Glide range circle

[STEVE CANTARUTTI]

After upgrading my tablet due to what I learned in this thread: https://groups.google.com/g/apps4av-forum/c/ugfaCCYAc-k , I am now running a Samsung Galaxy Tab S7 with 8gb RAM and 512 gb storage on Android version 11.  I installed Avare and am now running the latest version of Avare.  Eager to use the glide rings, I set out to adjust preferences.  Here is what I discovered...

When I turn on glide rings, I have to turn off the 2,5,10 mile circles and choose one or the other.  I am unable to display both concurrently.  This is unfortunate as now I don't know how far traffic and items displayed on the map are from my location.  Yes, I could turn on the side tape but my eye seems to interpret the ring more naturally.

The glide ring does seem to loosely correlate to what my plane is capable of but on descent into an airport, I found the ring to jump from at the runway beginning to about a 1/2 mile short to about a mile beyond the airport.  It was jumping around this significantly even when I was close to the runway, maybe 3 miles from the runway and around 3000 AGL.  Previously when I have used a software that painted an arc representing point of ground impact, it was rock solid accurate in real time.  It did not jump around; I could move the arc in and out based on adding or removing drag but it would smoothly move in or out based on what I did to make it move.  I could peg the arc on the numbers and I would land on the numbers.

I was excited to try the glide ring feature.  After using it, I am disappointed.  In order for it to be useful, it needs work.  Not sure how to make it better.  Perhaps it is a refresh rate issue?  I don't know the algorithm used in the other software I used previously so I cannot offer help there.  I would be happy to serve as a beta tester for modifications related to this issue if that would be helpful.

And, thank you to the good folks who are behind this software.

[Zubair Khan]

There is not enough information on glide ring. Did you download weather?


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[STEVE CANTARUTTI]

Not enough information on glide ring?  I don't understand. 

No, I did not download weather.

[Jeffrey Ross]

Avare needs the winds aloft to calculate the glide distance

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[Zubair Khan]

How can you expect glide ring to work without weather? Your glide range is affected by your direction and wind. Pretty basic stuff.

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[STEVE CANTARUTTI]

I never had weather on the other software, and typically don't download it on Avare.

Perhaps this is why the other software I used worked so well and this does not.  It appears Avare uses winds and a glide ratio input by the user to somehow calculate a glide distance.  The other software didn't have any wind data or glide ratio data to go on.  It calculated where the plane would hit the ground based solely on what the plane was doing relative to the ground.

[Zubair Khan]

That other software is wrong because your best place to land is not always in front go you.
Z

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[STEVE CANTARUTTI]

I agree the best place to land may be behind you.  That isn't what I am taking issue with.

The other software didn't draw a circle, they painted a narrow arc in front of the planes current path.   So perhaps glide range isn't the best term for what they were trying to accomplish.  Perhaps a ground impact arc would be a better descriptor.   If I cut my throttle at 10 miles out and 10,000 agl, the glide range circle in Avare will tell me that I can likely make the airport.  If I did the same with the other software I used in the past, it would tell me I would likely make the airport and (more importantly) in real time provide accurate feedback to insure I can nail a touchdown location with precision.  It really was magic.  I would like for Avare to have that capability. 

[Zubair Khan]

For the records I state the formula which is pretty complicated...

Find the altitude at discretion from GPS altitude minus nearest airport altitude and divide it in 500 ft sections.

Do a loop for each 500 ft. segment:
Do a loop for 20 directions around the 360 circle:
Calculate ground speed at each altitude and in each direction based on wind speed / direction and hypothetical direction and true airspeed adjusted for that hypothetical altitude
Calculate time spent in each 500 ft segment
Calculate altitude lost in that segment from sink rate and time in that sgement
Add turn penalty in that direction at standard rate turn assuming sink rate does not change with the bank angle

Integrate all results in each direction and find total distance travelled in each direction.
Draw the ring

If there is a mountain in the way, you will crash on it because terrain is not accounted for in this ring.

This is an emergency feature and has a bunch of approximations. Use with a grain of salt.

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[STEVE CANTARUTTI]

Looks complicated.

[Andrew Sarangan]

I had no idea this feature was implemented in the recent version. Thanks for bringing that up. 

I suspect your "other software" is using a no-wind glide range. If the POH says you can glide 5 miles, would you still be able to glide 5 miles into a 30 knot headwind?

