Downwind turn Myth
01-14-2014, 10:09 PM
#1101
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As to the article, no real points to support the downwind turn phenomenon are made. He didn't want to bore us common folk with the math but, because he's an astronaut, some will hold the article up as authoritative.
01-15-2014, 01:39 AM
#1102
Well you didn't nit pick but you did cherry pick. The first section of the article does talk about the visual queues a full scale pilot uses while maneuvering near the ground being effected by changing winds relative to the acft. Obviously this has nothing to do with what we are talking about here. A large part of the rest of the article goes on to describe aerodynamic affects on the airframe from turning down wind that can contribute to dangerously low airspeed. I think he even uses words like 'push', 'inertia', 'acceleration'. Words that should not even exist in "the downwind turn is a myth" world. Well, here's a quote...
The other reality we face is windshear. This sudden change in windspeed or direction instantaneouslychanges our indicated speed.Instantaneous changes from head-to tailwind don’t allow enough time for the wind to accelerate theaircraft (per the physics discussionabove) and will result in a drop ofindicated speed. So wind shear,rather than steady wind, is the killer.Combine the groundspeed changesensation with wind shear affectsand you have a handful.
In our yank-n-bank world of RC I'd say we experience this pretty much all the time.
Eric
The other reality we face is windshear. This sudden change in windspeed or direction instantaneouslychanges our indicated speed.Instantaneous changes from head-to tailwind don’t allow enough time for the wind to accelerate theaircraft (per the physics discussionabove) and will result in a drop ofindicated speed. So wind shear,rather than steady wind, is the killer.Combine the groundspeed changesensation with wind shear affectsand you have a handful.
In our yank-n-bank world of RC I'd say we experience this pretty much all the time.
Eric
If you quote a paragraph describing horses as support for the existence of unicorns, then you obviously understand neither.
01-15-2014, 05:40 AM
#1103
The biggest mistake downwind turn deniers make is that look only and the two end points - upwind and downwind. They do not even consider what happens DURING the turn. And they insist that the leading edge of the wing is an inertial reference point. Look at the arguments above - they talk about AIRSPEED not AIR VELOCITY. During the turn there are many forces acting on the wing, INCLUDING THE TENDENCY TO TRAVEL IN A STRAIGHT LINE (aka momentum) and momentum is based on speed refence to the earth inertial reference point. The deniers insist that aircraft weight has nothing to do with it.
But this argument has been shouted down for over 20 years - even though I showed that the Navy's flight simulators did, indeed, include aircraft weight and kept the inertial reference point ground based.
But this argument has been shouted down for over 20 years - even though I showed that the Navy's flight simulators did, indeed, include aircraft weight and kept the inertial reference point ground based.
01-15-2014, 06:13 AM
#1104
Another thread contains a postulation that a model crashed due to the wind direction relative to the models flight path as it topped a loop. In other words, the model might not have crashed if the nose had been pointed into the wind over the top. (sigh)
Most of you learned better a long time ago, but this myth just keeps hanging in there. It's persists (sadly) even in the lower rungs of full scale aviation, and among pilots who have had enough training to know better. Lets set the record straight once and for all please.
It does seem counter-intuitive, but here is the truth:
Once an a/c has broken ground, steady state winds have no effect on airspeed (hence, lift) whatsoever, and airspeed does not change simply because one is flying upwind, downwind, crosswind, or even when alternating between any combinations of the above. Period. That is the beginning, middle, and end of the story.
As an aid to understanding this seemingly counter-intuitive fact, imagine yourself boating in a wide river with a 10 knot currrent. If you are putting along at 5 knots indicated speed, the water does not come crashing over the side simply because you are traveling from one bank to the other perpendicular to the current. It does not wash over the stern when headed down stream, as if you were suddenly traveling at a speed of five knots negative.
Or go for a swim in the ocean where the current is flowing parallel to the beach.
Or go scuba diving.
You will be carried along with the current, but not feel it, no matter which way you face or swim.
Or note that airliners don't fall out of the sky when making a 180 degree turn from a 150 kt headwind to a 150 tailwind, even though that net 300 kt difference in the wind is TEN TIMES the typical stall speed margin at the altitudes where such winds are encountered.
Birds fly just fine downwind, and don't suddenly crash into the trees when turning in that direction.
We could go on and on...but hopefully that's not necessary?
Don.
