Downwind turn Myth
09-13-2015, 10:01 PM
#1577
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"Erroneous momentum problem", in physics there is no erroneous momentum problem. The energy is in the fluids density and the planes collisions with that fluid. Gravity is center of mass to center of mass.
Throw a ball in the water near a rocky shore and watch the wave action smash the ball against the rocks or a pier pilling.
The ball's momentum is changing constantly, as is a planes. When the water smashes the ball into the rocks it has nothing to do with a downstream turn, it is the power of the fluid that smashes it.
The power of the fluid is a little harder to see when it is invisible (air is invisible).
But, it is not the planes turn, which changes the momentum slightly it is by the added drag of manuvering slowing it's relative speed.
It is the fluid that the plane is captive in where the power lies. With all physics it is the case that the energy is conserved. There is no loss that is not easily seen as a gain elsewhere. Nor gain that is not seen as a loss elsewhere.
14 pounds per square inch pressure @ STP is enough at speed to fly a 1,000,000 lb 747 at take off speed in that invisible fluid.
Downwind turn is a myth! Attitude plus power equals performance.
Throw a ball in the water near a rocky shore and watch the wave action smash the ball against the rocks or a pier pilling.
The ball's momentum is changing constantly, as is a planes. When the water smashes the ball into the rocks it has nothing to do with a downstream turn, it is the power of the fluid that smashes it.
The power of the fluid is a little harder to see when it is invisible (air is invisible).
But, it is not the planes turn, which changes the momentum slightly it is by the added drag of manuvering slowing it's relative speed.
It is the fluid that the plane is captive in where the power lies. With all physics it is the case that the energy is conserved. There is no loss that is not easily seen as a gain elsewhere. Nor gain that is not seen as a loss elsewhere.
14 pounds per square inch pressure @ STP is enough at speed to fly a 1,000,000 lb 747 at take off speed in that invisible fluid.
Downwind turn is a myth! Attitude plus power equals performance.
09-14-2015, 07:27 AM
#1578
Hi Bob,
Jack is correct..
The Inertia of an object has nothing to do with the planet earth.. The definition of inertia; “is a bodies tendency to resist acceleration The tendency of a body at rest to remain at rest or of a body in motion to stay in motion in a straight line unless acted on by an outside force.
This article explains it nicely.
http://www.flyingmag.com/pilots-plac...d-turns-really
Jack is correct..
The Inertia of an object has nothing to do with the planet earth.. The definition of inertia; “is a bodies tendency to resist acceleration The tendency of a body at rest to remain at rest or of a body in motion to stay in motion in a straight line unless acted on by an outside force.
This article explains it nicely.
http://www.flyingmag.com/pilots-plac...d-turns-really
09-14-2015, 07:40 AM
#1579
Hi Bob,
I have great respect for you, your modelling skills, (BVM F100F) and your general knowledge of aviation both model and full size. However, in this instance, you, and Mr McClellen are wrong. (or perhaps as we say in Australia ”having a lend of us”).
Jack is correct..
The Inertia of an object has nothing to do with the planet earth.. The definition of inertia; “is a bodies tendency to resist acceleration The tendency of a body at rest to remain at rest or of a body in motion to stay in motion in a straight line unless acted on by an outside force.
This article explains it nicely.
http://www.flyingmag.com/pilots-plac...d-turns-really
My Experiment. (as if we need another one!!)
The plane is now in a stable condition, completing a360 deg turn once every 60 seconds. (albeit drifting in the direction the wind is blowing.)
As the plane completes each lap, you will not see the plane “zoom” as it turns towards the wind direction. You will not see the plane “sag” as it turns away from the wind direction. There is no momentary "sag" in airspeed as the plane turns away from the wind direction, while it’s inertia catches up.. And there is no excess of inertia causing a "zoom" as it turns toward the wind direction.
With controls locked, the plane will happily circle at constant airspeed/height all day, until fuel runs out!!
