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Old Sep 03, 2012, 12:44 AM
Augernaut
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United States, KS, Overland Park
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Originally Posted by eflightray View Post
Well as your eye's are in your head, then I guess you could say "that it's all in my head" , it a problem with perception between air speed and ground speed.

Just don't fly on a windy day to start with, try to pick a calm day and you should have no upwind and down wind turn problems.

As you gain experience of flying then you can try slightly windier days.

By the way, your Radian doesn't have to be flying close to the stall, a little down trim will cure that, (just a click or two on the trim). Flying too close to the stall is what this thread is all about. People do it, slow down a bit more, then blame the resulting crash on everything else except themselves.

Hope you enjoy the Radian.
For some of us there is no such thing as a calm day. Or at least it is a relative term. Under 10MPH is considered a remarkably calm day. They build windmills here for a reason.
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Old Sep 03, 2012, 04:10 AM
Wake up, feel pulse, be happy!
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United States, AK, Fairbanks
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It's baffling that this still exists.

I mean, I understand that it defies some basic sensory logic and I can see where some people wouldn't immediately recognize what's going on, but I completely fail to comprehend how they can still not get it after it's been explained. Analogies, thought experiments, mental models... None of it seems to work.

I'll give it a shot myself. Why not?

Let's pretend we have an An-450 to play with (it's TWICE the size of the Antonov An-225). It's had some interior decorating done and now sports a small onboard airfield for our ParkZone Vapor. Let's get that Vapor and fly it around inside this big ole Russian beast while we sit on the tarmac and wait to take off. The little Vapor flies around happily in circles.

Now we're flying home to Minneapolis for a visit. We're at like 30,000' AGL and we're going maybe 480mph groundspeed. We get bored with writing this analogy (the in-flight wifi is cool, though), so we pull out the Vapor and do some more flying. We're still just flying the Vape in circles, and by all counts the little thing seems to be doing fine.

Wait. Did I mention that the whole An-450 is made of glass? It's totally clear- in fact, we're not entirely sure if there's a plane there at all. We might as well be riding in a bubble of air moving at 480mph relative to the ground... Hang on. That sounds an awful lot like a description of wind

And yet that darn Vapor just keeps making those circles.
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Old Sep 03, 2012, 02:54 PM
Augernaut
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United States, KS, Overland Park
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Quote:
Originally Posted by C₄H₁₀ View Post
It's baffling that this still exists.

I mean, I understand that it defies some basic sensory logic and I can see where some people wouldn't immediately recognize what's going on, but I completely fail to comprehend how they can still not get it after it's been explained. Analogies, thought experiments, mental models... None of it seems to work.

I'll give it a shot myself. Why not?

Let's pretend we have an An-450 to play with (it's TWICE the size of the Antonov An-225). It's had some interior decorating done and now sports a small onboard airfield for our ParkZone Vapor. Let's get that Vapor and fly it around inside this big ole Russian beast while we sit on the tarmac and wait to take off. The little Vapor flies around happily in circles.

Now we're flying home to Minneapolis for a visit. We're at like 30,000' AGL and we're going maybe 480mph groundspeed. We get bored with writing this analogy (the in-flight wifi is cool, though), so we pull out the Vapor and do some more flying. We're still just flying the Vape in circles, and by all counts the little thing seems to be doing fine.

Wait. Did I mention that the whole An-450 is made of glass? It's totally clear- in fact, we're not entirely sure if there's a plane there at all. We might as well be riding in a bubble of air moving at 480mph relative to the ground... Hang on. That sounds an awful lot like a description of wind

And yet that darn Vapor just keeps making those circles.
All fine and dandy until the ground is taken into the equation. Or in your analogy, now you are trying to land in this giant plane on a sheet of plywood on a moving rc car. gets trickier now doesn't it? You aren't seeing the argument because you are negating any relation to the ground. That works great when in the pattern, but when you come in to land now you have to adjust. as your turning around you have a tailwind at 20 mph at the halfway point you are going to have to bring her around hard to end the turn lined up with the runway. People get in trouble because in a pattern you are flying an oval. to land you take that oval and turn it into a raindrop shape.
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Old Sep 03, 2012, 03:21 PM
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I never had a problem with the upwind/downwind scenario you cite, when i'm flying my Picocub at 20mph in a prevailing 5mph I realise there is no such thing as an upwind/downwind situation but when i'm flying my Radian at 10mph in a 5mph prevailing it does occur, I realise that turning downwind will induce a stall situation, the tighter I turn the worse it will be and I have to fly accordingly..

to quote Dave Thornburg, from the "Old Buzzards Soaring Book" which I am led to believe is the bible according to Glider pilots all over the world..

