The Windward Turn Theory
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I want to make it clear that nowhere in my website do I say that groundspeed affects an aircraft in flight.
Read the link at post #102 and you will find a rational explanation of the effect of the wind during turning flight.
Stall spin crash burn - beware the downwind turn. But it is mostly pilot error.
Read the link at post #102 and you will find a rational explanation of the effect of the wind during turning flight.
Stall spin crash burn - beware the downwind turn. But it is mostly pilot error.
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I'll ask you the same question that the other Myth-ers couldn't handle. (either refused to answer or answered incorrectly)
2 identical airplanes with a cruise airspeed of 100 knots. Both are flying east. Airplane A is in still air. Airplane B is flying into a 50 knot wind blowing out of the east. Both turn 180 degrees and fly west. What is the change in velocity from before the turn to after the turn for each plane?
Last edited by A Squared; 30th Jul 2018 at 06:45.
I want to make it clear that nowhere in my website do I say that groundspeed affects an aircraft in flight.
Read the link at post #102 and you will find a rational explanation of the effect of the wind during turning flight.
Stall spin crash burn - beware the downwind turn. But it is mostly pilot error.
Read the link at post #102 and you will find a rational explanation of the effect of the wind during turning flight.
Stall spin crash burn - beware the downwind turn. But it is mostly pilot error.
You are a patient man Wiz.
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No, you will not, you will find complete nonsense which ignores physics, couched in pseudo-scientific terms not understood by the author.
I'll ask you the same question that the other Myth-ers couldn't handle. (either refused to answer or answered incorrectly)
2 identical airplanes with a cruise airspeed of 100 knots. Both are flying east. Airplane A is in still air. Airplane B is flying into a 50 knot wind blowing out of the east. Both turn 180 degrees and fly west. What is the change in velocity from before the turn to after the turn for each plane?
I'll ask you the same question that the other Myth-ers couldn't handle. (either refused to answer or answered incorrectly)
2 identical airplanes with a cruise airspeed of 100 knots. Both are flying east. Airplane A is in still air. Airplane B is flying into a 50 knot wind blowing out of the east. Both turn 180 degrees and fly west. What is the change in velocity from before the turn to after the turn for each plane?
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During the turn the lift vector, which is identical whether the wind blows or not, causes a turn of constant rate and constant (air) radius.
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Nope, not irrelevant at all. It is the very crux of the "downwind turn" fallacy and the fact that you are trying to dismiss it as irrelevant just illustrates that you don't have the fundamental grasp of physics required to understand why you are mistaken.
I want to make it clear that nowhere in my website do I say that groundspeed affects an aircraft in flight.
Read the link at post #102 and you will find a rational explanation of the effect of the wind during turning flight.
Stall spin crash burn - beware the downwind turn. But it is mostly pilot error.
Read the link at post #102 and you will find a rational explanation of the effect of the wind during turning flight.
Stall spin crash burn - beware the downwind turn. But it is mostly pilot error.
You state (when discussing an aircraft, in a steady wind, doing a constant rate turn)
1.3 If you think, at this point, that the wind is irrelevant to an aircraft in flight, remember that the spiral ground track is the vector sum of aircraft velocity relative to the air and wind-velocity relative to the ground. The acceleration of the aircraft is caused by forces acting on the aircraft and is seen as acceleration components of air-velocity and ground-velocity. In this context, the acceleration of the aircraft is affected by the wind.
1. You can only get an acceleration by applying a net force.
The only force, acting on the aircraft, "caused" by the earth, is gravity.
Yet you seem to argue that somehow the earth acts to accelerate the aircraft laterally. How? What force is this, where does it come from and how does it act on the aircraft?
2. That spiral path would appear exactly the same for any circling object if it was viewed from a constantly moving point of reference. No additional force is required to make the spiral path. (eg one of those conical pendulums dropping sand on paper - pull the paper at a constant rate and you get the very same spiral.) Not getting where any additional force is needed to get that pattern.
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I have looked at that site.
You state (when discussing an aircraft, in a steady wind, doing a constant rate turn)
I don't get what you are saying and it seems to be the crux of your argument.
1. You can only get an acceleration by applying a net force.
The only force, acting on the aircraft, "caused" by the earth, is gravity.