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[STEVE CANTARUTTI]

This is correct in that it doesn't know the wind, but doesn't need to because it sees the effect of the wind on your actual rate of descent and ground speed:

I suspect your "other software" is using a no-wind glide range.

This is rhetorical of course:

If the POH says you can glide 5 miles, would you still be able to glide 5 miles into a 30 knot headwind?

The point isn't if I can glide 5 miles or a little more or a little less.  I don't really care if it is a little more or a little less.  What is more important to me is having an accurate arc painted in front of the plane telling me where on the ground I am going to end up when the rubber meets the road so to speak. 

[Zubair Khan]

I am telling you that your ground speed changes with altitude because primarily the wind changes with altitude.

If your other software is giving you very accurate results then it's probably using the weather, or your weather that day was pretty calm and uniform through the altitudes.

Let me know when you try again with weather.

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[Andy]

Not saying that Avare needs this so just FYI the instruments that gliders use can calculate the wind speed and direction in real time w/o any weather input. Circling is required (I think) and it works quite well.

[Andrew Sarangan]

>>This is correct in that it doesn't know the wind, but doesn't need to because it sees the effect of the wind on your actual rate of descent and ground speed:

This is partly true. If the TAS is known then all we need is ground speed along two different directions to calculate the wind vector. One ground speed is not enough. We need two. This would require the airplane to make a turn. A 360 would be ideal. But who is going to spend time making a 360 in an emergency?  

>>The point isn't if I can glide 5 miles or a little more or a little less.  I don't really care if it is a little more or a little less.  What is more important to me is having an accurate arc painted in front of the plane telling >>me where on the ground I am going to end up when the rubber meets the road so to speak. 

You might be underestimating the effect of wind. It is not a little more or little less. If your best glide speed is 70 knots and the wind is 35 knots (which is not unrealistic), you are going to glide twice as much in one direction and half as much in the other. 

[STEVE CANTARUTTI]

>>This is correct in that it doesn't know the wind, but doesn't need to because it sees the effect of the wind on your actual rate of descent and ground speed:

This is partly true. If the TAS is known then all we need is ground speed along two different directions to calculate the wind vector. One ground speed is not enough. We need two. This would require the airplane to make a turn. A 360 would be ideal. But who is going to spend time making a 360 in an emergency?  

When I said " that it doesn't know the wind " I was referring to the other software that worked so well for me (and others).

Honestly I don't understand the fixation on knowing the wind.  Yes, I can see that knowing wind would greatly help the software draw a circle initially, but once the plane starts down the software can see what the actual performance of the aircraft is rather than some theoretical estimate of what it may be based on wind data that may be hours old and collected from a location miles away.

You might be underestimating the effect of wind. It is not a little more or little less. If your best glide speed is 70 knots and the wind is 35 knots (which is not unrealistic), you are going to glide twice as much in one direction and half as much in the other.

My best glide is 104 kts.  I typically know what the wind is; there is a depiction of wind direction and velocity on my EFIS at all times.

I understand the wind will help or hurt my glide depending on what direction I choose to go.  Rather than a software tell me I can likely glide somewhere within a circle, I would get much more benefit for it to tell me accurately where I am going to impact the ground in the direction I am heading (whichever direction I choose to turn).

[Zubair Khan]

Sorry you are wrong.

An airplane at 10000 feet can estimate wind speed at 10000 feet by making circle at 10000 feet.
An airplane at 10000 feet cannot estimate wind speed at 2000 feet by making circles at 10000 feet.

Use ADSB to get the latest winds aloft. You don't have stale data.





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[Jeffrey Ross]

Andy,

Although I'm not a glider pilot, I only have about an hour in one roughly 20 years ago, the instrument you are referring to I'm guessing is calculating the winds aloft in real time based upon the circling requirement you mentioned, and it can only calculate the winds at that specific altitude you circled at as the winds aloft can change direction and speed as you climb or descend.  The way a glider is flown vs the way a powered aircraft is flown is quite different.  I see to recall the instructor telling me to shoot for a "best sink speed" and ignore the altitude while I'm used to shooting for a specific altitude and doing a lot of circling which I would not be doing in a powered aircraft.

Regarding winds aloft, to give you an idea of how much of an impact they can play, I fly an airplane with a true airspeed of about 160kt, I can recall one flight that while in level flight I had a hell of a tailwind at 7000 ft which gave ground speed of 240kt, I'm sure that would have a major effect on my gliding distance.