Most of you learned better a long time ago, but this myth just keeps hanging in there. It's persists (sadly) even in the lower rungs of full scale aviation, and among pilots who have had enough training to know better. Lets set the record straight once and for all please.
It does seem counter-intuitive, but here is the truth:
Once an a/c has broken ground, steady state winds have no effect on airspeed (hence, lift) whatsoever, and airspeed does not change simply because one is flying upwind, downwind, crosswind, or even when alternating between any combinations of the above. Period. That is the beginning, middle, and end of the story.
As an aid to understanding this seemingly counter-intuitive fact, imagine yourself boating in a wide river with a 10 knot currrent. If you are putting along at 5 knots indicated speed, the water does not come crashing over the side simply because you are traveling from one bank to the other perpendicular to the current. It does not wash over the stern when headed down stream, as if you were suddenly traveling at a speed of five knots negative.
Or go for a swim in the ocean where the current is flowing parallel to the beach.
Or go scuba diving.
You will be carried along with the current, but not feel it, no matter which way you face or swim.
Or note that airliners don't fall out of the sky when making a 180 degree turn from a 150 kt headwind to a 150 tailwind, even though that net 300 kt difference in the wind is TEN TIMES the typical stall speed margin at the altitudes where such winds are encountered.
Birds fly just fine downwind, and don't suddenly crash into the trees when turning in that direction.
We could go on and on...but hopefully that's not necessary?
Don.
then I think we should stop all of this , cause all of you guys sound correct , the bottom line is it seems against all we have been taught , which by the way has worked and is still working , following some of the points made , I think we could see an increase in accidents because from a layman's point of view some of the things said , although could be true try them and I am sure with our turbine powered models disaster is sure .Great conversation , but I have not learnt anything from it , it has possibly confused me .
Very impressed at the level of knowledge .
Welcome to the NEW YEAR and happy flying
01-15-2014, 09:26 AM
#1105
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This is so true. I think all mountain pilots would agree and likely what got Fossett.(a mountain lee w/ associated rotors)
The other reality we face is windshear. This sudden change in windspeed or direction instantaneously changes our indicated speed.Instantaneous changes from head-to tailwind don’t allow enoughtime for the wind to accelerate the aircraft (per the physics discussion above) and will result in a drop of indicated speed. So wind shear,rather than steady wind, is the killer.
The other reality we face is windshear. This sudden change in windspeed or direction instantaneously changes our indicated speed.Instantaneous changes from head-to tailwind don’t allow enoughtime for the wind to accelerate the aircraft (per the physics discussion above) and will result in a drop of indicated speed. So wind shear,rather than steady wind, is the killer.
Last edited by dbsonic; 01-15-2014 at 10:40 AM.
01-15-2014, 01:21 PM
#1106
A lot of people want to try to impress others with their "knowledge", but few have actually put it to the test themselves, they just like to debate the subject. That's all fine, but I made an offer further back in this thread that still stands. No one has taken me up on it yet. Crop duster pilots and people who have actually tested the theory know how downwind turns can affect their planes. The biggest problem in the debate is the matter of ground track. Most full scale pilots are not concerned with following a precise ground track. And most RC pilots have learned either correctly or sudo-correctly how to give the right inputs to achieve the turn they want. Set up a square pylon course that is 200 x 400 feet with 15 to 20 feet between the innner and outer pylons. In other words, a 20 foot wide race track with 400 foot front and back straightways, and 200 foot straighways on the ends. My 1/4 scale cub can fly this pattern on a calm day at 1/2 throttle or less. Now fly this pattern on a good windy day, like at least 10mph wind. Take off and get up about 60 feet high and then set the throttle at a low setting that is adequate to fly, but not much above what's needed to stay in the air. Now try to fly the pattern 4 feet off the ground and maintain that altitude all the way around the course without adjusting the throttle. Video this and post it here, I want to see your control inputs as well as the entire flight of the plane around the pattern.
When I see this, I will consider debating the results with you. If I'm wrong, I will admit it and start doing things "the right" way. I would love to be "proven" wrong, but until that day, I'm going to keep flying the way I know is working and I will keep teaching my students what I "know" right now. And what I know right now is : Your plane is likely to loose some altitude when you make downwind turns, so be ready for it and plan accordingly.
