The VOR indication is according to the aircraft position relative to the station, not the heading. If there is disagreement when flying through a VOR (TO or FROM) between your heading number and the heading indicator as set with the compass you will experience "reverse sensing". With 'reverse sensing' flying toward the needle just makes it go further from the center. Once the needle is at full 10-degree deflection you can no longer detect reverse sensing.

One of the major difficulties with the VOR is in interpreting ATC directions for what you are to do relative to radials. Radials begin at the VOR and extend out from the station. ATC always names the radial from the VOR. Use the reciprocal of the radial if ATC includes the term 'inbound'. If an intercept is expected they will usually include an intercept heading. This is true whether they want to fly to, from, or intercept. The problem mainly exists when the pilot confuses bearing and radial.

One thing to understand about a VOR, it does not read differently as you turn the airplane around in a tight circle (assuming you are 30 miles from the VOR). Another way of saying it, is, the VOR doesn't care which way you are heading.
There are four modes of the VOR head and airplane direction.
1. Flying towards the station with a TO flag (Normal sensing)
2. Flying away from the station with a TO flag. (Reverse sensing)
3. Flying away from the station with a FROM flag. (Normal sensing)
4. Flying toward the station with with a FROM flag. (Reverse sensing)

Most ATC and charts use FROM radials. Tell an ATC guy that you are on a TO heading in identifying your location and they get confused.

Second Opinion:
The VOR Receiver quite simply is incapable of reverse sensing, any reverse sensing that goes on is in the mind of the interpreter. The VOR receiver is a dumb machine and does what it is told. If the aircraft is on a heading of 090 and the person using the VOR inputs a heading of 270 the VOR correctly interprets this as if the plane were heading 270 and gives corresponding course corrections that are accurate for the situation. This type of situation arises usually in conjunction with holding .

Flying outbound in the pattern to intercept the holding course inbound. If the inbound course is i.e.. 270 the outbound in no wind conditions is 090 the OBS is set to 270 and you are to the 090 radial. The CDI indication would be a left needle deflection which would be correct if you were flying 270 which is what the pilot told the VOR. In other words the needle does NOT tell the pilot which way to turn , it indicates which way the selected course is from your present position. In the case of the holding pattern if the pilot stopped his actions on a heading of 090 what would be the shortest direction to turn to intercept the 270 course( 090 Radial) You guessed it ,turn right even though the needle showed a left deflection , This is not a case of reverse sensing on the instruments account. Try this exercise and look at the relationship of the DG and the OBS,CDI indications. Do you notice the 45 degree hack marks on the DG ? They help with interpretation and course intercept.
R.Wallace CFIAIM

Flying the VOR Step by Step
---Crossing the VOR, you should initially parallel your new course before planning your intercept.
---A radial is always FROM.
---Fly THROUGH rather than TO.
---Always check your VOR accuracy.
---You can only track a VOR radial if you can fly a heading.
---Fly your needle within a needle width.
---Nibble at your heading corrections to keep the needle centered.
---Large heading changes should never be required to keep the needle centered.
---Large heading corrections will only be required at low airspeeds.
--- It takes a direct crosswind of 1/2 true airspeed to require a 30-degree crosswind correction.
---On station passage
..Note time of passage
..Change OBS
..Turn to new course
..Report to ATC
..Confirm your climb/descent limits.

Revisiting the VOR
--First confirm your frequency and ident.
--Make your from or through decision. Never fly TO a VOR always fly through it.
--Confirm to or through by reference to heading indicator and compass. This prevents reverse sensing.
--Reverse sensing is most disorienting when location of VOR is unknown.
--Any difference between the heading of the aircraft and the VOR radial will be a wind correction angle.

VOR Lesson
After a student has read about the VOR and its theory of operation, I like to take a flight of about an hour to actually watch the needle and flag movements as a flight is made in the vicinity of the VOR. The flight altitude is best to be at a safe altitude that is within 3000 feet of the surface. The lower and closer to the VOR that this can be done the more precise will be the needle and flag changes and reversals. To best understand this process you might wish to follow the diagram or the flight as I tried to illustrate it below.

The demonstration that is an exception to this is the 360 turn on a radial. For lesson efficiency this maneuver is best performed more than three miles southeast from the VOR. The needle is centered on a radial that corresponds with the aircraft heading from the VOR, preferably on the 135 radial. As immediate tight 360 is performed. (Station #1) It should be noted that the needle will remain inside the 'doughnut' regardless of the direction of the aircraft. To emphasize the validity of aircraft heading having no relationship to the immediate centering of the needle the turn should be done again in the opposite direction. This concept is important. Everything is not correct just because the needle is centered. Where the intent is to keep the needle centered, the pilot must fly an appropriate heading to keep it centered. Now proceed toward the VOR until about one-mile to the southeast side of the VOR.