"Any time you turn downwind, your model has to accelerate (relative to the earth) in order to catch up with the river of air and regain a comfortable airspeed. This acceleration costs you some altitude, and while it's happening the rudder is going to be sluggish, since it is to short of airspeed."

This to me as i glider pilot is realworld..it happens, but you are telling me it doesn't..I don't fly a Vapor inside a large aircraft somewhere over the states.. I fly a Glider down at my local playing fields..

Sorry if my post appears "newbie and borderline moronic" ..
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Old Sep 03, 2012, 04:14 PM
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United States, IA, Hampton
Joined May 2012
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I trim my gliders, as near as I can, for L/Dmax, the speed where lift is at a maximum and drag at a minimum. This in 99% of airfoils is nowhere near stall speed. Now when I make a shallow turn i dont add elevator and lose little to no altitude and no matter what direction, in relation to the wind get exactly the same result as far as altitude loss/gain and controllability are concerned. As far as ground track and speed, that is a different story. Where most, even glider pilots, have the problem is they fly ground speed. You see your plane speed up on down wind and expect more lift then when you are upwind see a slow speed and expect less lift. Keep your plane trimmed and let it maintain that speed and you will find it performs better and handles better throughout the flight. I have been flying gliders this way for 30+ years and haven't had a problem.
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Old Sep 06, 2012, 02:03 PM
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I am amazed that there are still people out there that believe the downwind turn/stall myth. There is no such thing. Wind has no effect on an airplane in flight except as it affects ground-based maneuvers such as takeoffs, landings and ground track. Thanks to my Cessna flight instructor who drilled that into me endlessly.
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Old Sep 06, 2012, 02:09 PM
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I have been watching a few friends, who have trouble with 'the dreaded downwind turn', and they seem to climb a little during the turn, climbing into faster tailwind, thereby losing airspeed. (The the bad side of the wind gradient.)
By letting the plane sink a bit during the turn, they would increase the airspeed, because of entering a slower tailwind. (The good side of the wind gradient).

Look around, please, and see, if that could be a factor in downwind stalls. (They are actually doing a sort of opposite dynamic soaring).
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Old Sep 06, 2012, 02:10 PM
Augernaut
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Quote:
Originally Posted by kaptondave View Post
I am amazed that there are still people out there that believe the downwind turn/stall myth. There is no such thing. Wind has no effect on an airplane in flight except as it affects ground-based maneuvers such as takeoffs, landings and ground track. Thanks to my Cessna flight instructor who drilled that into me endlessly.
so, no effect except when you are taking off, in the air, and landing?
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Old Sep 06, 2012, 02:11 PM
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Quote:
Originally Posted by kaptondave View Post
I am amazed that there are still people out there that believe the downwind turn/stall myth. There is no such thing. Wind has no effect on an airplane in flight except as it affects ground-based maneuvers such as takeoffs, landings and ground track. Thanks to my Cessna flight instructor who drilled that into me endlessly.

Then can you explain this quote...

"Anytime you turn downwind, your model has to accelerate (relative to earth) in order to catch up with the river of air and regain a comfortable airspeed. This acceleration costs you some altitude, and while it's happening the rudder is going to be sluggish, since it too is short on airspeed."

Dave Thornburg, Old Buzzards soaring book.
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Old Sep 06, 2012, 04:19 PM
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Originally Posted by Kickstart View Post
Then can you explain this quote...

"Anytime you turn downwind, your model has to accelerate (relative to earth) in order to catch up with the river of air and regain a comfortable airspeed. This acceleration costs you some altitude, and while it's happening the rudder is going to be sluggish, since it too is short on airspeed."

Dave Thornburg, Old Buzzards soaring book.
He's just flat-out wrong, that's all there is to it.

Now mind you, if you moved to a region with a different wind speed or direction (vertical included) you could see what looked just like what he describes.
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Old Sep 06, 2012, 05:58 PM
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Originally Posted by Kickstart View Post
... when i'm flying my Radian at 10mph in a 5mph prevailing it does occur, I realise that turning downwind will induce a stall situation, the tighter I turn the worse it will be and I have to fly accordingly..

to quote Dave Thornburg, from the "Old Buzzards Soaring Book" which I am led to believe is the bible according to Glider pilots all over the world..

"Any time you turn downwind, your model has to accelerate (relative to the earth) in order to catch up with the river of air and regain a comfortable airspeed. This acceleration costs you some altitude, and while it's happening the rudder is going to be sluggish, since it is to short of airspeed."