When I see this, I will consider debating the results with you. If I'm wrong, I will admit it and start doing things "the right" way. I would love to be "proven" wrong, but until that day, I'm going to keep flying the way I know is working and I will keep teaching my students what I "know" right now. And what I know right now is : Your plane is likely to loose some altitude when you make downwind turns, so be ready for it and plan accordingly.
01-15-2014, 02:01 PM
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Jerry,
I think your test would be a good one and I would like to see that too. Furthermore, if you were to fly your Cub in dead calm conditions and you were as talented as someone like say Quique Somenzini you would be able to fly that pattern withouth having to make throttle adjustments or really much of any other adjustments. It wouldn't be the case in a steady state 20knot wind let alone a gusting one. It has been postulate that it shouldn't matter. I'll come off my high horse now.
Lars
I think your test would be a good one and I would like to see that too. Furthermore, if you were to fly your Cub in dead calm conditions and you were as talented as someone like say Quique Somenzini you would be able to fly that pattern withouth having to make throttle adjustments or really much of any other adjustments. It wouldn't be the case in a steady state 20knot wind let alone a gusting one. It has been postulate that it shouldn't matter. I'll come off my high horse now.
Lars
01-15-2014, 02:08 PM
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I am a professional jet pilot with over 13K flying hours and a life long R/C pilot. This argument has been going on since the Wright Bros. first flew.
Hear's my contribution: I have been in a holding pattern with an assigned airspeed of 200kts., with a tailwind of 100kts. By necessity high performance aircraft instrumentation is very accurate. We have readouts of ground speed, Mach no., airspeed, geographic coordinates determined by GPS, Inertial, and highly accurate location by triangulation computation (DME/DME) . All of these must agree or the Flight Management System cries foul! I was in this holding pattern for over 45 minutes so I had plenty of time to contemplate the "downwind turn argument". All forms of airspeed measurment i.e. by the pitot system, inertial system, GPS system, and Mach comp., showed 200kts exactly. On the inbound leg ground speed readout calculated by the FMS using all the above data showed 300kts and on the outbound leg showed 100kts. The airspeed stayed constant without ever moving the throttles except during the turn where (naturally) the increase in drag required a very slight power increase, a few percent . When no power was added in the turns airspeed droppped by 3 to 5 kts., So you see, even when the wind is 50 pct. of airspeed in still air. no altitude is lost in turns.
Hear's my contribution: I have been in a holding pattern with an assigned airspeed of 200kts., with a tailwind of 100kts. By necessity high performance aircraft instrumentation is very accurate. We have readouts of ground speed, Mach no., airspeed, geographic coordinates determined by GPS, Inertial, and highly accurate location by triangulation computation (DME/DME) . All of these must agree or the Flight Management System cries foul! I was in this holding pattern for over 45 minutes so I had plenty of time to contemplate the "downwind turn argument". All forms of airspeed measurment i.e. by the pitot system, inertial system, GPS system, and Mach comp., showed 200kts exactly. On the inbound leg ground speed readout calculated by the FMS using all the above data showed 300kts and on the outbound leg showed 100kts. The airspeed stayed constant without ever moving the throttles except during the turn where (naturally) the increase in drag required a very slight power increase, a few percent . When no power was added in the turns airspeed droppped by 3 to 5 kts., So you see, even when the wind is 50 pct. of airspeed in still air. no altitude is lost in turns.
01-15-2014, 02:10 PM
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High Horse (aptly named), you are the man. You make me want to believe you immediately. The zingers just keep on coming. You must be a laugh a minute in the cockpit. Seriously, I loved reading this string, but it gave me a headache. I even took notes. Anyway....
... So I'm out at the field flying this little foamie jet with an overpowered motor and fan unit, and I'm clocked at 130 with a radar gun -- downwind. A good gun, I might add. I turn into the wind out of a split S, and this time I'm clocked at 110. I do this five times, and the results are always the same within a couple of mph. Looks faster, seems faster, clocks faster downwind. It sure did seem to me it WAS faster downwind. Can't figure that out.
Don't ridicule me now. My cousin Vinny will get upset. You don't want to deal with cousin Vinny under any circumstances. Besides, I need a beer to relieve my headache, so I'm off. Keep up the good work. I'm impressed with your knowledge. Seriously. And it's convincing. By the way, my last two crashes came turning into a strong wind, into the downwind base leg. Pilot error for sure, I admit it. If I had only advanced the throttle!