Roger
I have great respect for you, your modelling skills, (BVM F100F) and your general knowledge of aviation both model and full size. However, in this instance, you, and Mr McClellen are wrong. (or perhaps as we say in Australia ”having a lend of us”).
Jack is correct..
The Inertia of an object has nothing to do with the planet earth.. The definition of inertia; “is a bodies tendency to resist acceleration The tendency of a body at rest to remain at rest or of a body in motion to stay in motion in a straight line unless acted on by an outside force.
This article explains it nicely.
http://www.flyingmag.com/pilots-plac...d-turns-really
My Experiment. (as if we need another one!!)
- Take a constant state wind condition. (Pick your own wind strength, 25 knots will do).
- Add an air plane, in flight. C 172 will do.
- Put said airplane into a rate two turn (6 deg per second).
- Set throttle to maintain this turn at constant bank angle, constant air speed, and constant height.
- Freeze the controls, and throttle, so the turn continues indefinitely, maintaining height and speed in the moving mass of air.
- Continue this turn indefinitely.
The plane is now in a stable condition, completing a360 deg turn once every 60 seconds. (albeit drifting in the direction the wind is blowing.)
As the plane completes each lap, you will not see the plane “zoom” as it turns towards the wind direction. You will not see the plane “sag” as it turns away from the wind direction. There is no momentary "sag" in airspeed as the plane turns away from the wind direction, while it’s inertia catches up.. And there is no excess of inertia causing a "zoom" as it turns toward the wind direction.
With controls locked, the plane will happily circle at constant airspeed/height all day, until fuel runs out!!
Roger
Thanks, I think...
I can get my head around that thought experiment, I can even see adding a balloon (even one with a glass gondola with disappearing walls...)
Where I run into trouble, conceptually, at least, is a wind gradient - i.e., which frame of reference do I use to explain that flying into the headwind from a microburst results in an increase in airspeed, or that flying into the tailwind from a microburst results in a decrease in airspeed?
Dynamic soaring is also hard to me to get my head around - i.e., how can I add energy to a non-powered aircraft by flying into and out of, the same wind gradient?
Bob
09-14-2015, 07:57 AM
#1580
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"Dynamic soaring is also hard to me to get my head around - i.e., how can I add energy to a non-powered aircraft by flying into and out of, the same wind gradient?"
https://en.wikipedia.org/wiki/Dynamic_soaring
By using gravity and flying a loop or other manuaver that uses a vertical element.
Jaybird
https://en.wikipedia.org/wiki/Dynamic_soaring
By using gravity and flying a loop or other manuaver that uses a vertical element.
Jaybird
09-14-2015, 08:01 AM
#1581
Roger,
Thanks, I think...
I can get my head around that thought experiment, I can even see adding a balloon (even one with a glass gondola with disappearing walls...)
Where I run into trouble, conceptually, at least, is a wind gradient - i.e., which frame of reference do I use to explain that flying into the headwind from a microburst results in an increase in airspeed, or that flying into the tailwind from a microburst results in a decrease in airspeed?
Dynamic soaring is also hard to me to get my head around - i.e., how can I add energy to a non-powered aircraft by flying into and out of, the same wind gradient?
Bob
Thanks, I think...
I can get my head around that thought experiment, I can even see adding a balloon (even one with a glass gondola with disappearing walls...)
Where I run into trouble, conceptually, at least, is a wind gradient - i.e., which frame of reference do I use to explain that flying into the headwind from a microburst results in an increase in airspeed, or that flying into the tailwind from a microburst results in a decrease in airspeed?
Dynamic soaring is also hard to me to get my head around - i.e., how can I add energy to a non-powered aircraft by flying into and out of, the same wind gradient?
Bob
09-14-2015, 08:39 AM
#1582
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If this is true why does an air plane go faster with the wind than against it or take a blimp why does it go faster with the wind or a kite you cant fly a kite with the wind
09-14-2015, 10:18 AM
#1586
"Dynamic soaring is also hard to me to get my head around - i.e., how can I add energy to a non-powered aircraft by flying into and out of, the same wind gradient?"
https://en.wikipedia.org/wiki/Dynamic_soaring
By using gravity and flying a loop or other maneuver that uses a vertical element.
