In testing, I had 0 winds. I was trying to fly a 058 radial FROM the OVR VOR, Course was set to 058 on the HSI, aircraft heading was 061 to fly it accurately, and the GPS along that same line showed a direct track and track of 065.
I did hit D to re-adjust the gyro as carenado oddly doesn’t model a slaved HSI.
This made it rather difficult to fly an accurate route. Is this just a modeled issue with VOR and magnetic variation or is this something that should not be seen in the simulator?
VORs radials are set to a specific geographical azimuth. At the time they first did this, they would set the 0 radial to magnetic north at that time. Over time, magnetic north has shifted, but most VORs haven’t been recalibrated for decades, if ever. Magnetic variation in the GPS database is updated frequently, thus the discrepancy.
This is exactly correct and realistic. The OVR VOR was put into service in 1965, at which time the magnetic variation for that location was 8 degrees east. The current variation in 2025 is 2.1 degrees east. The zero degree radial was set to point at magnetic north based on where is was in 1965 and it has never been changed since.
A common misunderstanding about VORs is that a radial does not represent the magnetic heading that the radial points to - it represents the number of degrees that the radial is offset from that specific VOR’s zero degree radial, and the zero degree radial is based on the variation that existed when the VOR was built, which may be very different that the variation today. The path that the radial follows over the ground does not change. It is the same today as it was 60 years ago.
It is the number that you would set into your HSI’s course selector. As long as you keep the needle centered, you will correctly track the radial’s geographic path, but the magnetic heading you have to fly to keep the needle centered may be quite different than the radial’s “heading”. It depends on where you are located in the US and how long ago the VOR was put into service.
The magnetic variation in the western US has changed substantially in the last 40 years, while the variation in the northeastern US has changed very little in the same time period.
