Perfect!. You got it.

Since the discussion has led to vector calculations and you understand compass directions… try this link.

http://www.csgnetwork.com/e6bcalc.html

It is an online version of an e6b calculator - it does the vector calculations for you.

Two examples. (with diagrams to illustrate the difference)

Example 1 - use box 4 in the calculator (Course, Ground Speed and wind correction angle)

Your aircraft is flying north (0 degrees) at 30 Mph - Vector 1

Wind is from the west, 270 degrees at 10 Mph - Vector 2

Combine these vectors you get the resultant, a ground track of 18 degrees at a speed of 32 Mph.

IE the westerly wind has moved your course over the ground to the right (right drift)



Example 2 - use box 3 in the calculator (Heading, Ground speed and Wind correction angle)

Wind is from 270 again at 10 mph.

But this time you want to fly a Ground track of 0 (due north)

Your aircraft airspeed is 30 Mph.

The calculator computes a heading of 341 degrees. IE when you aircraft is pointing at 341, it will be moving across the ground in the direction of North (0 degrees)



At no stage do you need to hold rudder to compensate for the cross wind. The vector of your aircraft flight path will do that once you have the correct heading.

Its all done by eyeball with RC aircraft but when you understand the theory behind it, it makes more sense.

Credit to NASA again for the diagrams.

You guys have got it simple. Six of my vectors (technically phasors in our world 'cos they're a rotating vector) spin around their origin 50 times a second changing magnitudes and phase relationships while another 6 fling around the outside joining the tips of the first 6 together ;-)

And that's just the voltages and currents..

http://www.youtube.com/watch?v=FlRUmkqMIe8

Rob2160: "At no stage do you need to hold rudder to compensate for the cross wind". That was what I was not sure about; I was thinking the best way to test this was.... to do it!!!

So, I'll try that, and keep in the back of my mind that I might have to just nudge the nose in the right direction, then return rudder to neutral.

There is a force-vector reason that you might need to hold rudder; but this might not prove to be true for a "real" model or airplane. With a cross wind, there's some sideways force. This is applied against the entire side of the craft. The total force behind the CG is trying to make the plane turn into the wind; the total force in front of the CG is trying to turn the plane away from the wind. If those forces equal; then there's no need to hold rudder.

The vertical stabilizer has a lot of area; the area behind the CG could be greater than the area in front; and the plane would essentially want to weathervane, ie , turn into the wind.

This is all theoretical of course. I would not be surprised if most airplane designs were such that the area of the airplane behind the CG is close to the area in front, so that the plane doesn't experience these imbalances

Regards

ONLY if the speed or direction of the crosswind is changing and only for the duration of time it takes for the airplane to weathercock (fraction of a second for an rc plane) to the new heading to maintain the original groundtrack. With the low rotational moments of inertia for an RC plane, the only time "wind" can act significantly on the side of the plane is if you're forcing it to by holding in rudder.

If the speed (or direction) of the crosswind changes suddenly the aircraft should weathercock to the new heading and change it's airspeed to continue along the same groundtrack (inertia plays it's part here) at the same groundspeed. As it returns to it's original trimmed airspeed (either speed up or slow down) it's ground track will then change because there's a resultant force vector along the plane's heading that's at an angle to it's groundtrack.

ONLY if the speed or direction of the crosswind is changing and only for the duration of time it takes for the airplane to weathercock (fraction of a second for an rc plane) to the new heading to maintain the original groundtrack.

Kinda like speed stated, just tickling the rudder at the right moments to keep the desired ground track while looking smooth for the judges during R/C competition IMAC or pattern flying, not 3D flying for those that obviously don't know the difference as indicated in earlier posts, and again the dreaded ever so gentle stick pressure of crossing up of the ailerons against the rudder with these type of airplanes that does keep the wings level through it all. I know, this is a beginners forum and one should never attempt to cross the controls, or high alpha roll, or learn something outside the box... Its just wrong!!!! Much safer to fly in circles and hold your breath until the moment of touchdown.

Bob

You can change heading with rudder, and when you release that rudder the plane will yaw slightly back to neutral.

You can also change heading with bank, using rudder only to balance the adverse yaw. This is actually a more efficient way of changing heading.

Yawing the body of the aircraft away from the flight path increases profile drag, this is why side slipping is a very good way of losing height quickly without gaining speed.

Using bank to change heading while keeping the aircraft in balance produces far less drag.

When you roll out on the desired heading, the plane will stay there. There is no weathercock effect in steady winds as the plane is moving with the wind.

Here is one way to understand it. You are flying in a commercial jet at 500 Mph. The air inside that jet is moving at 500 Mph relative to the ground. How much wind do you feel?

