The dreaded down-wind turn, fact or fiction? - Page 16 - RC Groups
 Sep 16, 2012, 10:59 PM Foxman KaptonDave, as you so rightly say "the ground speed would be reduced as it pulled out into wind and increased as it pulled out downwind. The words "increase" and "reduced" indicate that a certain time is taken for the speed to equalise. Also did you actually read what I wrote as I said the model would have to dive vertically in relation to a fixed point on the ground, not as you said that it would be moving at 20 mph relative to the ground. We all know that the model will eventually regain normal airspeed but I think it would take a small amount of time to do this. What possible problem would there be with pulling out of a vertical dive?. I do it every flight in some way. Do you fly models? Do you never dive vertically? I guess if you do then you will need to pull out at some point or only do it once. I cannot remember seeing a model stall while pulling out of a vertical dive. I'm not saying it's impossible but come on, you're just trying to be difficult.
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Sep 16, 2012, 11:23 PM
3D? I only got two thumbs!
Quote:
 Originally Posted by Fox-composites What possible problem would there be with pulling out of a vertical dive?. I do it every flight in some way. Do you fly models? Do you never dive vertically? I guess if you do then you will need to pull out at some point or only do it once. I cannot remember seeing a model stall while pulling out of a vertical dive. I'm not saying it's impossible but come on, you're just trying to be difficult.
Snap roll. Some planes have a tendency to "snap out" with any hard pull, or even lesser pulls at lower speeds. Even going straight down.
Sep 16, 2012, 11:54 PM
Registered User
Quote:
 Originally Posted by Fox-composites ... did you actually read what I wrote as I said the model would have to dive vertically in relation to a fixed point on the ground, not as you said that it would be moving at 20 mph relative to the ground. We all know that the model will eventually regain normal airspeed but I think it would take a small amount of time to do this.
You may be surprised to hear that yes, I actually read the question. As to the dive angle I felt that you were making the scenario more complex than necessary and so took the liberty of simplifying it a bit. The outcome would be the same. Likewise I see no significance to the fact that it would take a small amount of time for the speed to stabilize after the turn. If you feel that those simplifications invalidates the analysis then hopefully you can find someone else to redo it to your satisfaction.

Quote:
 What possible problem would there be with pulling out of a vertical dive?. I do it every flight in some way. Do you fly models? Do you never dive vertically? I guess if you do then you will need to pull out at some point or only do it once.
You are being really snide with your remarks and that is uncalled for. I was trying to be helpful. I have explained what the problem with abrupt turns might be. If you do not understand accelerated stalls or believe they can be caused by abrupt turns that is OK by me.
 Sep 17, 2012, 03:04 AM You can't take the sky from me Why does the "air speed" need to equalize? If you subscribe to the inertia issue you obviously don't understand the actual concept. The Mythbusters proved that point. They backed a car out of a tractor trailer at about 2 mph while it was travelling ~40 mph and instantly were doing ~38 mph with no control problems and no lag as the cars inertia "caught up". It went from ~2 mph backwards to ~38 mph forwards instantly and nothing happened, it just continued driving. How did it do that? Because it was doing 38 mph in relation to the road the whole time, it was just going 2 mph backwards in relation to the trailer. So why is the car exempt from the whole inertia thing but airplanes aren't?
Sep 17, 2012, 09:19 AM
Registered User
Quote:
 Originally Posted by cfircav8r Why does the "air speed" need to equalize? If you subscribe to the inertia issue you obviously don't understand the actual concept.
+1. It would take a little time for the ground speed to stabilize but the air speed would remain constant, assuming perfect piloting.
 Sep 17, 2012, 09:58 AM DX5e fatal flaw- PM me!!!! I made a downwind-turn today and didn't allow for the plane to catch up to the wind and the wind raped my dog. Ugly.
 Sep 18, 2012, 04:35 AM Foxman Aeroken, if the model snap rolls pulling out of a dive then you have too much elevator throw or a rearward CG or a very nasty model. Of course I know that some models have a tendency to snap but that is missing the point I was trying to make. Kapton Dave, I was not making it more complex but I used to fly aerobatics and many of the things we had to do involved a vertical dive and you had to allow for any wind there was and make it look vertical to a fixed point on the ground. If you drifted off downwind you lost marks.. If you are flying a square loop for example you have to do a reasonably sharp turn at all four corners of the loop. No one ever snapped rolled out that I saw. I don't really know if the speed would change if you pulled up wind or downwind after a vertical dive and I don't really think anyone here knows either. I would like to fit some monitoring equipment and find out. I think for a split second the "ground" speed would be the same up or downwind. A bit like being dropped onto a moving walkway at the airport. It would depend which way you were facing as to what would happen. One way you would fall backwards, the other way you would fall forwards before stabilising your bodies speed with the walkway Where can I buy an Eagle Tree?
Sep 18, 2012, 10:18 AM
Registered User
Quote:
 Originally Posted by Fox-composites Of course I know that some models have a tendency to snap but that is missing the point I was trying to make.
Then sorry, but I can't determine what point you were trying to make. I understand the part about making vertical acro figures symmetric but you were talking about speed. I guess I should not have mentioned accelerated stalls because that has confused the issue.
 Sep 18, 2012, 10:21 AM You can't take the sky from me Unless you hit the ground it has nothing to do with the airplane or its air speed. The pull out from vertical into the wind will loose less speed due to the fact that it will be a smaller angle change. The pull out down wind will loose more speed due to the fact that it will require a larger angle change. To have them appear the same you will have a greater loading on down wind and therefore more drag. Again wind is not causing any of this, your attempt to make your airplanes ground track the same is what is causing it.
Sep 21, 2012, 10:41 PM
Foxman
Quote:
 Originally Posted by cfircav8r Unless you hit the ground it has nothing to do with the airplane or its air speed. The pull out from vertical into the wind will loose less speed due to the fact that it will be a smaller angle change. The pull out down wind will loose more speed due to the fact that it will require a larger angle change. To have them appear the same you will have a greater loading on down wind and therefore more drag. Again wind is not causing any of this, your attempt to make your airplanes ground track the same is what is causing it.
So what you are actually saying is that "pulling up downwind is not the same as pulling up into wind".??
You have just admitted it. Isn't this the whole point of what I said??
You can add angles into the equation and fixed points on the ground but you still said it would be different.
Only a Free flight model does it perfectly with no airspeed change and no body interfering with it of course.
Only if you let the model drift downwind at wind speed then there is no difference.