Jaybird
https://en.wikipedia.org/wiki/Dynamic_soaring
By using gravity and flying a loop or other maneuver that uses a vertical element.
Jaybird
From the Wikipedia article you site:
"While different flight patterns can be employed in dynamic soaring, the simplest example to explain the energy extraction mechanism is a closed loop across the boundary layer between two airmasses in relative movement. The gain in speed can be explained in terms of airspeed or groundspeed:
- The glider gains airspeed twice during the loop, when it pierces the boundary layer at an acute angle. Since the 180° turns retain most of the airspeed the glider completes the loop within the initial airmass at a higher airspeed.
- The gain in groundspeed occurs when the glider performs a 180° downwind turn within the moving airmass. Since the opposite 180° turn is done within the stationary airmass the groundspeed gain is not reversed.
Say what??? Somebody draw me the vector diagrams for that, my head hurts...
Bob
Last edited by rhklenke; 09-14-2015 at 10:22 AM.
09-14-2015, 10:32 AM
#1587
Like I said, I got the downwind turn in a consistent (i.i, non-changing) airmass moving at a constant speed - the previous examples make sense (except Peter Garrison's article, but I never liked his articles in Flying anyway - I think he should stick his head out the window of that 70MPH train and then turn frontwards and backwards and see if he feels a difference...
). Bob
Last edited by rhklenke; 09-14-2015 at 10:45 AM.
09-14-2015, 12:50 PM
#1589
There are probably 100 posts in this thread specifically stating that wind SHEAR is a completely different topic. That's a sudden change in the velocity and/or direction of the wind. Think of them as uber-gusts. Gusting conditions can either add or subtract airspeed, are not the topic of this thread, and are not material to the discussion of the downwind turn myth.
09-14-2015, 12:57 PM
#1591
We all know what a microburst is - there are plenty of pictures of it out there, but I don't know what you mean when you say "all bets are off in a micro burst." The laws of physics aren't repealed in a microburst, so what frame of reference should you use for the aircraft's inertia to explain the gain, and subsequent loss, of airspeed in a microburst encounter? How RAPID does the change in wind direction need to be to make the effect noticeable vs. the aircraft's mass?
Like I said, I got the downwind turn in a consistent (i.i, non-changing) airmass moving at a constant speed - the previous examples make sense (except Peter Garrison's article, but I never liked his articles in Flying anyway - I think he should stick his head out the window of that 70MPH train and then turn frontwards and backwards and see if he feels a difference...).
Bob
Like I said, I got the downwind turn in a consistent (i.i, non-changing) airmass moving at a constant speed - the previous examples make sense (except Peter Garrison's article, but I never liked his articles in Flying anyway - I think he should stick his head out the window of that 70MPH train and then turn frontwards and backwards and see if he feels a difference...
). Bob
I mean that Micro Burst have nothing to do with Down Wind Turn thingy. So bets off.
Micro Bursts are a form of wind shear and is not a constant mass of moving air. Neither are Gusty wind conditions. It's not a factor if U "KEEP THE SPEED UP" in gusty conditions. Everyone knows that the stall speed goes up & down with increased bank angle and plane configure condition. i.e. Weight, forward or reward center of BALANCE, Gear up or down and Flap Settings
09-14-2015, 02:32 PM
#1593
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Another factor in the downwind myth is the related transmitter stare.
Many pilots after a crash look down at their transmitter and stare at it. They stare as if somehow the fact that everybody was watching and knows pilot error was the cause of the crash that just occurred, if they stare in disbelief long enough they can convince someone that the transmitter was at fault.
I saw a video of dynamic soaring and it was amazing.
