to fly a spiral around a coffee tin. If you start out with the correct yaw angle it's clear that rudder isn't the control we need to be using to 'fly" the spiral around the tin. The plane fly's straight around the tin in a spiral with just needing aileron (and elevator of course), and you'll see how any rudder will muck up the line. In a crosswind the flightpath through the airmass should be a spiral to maintain your groundtrack. Edit: It might be easier with a little toy car, put it on the tin at an angle and drive it around in a straight line (or rotate the tin), which would form a spiral around the tin which is exactly what we want to fly for a loop in a crosswind. The car doesn't need to be "steering" to one side.

Yes it was blunt, but given the number of posts on the topic I don't feel I've just walked into a conversation, my apologies in any case. I just hope that when I exit a 1/2 Reverse Cuban turnaround (or whatever) in a crosswind and don't have to touch the rudder for the full length of the baseline because I've exited on the correct flightpath, that the bloke sitting in the chair behind me isn't docking me points because my nose was yawed in or out on the exit.

speedracerntrixie

My Feedback: (29)

As previously stated, when I have a worthy airplane flying I will give it a try. There is always room for improvement and if it works better for me I will be sure to let you know. The blokes in the chairs would be another whole can of worms. I have seen judging differ from region to region so I can't say what it would be like in another country. IMO the judges here in the US may feel they have more liberties in the definitions. Snap rolls seem to be the devil in disguise. I have been downgraded for not holding pitch deviation long enough at an IMAC contest and initially told by a pattern judge that I didn't stall the airplane at the top of an avalanche. My reply to that one was " Duh, these airplanes don't stall during a snap". We got the CD involved in that one and in the end I was told that Andrew Jeskey had just won the words so guys are looking for faster snaps " Like Andrew does them ". The judge also had admitted that he had noticed my snaps in a previous round that he was not judging and made a mental note that they should have been zeroed so he took that mindset to the chair with him. Like I said, can't get away from the human factor. Looks like this one is finally winding down, I hope some beginners were able to learn from our at times dribble. In the end it's all about having fun and hanging out with guys that have the same love for model airplanes.

Rob2160

As promised in my last post here is a video taken on a flight recently across the Pacific, tracking to Honolulu (PHNL)

The inverted Magenta triangle is the aircraft's ground Track. (The direction of movement across the ground)

The Inverted white triangle is the heading (the direction the aircraft is physically pointing)

The little arrow pointing left with 75 is the actual wind speed and direction IE (75 <--)

You can see the heading of the aircraft is 242 degrees, but the ground track is 233 degrees,

This means there was 9 degrees of left drift.

Another relevant point is the upright white triangle at the top of the pitch ladder (under the AP1)

This is the electronic version of the Balance Ball and is actually a split triangle where the bottom half slides left and right if you are not flying in balance. You can see the aircraft is completely in balance during this video.

Other things of note, the Indicated airspeed is only 242 knots but the True airspeed is 485 knots (The difference is due to much thinner air at altitude)

You can also see another aircraft, 2000 feet below us and to the left on the TCAS (Traffic collision avoidance system) - its the blue icon with -20 beside it.

https://www.youtube.com/watch?v=crnrJ9jWDuw