Egos, egos, eggos...toot, toot, toot! Pat, pat, pat! Puff, puff, puff!

Kurt

LOL, well we are men after all. which is why women make the best pilots.

JPerrone, R2160 beat me to it. All I will add is that the wind is always head on to the plane, unless you misuse the rudder of course!

As I stated and R2160 repeated, the wind is not a force to a plane in flight because there is no acceleration. For a plane in flight it is the ground that is making odd movements, not the plane.

Ok, with all the knowledgeable people weighing in and confirming that cross wind exerts no force or acceleration on the aircraft, I'll accept that as fact.

This original post was regarding making turns, and the reason, partially, for that was to improve landings. The next question/observation is related to that, so we aren't off topic.

I'll present two cases
Case A: Aircraft is lined up with strip, wind is on the nose, straight on. The airplane heading is aligned with the strip and it lands nicely (with practice of course)
Case B. Aircraft is lined up on the strip, wind is off to the side a bit. Just for this case, lets say its 30 degrees off, coming from right to left. Observation of a real model airplane is that, holding rudder straight and ailerons flat, the airplane will tend to drift a bit to the left, away from the wind..

There is no sideways force from the cross wind, no acceleration, the wind is coming straight on the nose even though the true wind is coming 30 degrees off the nose.


So why does it drift like that? The plane should continue going straight.

There's 3 elements in there: the plane, the wind, the ground. I'm going to go out on a limb and say the ground is not moving any differently than it is moving in case A. So it has something to do with either the plane or the wind.



Regards

With case B, the plane will drift left if drag is greater than thrust and the plane is slowing down. IF the plane is traveling at constant airspeed (thrust = drag) then it should track straight down the strip if it's actually tracking that way already.

The reason for drift left with decreasing airspeed (more specifically thrust less than drag) is that drag vector can be broken up into two components, one aligned with the ground track and a 2nd one 90 deg to the left side of the ground track. The thrust vector (engines and a bit of gravity if you're descending) can be split the same two ways but at constant airspeed would be of equal and opposite magnitude.

If you reduce the thrust, this balance no longer exists and the plane will experience an acceleration (change in ground track) with respect the the magnitudes of those two components, ie the component normal to the strip will accelerate the plane at a certain rate to the left of the strip while the component aligned with the strip will accelerate the plane backwards with respect to the strip. The result is a curving groundtrack drifting left of the strip as you slow down but the heading of the plane won't change as it really only "feels" the drag pulling it directly backwards at an angle of 30deg to the strip.

Beginners; it is time for you to just go out and fly, get help/advice from the guys that are getting it done at your own fields, they are usually the ones that are doing all the flying every week instead of talking legend of flying every week. There are many of us that learned to fly long before there was internet, or buddy box for that matter, so you don't need the expert opinions in this forum to get the job done correctly, what you need is stick time while expanding your envelope just a little every week whatever that may be and you will get there. These forums have far too many book smart experts giving absolutions to scenarios without much of their practical behind them, Oh we hear about the practical they possess, but in many cases have nothing they can or are willing to show us, so take what they say with a grain of salt and go get your own practical experience, you will get much further down the road then coming in here over analyzing every little issue.

Bob

thread needs to be longer... a question a topic that is super basic super easy clearly needs to be longer and needs more expert opinions that contradict each other

That is a fair question and easily answered.

You are right, in B, the ground is not moving any differently.

But the wind is. The wind is moving sideways relative to the runway in B.

The plane is being carried sideways by the wind. At the same speed as the wind, IE no acceleration and no force being applied to the aircraft.

The apparent wind is directly from the front of the plane, but the entire air mass is moving across the ground, carrying the plane with it at the same speed and not accelerating the plane.

The path through the air is straight, relative to the air, but the path across the ground is forward and sideways (relative to the runway)

The wind is carrying the plane sideways, not accelerating it sideways. There is a difference.

JPerrone,

A useful way of getting this is to think of a hot-air balloon in a steady wind. The balloon will go where the wind goes, but the wind is not blowing against the side of the balloon: the people in the balloon will feel no wind at all. If you were to hand launch an RC plane from the balloon and fly it, you would feel exactly like you would feel flying on the ground in a dead calm. People in open-cockpit planes flying in steady crosswinds don't feel a breeze from the side. If they did, the air would have to be moving toward the plane faster than it was carrying the plane sideways, and, unless the wind speed changes, that would be impossible. Similarly, the yaw string on a glider points straight up in coordinated flight in a steady wind, no matter which way the wind is blowing. A steady wind doesn't blow against a plane in the air, the wind is a mass of air in which the plane is flying. When that mass moves, the plane goes with it.

On the ground, it's an entirely different matter. Taxi straight down the runway in a strong crosswind and the wind striking the plane's tail will tend to make it turn toward the wind. That's because the friction between the wheels and the ground keeps the whole plane from moving sideways in the wind.

Maybe all of these complex explanations could be simplified using a boat in water? Water moves. Boat on water moves in direction water is pushing. Controls on boat (engine and rudder) are used to move boat where the driver wants it to be. Engine and rudder must overcome/compensate for force of water trying to move it.

Rudder use in aircraft is no different.
Except when design of aircraft causes a ROLLING when using the rudder; that is the AIRPLANE's problem, not the physics of air mass on an object in it.