.
Last edited by Fox-composites; Sep 21, 2012 at 10:51 PM.
 Sep 21, 2012, 11:15 PM You can't take the sky from me No I said it was different if you were trying to adjust your ground track. To say it was the wind would be like blaming the phone for your accident because you were texting while driving. the phone didn't physically do anything, you chose to look at your phone instead of the road. What we are arguing is that the wind doesn't push the plane or get under, across or behind the wing and cause a loss of lift as some seem to believe. So if you believe that the wind somehow causes the wing to loose lift then you are wrong, if you believe that the pilot stalls in an attempt to compensate for ground speed and track then you would be right.
 Sep 24, 2012, 11:55 PM Foxman If flown like a Free Flight model then there is no difference at all in what the aircraft would see on an on board airspeed indicator. No argument there. If flown to a point on the ground then as you say, there is a difference, you admit that. Why do you keep mentioning stalling? I am talking about airspeed. Yes I know if you fly too slowly you can stall but I'm not talking about stalling. I have been flying for 38 yrs and have seen it all along with this argument that has been raging for as long as I remember. I know that some aspects of flying models can feel different depending on whether you are turning into or downwind and if you are flying fast or slow. No I don't believe that the wind hits the model from behind or from the side, that is stupid. As you say, "attempts to make the aircraft fly in relation to the ground is causing the problem", lets see, Aerobatics, Pylon racing, landing, take off, control line, slope soaring, everyone of those involves a fixed point on the ground. Letting a model drift around and almost letting it do what it wants never was a problem to anyone.
 Sep 25, 2012, 12:28 AM You can't take the sky from me That is the point of the down wind turn myth, that the "airspeed" drops when you turn down wind and increases when you turn up wind. I as well as others have been saying that the only change in airspeed is due to the pilots inputs in an attempt to maintain ground track and/or ground speed and not the wind speed or direction. You don't have to let the model drift around but you do have to stay within the envelope. Often all it takes is to time your turns better and change the amount you turn. Where the problems arise is when people believe that the wind direction and speed affect the plane aerodynamically, when it is just their improper correction to wind drift and ground speed changes. Poor understanding of what is occurring leads to poor decisions in flight. So yes when wind is added to the mix turns will be different depending on the wind speed and direction, but the down wind turn myth is not the correct answer as to why.
 Sep 25, 2012, 11:50 PM Foxman I agree. Jim
Oct 12, 2012, 06:21 AM
Registered User

# sailplane high

i just was talked into this thread, and want to ask why when flying my sailplanes high up there, and trying to stay into a weak thermal (or no thermal at all), my plane stays longer if i turn only facing the wind (as in lazy 8's) than if i do full turns (that is, going downwind).

am not trying to say nothing in favor or against upwind or downwind turns, just trying to hear opinions why.

but i have noticed that whenever i turn upwind, the plane goes up-and stays there, whilst when turning downwind the plane sinks-and stays there. even if i try to correct the plane's attitude.
please notice that am not talking about flying near the ground, only up high, away from ground effect or turbulence.
thanks

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