... So I'm out at the field flying this little foamie jet with an overpowered motor and fan unit, and I'm clocked at 130 with a radar gun -- downwind. A good gun, I might add. I turn into the wind out of a split S, and this time I'm clocked at 110. I do this five times, and the results are always the same within a couple of mph. Looks faster, seems faster, clocks faster downwind. It sure did seem to me it WAS faster downwind. Can't figure that out.
Don't ridicule me now. My cousin Vinny will get upset. You don't want to deal with cousin Vinny under any circumstances. Besides, I need a beer to relieve my headache, so I'm off. Keep up the good work. I'm impressed with your knowledge. Seriously. And it's convincing. By the way, my last two crashes came turning into a strong wind, into the downwind base leg. Pilot error for sure, I admit it. If I had only advanced the throttle!
01-15-2014, 03:08 PM
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It does seem counter-intuitive, but here is the truth:
Once an a/c has broken ground, steady state winds have no effect on airspeed (hence, lift) whatsoever, and airspeed does not change simply because one is flying upwind, downwind, crosswind, or even when alternating between any combinations of the above. Period. That is the beginning, middle, and end of the story.
Don.
Once an a/c has broken ground, steady state winds have no effect on airspeed (hence, lift) whatsoever, and airspeed does not change simply because one is flying upwind, downwind, crosswind, or even when alternating between any combinations of the above. Period. That is the beginning, middle, and end of the story.
Don.
Jack
01-15-2014, 04:03 PM
#1111
I am a professional jet pilot with over 13K flying hours and a life long R/C pilot. This argument has been going on since the Wright Bros. first flew.
Hear's my contribution: I have been in a holding pattern with an assigned airspeed of 200kts., with a tailwind of 100kts. By necessity high performance aircraft instrumentation is very accurate. We have readouts of ground speed, Mach no., airspeed, geographic coordinates determined by GPS, Inertial, and highly accurate location by triangulation computation (DME/DME) . All of these must agree or the Flight Management System cries foul! I was in this holding pattern for over 45 minutes so I had plenty of time to contemplate the "downwind turn argument". All forms of airspeed measurment i.e. by the pitot system, inertial system, GPS system, and Mach comp., showed 200kts exactly. On the inbound leg ground speed readout calculated by the FMS using all the above data showed 300kts and on the outbound leg showed 100kts. The airspeed stayed constant without ever moving the throttles except during the turn where (naturally) the increase in drag required a very slight power increase, a few percent . When no power was added in the turns airspeed droppped by 3 to 5 kts., So you see, even when the wind is 50 pct. of airspeed in still air. no altitude is lost in turns.
Hear's my contribution: I have been in a holding pattern with an assigned airspeed of 200kts., with a tailwind of 100kts. By necessity high performance aircraft instrumentation is very accurate. We have readouts of ground speed, Mach no., airspeed, geographic coordinates determined by GPS, Inertial, and highly accurate location by triangulation computation (DME/DME) . All of these must agree or the Flight Management System cries foul! I was in this holding pattern for over 45 minutes so I had plenty of time to contemplate the "downwind turn argument". All forms of airspeed measurment i.e. by the pitot system, inertial system, GPS system, and Mach comp., showed 200kts exactly. On the inbound leg ground speed readout calculated by the FMS using all the above data showed 300kts and on the outbound leg showed 100kts. The airspeed stayed constant without ever moving the throttles except during the turn where (naturally) the increase in drag required a very slight power increase, a few percent . When no power was added in the turns airspeed droppped by 3 to 5 kts., So you see, even when the wind is 50 pct. of airspeed in still air. no altitude is lost in turns.
01-15-2014, 05:06 PM
#1112
Another thread contains a postulation that a model crashed due to the wind direction relative to the models flight path as it topped a loop. In other words, the model might not have crashed if the nose had been pointed into the wind over the top. (sigh)
Most of you learned better a long time ago, but this myth just keeps hanging in there. It's persists (sadly) even in the lower rungs of full scale aviation, and among pilots who have had enough training to know better. Lets set the record straight once and for all please.
It does seem counter-intuitive, but here is the truth:
Once an a/c has broken ground, steady state winds have no effect on airspeed (hence, lift) whatsoever, and airspeed does not change simply because one is flying upwind, downwind, crosswind, or even when alternating between any combinations of the above. Period. That is the beginning, middle, and end of the story.
