Error in ground speed and wind correction angle calculation

[Ibrahim C]

Hi,

I just downloaded AvareX and am evaluating it.

I like using Avare (it was very helpful for my multi check ride), but I can't seriously use it for cross-country planning as often the total trip time is way off compared to sites like Skyvector, especially if I'm doing a quick look by only entering the origin and destination and these points are fairly far apart. I determined this is because Avare only uses the winds at the destination and does not average winds along the route. I hoped that AvareX would remedy this, but it appears to only use the winds at the origin and also does not average, even though it shows intermediate wind speeds on the wind speed/terrain histogram with only two waypoints entered.

However, I'm posting today about something more insidious, particularly in a high wind situation in a location with significant magnetic declination like Washington state.

It appears that AvareX is either using true winds with magnetic course to calculate ground speed and wind correction angle, or magnetic winds with true course. To be correct, true course should be used with true winds (as imported from the aviation weather service).

I checked Avare and it has the same issue.

Here's a sample plan I did from KPAE to KSEA. I used 30,000 feet as the winds were high enough to make the problem more clear. With a TAS of 150 kts and a true course of 183 degrees, both Avarex and Avare calculated a groundspeed of 197 kts and a wind correction angle of 11 degrees.

However, using true wind and true course on an E6-B yields a ground speed of 187 kts and a wind correction angle of 15 degrees.

So it appears that AvareX and Avare are using magnetic course instead of true course when making the groundspeed/WCA calculation with the true winds aloft data.

This is probably not very noticeable in the Midwest but could be significant on the coasts and could cause fuel reserves to be inadequate.

[Apps4av Support]

Ibrahim

Thanks for a comprehensive test report and a possible bug. Investigating ...

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Regards,

Apps For Aviators Support,

We encourage users to use the Forum for all questions. Any updates to the forum will help other users, who might have similar questions.
Forum: https://groups.google.com/forum/#!forum/apps4av-forum

[Apps4av Support]

I have found that you are right about not averaging wind along a long route. This is for simplicity as Avare(X) assumes travel in small aircrafts. This can be corrected.

True wind with True heading is used. I have not found an issue here yet but here are the formulas used (you can see that true course with true wind is used):

windCorrectionAngle = atan2(ws * sin((trueCourse - wd) * pi / 180.0), _speed - ws * cos((trueCourse - wd)))
magneticCourse = trueCourse + variation
course = (magneticCourse + windCorrectionAngle) % 360;

On Fri, Apr 17, 2026 at 10:09 AM Ibrahim C <igc...@gmail.com> wrote:

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[Apps4av Support]

I did not find a bug as you described (magnetic heading with true wind), but I have changed wind correction formulas to match https://e6bx.com/e6b/

Will also look into re-calculating with winds at 50 miles intervals for long routes.

Next release should see this change.

On Fri, Apr 17, 2026 at 10:09 AM Ibrahim C <igc...@gmail.com> wrote:

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[Apps4av Support]

Thanks for pointing this. Now winds are calculated at every 50 miles.

Also, in the process found that wind was not available near canada so 0 wind was used. Fixed that bug. 

So good changes overall. Version 99 will have a much better experience for long cross countries calculations.

On Fri, Apr 17, 2026 at 10:09 AM Ibrahim C <igc...@gmail.com> wrote:

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[Ibrahim C]

This is great news! Sorry about the initial incorrect diagnosis of magnetic course being used instead of true course. Will the formula for ground speed also be corrected? It would be nice if the corrections could also be made to Avare for legacy users.

I also noticed about AvareX that, unlike Avare, it doesn't let you save user-defined waypoints, nor does it have simulator mode or static stadium TFR rings. Static stadium TFR rings are helpful as neither Avare nor AvareX download actual stadium TFR's.

[Apps4av Support]

It's going to be hard to accomplish the wind calculation along the route in legacy. Can change the formulas but that makes very small difference. 

X does have user waypoints, but you enter them one at a time. Can look into importing from excel.

Regards,

Apps For Aviators Support,

We encourage users to use the Forum for all questions. Any updates to the forum will help other users, who might have similar questions.
Forum: https://groups.google.com/forum/#!forum/apps4av-forum

To view this discussion visit https://groups.google.com/d/msgid/apps4av-forum/95457eb6-d0d2-485c-aba7-466c74eb42e6n%40googlegroups.com.

[Ibrahim C]

I'm not finding how to save a user waypoint in AvareX. Nothing is mentioned in the manual.

[Apps4av Support]

Just go to Find screen and press the edit button under a waypoint to name it.

[Ibrahim C]

Ok, I see how to name a waypoint after I create one by pressing on the screen. But can I create one by entering lat/long coordinates? Also the custom waypoint doesn't show up on the map unless it's part of a route.

You mentioned it's too difficult to add wind averaging to Avare. That's ok, I can manually add a few intermediate waypoints on a direct route to bring in more localised wind data.

However, I would really appreciate it if you could issue an update to Avare that fixes the groundspeed and wind correction angle/heading formulas as I plan to use Avare as long as possible. Thanks.