One of the things I've learned about helping with Avare is how people use the software differently than I do, I thought I used it "properly" and most users would use it the same way as I fly out of a major metropolitan area in some of the busiest airspace in the world.  I was shocked to find that some pilot's don't even use what I would consider the basic features of the application because it doesn't fit with their type of flying, they simply wanted terrain charts so they could identify their favorite uncharted airport.

In terms of calculating winds aloft in real time, eg EFIS or "air data computer", you need to know several things, IAS, TAS, Temperature, magnetic heading, ground track, ground speed, and barometric pressure, with this information the winds aloft and direction can be computed instantly, or in about 5 minutes by hand with an E6-B (think back to your student pilot days and dead reckoning on cross country flights).  Since Avare doesn't have access to all of the above it cannot compute the winds aloft and therefor needs external input.

So my point is, not to belittle your request as a bad one, but on the contrary I'm sure it can be very useful but development resources are always limited and features have to be chosen carefully based upon fixing what is broken/wrong and then what creates the most "bang for the buck".

Jeff

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[Andy]

Jeff, all good thoughts especially about how the software is used so differently than what you thought. I for one haven't filed a flight plan for for more than 3 decades and how could I when I rarely know what direction to head when I go out which is why I often mention how nice it would be to have topo maps for the U.S.A.

I don't think that Avare needs to be a glide computer, really no need to use the limited resources you have but it might be nice to have distance rings and the glide ring at the same time but while the latter is cool the label does take up valuable screen space. It's very different flying low and slow like I do where really the only time traffic is of interest is when it's very near by and that's when it can be hard to read when you have labels or even runway extensions, things get cluttered pretty quick.

Great effort by the Avare team for sure, wish I had the skills to help out.

-Andy 

[Chip Davis]

I haven't flown since before "the recent unpleasantries" (as we say down here in the South about all sorts of trying times) so I haven't tried out the "glide ring", but I think it's a valuable addition.

IMHO the true value of the glide ring is not simply as a tool to allow me to nail the threshold; I can do that quite well on my own.  If I turn on the glide ring, it will be as the second step of the Aviate-Navigate-Communicate emergency triad.  Once the aircraft is under control, I want to determine where I will end up.  If my best bet is 150° aft due to winds, I want to know that.  Now, before I initiate any turns.

Not knowing how it is currently implemented, here is what I would like it to do.  The indication on my screen must take into account the winds aloft, all the way down, as well as my current airspeed.  Thus, the "ring" will not be circular unless no-wind conditions exist from my altitude to the ground.  A first-order approximation would be an oblate teardrop with the pointy end downwind.  Ideally, all aerodromes within the teardrop would be slightly highlighted.

Because my anticipated usage is primarily as an emergency procedure, I would like the ability to turn it on with a minimum of tablet-touching, akin to my COM which automatically tunes 121.5 if I hold down the selector button.  If I have distance rings already selected, the glide ring should be readily distinguishable without a label, perhaps by being displayed as a red hashed line.  A side benefit would be that one could "fly the ring" to ensure you are maintaining best glide speed during a busy time with lots of distractions.

Extra credit will be awarded when the terrain database is loaded, and if the glide slope intersects cumulo-granite, the teardrop reflects that fact.

Does the glide range ring already do those things (not counting the terrain feature)?  If not, is that asking too much for a valuable emergency feature, Zubair?

-Chip-

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[Andrew Sarangan]

More than as an emergency tool, the glide range depiction can be a very useful training aid. I find it useful to look at it during cruise and be entertained by which airports are within glide range and which ones are too far, and check if I would have guessed that without Avare. The old version used to list the airports within glide range. The new version with the glide ring is more useful. I don't know if accounting for changes in topography is worth the effort. Winds aloft in mountainous areas are not accurate anyway, especially below the peaks. I have seen how Foreflight paints a dynamic glide ring, which is nice to watch, but I am not so sure if it is really that useful. 

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[STEVE CANTARUTTI]

In follow up with Zubair and others who have contributed here,

I flew another cross country today with Avare.  I was mistaken when I stated previously that Avare did not have weather when the glide range was jumping in and out on approach to landing.  It was connected to ads-b weather and I had the use ads-b weather box checked.  The glide ring was depicting the wind notification box with speed and direction at the top of the glide range circle.

Other information, I have been running the tablet connected to both bluetooth Garmin GLO, and WIFI Dynon DRX for ads-b.  I have noticed occasional black screen on Avare with the statement download database.  This black screen could be completely eliminated by stopping listening to the Dynon.  I believe it is losing GPS lock during these dropouts.  I suspect the Dynon has poor reception which may be improved with relocation.