Yet you seem to argue that somehow the earth acts to accelerate the aircraft laterally. How? What force is this, where does it come from and how does it act on the aircraft?
2. That spiral path would appear exactly the same for any circling object if it was viewed from a constantly moving point of reference. No additional force is required to make the spiral path. (eg one of those conical pendulums dropping sand on paper - pull the paper at a constant rate and you get the very same spiral.) Not getting where any additional force is needed to get that pattern.
You state (when discussing an aircraft, in a steady wind, doing a constant rate turn)
I don't get what you are saying and it seems to be the crux of your argument.
1. You can only get an acceleration by applying a net force.
The only force, acting on the aircraft, "caused" by the earth, is gravity.
Yet you seem to argue that somehow the earth acts to accelerate the aircraft laterally. How? What force is this, where does it come from and how does it act on the aircraft?
2. That spiral path would appear exactly the same for any circling object if it was viewed from a constantly moving point of reference. No additional force is required to make the spiral path. (eg one of those conical pendulums dropping sand on paper - pull the paper at a constant rate and you get the very same spiral.) Not getting where any additional force is needed to get that pattern.
Try again talking us all through an upwind turn, explaining what’s happening to all the forces as you go.
I await your reply with great interest.
Last edited by Jet_Fan; 1st Aug 2018 at 17:01.
Your argument (as I read it) is that in a constant wind, an aircraft in a constant rate turn, will have (small) changes of airspeed as it moves from a headwind (relative to the ground) to a tailwind (relative to the ground). Is that correct?
Would you agree in this situation that the only forces that are directed laterally on the aircraft are thrust and drag and inclined lift, all are acting due to interaction with the air?
The angle of bank doesn't change so the lateral component of lift is constant.
We do not change thrust.
The aircraft can only generate an acceleration (which would be required to change the airspeed that you say happens) is if we change drag - that is the only force we have left (as far as I can see).
Why does drag change?
The only way I can see that changing is because airspeed changes but that is assuming the effect we are trying to find the cause of - it would appear to me to be the airspeed changes because the drag changes and the drag changes because the airspeed changes therefore the airspeed changes... ?? ie we are assuming the effect we are trying to prove occurs.
I am not getting where an unbalanced force can come from that causes the (small) airspeed changes you claim are occur.
Now if the wind velocity varied (eg a gust or windshear in descent/climb etc) then that would cause a change in airspeed but not in a constant wind. What am I missing here?
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I hesitate to get involved in this argument as the positions are so entrenched. However, a little observational input may assist.
I was working as local/tower controller at Valley in Anglesey. It was a quiet Sunday and as was quite common there the wind was gale force although steady and not gusting as it came off the Irish Sea. The surface wind was almost due West and probably 50Kts at least (it was a mbmmble time ago).
A Stampe biplane wished to depart back to England to the East and 'taxied' if that is the right word for driving straight into wind onto the grass at close to full throttle with members of the visiting aircraft flight on both wings and fuselage near the tail plane. The pilot asked for takeoff and waved off the VAF crew and the tail of the Stampe lifted up and then the aircraft effectively took off close to vertically into wind. The aircraft climbed to around 200 ft straight up, then turned left steeply cross wind then downwind onto East. As it did so it lost a significant amount of height as it also gained a significant amount of speed. The last call to me in the tower from the pilot was: "I won't be coming back!".
Yes I know all the arguments about being in a windfield so the ground speed doesn't matter - but I had the feeling that it did. The inertia of the aircraft that was close to stationary had to be overcome for the aircraft to depart at (guess) wind of 60 kts at 200ft plus aircraft eventual flying speed of say 60kts meant that the airframe had to accelerate from stationary to 120kts - agreed helped by the airmass it was in. That inertia has to be overcome regardless and that is due to the frame of reference to the Earth/ ground speed of the airframe. So an extreme example but I assure you that the aircraft lost a lot of height in the turn going past at my eye level in the tower. A more gentle turn may have masked the effect but it would still have been there.
I think it is a case of relative speeds: wind speed to aircraft speed. A military fighter at 400 kts + in a relatively low wind may not notice the effect. An albatross at 20kts may notice the inertial effect of a turn in a wind of equal velocity.