As an aid to understanding this seemingly counter-intuitive fact, imagine yourself boating in a wide river with a 10 knot currrent. If you are putting along at 5 knots indicated speed, the water does not come crashing over the side simply because you are traveling from one bank to the other perpendicular to the current. It does not wash over the stern when headed down stream, as if you were suddenly traveling at a speed of five knots negative.
Or go for a swim in the ocean where the current is flowing parallel to the beach.
Or go scuba diving.
You will be carried along with the current, but not feel it, no matter which way you face or swim.
Or note that airliners don't fall out of the sky when making a 180 degree turn from a 150 kt headwind to a 150 tailwind, even though that net 300 kt difference in the wind is TEN TIMES the typical stall speed margin at the altitudes where such winds are encountered.
Birds fly just fine downwind, and don't suddenly crash into the trees when turning in that direction.
We could go on and on...but hopefully that's not necessary?
Don.
Most of you learned better a long time ago, but this myth just keeps hanging in there. It's persists (sadly) even in the lower rungs of full scale aviation, and among pilots who have had enough training to know better. Lets set the record straight once and for all please.
It does seem counter-intuitive, but here is the truth:
Once an a/c has broken ground, steady state winds have no effect on airspeed (hence, lift) whatsoever, and airspeed does not change simply because one is flying upwind, downwind, crosswind, or even when alternating between any combinations of the above. Period. That is the beginning, middle, and end of the story.
As an aid to understanding this seemingly counter-intuitive fact, imagine yourself boating in a wide river with a 10 knot currrent. If you are putting along at 5 knots indicated speed, the water does not come crashing over the side simply because you are traveling from one bank to the other perpendicular to the current. It does not wash over the stern when headed down stream, as if you were suddenly traveling at a speed of five knots negative.
Or go for a swim in the ocean where the current is flowing parallel to the beach.
Or go scuba diving.
You will be carried along with the current, but not feel it, no matter which way you face or swim.
Or note that airliners don't fall out of the sky when making a 180 degree turn from a 150 kt headwind to a 150 tailwind, even though that net 300 kt difference in the wind is TEN TIMES the typical stall speed margin at the altitudes where such winds are encountered.
Birds fly just fine downwind, and don't suddenly crash into the trees when turning in that direction.
We could go on and on...but hopefully that's not necessary?
Don.
Seriously ... Your "postulation" has more holes in it than a spaghetti strainer. And to see this nonsense theory has been going on for more than three years and 45 pages?! Geeze!
And that water parable! Say what!!?
Air and water cannot be compared in this application. The principles are different, and water is nearly 1000 times more dense than air.
Ever been in a 5 knot current? How about a river? Water running at just 5 knots will carry many things with it. Eight inches of water travelling at 10 knots can knock a person down. Can air travelling at 10 knots do that? NO. Air will simply pass over the object. So, your water theory is debunked, as well as the topic.
A plane turning downwind will not be pushed by air. The amount of air that will pass over the object (wings) from a forward direction will be severely reduced due to the change in direction. Thus the plane wil suffer a loss of airspeed when turned downwind. The plane will not be able to sustain level flight at the same altitude. That is why extra power is needed on downwind. Just try flying at stall speed into the wind and turn downwind without adding power. Guess what will happen! ... Your airspeed and lift will drop off, then the plane will stall.
Now lets say, the plane made the turn at higher than MCA, and is flying downwind at MCA+10 mph. Then the downwind plane encounters a gust of 10 - 15 mph from the rear ... Airspeed drops, lift drops, and the plane drops ... That gust of wind didn't push the plane ... It just went past the plane and reduced the airspeed of the plane. Down she goes!
You guys who think there is no difference can do it to your planes (r/c toy or real plane), and probably die in the process. But don't tell anyone coming into this hobby there is no difference (or loss of) airspeed when turning downwind. There IS a loss of lift, and airspeed. NASA, Lockheed-Martin, General Dynamics, Boeing, NTSB, and many others say so, and that's good enough for me too. Just because a few people post a "blog" on the internet to the contrary doesn't make them an authority on the subject. Remember, not everything you read on the internet is true!
Why did someone bring this topic back to life?
Last edited by Airplanes400; 01-15-2014 at 07:33 PM. Reason: typo
01-15-2014, 06:23 PM
#1113
Wahooo, my fav thread is back….. And with a VENGENCE.