Boats are a good analogy Bob because the vectors of boat movement within a steady moving current are the same as our aircraft movement within a steady moving air mass.

If there is a difference, it is because the boat must use rudder to change direction, but an aircraft can change direction without using the rudder at all.

I'll throw another idea into the mix.

Many slope soarers do not even have a rudder. IE ailerons and elevator only or Elevons only

Yet they spend their entire life flying in strong crosswinds.

They can easily fly in a straight line parallel to the slope

How do they do it without a rudder?

OK, that analogy works, sort of. Suppose you have a boat that does 10 knots, and you want to cross a north-south stream moving south at ten knots. You are on the west side. River is 10 miles wide (simplifies math).

If you point the bow east and go straight, the current will carry you ten nautical miles south by the time you get to the other side. so you start out and use your rudder to turn the boat so its heading is 045 degrees. Then you neutralize the rudder, go straight on that heading, and you'll end up due east of where you started. The boat will go due east (with the bow pointed northeast).

Just like flying a plane in a crosswind, except that most planes turn by banking.

Oops: make the boat's speed 14.1. Should have done the math before typing. My bad.

can we kill the thread just fly the plane ... REALLY it's not hard

Except that in reality the boats path will be an arc not a strait line.

Are you saying that in a steady unchanging current, with a steady unchanging boat speed and heading, the actual path will be an arc?

Please elaborate.

The people who know what they are talking about have all agreed all the way through. Contradictions have only come from posters who don't know the basics of piloting a plane.

Where is the head-banging smiley?

It would help for some to review basic vector concepts also.

A picture is worth a thousand words.

http://www.rcuniverse.com/forum/atta...mentid=1976019

[QUOTE=HarryC;11753856]The people who know what they are talking about have all agreed all the way through. Please Harry show us all that don't know the basics of piloting an R/C plane what your piloting skills really are, as a self proclaimed expert R/C pilot as stated in your profile you must have at some point had some video of your very own precision or freestyle thumb work that would assist us beginners by watching to understand more of the proper use of rudder input...

Thanks in advance,

Bob

I know Rob2160?? I've got no problem if he want to fly crooked and win comps like that but could he admit he's wrong, stop telling beginners he's right and just get back to winning comps again.

Sensei, I won't get dragged into a chest bumping competition over flying credentials and I've explained my reason why credentials mean nothing to me whether the holder is some bloke whose passionate about his hobby or someone who's got more real qualifications than I have. I will however add because it's a sticking point with you that I won my class in the first RC aerobatic comp I entered and it was a national championship. Just because after a few years of never placing lower than 2nd in the handfull of following comps in higher classes, I chose to to persue other more grown up activites (I was only a high school kid at the time with all the the latest F3A kit), doesn't mean I was doing it 100% correct back then or mean I don't know what I'm talking about now.

I always try to understand things from another person's perspective but I was lost with the comment about the boat's path being an arc.

The only thing I can imagine is that Speed was keeping the nose of the boat pointed at the destination on the other bank, effectively like "homing" to an NDB in which case I agree the path is an arc.

Tracking and Homing to a destination are two completely different things. In Harry's example the boat was tracking and the path is definitely straight.

http://www.qva-airways.org/cfi/tutorials/NDB/page2.htm

As the original OP I'm going to weigh in and say that my original objective for the thread has been met. I know a lot more about turns using rudder, and certainly understand better what the possible downsides of cross controlling are. As stated earlier, I don't think I'll be trying that. Except in flight simulator to see if I can break something!.

Lots of interesting input and it raised my curiosity in a different area, which implies a different thread. That would be the basic fundamentals of the forces on the airplane, ie, thrust, lift, drag and weight. The NASA link was very useful for getting a start on that. I don't intend to introduce this thread...


I'll go out on a limb (do that frequently) and toss out a completely unsubstantiated theory that a large amount, maybe most, of the talking about flying is not as useful as just going out there and doing it. Having said that, I went out this morning, flew, practiced landings, and had a great time. I am curious about the behavior of my PZ micro P-40 vs PZ micro T28 in wind, but I'll raise that as another thread just on that subject.

Thanks for everyone's input. Even those items that seemed bone headed were useful in some way!!!

Regards

Hey professor I wasn't talking to you was I, and for somebody that wasn't going to get dragged into a chest bumping over flying credentials you were sure fast to list your alleged R/C accomplishments to a question not even directed to you. Oh but wait, all this was accomplished as a high school kid and and since then you have chosen to pursue other more grown up activities. Question; if that in fact is true then why are you hanging around in a beginners R/C airplane forum in the first place, certainly you have left all that behind you... One more thing hot shot, bumping your own chest about your credentials as you have just done really isn,t necessary, so I will ask one more time, show us through your own videos how well all this stuff that you, I, or anyone can read in countless books is working for you on the sticks in the real world.

Bob

Interesting that the graphic illustrates the boat analogy. Although as a FS pilot, I learned about crab angle, and wind drift in my Taylorcraft years ago. I have NO illusions about which way an airplane will move in a "wind" (a.k.a. "moving air mass") and how vitally-important the rudder is to getting where one intends to go.

Thx, Rob