In troubleshooting I planned to check how the glide ring worked with no ads-b weather data.  But, I had turned off the glide ring in favor of the 2/5/10 rings as I find them much more useful.  Also, even if I had the glide rings on, the airport I was going into was very busy with traffic in the pattern to both intersecting runways concurrently so I wouldn't have been able to observe the glide ring performance.

Agree with the assessment that some use the software very differently than others.  If I were in the J5 which is low, slow, slips well, lands slow, I wouldn't be as interested in an accurate ground impact arc either.  In the plane I fly which Australia refuses to issue an airworthiness certificate to due to landing qualities, Canada requires a type rating,  the instructor taught me to cross numbers in at 90 kts, slips are completely ineffective, lacks speed brakes,  best glide is 104 kts, that I fly at night, IFR in the mountains, having an accurate ground impact arc is a game changer.  Those who have seen what a capable ground impact arc can do and flying a plane such as the one I do, might see the value it brings to the table.

[STEVE CANTARUTTI]

By the way, what is dynamic under the glide ring selection options?

[Zubair Khan]

Hi Chip

People in the South write well too.
Thanks for explaining it well, just like it is.

Zubair

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[Dean Gibson ATP/CFI]

Unless the wind varies by POSITION (which you are not going to get from any forecast), the rings will be CIRCULAR, all the way to level ground, unless terrain elevation intervenes.  The variation of wind speed & direction by altitude, will shift the circle, but it will still be a circle.  That's the mathematics of the situation.

Are you asking for the rings to take variable terrain into consideration?

On Monday, April 5, 2021 at 12:08:46 PM UTC-7 avia...@gmail.com wrote:

...The indication on my screen must take into account the winds aloft, all the way down, as well as my current airspeed.  Thus, the "ring" will not be circular unless no-wind conditions exist from my altitude to the ground.  A first-order approximation would be an oblate teardrop with the pointy end downwind. 

[Zubair Khan]

Dean please explain how glide ring will be circular. Assume your best glide airspeed is 60 kt, and you have 60 kt wind from the north.
Thanks

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[Dean Gibson ATP/CFI]

First I will explain how I teach horizontal wind triangles on a map.  You must imagine a fictitious universe where you can:

(a) turn on & off the wind;
(b) turn on & off the airspeed; and
(c) turn on & off the weight of the aircraft (so it just floats in the air like a balloon).

1. You start out by turning off the airspeed & weight.  You let the wind blow for an hour, & you draw that line on a map from your starting position (you have already drawn a course line from your starting position to your destination).
2. You now turn off the wind, & turn on the airspeed (weight doesn't matter here).  You now draw a new line from the end of the first line, to intercept (at a distance equal to one hour of true airspeed) your course line (just like you would do with a drafting compass).  Obviously, the angle (relative to north) of this 2nd line is your true heading, & the length of the intercepted course line is your groundspeed.

Now for the glide distance circle:

1. You turn off the airspeed.  You let the airplane descend at its normal descent rate in a max glide ratio configuration.
2. When the airplane is one inch from the ground, you note the time for the descent, & the position.  You turn off the wind & weight, and now apply the (best glide ratio) airspeed.  You let the (weightless) airplane "glide" for the same amount of time that it took to descend.  When applied to all directions of the compass, that will be your circle (from the one inch descent point)!
   

In your 60kt/60kt example, you draw a line due south from your initial position, with a length of whatever period of time it will take to descend to the ground.  You then draw a circle (of the same length in this particular example) from that point.  Clearly that circle just touches your initial starting point.  That will be your ring.

Note that in your example, if you head due north, you choice of landing destinations will be exactly one spot, but your groundspeed will be zero upon arrival!  This has obvious advantages ... :)


-- Dean ( http://airmen.mailpen.com/airman/dean/ )

[Andrew Sarangan]

With no wind, the glide range will be a circle. That should obvious. With wind, the circle gets displaced by the wind vector. Mathematically it would be the circle + wind vector. The result remains a circle, but it's center will no longer be at the aircraft's starting position. 

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[Dean Gibson ATP/CFI]

Note that in my glide circle universe, a varying wind in step #1 during the descent governs the location of the "one inch" position, but since the wind is turned off in step #2, it is not a factor in the shape or radius of the circle.

Same for doing constant bank/airspeed turns over the ground with a wind.  The ground or wind is not a factor until you look down (or touchdown).

