Editing VHF omnidirectional range (section)

==Using a VOR==
[[File:Vor indicator.png|thumb|A mechanical cockpit VOR indicator]]
[[File:OceanSideVortac.jpg|thumb|Oceanside VORTAC in California]]
If a pilot wants to approach the VOR station from due east then the aircraft will have to fly due west to reach the station. The pilot will use the OBS to rotate the compass dial until the number 27 (270°) aligns with the pointer (called the ''primary index'') at the top of the dial. When the aircraft intercepts the 90° radial (due east of the VOR station) the needle will be centered and the To/From indicator will show "To". Notice that the pilot sets the VOR to indicate the reciprocal; the aircraft will follow the 90° radial while the VOR indicates that the course "to" the VOR station is 270°. This is called "proceeding inbound on the 090 radial." The pilot needs only to keep the needle centered to follow the course to the VOR station. If the needle drifts off-center the aircraft would be turned towards the needle until it is centered again. After the aircraft passes over the VOR station the To/From indicator will indicate "From" and the aircraft is then proceeding outbound on the 270° radial. The CDI needle may oscillate or go to full scale in the "cone of confusion" directly over the station but will recenter once the aircraft has flown a short distance beyond the station.

In the illustration on the right, notice that the heading ring is set with 360° (north) at the primary index, the needle is centred and the To/From indicator is showing "TO". The VOR is indicating that the aircraft is on the 360° course (north) ''to'' the VOR station (i.e. the aircraft is ''south'' of the VOR station). If the To/From indicator were showing "From" it would mean the aircraft was on the 360° radial ''from'' the VOR station (i.e. the aircraft is ''north'' of the VOR). Note that there is absolutely no indication of what direction the aircraft is flying. The aircraft could be flying due West and this snapshot of the VOR could be the moment when it crossed the 360° radial.

===Testing===
Before using a VOR indicator for the first time, it can be tested and calibrated at an airport with a ''VOR test facility'', or VOT. A VOT differs from a VOR in that it replaces the variable directional signal with another omnidirectional signal, in a sense transmitting a 360° radial in all directions. The NAV receiver is tuned to the VOT frequency, then the OBS is rotated until the needle is centred. If the indicator reads within four degrees of 000 with the FROM flag visible or 180 with the TO flag visible, it is considered usable for navigation. The FAA requires testing and calibration of a VOR indicator no more than 30 days before any flight under IFR.<ref name="VOT">{{Cite web
|title = VOR Navigation
|last = Wood
|first = Charles
|year = 2008
|url = http://www.navfltsm.addr.com/vor-nav.htm
|access-date = January 9, 2010
|archive-date = October 11, 2007
|archive-url = https://web.archive.org/web/20071011051729/http://www.navfltsm.addr.com/vor-nav.htm
|url-status = live
}}</ref>

===Intercepting VOR radials===
[[File:VOR Course Deviation Indicator explanation.gif|thumbnail|780px|center|On the course deviation indicator the radial is selected, and together the needle and TO/FR flag show the aircraft's position.]]

There are many methods available to determine what heading to fly to intercept a radial from the station or a course to the station. The most common method involves the acronym T-I-T-P-I-T. The acronym stands for Tune – Identify – Twist – Parallel – Intercept – Track. Each of these steps are quite important to ensure the aircraft is headed where it is being directed. First, tune the desired VOR frequency into the navigation radio, second and most important, Identify the correct VOR station by verifying the Morse code heard with the sectional chart. Third, twist the VOR OBS knob to the desired radial (FROM) or course (TO) the station. Fourth, bank the aircraft until the heading indicator indicates the radial or course set in the VOR. The fifth step is to fly towards the needle. If the needle is to the left, turn left by 30–45° and vice versa. The last step is once the VOR needle is centred, turn the heading of the aircraft back to the radial or course to track down the radial or course flown. If there is wind, a wind correction angle will be necessary to maintain the VOR needle centred.

[[Image:VOR Tracking.GIF|thumb|Aircraft in NW quadrant with VOR indicator shading heading from 360 to 090 degrees]]

Another method to intercept a VOR radial exists and more closely aligns itself with the operation of an HSI ([[Horizontal Situation Indicator]]). The first three steps above are the same; tune, identify and twist. At this point, the VOR needle should be displaced to either the left or the right. Looking at the VOR indicator, the numbers on the same side as the needle will always be the headings needed to return the needle back to centre. The aircraft heading should then be turned to align itself with one of those shaded headings. If done properly, this method will {{em|never}} produce reverse sensing.{{Definition needed|date=September 2024}} Using this method will ensure quick understanding of how an HSI works as the HSI visually shows what we are mentally trying to do.

In the adjacent diagram, an aircraft is flying a heading of 180° while located at a bearing of 315° from the VOR. After twisting the OBS knob to 360°, the needle deflects to the right. The needle ''shades'' the numbers between 360 and 090. If the aircraft turns to a heading anywhere in this range, the aircraft will intercept the radial. Although the needle deflects to the right, the shortest way of turning to the shaded range is a turn to the left.