Many pilots after a crash look down at their transmitter and stare at it. They stare as if somehow the fact that everybody was watching and knows pilot error was the cause of the crash that just occurred, if they stare in disbelief long enough they can convince someone that the transmitter was at fault.
I saw a video of dynamic soaring and it was amazing.
Last edited by kmeyers; 09-14-2015 at 02:35 PM.
09-14-2015, 04:10 PM
#1596
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Best answer is storms are an uncomfortable ride for the paying passengers. An airplane on the ground has nothing to do with this discussion; all objects with light weight and enough surface area are prone to wind damage. I have never seen a tree make a downwind turn but I have seen trees loose limbs or be blown completely over by wind.
09-15-2015, 07:46 AM
#1599
"Erroneous momentum problem", in physics there is no erroneous momentum problem. The energy is in the fluids density and the planes collisions with that fluid. Gravity is center of mass to center of mass.
Throw a ball in the water near a rocky shore and watch the wave action smash the ball against the rocks or a pier pilling.
The ball's momentum is changing constantly, as is a planes. When the water smashes the ball into the rocks it has nothing to do with a downstream turn, it is the power of the fluid that smashes it.
The power of the fluid is a little harder to see when it is invisible (air is invisible).
But, it is not the planes turn, which changes the momentum slightly it is by the added drag of manuvering slowing it's relative speed.
It is the fluid that the plane is captive in where the power lies. With all physics it is the case that the energy is conserved. There is no loss that is not easily seen as a gain elsewhere. Nor gain that is not seen as a loss elsewhere.
14 pounds per square inch pressure @ STP is enough at speed to fly a 1,000,000 lb 747 at take off speed in that invisible fluid.
Downwind turn is a myth! Attitude plus power equals performance.
Throw a ball in the water near a rocky shore and watch the wave action smash the ball against the rocks or a pier pilling.
The ball's momentum is changing constantly, as is a planes. When the water smashes the ball into the rocks it has nothing to do with a downstream turn, it is the power of the fluid that smashes it.
The power of the fluid is a little harder to see when it is invisible (air is invisible).
But, it is not the planes turn, which changes the momentum slightly it is by the added drag of manuvering slowing it's relative speed.
It is the fluid that the plane is captive in where the power lies. With all physics it is the case that the energy is conserved. There is no loss that is not easily seen as a gain elsewhere. Nor gain that is not seen as a loss elsewhere.
14 pounds per square inch pressure @ STP is enough at speed to fly a 1,000,000 lb 747 at take off speed in that invisible fluid.
Downwind turn is a myth! Attitude plus power equals performance.
Look, there are those who will believe what they want to believe no matter what. This conversation has been going on since usenet (even before rec,models.rc.air). Even when I wrote on rec.model.rc.air about my conversation with the engineers at the NAVAIR flight simulation program for the F-18 very few minds were changed. It's really a waste of time, at least for me, and I think this will be my last post on the subject. Some of you will silently appaud tha decision. Heck, most of you will silently applaud.
09-15-2015, 08:01 AM
#1600
We all know what a microburst is - there are plenty of pictures of it out there, but I don't know what you mean when you say "all bets are off in a micro burst." The laws of physics aren't repealed in a microburst, so what frame of reference should you use for the aircraft's inertia to explain the gain, and subsequent loss, of airspeed in a microburst encounter? How RAPID does the change in wind direction need to be to make the effect noticeable vs. the aircraft's mass?
Like I said, I got the downwind turn in a consistent (i.i, non-changing) airmass moving at a constant speed - the previous examples make sense (except Peter Garrison's article, but I never liked his articles in Flying anyway - I think he should stick his head out the window of that 70MPH train and then turn frontwards and backwards and see if he feels a difference...).
Bob
Like I said, I got the downwind turn in a consistent (i.i, non-changing) airmass moving at a constant speed - the previous examples make sense (except Peter Garrison's article, but I never liked his articles in Flying anyway - I think he should stick his head out the window of that 70MPH train and then turn frontwards and backwards and see if he feels a difference...
). Bob