I will be checking RCU a lot more often now. This thread is entertainment PLUS. The only thing that could possibly make it any better would be a written legal threat, (possibly from a Pelican), over runway incursions.
I salute you Don.
Keep trying to educating the masses, (and try not to take posts from the un-educatable too seriously)
Roger
I will be checking RCU a lot more often now. This thread is entertainment PLUS. The only thing that could possibly make it any better would be a written legal threat, (possibly from a Pelican), over runway incursions.
I salute you Don.
Keep trying to educating the masses, (and try not to take posts from the un-educatable too seriously)
Roger
01-15-2014, 07:49 PM
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1114 posts on this myth? Unbelievable.
Those that KNOW there is no truth to this "phenomenon" can rest easy. There is no truth to it. None. I would rather look for the Easter Bunny than look for downwind turn effects. You will not find either.
Those that believe in this easily debunked myth will never be dissuaded, no matter how many pages of time wasting explanations appear here. Many analogies and explanations of the truth are very good, by the way. Some refuse to be educated and will never learn.
I am an aero engineer, and it is my business to know this kind of stuff.
Those that KNOW there is no truth to this "phenomenon" can rest easy. There is no truth to it. None. I would rather look for the Easter Bunny than look for downwind turn effects. You will not find either.
Those that believe in this easily debunked myth will never be dissuaded, no matter how many pages of time wasting explanations appear here. Many analogies and explanations of the truth are very good, by the way. Some refuse to be educated and will never learn.
I am an aero engineer, and it is my business to know this kind of stuff.
01-15-2014, 07:53 PM
#1116
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High Horse (aptly named), you are the man. You make me want to believe you immediately. The zingers just keep on coming. You must be a laugh a minute in the cockpit. Seriously, I loved reading this string, but it gave me a headache. I even took notes. Anyway....
... So I'm out at the field flying this little foamie jet with an overpowered motor and fan unit, and I'm clocked at 130 with a radar gun -- downwind. A good gun, I might add. I turn into the wind out of a split S, and this time I'm clocked at 110. I do this five times, and the results are always the same within a couple of mph. Looks faster, seems faster, clocks faster downwind. It sure did seem to me it WAS faster downwind. Can't figure that out.
Don't ridicule me now. My cousin Vinny will get upset. You don't want to deal with cousin Vinny under any circumstances. Besides, I need a beer to relieve my headache, so I'm off. Keep up the good work. I'm impressed with your knowledge. Seriously. And it's convincing. By the way, my last two crashes came turning into a strong wind, into the downwind base leg. Pilot error for sure, I admit it. If I had only advanced the throttle!
... So I'm out at the field flying this little foamie jet with an overpowered motor and fan unit, and I'm clocked at 130 with a radar gun -- downwind. A good gun, I might add. I turn into the wind out of a split S, and this time I'm clocked at 110. I do this five times, and the results are always the same within a couple of mph. Looks faster, seems faster, clocks faster downwind. It sure did seem to me it WAS faster downwind. Can't figure that out.
Don't ridicule me now. My cousin Vinny will get upset. You don't want to deal with cousin Vinny under any circumstances. Besides, I need a beer to relieve my headache, so I'm off. Keep up the good work. I'm impressed with your knowledge. Seriously. And it's convincing. By the way, my last two crashes came turning into a strong wind, into the downwind base leg. Pilot error for sure, I admit it. If I had only advanced the throttle!
01-15-2014, 09:54 PM
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I've got pictures of the Easter Bunny and I actually spoke with him. Nice bunny, turns out he has a degree in aeronautical engineering and is an experienced commercial pilot. He emphatically stated that the downwind turn IS NOT a myth! Furthermore, he advised that one should believe less in those who advertise their expertise with high airtime, higher technical degrees, and the like. I'm not sure what to make of that advice given his own credentials?
lars
lars
01-15-2014, 10:17 PM
#1119
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OK I have the proof that downwind turns do not decrease airspeed. Unfortunately, I don't know how to post a Real Flight recording on here, but ANYBODY WITH RealFlight or any good simulator CAN PROVE to their own satisfaction that THE MYTH IS A MYTH. Here's how:
Set wind speed to 8 or 9 MPH, and wind turbulence to zero. (Note the wind speed at ground level will be lower than what you set. You need to get up about 30 feet for speed to match whatever you set).