Planes fly all around the world every day, across jet streams over 150 mph that can be all crosswind for hours and never "hold rudder" to compensate.

Speed uses his rudder to change the heading of his plane in contests for a very specific reason, to avoid being down graded by the judges for banking.

If you don't have that limitation then turning by banking is always far more efficient.

I think you misunderstood my post Bob, the 3D reference was generic as 3D flying actually uses far more 'unconventional" control inputs than Pattern flying.. IE a greater contrast to the more conventional control inputs used for scale flying which was the message in my post.

My bad if that wasn't clear.

You're still not getting it JPerrone. That is seriously wrong. There is NO sidewind to the aircraft. It does not feel a sidewind blowing on its fin or fuselage.
A steady wind does NOT cause a force on an aircraft in flight. Forces cause accelerations and there is no acceleration. The moving air mass is a frame of reference that is moving relative to the ground and the entire set of dynamics of the aircraft is in the air's frame of reference. You are still trying to do flight dynamics based on a point on the ground but aircraft handling knows nothing about the ground, only the air it is in. It doesn't know there is a steady state wind at all.
The wind is only relevant to us for navigation.
You are over-thinking this and introducing fake physics to make this far too complicated and in error.
It's very simple. If the plane is going a bit to the left of where the pilot wants, he turns a bit to the right. Turn by banking, not yawing by rudder. Assess and adjust as required. It really is that easy.

You mean more conventional like this kind of full scale flying?

http://www.google.com/url?sa=t&rct=j...62577051,d.b2I

LOL, yes, like that. Great video, Impressive flying and a professional commentary.

Note the incredible use of RUDDER in a variety of nearly-uncontrolled gyroscopic maneuvers....with some pretty cool FLAT rudder-only turnarounds (of course he was cross-controlling aileron, but we won't deduct points...)

I'm glad I've been lurking on this thread if for no other reason than to see that video link, and read some incredibly-well-intentioned but woefully-misinformed theories on the need/use of rudder. Interesting "snow day" reading. Thanks!!!

No. There isn't. Sorry.

That is the whole point of of cross controlling the ailerons to keep the wings level while keeping the ground track by yawing with rudder gently into the wind being as smooth as possible so you don't loose points...

Bob

Nobody has claimed people shouldn't use rudder. Nobody has claimed that flat turns are bad when doing aerobatics. Nobody has claimed that crossed controls are always bad (even in everyday flying, you may need to slip, and of course aerobatics sometimes require crossed controls). What this thread has been about is that pilots, even of models, should learn how to make coordinated turns, and should not make turning with controls crossed their normal way of turning.

We have had a couple of detours along the way: one about the "holding rudder" myth about crosswinds and a number of comments dumping on people for referring to full-scale planes, though always without analysis. And now we have a reference to woefully misinformed comments, though without the correct information to enlighten us. I'm sure that will be of great value to beginners.

There, fixed it for you.

Thank you so much,

Question for you, Do you actually fly an R/C airplane? If so do you fly nearly as well as you talk the talk about it? So many in these threads talk a great game but when it comes right down to it they are not much more then beginners themselves with limited skills in flying anything much outside the realm of a trainer type platform.

Bob

I fly R/C Bob and in my profession I deal with people who have FORMAL qualifications with years of professional INDUSTRY experience and I'm not backward in telling them when they're wrong if/when they are and WHY. When a person is prepared to put aside something they've "known" for years because they heard it somewhere and never questioned it, and actually looks at it with a clean set of eyes and thinks about it for themselves then they can explain to me WHY I'm wrong.

Many years in a HOBBY and trophies on a shelf doesn't mean sombody is right, although I understand in some cultures not questioning elders and those more "experienced" is the norm.

I understand this is a waste of time. I have several times attempted to explain my point of veiw. I have explained that the differences are wing and power loadings. I have explained that because models are flown in a strait line for only a few seconds at a time and not hours. I can continue that models fly close to the ground with pilots on the ground that can feel which was and how fast the wind is blowing. The wind at 30,000 feet is certainly going to be different. The effects of wind on an airplane traveling at 400 mph as opposed to a model traveling at 80 mph is going to be different. I could go on more but you guys have been closed minded for 9 pages I don't see it changing now.

bjr, having a wall full,of trophies from competing at the level I have DOES mean that I am correct as it applies to MODELS. If any of you guys had any success as a competition r/c pilot you would have an understanding that to rise to flying IMAC unlimited is not an easy task and one that requires attention to detail in airplane set up and trimming as well as lots of practice. If I was not flying my aircraft correctly then I would not have made it to that level. Think about it for a minute, in the US there are less then 200 IMAC unlimited pilots.

obviously I do not have an aeronautical education and there are some things I do in designing, building and piloting my airplanes that I am not able to fully explain. Should that mean that all these things that I do based on EXPERIENCE don't work simply because I am not able to fully explain why they work? Do I need to know every detail how an automatic transmission works in order to instruct someone how to drive?