I was working as local/tower controller at Valley in Anglesey. It was a quiet Sunday and as was quite common there the wind was gale force although steady and not gusting as it came off the Irish Sea. The surface wind was almost due West and probably 50Kts at least (it was a mbmmble time ago).
A Stampe biplane wished to depart back to England to the East and 'taxied' if that is the right word for driving straight into wind onto the grass at close to full throttle with members of the visiting aircraft flight on both wings and fuselage near the tail plane. The pilot asked for takeoff and waved off the VAF crew and the tail of the Stampe lifted up and then the aircraft effectively took off close to vertically into wind. The aircraft climbed to around 200 ft straight up, then turned left steeply cross wind then downwind onto East. As it did so it lost a significant amount of height as it also gained a significant amount of speed. The last call to me in the tower from the pilot was: "I won't be coming back!".
Yes I know all the arguments about being in a windfield so the ground speed doesn't matter - but I had the feeling that it did. The inertia of the aircraft that was close to stationary had to be overcome for the aircraft to depart at (guess) wind of 60 kts at 200ft plus aircraft eventual flying speed of say 60kts meant that the airframe had to accelerate from stationary to 120kts - agreed helped by the airmass it was in. That inertia has to be overcome regardless and that is due to the frame of reference to the Earth/ ground speed of the airframe. So an extreme example but I assure you that the aircraft lost a lot of height in the turn going past at my eye level in the tower. A more gentle turn may have masked the effect but it would still have been there.
I think it is a case of relative speeds: wind speed to aircraft speed. A military fighter at 400 kts + in a relatively low wind may not notice the effect. An albatross at 20kts may notice the inertial effect of a turn in a wind of equal velocity.
I hesitate to get involved in this argument as the positions are so entrenched. However, a little observational input may assist.
I was working as local/tower controller at Valley in Anglesey. It was a quiet Sunday and as was quite common there the wind was gale force although steady and not gusting as it came off the Irish Sea. The surface wind was almost due West and probably 50Kts at least (it was a mbmmble time ago).
A Stampe biplane wished to depart back to England to the East and 'taxied' if that is the right word for driving straight into wind onto the grass at close to full throttle with members of the visiting aircraft flight on both wings and fuselage near the tail plane. The pilot asked for takeoff and waved off the VAF crew and the tail of the Stampe lifted up and then the aircraft effectively took off close to vertically into wind. The aircraft climbed to around 200 ft straight up, then turned left steeply cross wind then downwind onto East. As it did so it lost a significant amount of height as it also gained a significant amount of speed. The last call to me in the tower from the pilot was: "I won't be coming back!".
Yes I know all the arguments about being in a windfield so the ground speed doesn't matter - but I had the feeling that it did. The inertia of the aircraft that was close to stationary had to be overcome for the aircraft to depart at (guess) wind of 60 kts at 200ft plus aircraft eventual flying speed of say 60kts meant that the airframe had to accelerate from stationary to 120kts - agreed helped by the airmass it was in. That inertia has to be overcome regardless and that is due to the frame of reference to the Earth/ ground speed of the airframe. So an extreme example but I assure you that the aircraft lost a lot of height in the turn going past at my eye level in the tower. A more gentle turn may have masked the effect but it would still have been there.
I think it is a case of relative speeds: wind speed to aircraft speed. A military fighter at 400 kts + in a relatively low wind may not notice the effect. An albatross at 20kts may notice the inertial effect of a turn in a wind of equal velocity.
I was working as local/tower controller at Valley in Anglesey. It was a quiet Sunday and as was quite common there the wind was gale force although steady and not gusting as it came off the Irish Sea. The surface wind was almost due West and probably 50Kts at least (it was a mbmmble time ago).
A Stampe biplane wished to depart back to England to the East and 'taxied' if that is the right word for driving straight into wind onto the grass at close to full throttle with members of the visiting aircraft flight on both wings and fuselage near the tail plane. The pilot asked for takeoff and waved off the VAF crew and the tail of the Stampe lifted up and then the aircraft effectively took off close to vertically into wind. The aircraft climbed to around 200 ft straight up, then turned left steeply cross wind then downwind onto East. As it did so it lost a significant amount of height as it also gained a significant amount of speed. The last call to me in the tower from the pilot was: "I won't be coming back!".