Load up any 3 channel "slow stick" type model. I used BLT Park Flyer (which flew at 15 MPH, less than twice the wind speed). Open up the Nav Guide or other window that shows you airspeed, windspeed and altitude.
Set throttle about 3/4 up and put in about 10 or 15 clicks of Right or Left rudder trim. Adjust the throttle and rudder trims a few clicks up or down until the plane maintains a nice gentle turn with stable altitude with hands off the sticks. Get her up to 30 feet or so and LET GO of the sticks. Just let the plane fly itself in the steady breeze and WATCH!
You will see the plane spiral lazily downwind forever, with minor random variation in altitude, certainly nothing dramatic up or down as she turns upwind and downwind. You will observe NO change in airspeed as the plane turns, no matter what speed the wind in relation to the plane. You will SEE a big change in ground speed as the plane turns. I have several RealFlight recordings that vary by only 2 or 3 feet of elevation over several minutes of flying WITH HANDS OFF THE CONTROLS IN A 9 MPH WIND! Airspeed remains perfectly stable the whole time. TRY IT!
(I must admit that I sometimes find a bit of altitude loss as the plane turns downwind at very low altitudes, but this is inconsistent and only below 35 feet elevation or so. I suspect it is something inaccurate about the modeling of the simulator. In any case, the attitude and altitude and airspeed remain stable enough to thoroughly dispel the downwind turn myth).
I challenge any believer of the "myth", especially Hugger-4641, to try this a bunch of times.
Set wind speed to 8 or 9 MPH, and wind turbulence to zero. (Note the wind speed at ground level will be lower than what you set. You need to get up about 30 feet for speed to match whatever you set).
Load up any 3 channel "slow stick" type model. I used BLT Park Flyer (which flew at 15 MPH, less than twice the wind speed). Open up the Nav Guide or other window that shows you airspeed, windspeed and altitude.
Set throttle about 3/4 up and put in about 10 or 15 clicks of Right or Left rudder trim. Adjust the throttle and rudder trims a few clicks up or down until the plane maintains a nice gentle turn with stable altitude with hands off the sticks. Get her up to 30 feet or so and LET GO of the sticks. Just let the plane fly itself in the steady breeze and WATCH!
You will see the plane spiral lazily downwind forever, with minor random variation in altitude, certainly nothing dramatic up or down as she turns upwind and downwind. You will observe NO change in airspeed as the plane turns, no matter what speed the wind in relation to the plane. You will SEE a big change in ground speed as the plane turns. I have several RealFlight recordings that vary by only 2 or 3 feet of elevation over several minutes of flying WITH HANDS OFF THE CONTROLS IN A 9 MPH WIND! Airspeed remains perfectly stable the whole time. TRY IT!
(I must admit that I sometimes find a bit of altitude loss as the plane turns downwind at very low altitudes, but this is inconsistent and only below 35 feet elevation or so. I suspect it is something inaccurate about the modeling of the simulator. In any case, the attitude and altitude and airspeed remain stable enough to thoroughly dispel the downwind turn myth).
I challenge any believer of the "myth", especially Hugger-4641, to try this a bunch of times.
Last edited by RZielin; 01-16-2014 at 04:09 AM. Reason: clarity
01-16-2014, 01:21 AM
#1120
A lot of people want to try to impress others with their "knowledge", but few have actually put it to the test themselves, they just like to debate the subject. That's all fine, but I made an offer further back in this thread that still stands. No one has taken me up on it yet. Crop duster pilots and people who have actually tested the theory know how downwind turns can affect their planes. The biggest problem in the debate is the matter of ground track. Most full scale pilots are not concerned with following a precise ground track. And most RC pilots have learned either correctly or sudo-correctly how to give the right inputs to achieve the turn they want. Set up a square pylon course that is 200 x 400 feet with 15 to 20 feet between the innner and outer pylons. In other words, a 20 foot wide race track with 400 foot front and back straightways, and 200 foot straighways on the ends. My 1/4 scale cub can fly this pattern on a calm day at 1/2 throttle or less. Now fly this pattern on a good windy day, like at least 10mph wind. Take off and get up about 60 feet high and then set the throttle at a low setting that is adequate to fly, but not much above what's needed to stay in the air. Now try to fly the pattern 4 feet off the ground and maintain that altitude all the way around the course without adjusting the throttle. Video this and post it here, I want to see your control inputs as well as the entire flight of the plane around the pattern.