Bottom line is fly your airplanes the way you want, I really don't care but DO NOT tell me I have been flying mine wrong, I have litterally thousands of scored flights that say otherwise, that is unless you have something to show me where you have been at least as successful as a competitive R/C pilot.

HarryC, post 209
Well that is certainly food for thought!
If there is NO sidewind against an aircraft, that would imply
- All the force vectors linked in post 189 are wrong;
- The force vectors referenced in 201 are wrong;

And if the wind is always aligned with the aircraft, with no side wind, then the following scenario would have to be true.

- Lets start the plane flying North, into a North wind. Airplane and wind are perfectly aligned.
- The plane turns a little, lets say 15 degrees. The apparent (not true) wind is still aligned with the aircraft
- At 90 degrees, the true wind is straight from the side; but the frame of reference makes the wind still aligned with the airplane, and it should still be coming from in front on the nose
- Let now turn a total of 120 degrees. The wind is coming from behind the plane. Is the apparent wind still coming from in front of the plane?
- Let's complete the turn, at 180 degrees the plane is going in the same direction as the wind. Seems like the true and apparent wind and aircraft are aligned, but now the wind is on the tail.

For there to NEVER be a crosswind, somewhere around 90 degrees, the apparent wind would have to switch from on the nose to on the tail...

It could happen I guess.

JPerrone,

You are going to get pummeled for your response. I would grab a drink and a snack and stand by...

Kurt

I know!!! It's what some people call "pull the pin, throw, run".

Speedracerntrixie, I have explained to you why you are using rudder the way you do to fix the "mistakes" you are making. I have explained to you what inputs you need to make so you don't have to use the rudder to correct the aircraft's flightpath. If you pitch through 90deg to fly an upline into a headwind of course you'll have to lean on the down elevator to fix the incorrect track of the upline we'd both agree on that. So why is it difficult to believe that when you pull out of a turnaround onto your baseline with a crosswind blowing in and you have to use the rudder to get the nose out again that your flightpath on the turnaround exit must have been crooked too?

Can yourself and Sensei put the egos aside? If you tell a beginner he needs to hold rudder to counteract the force of a crosswind then you are telling him something that's wrong, and I'm not the only person on this forum who has provided an explanation why that's wrong. If you tell a beginner that applying the rudder for a short period while holding the wings level won't change the ground track then that's wrong too, the ground track will change.

Please tell me where any statement I've made about rudder usage is wrong? The only support you have for your statements is RC planes fly different and I win lots of stuff doing it like that.

I have enough trophies in my cabinet for more than just RC aerobatics to recognise that not all of them were won because I was doing things correctly with full understanding, but because I just happened to be doing it better than the other blokes. There's a huge difference.

This discussion is like the bloke that had to 3D model the control line stunt schedule because the old guys wouldn't/couldn't accept some of the geometry relationships in the maneuver descriptions that they've held sacrosanct their whole lives were not possible...

Any force applied to an object will result in acceleration of that object.

If you believe there is a constant force being applied to the side of an aircraft when flying in a cross wind, that means there is a constant acceleration of the aircraft in the direction of the wind. This is not true. Acceleration is completely different to "movement"

Lets assume a steady constant unchanging wind from the north of 10 Mph.

The aircraft accelerates along the runway, takes off and is immediately influenced by the wind. Whatever direction the wind is coming from, it will apply a force to the aircraft. The aircraft will accelerate in the direction of the wind until it reaches equilibrium in the moving air mass. (within a few seconds of take off)

The aircraft is now moving wholly within the moving air mass and there is no further acceleration from the wind (IE no further force applied to the aircraft by the wind) regardless of the direction of the aircraft heading.

The only forces the aircraft now experiences is from it own movement within that airflow, because it is no longer being accelerated by the wind.

This principle is so easy to demonstrate in many ways.

Close your eyes and walk east. (with the earth's rotation)

Now close your eyes and walk west (against the earths rotation)

Can you tell the difference? Can you feel any force being applied by the rotation of the earth?

NO.. because from the moment you were born, you have been moving "with" the rotation of the earth.

Your speed matches the speed of the rotation of the earth, so you cannot feel any force regardless of which direction you walk.

The same concept applies to aircraft and explains why an aircraft does not experience a side force when flying in a cross wind.

Because it is already moving with the wind since shortly after take off.

There are many stories about airliners crashing due to the captain making mistakes while the copilot sat there saying nothing because in his culture it was unthinkable to question the captain.