Sorry if my post appears "newbie and borderline moronic" ..
Thomburg is the one that is borderline moronic. You are guilty only of believing that if it is in a book it must be true. The reason you are stalling your Radian in the turn is that you are flying upwind too close to the stall speed. When you turn you are converting part of your lift to aq turning force and do not have enough left to support the plane's weight. I fly a Radian and have seen it happen when I slow it down too much.
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Old Sep 06, 2012, 06:04 PM
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so, no effect except when you are taking off, in the air, and landing?
If that is what you got from that your reading comprehension is somewhat lacking.
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Old Sep 06, 2012, 06:41 PM
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Quote:
Originally Posted by C₄H₁₀ View Post
It's baffling that this still exists.
I mean, I understand that it defies some basic sensory logic and I can see where some people wouldn't immediately recognize what's going on, but I completely fail to comprehend how they can still not get it after it's been explained. Analogies, thought experiments, mental models... None of it seems to work.
I guess some people don't/can't believe what they can't see for themselves. I work at a Uni and some students have difficulties with certain behaviours of electrical systems until they can be provided with a suitable mechanical analogue then the light comes on and they "see" what's going on.

To be honest, the blame lies partly with the educational system when students are taught physics by some "kid" that scraped a pass on his physics course during his teaching degree and whose probably forgotton half of that already.

The lack of understanding of what the kinetic energy calculations are actually useful for come about because of the silly, simplified questions students in high school are asked about cars hitting walls. Students then tend to walk away thinking kinetic energy is some fixed quantity that objects posess like 50 litres of fuel in a tank while not fully understanding that a plane circling a building at 1000mph has NO kinetic energy relative to a person standing on top of the building and a constantly varying kinetic energy relative to anything not located at the centre of the circle.

Anyway, it's like that math brain teaser about the Bellhop that has to give the customer back some change and he keeps a bit, and sombody else keeps a bit and suddenly all the amounts don't add up to the original quantity anymore. When you do the math wrong, of course the answer doesn't make sense...
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Old Sep 06, 2012, 08:53 PM
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Surely the very fact that this thread has been running for so long would indicate that some people do have a problem with the "downwind turn".
So is there a difference between up wind and down wind turns?
I am convinced that the problem lies with peoples perception of what is actually happening. Because we are standing still and flying in a moving body of air things do look different.
Many flyers do have hang ups about certain things. Some people cannot turn right for example although there is no reason that right hand turns are any more difficult than left ones.
Downwind turns are no more difficult than upwind but they can feel different.
People go on about full size flying and that they never have this problem but if they had to fly over a course which was fixed on the ground and they had to fly it exactly then there would have to be all sorts of corrections required.
I have flown full size and flying to a point on a map does not mean you point at it and go. If there is a crosswind you need to aim at a different point and let the wind blow you sideways so you end up at the place you want to go.
Jim
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Old Sep 07, 2012, 12:11 AM
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Originally Posted by Fox-composites View Post
Surely the very fact that this thread has been running for so long would indicate that some people do have a problem with the "downwind turn".
So is there a difference between up wind and down wind turns?
I am convinced that the problem lies with peoples perception of what is actually happening. Because we are standing still and flying in a moving body of air things do look different.
Many flyers do have hang ups about certain things. Some people cannot turn right for example although there is no reason that right hand turns are any more difficult than left ones.
Downwind turns are no more difficult than upwind but they can feel different.
People go on about full size flying and that they never have this problem but if they had to fly over a course which was fixed on the ground and they had to fly it exactly then there would have to be all sorts of corrections required.
I have flown full size and flying to a point on a map does not mean you point at it and go. If there is a crosswind you need to aim at a different point and let the wind blow you sideways so you end up at the place you want to go.
Jim
Maybe off topic but this made me think of something. Okay so imagine I am flying a circuit while standing in the pits on the side of the middle of the runway. I find that when I am flying off to the right of myself, right turns feel a little uncomfortable. However when the plane is to the left of me, right turns are comfortable but left feel a little uncomfortable. Kinda interesting. Must have something to do with fields of vision and "where" they are perceived in the brain. I'm right handed also.
It is like I just have to think about what I'm doing a little more consciously when I make a right turn towards myself when looking at the plane to the right of me, and vice versa. A left turn seems completely natural from the right field of vision, but a right turn makes me consciously think about which direction I need to keep holding aileron and rudder till the nose is pointing towards me again. I try to practice these things that make me uncomfortable to increase my skill level a bit every time I fly.
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