-- Dean  ( http://airmen.mailpen.com/airman/dean/ ) 

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[Zubair Khan]

Dean
I have a formula and I am doing it mathematically. I am not getting perfect circles especially at lower altitudes.
There is a turn penalty which diminishes the higher you go in altitude.
The 'circle' in my 60/60 example is more of a tear drop, the shape of which changes with altitude.





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[Dean Gibson ATP/CFI]

Exactly!  A varying wind speed/direction as you descent affects the location of the center of that circle, but not its radius.

-- Dean  ( http://airmen.mailpen.com/airman/dean/ ) 

On 2021-04-05 17:41, Andrew Sarangan wrote:

With no wind, the glide range will be a circle. That should obvious. With wind, the circle gets displaced by the wind vector. Mathematically it would be the circle + wind vector. The result remains a circle, but it's center will no longer be at the aircraft's starting position. 

On Mon, Apr 5, 2021, 8:24 PM Dean Gibson ATP/CFI <a...@mailpen.com> wrote:

First I will explain how I teach horizontal wind triangles on a map.  You must imagine a fictitious universe where you can:

(a) turn on & off the wind;
(b) turn on & off the airspeed; and
(c) turn on & off the weight of the aircraft (so it just floats in the air like a balloon).

1. You start out by turning off the airspeed & weight.  You let the wind blow for an hour, & you draw that line on a map from your starting position (you have already drawn a course line from your starting position to your destination).
2. You now turn off the wind, & turn on the airspeed (weight doesn't matter here).  You now draw a new line from the end of the first line, to intercept (at a distance equal to one hour of true airspeed) your course line (just like you would do with a drafting compass).  Obviously, the angle (relative to north) of this 2nd line is your true heading, & the length of the intercepted course line is your groundspeed.

Now for the glide distance circle:

1. You turn off the airspeed.  You let the airplane descend at its normal descent rate in a max glide ratio configuration.
2. When the airplane is one inch from the ground, you note the time for the descent, & the position.  You turn off the wind & weight, and now apply the (best glide ratio) airspeed.  You let the (weightless) airplane "glide" for the same amount of time that it took to descend.  When applied to all directions of the compass, that will be your circle (from the one inch descent point)!
   

In your 60kt/60kt example, you draw a line due south from your initial position, with a length of whatever period of time it will take to descend to the ground.  You then draw a circle (of the same radius in this particular example) from that point.  Clearly that circle just touches your initial starting point.  That will be your ring.

Note that in your example, if you head due north, you choice of landing destinations will be exactly one spot, but your groundspeed will be zero upon arrival!  This has obvious advantages ... :)


-- Dean ( http://airmen.mailpen.com/airman/dean/ )

On 2021-04-05 16:47, 'Zubair Khan' via Apps4Av Forum wrote:

Dean please explain how glide ring will be circular. Assume your best glide airspeed is 60 kt, and you have 60 kt wind from the north.
Thanks


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On Apr 5, 2021, 7:36 PM, Dean Gibson ATP/CFI < a...@mailpen.com> wrote:

Unless the wind varies by POSITION (which you are not going to get from any forecast), the rings will be CIRCULAR, all the way to level ground, unless terrain elevation intervenes.  The variation of wind speed & direction by altitude, will shift the circle, but it will still be a circle.  That's the mathematics of the situation.

Are you asking for the rings to take variable terrain into consideration?

On Monday, April 5, 2021 at 12:08:46 PM UTC-7 avia...@gmail.com wrote:

...The indication on my screen must take into account the winds aloft, all the way down, as well as my current airspeed.  Thus, the "ring" will not be circular unless no-wind conditions exist from my altitude to the ground.  A first-order approximation would be an oblate teardrop with the pointy end downwind. 

--

[Dean Gibson ATP/CFI]

If you are figuring in an initial turn penalty, that effect would minimal, I would think.  And if you figure in an initial turn, you are also going to figure in a final turn into the wind for landing.  This all so much depends upon the skill of the pilot, that I think accounting for it, is a mistake.  For one thing, the decision process when losing an engine, & the delays therein, are a much bigger factor that any actual turn penalty(s).

OT:  In a modern Cessna with an integrated Garmin display (& integrated fuel flow meter), it is fun to watch the endurance ring expand & contract with the adjustments in power.  In fact, this is useful in determining maximum (powered) range, as that point does not occur at full or idle power.  It varies by aircraft, but it's typically close to 55% power in most airplanes, I think.