Set the OBS to 0 (North) and turn the aircraft to fly due North. The flag will read TO and the needle will be at full left deviation toward the VOR. At the flight proceeds northward to the needle will always full left but when we get within ten degrees of due east the TO will gradually go to RED and then to FROM. Continue North for about a mile and turn quickly to due West. While proceeding west the needle will remain to a full left deflection until you arrive within ten degrees of North. Gradually the needle will move toward the center and then move away to full deflection to the right. This movement is characteristic of approach, interception, and passage beyond any radial that might be used as a checkpoint reference on a cross-country flight. After the needle has moved to full deflection to the right continue again for about a mile and turn due South.

We have deliberately set up a reverse sensing situation. The OBS is set to North but we are heading South. The needle points away from the VOR The TO/FROM flag will give a false indication except when passing within ten degrees of due west, at which time the RED flag will indicate a region of ambiguity. Again at one mile to the south you should turn due East and again the needle will begin to move toward the center when you are within ten degrees of the 180 degree radial and toward the VOR as you pass beyond 180. At one mile out do a 90/270 course reversal and fly the rectangle again in the opposite direction. On completion of the second rectangle try to determine the wind direction from surface indicators or by contacting a nearby FSS.

Now we are preparing to practice flying TO and FROM the VOR with course reversals. Initially we will fly as nearly upwind and downwind as we can. The process begins proceeding upwind. We center the OBS needle and determine that the heading indicator and compass are in near agreement. Proceed to the VOR and note that there is ever increasing sensitivity in the needle movement. Try making small corrections by using and holding the rudder. Once the needle begins to move quickly maintain present heading that you have determined will fly you out of the cone rising from the VOR. The higher you are above the VOR the larger will be the cone and the more time it will take for the needle to settle down on the other side of the VOR. Find a remote VOR if you really want to see how quickly it can reverse from TO to FROM when crossed at a low altitude.

Once the needle has settled down fly upwind from the VOR so as to distance yourself far enough from the VOR to execute a 90/270 course reversal. While in the 270 part of the reversal be sure to turn the OBS needle 180 degrees to the direction you will be returning to the VOR. Since you will be flying downwind now, try to anticipate any heading adjustments by timing the last few degrees of your turn. Correct your heading as needed for keeping the needle centered. If the tail wind is substantial, expect things to happen more quickly. Complete at least two full crossings with minimum required wind corrections before doing the procedure at 90 degrees to the wind.

Flying a VOR radial at 90 degrees to the wind requires that you set the radial into the OBS and after confirming the HI and compass agreement, make an estimate of the heading correction required to keep the needle centered. It is unlikely that your initial estimate will be accurate. You then must make a new heading correction estimate. This estimate will be a specific heading number that you believe will cause the needle to move to the center of the 'doughnut'. If you guess correctly and the needle moves to the center, now you must make another estimate of the heading that will stop the needle and keep it centered. The selection of both the corrective heading and the stopping heading requires repeated practice. Since the process may need to be done more than once it wise to get somewhat further from the VOR before beginning the process. Ideally you will get the needle stopped and have determined the heading that keeps it stopped as you cross the VOR. Even though the needle begins to move and flip quickly, hold the heading until leaving the ambiguity cone. If the needle remains centered as you fly from the VOR, all is well. If the needle moves from the 'doughnut' you must again repeat the process of finding a heading that re-centers the needle and a heading to stop it and keep it centered.

The course reversal in this situation requires that the direction and the bank of the reversal be carefully planned so as to allow you to come out of the turn with a heading correction that will either correct or hold the needle in the 'doughnut'. The sooner you get the needle in the center the sooner you can find the heading required to keep it there. Since you are flying as nearly 90 degrees to the wind only in a reverse direction, very nearly the same upwind correction will work in both directions. If time becomes a factor this last procedure might be delayed for another time.

One very useful exercise to become acquainted with the workings of the VOR is to 'box' it. By this, I mean fly a square around the VOR from about a mile away. Select the four cardinal directions for your 'box' and set in 360 on the OBS. Begin your flight at the southeastern corner of you 'box' on a 360 heading.

Fly the entire 'box' and watch the way the needle acts. After completing the 'box' make a course-reversal and go around the other way. Try to anticipate just what the needle will do this time around. Use a safety pilot if you can. Otherwise do it at 700' AGL which should be below any other likely traffic.

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