What's up with the headings (and radials) in Aerofly?

  • I noticed that when I plan a flight in Aerofly itself the headings I am getting from a VOR to an airport I want to get to are wrong. Or at least they are different from the radials I am trying to fly. I notice this everytime. For example I tried to fly from the HBU VOR to KMTJ using NAV in the C172. When I create a plan in Aerofly it tells me the heading from HBU to KMTJ is 265 so I am using that as the radial to fly from. This however leads me to the right of the path I should fly, totally missing the airport. When I recreate the same leg using SkyVector I get a heading of 261 and when I use that as the radial to fly from I end up right above the airport. Perfect and spot on.


    Why are the headings and hence radials off in Aerofly?


    Obviously from now on I will be using SkyVector to plan my flights (also because it takes a few workarounds to accomplish a flight like this in Aerofly) but still, it would be nice if I could do it in Aerofly itself.

    • Official Post

    There could be all sorts of reasons for this

    - inaccuracies in the code to calculate the heading (trigonometry gets quite complicated on the oblate spheroid Earth model we use)

    - great circle flying vs. local directions (headings should constantly change as you fly along, there is no "one" heading to get from a to b in the shortest way possible)

    - model of the magnetic variations we use

    - wind in the simulator pushes you off the correct track (headings are not good to fly a ground track), check that wind is indeed set to 0.0

  • The heading you fly may be different from the radial you are flying on but as long as you stick to the radial you should get where you want to go. The correct radial to fly from a certain VOR to an airport will never change because of wind. If the heading that Aerofly calculates is wrong it should be fixed. It is odd that flying from HBU to KMTJ is 261 everywhere but not in Aerofly. It is even more odd that flying 261 regardless of what Aerofly says DOES get you to the airport correctly. What is the use of showing track on the route page if those numbers are wrong?


    EDIT

    Another flight: FFU VOR to U42. According to AFS2 the track is 342 and according to SkyVector 337. Which makes quite a difference imho. SkyVector was right again. Seems the information provided on the route page isn't of much value (at least for flights like these in which you want to be in control).

  • Great post Robert, sometimes Aero is "blamed" for odd real life phenomena. It is not unlike a runway 27 having a heading of 264, a troublesome renumbering would be due.

    Here is a fairly good heading plotted to align with the VOR north index, it must have been surveyed a long time ago.


  • With a real chart you would plot off the VOR symbol using a VOR protractor aligned with the chart's VOR north indicator. I used to draw my track and put a long arm VOR plotter on the track and read off the track from the chart indicator. The protractor read in reverse so 045 was to the left. When the long arm was laid over a 045 track, the 045 on the protractor was on top of the chart's VOR north index.

    This is what a 090 track would look like.

    J Van E you need to plot VOR radials using the VOR information, you can use a chart or for on screen navigation, you can look up the published VOR information and adjust any electronic track that does not take the VOR into account. There are probably VOR track calculators online. If you look at the SkyVector chart there is a VOR defined airway heading showing the 261 radial to your chosen airport.

    Flying from one VOR to another is complicated by the different survey alignments and magnetic variations at each VOR. Going out on a 090 radial is rarely paired with arriving on a 270 radial.

  • Excellent post, excellent answers. Thanks guys learnt a lot.


    Taranakian/Jim

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