-- Dean  ( http://airmen.mailpen.com/airman/dean/ ) 

[Zubair Khan]

And that's why glide ring is not a perfect circle. If you add several non concentric circles you get a potato.

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[Zubair Khan]

The turn penalty is huge that's why we don't turn back to the take off runway below typically a thousand feet. It diminishes with altitude. You are right that it's also pilot skill.
Glide ring is an interesting toy at best.

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[Dean Gibson ATP/CFI]

Nope.  For a given glide speed, it's always a circle, regardless of how the wind varies with altitude.  The way to add non-concentric circles, is to add the circles as though they were concentric, & then add the vector offsets, resulting in a displaced circle.

The mathematics is as follows:

Imagine a wind vector function W(h), which returns a vector wind velocity for altitude "h".

Imagine a gliding aircraft velocity vector function G(a,h) in no wind, which returns a vector aircraft velocity for heading "a" & altitude "h".  In our discussion so far, we have imagined that this vector is a constant with respect to altitude, but it turns out it doesn't matter:

For each tiny increment of time, the distance traveled from the previous spot, is the vector S = (W(h) + G(a,h))x(the tiny increment of time).  Expressed in calculus terms, it's:

dS = (W(h) + G(a,h)) dt

Integrating, we get the vector S = (integral of W(h) dt)  +  (integral of G(a,h) dt)

But (integral of W(h) dt) = where the wind will blow you if you make no progress in the body of air you are in.

And (integral of G(a,h) dt) = where you will end up if there is no wind.  If "a" is a constant, the integral is a line of constant length, in the direction of "a"

Note that where you end up is the vector sum of these two integrals:

1. Where the wind blows a similar object that makes no progress in the air mass; and
2. Where the airplane would glide without any wind, which ends up being a circle.

As Andrew Sarangan said, a circle displaced by a vector is still a circle.

OT but important (& I agree with you that the "glide ring is an interesting toy at best"), and to muddy the water further:  The best glide SPEED changes, depending upon whether or not you are heading into the wind or away from it.  To take your 60kt glide with a 60kt wind, it's obvious that if you maintain the same glide speed, you will make zero forward progress.  So you must increase the normal glide speed in order to make the best angle of glide.  How much?  It depends upon the particular airplane's aerodynamics (the drag curve), but a rule of thumb is  1/2 the headwind.  That does mean fly 90kts in your 60kt headwind!  Conversely, with a tailwind, to get the best glide angle, you reduce the glide speed, but NEVER below the minimum sink speed (typically 5-10 knots above stall in a light airplane).  In fact, if you take the graph of any airplane's drag curve (expressed as rate of descent as a function of true airspeed), the minimum sink speed is at the bottom of the drag curve, & the best glide speed in still air, is found as a line from the (0,0) point on the graph to the tangent on the drag curve.  The best glide speed in a wind, is found in the same way, but with the starting point of the tangent line as the headwind or tailwind component of the wind, on the x-axis of the graph (with that point being on the negative part of the x-axis for a tailwind).

I remember doing slow-flight in Wisconsin in a Cessna 150 at 3,000 AGL, & going backwards over the ground.


My background in math:

As a junior in high school, I studied calculus on my own.  At the end of my junior year, I asked for permission to take the final exam of the high-school's advanced placement calculus class for seniors.  As a result, the school had me take 2nd year calculus at the local junior college, where I was also asked to grade the homework papers of those taking 1st year calculus (my first real job).  When admitted to Caltech as a freshman, I was given junior status in math, due to a perfect score on the exam for those transferring in at the junior level.  I graduated with a BS in math (I went on to major in computer science in grad school).

I've been a CFI for over 50 years, with over 2,000 hours of flight instruction given.  I've been the Chief Flight Instructor at two Part 141 flight schools.  I'm not always right, but I do have a pretty good understanding of the math & physics involved (that's another story at Caltech).

-- Dean  ( http://airmen.mailpen.com/airman/dean/ ) 

[Andy]

I flew yesterday using the glide ring but the wind direction was completely wrong (not complaining, I know this a  toy).

I got the weather via Internet just before takeoff, the label read W070@8 but the winds were from the north.

Long press on the local airport KLEB that has weather had the winds from the north as well.

Also noted that the label was way up above the circle which is different from the last time I flew.

Any idea what went wrong? User error?

[Zubair Khan]

No user error.
Winds aloft at a certain altitude are interpolations between two reported wind aloft values. How do you know the wind speed at that altitude? I have to check the code and find if station winds are used for interpolation. I think they are.
Z

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