When I see this, I will consider debating the results with you. If I'm wrong, I will admit it and start doing things "the right" way. I would love to be "proven" wrong, but until that day, I'm going to keep flying the way I know is working and I will keep teaching my students what I "know" right now. And what I know right now is : Your plane is likely to loose some altitude when you make downwind turns, so be ready for it and plan accordingly.
When I see this, I will consider debating the results with you. If I'm wrong, I will admit it and start doing things "the right" way. I would love to be "proven" wrong, but until that day, I'm going to keep flying the way I know is working and I will keep teaching my students what I "know" right now. And what I know right now is : Your plane is likely to loose some altitude when you make downwind turns, so be ready for it and plan accordingly.
The airplanes don't know and don't care where a steady state wind is coming from. Period. If the Myth were anything but, I'd be dead thousands of times over.
I can understand mis perceptions. What I don't get is those who take pride in willful ignorance of verifiable fact.
Last edited by highhorse; 01-16-2014 at 01:38 AM.
01-16-2014, 01:31 AM
#1121
I am a professional jet pilot with over 13K flying hours and a life long R/C pilot. This argument has been going on since the Wright Bros. first flew.
Hear's my contribution: I have been in a holding pattern with an assigned airspeed of 200kts., with a tailwind of 100kts. By necessity high performance aircraft instrumentation is very accurate. We have readouts of ground speed, Mach no., airspeed, geographic coordinates determined by GPS, Inertial, and highly accurate location by triangulation computation (DME/DME) . All of these must agree or the Flight Management System cries foul! I was in this holding pattern for over 45 minutes so I had plenty of time to contemplate the "downwind turn argument". All forms of airspeed measurment i.e. by the pitot system, inertial system, GPS system, and Mach comp., showed 200kts exactly. On the inbound leg ground speed readout calculated by the FMS using all the above data showed 300kts and on the outbound leg showed 100kts. The airspeed stayed constant without ever moving the throttles except during the turn where (naturally) the increase in drag required a very slight power increase, a few percent . When no power was added in the turns airspeed droppped by 3 to 5 kts., So you see, even when the wind is 50 pct. of airspeed in still air. no altitude is lost in turns.
Hear's my contribution: I have been in a holding pattern with an assigned airspeed of 200kts., with a tailwind of 100kts. By necessity high performance aircraft instrumentation is very accurate. We have readouts of ground speed, Mach no., airspeed, geographic coordinates determined by GPS, Inertial, and highly accurate location by triangulation computation (DME/DME) . All of these must agree or the Flight Management System cries foul! I was in this holding pattern for over 45 minutes so I had plenty of time to contemplate the "downwind turn argument". All forms of airspeed measurment i.e. by the pitot system, inertial system, GPS system, and Mach comp., showed 200kts exactly. On the inbound leg ground speed readout calculated by the FMS using all the above data showed 300kts and on the outbound leg showed 100kts. The airspeed stayed constant without ever moving the throttles except during the turn where (naturally) the increase in drag required a very slight power increase, a few percent . When no power was added in the turns airspeed droppped by 3 to 5 kts., So you see, even when the wind is 50 pct. of airspeed in still air. no altitude is lost in turns.
01-16-2014, 02:54 AM
#1122
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Confirming what Captainbob said.. Flying at Flight Level 390 in a corporate jet and doing a 360 degree turn at night on autopilot. We were in a Jet stream of 100+ knots but completely smooth.
Zero change in indicated airspeed and zero change in power setting. Big changes in ground speed throughout the turn. (vid is to prove I fly.. Not of the said turn) https://www.youtube.com/watch?v=B1G5w7pC2JU
Zero change in indicated airspeed and zero change in power setting. Big changes in ground speed throughout the turn. (vid is to prove I fly.. Not of the said turn) https://www.youtube.com/watch?v=B1G5w7pC2JU
Last edited by Rob2160; 01-16-2014 at 03:28 AM.
01-16-2014, 06:03 AM
#1123
My Feedback: (7)
I have never heard of this myth. Only thing I can add is years ago my instructor taught me to turn and and land in any wind be it against the wind, tailwind, crosswind.
His reason was sooner or later you will have a flame out and you will need to
turn whichever way and bring her in.
so I have no Idea what a downward turn myth is. .
His reason was sooner or later you will have a flame out and you will need to
turn whichever way and bring her in.
so I have no Idea what a downward turn myth is. .