Yes I know all the arguments about being in a windfield so the ground speed doesn't matter - but I had the feeling that it did. The inertia of the aircraft that was close to stationary had to be overcome for the aircraft to depart at (guess) wind of 60 kts at 200ft plus aircraft eventual flying speed of say 60kts meant that the airframe had to accelerate from stationary to 120kts - agreed helped by the airmass it was in. That inertia has to be overcome regardless and that is due to the frame of reference to the Earth/ ground speed of the airframe. So an extreme example but I assure you that the aircraft lost a lot of height in the turn going past at my eye level in the tower. A more gentle turn may have masked the effect but it would still have been there.
I think it is a case of relative speeds: wind speed to aircraft speed. A military fighter at 400 kts + in a relatively low wind may not notice the effect. An albatross at 20kts may notice the inertial effect of a turn in a wind of equal velocity.
Last edited by Jet_Fan; 1st Aug 2018 at 19:38.
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I suspect the answer lies in your own narrative:
A steep turn at 200 feet in that kind of wind doesn’t sound wise to me. Not because of the wind strength, and not because he was turning downwind, but because a 50kt wind at 200 feet is NEVER a steady air mass, and is thus irrelevant to this discussion.
Or maybe the pilot was a subscriber to the “downwind turn myth” and lowered the nose because he was scared of losing airspeed
turned left steeply
Or maybe the pilot was a subscriber to the “downwind turn myth” and lowered the nose because he was scared of losing airspeed
May also have succumbed to the (potentially deadly) skid/slip illusion. I see it sometimes with students (and sometimes licenced pilots) flying circuits in strong winds, they try and fly their turns using reference to the ground, they try and make things look the way they normally experience their path over the ground by over ruddering or over banking whilst using the same nose attitudes they normally do.
Both actions will reduce climb performance and increase descent rates. Can also set you up for stall/spin at low level
It is a powerful illusion when low to the ground at low airspeeds in strong wind.
Both actions will reduce climb performance and increase descent rates. Can also set you up for stall/spin at low level
It is a powerful illusion when low to the ground at low airspeeds in strong wind.
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estimation of distance (height) by the angle subtended at one's eye.
Hi Ian W,
Relative to you, the aircraft had to accelerate from 0 to 120 kts (change of 120 kts). Relative to the aircraft it had to accelerate from 60 kts heading North say to 60 kts heading South (i.e. 120 kts change in air speed vector - i.e. the same vector value)
Your estimation of distance is made using the apparent size of a known object (angle subtended at you eye). Your estimation of height is made using the angle between the object and the horizon. As the aircraft appeared to accelerate unusually rapidly down wind, it's distance from you increased unexpectedly rapidly and the angle between the horizon, the aircraft and your eyeball reduced rapidly giving you the illusion of a height loss.
The illusion is similar when observing a "slow" jumbo compared to a faster 737 on the approach when both are flying at say 160 kts. The jumbo appears slower because it appears closer and yet the change the angular position is the same as the "further away" 737.
Yes I know all the arguments about being in a windfield so the ground speed doesn't matter - but I had the feeling that it did. The inertia of the aircraft that was close to stationary had to be overcome for the aircraft to depart at (guess) wind of 60 kts at 200ft plus aircraft eventual flying speed of say 60kts meant that the airframe had to accelerate from stationary to 120kts - agreed helped by the airmass it was in. That inertia has to be overcome regardless and that is due to the frame of reference to the Earth/ ground speed of the airframe. So an extreme example but I assure you that the aircraft lost a lot of height in the turn going past at my eye level in the tower. A more gentle turn may have masked the effect but it would still have been there.
Your estimation of distance is made using the apparent size of a known object (angle subtended at you eye). Your estimation of height is made using the angle between the object and the horizon. As the aircraft appeared to accelerate unusually rapidly down wind, it's distance from you increased unexpectedly rapidly and the angle between the horizon, the aircraft and your eyeball reduced rapidly giving you the illusion of a height loss.
The illusion is similar when observing a "slow" jumbo compared to a faster 737 on the approach when both are flying at say 160 kts. The jumbo appears slower because it appears closer and yet the change the angular position is the same as the "further away" 737.