PompeyPaul,
Think of the VOR beacon as two separate beacons:
- One that does a very short "beep" exactly on the top of the second.
- Another that does a continuous "beep" but sweeps a narrow beam through 360 degrees in one second, pointing to magnetic north exactly on the top of the second.
The VOR receiver you have in your airplane measures the time difference between the two beeps. If the time difference is, for instance, a quarter of a second, you are 90 degrees magnetic from the VOR. If it's half a second, you are 180 degrees magnetic from the VOR. And the accuracy is theoretically infinite. If you've got equipment calibrated to 0.01 degree, and the VOR is also calibrated to that precision, you could fly a 123.45 radial if you wanted to. But such accuracy is generally not needed.
(Yes, this is technically not entirely accurate, but it works for now.)
The VOR equipment in the plane doesn't show these bearings as such, but shows it through the OBS display. Now the design of the OBS display is a little unexpected for a first-time user, but the reasoning behind it is that a pilot does not need to know his present position. He already knows it. Rather, he wants to fly a certain track or intercept a certain track. So the pilot sets whatever he wants to achieve on the OBS, and then the OBS tells him what he needs to do.
And with a bit of fiddling you can still let the OBS tell you where you are in reference to the VOR.
How to fly directly TO a VOR: Fiddle the OBS ring so that the flag shows TO, and the needle is in the middle. Then fly the magnetic course which is on top of the OBS. (Compensating for wind of course.)
How to fly directly FROM a VOR: Fiddle the OBS ring so that the flag shows FROM, and the needle is in the middle. Fly the magnetic course again.
How to intercept a course TO a VOR: Set the course to intercept on the OBS ring. If the needle is left of the center, fly 30-45 degrees left of the course to be intercepted until the needle centers. If the needle is right, fly 30-45 degrees right.
Intercepting a course FROM a VOR: Same thing. Set the course to intercept. Fly left of that course if the needle is left, fly right of that course if the needle is right.
How to determine your position (bearing) FROM a VOR? Fiddle the OBS ring so that the needle is centered and the flag shows FROM. Note the number at the top of the OBS ring. Take your map and draw a line FROM the VOR with this magnetic bearing. Your position will be along this line. (You need two VORs, or a VOR/DME to get your position.)
You can also fiddle until you have the TO flag and read off the bearing. But then you've got to draw a line from your aircrafts position TO the VOR along that bearing. Useful if you know where your aircraft is and the position of the VOR is unknown... :-) If you have a TO flag with the needle centered, add or subtract 180 degrees and you've got the bearing FROM the VOR TO your aircraft. Or just rotate the OBS through 180 degrees to get a FROM flag with the needle centered.
Ref your specific questions:
1. You are on the "90 degree radial and the flag shows FROM" (and the needle is centered I presume). This simply means that if you fly 90 degrees, then you are flying 90 degrees away FROM the VOR. So to fly directly TO the VOR you need to fly 270 degrees (90+180).
Note however, that if you just turn the aircraft around to 270 deg but leave the OBS ring as it is (90 degrees), it will show a FROM indicator (because 90 degrees would take you away FROM the VOR) and the needle will work backwards. This is called "reverse sensing". Don't do it. Always set the OBS ring to the magnetic course you want to fly (when following a VOR radial) or the magnetic track (radial) you are intercepting. Then TO and FROM only mean that the VOR is in front or behind you.
2. If you are flying a certain radial TO a VOR, then the TO flag will show. If you get close, you get into the "cone of confusion" for a minute or so where the flag will show an error (striped red/white most likely) and then the FROM flag will show. This means that you've passed the VOR and are now flying away FROM it.
MSFS works great for this, as mentioned. But if all you want is to understand VORs, then go to 3000 feet in the vicinity of a VOR and put it in "slew" mode. All of a sudden the laws of aerodynamics no longer apply, and you can hover, fly backwards, rotate on a pinpoint, you name it.
Just remember - the VOR does not tell you your present position. Rather, the VOR is something that you set your intentions in (via the OBS ring) and the OBS then tells you what you need to do to achive that.