CyberAirVA

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VOR/VORTAC

In the following sections I will go through VORs and VORTACs. First some general information about the two systems and then some examples on how to use them.

VOR
The three letter combination VOR stands for VHF Omni-directional Range. The VOR is a radio beacon operating in the frequency range of 108.0 to 117.95 MHz. Most VORs are equipped for voice transmission on the VOR frequency. VORs without voice capability are indicated by the letter "W" (without voice) included in the class designator (VORW). The method of identifying a VOR is by its Morse Code identification or by the recorded automatic voice identification which is always indicated by use of the word "VOR" following the range's name. The voice recording and Morse code alternate.

Advantages that VORs offer to the NDBs are that a VOR will always offer the course to reach the VOR. It will also offer a course away from the VOR. It does this because the ground station emits a signal in all directions. By convention, 360 different tracks, or radials (see below), are used. Radials are always From the VOR and in 1° increments, related to magnetic north. The normal accuracy of a VOR is ± 2° or better. Another advantage is that the VOR have a low interference from the atmosphere and it doesn't have any "night effects".

The VOR emits 360 tracks called radials.

DME
DME stands for Distance Measuring Equipment and is the reason we can see how long the distance is to the VOR (unless using TRACAN, see below). From AIM: In the operation of DME, paired pulses at a specific spacing are sent out from the aircraft (this is the interrogation) and are received at the ground station. The ground station (transponder) then transmits paired pulses back to the aircraft at the same pulse spacing but on a different frequency. The time required for the round trip of this signal exchange is measured in the airborne DME unit and is translated into distance (nautical miles) from the aircraft to the ground station. Operating on the line-of-sight principle, DME furnishes distance information with a very high degree of accuracy. Reliable signals may be received at distances up to 199 NM at line-of-sight altitude with an accuracy of better than 1/2 mile or 3 percent of the distance, whichever is greater. Distance information received from DME equipment is SLANT RANGE distance and not actual horizontal distance. DME operates on frequencies in the UHF spectrum between 962 MHz and 1213 MHz. Aircraft equipped with TACAN equipment will receive distance information from a VORTAC automatically, while aircraft equipped with VOR must have a separate DME airborne unit.

TRACAN
The AIM definition for TACAN is: "... For reasons peculiar to military or naval operations (unusual sitting conditions, the pitching and rolling of a naval vessel, etc.) the civil VOR/Distance Measuring Equipment (DME) system of air navigation was considered unsuitable for military or naval use. A new navigational system, TACAN, was therefore developed by the military and naval forces to more readily lend itself to military and naval requirements ...//... TACAN is a pulse system and operates in the Ultrahigh Frequency (UHF) band of frequencies. Its use requires TACAN airborne equipment and does not operate through conventional VOR equipment ..."

VORTAC
Why have I addressed the TRACAN, that wasn't mentioned at the beginning? The VORTAC is actually made up of two of parts, the VOR, and TRACAN. These together then becomes VORTAC which provides three individual services: VOR azimuth, TACAN azimuth and TACAN distance (DME) at one site. Even though the VORTACs are in fact a couple of different systems they are considered to be one. So why do we use the two systems together? Maybe the end of the next AIM quote can lend a hand: "... Transmitted signals of VOR and TACAN are each identified by three-letter code transmission and are interlocked so that pilots using VOR azimuth with TACAN distance can be assured that both signals being received are definitely from the same ground station. The frequency channels of the VOR and the TACAN at each VORTAC facility are "paired" in accordance with a national plan to simplify airborne operation ..." So by having the VOR paired with a TACAN (being a VORTAC) pilots can use the two systems together.

Using VOR
So how to use it. first lets take a look at the instruments in the cockpit. There are four instruments parts we will be interested in.

Omni Bearing Selector (OBS). This isthe course selector (in the lower left corner of the pictures below). This is simply the radials we fly towards or from.
Course Deviation Indicator (CDI). This is the needle in the middle. This will show when we are "off course".
To/From flag. As mentioned before you can use the VOR for flying courses to and from the VOR, this is where we se if we are heading towards (flag up) or away from (flag down) from the VOR.
On/Off indicator. Indicates if we are receiving a VOR station or not. If not then it will be red and white flag on the Cessna and a red X on the Lear HSI.

		VOR instrument when not receiving a station.
		VOR instrument when receiving the station but not on the right radial.
		VOR instrument when receiving the station and on the right radial (tune using OBS). Heading to the station.
		VOR instrument when receiving the station and on the right radial. Heading from the station.

Example 1
I think it's time for an example. Start your FS and go to Merrill C Miegs (KCGX). Now take-off and turn left, new heading 270 (west), climb to 1500ft. Now we are going to tune the VOR radio (NAV radio) to the O'HARE VOR (113.90). Bring out the radio stack, on the top right is the nav frequency. Set this to 113.90 which is the O'HARE VOR. Now we just have to wait a bit until the VOR comes into range. When it does it will look a bit like the second picture above. Now we are going to set our autopilot hold to 1500ft.

Next step is to turn the OBS knob until we are on the right radial (correct OBS course), as the third picture above. Now go back to the radio stack and click on the third button (from left), this will engage the NAV1 lock and we will fly towards the VOR. Now here is the thing that is special about VORs, we have now turned it to OBS course 312 (or about 312). This means that we will fly towards the VOR with a heading of 312 degrees, clever isn't it. Note that this doesn't mean we are using the 312th radial, actually in this case we are using the 48th radial

So now lets fly towards the VOR. When we get to it we can see that the heading flag will change from towards to from. The flag can sometimes flicker in this stage (called "zone of confusion"). No here comes the beauty part: We now want to fly toward the next waypoint which is DUPAGE VOR (108.40). To do this we will need the heading towards the new VOR, in this case 260 degrees. Now we turn our OBS course to that (see the fourth picture above). We will now fly that heading, using the "old" O'HARE VOR. This means that even if we aren't close enough to the next VOR to receive it, we can fly this new heading using the old VOR until we can receive the new VOR.

You can practice it a bit more, after DUPAGE fly to KANKAKEE (111.60) OBS=150.
Then fly to CHICAGO HEIGHTS (114.20) OBS=035.
Then head back for a landing at Miegs.
Note that in most of the aircrafts there are two NAV instruments, this makes it a bit easier to navigate between the VORs.

Example 2
You can also use the VORs without navigating completely to and from the VOR. In this example we will show how you can use two VORs to find an intersection. The principles behind it is that if we have two VORs (can also be one VOR and one NDB) and the OBS courses we can figure out where we are. The principle is better shown in the picture below.

Finding an intersection with the use of two VORs.

So lets try this for "real". Start your FS, fly out of Chicago O'Hare Intl. airport (KORD), NAV1 set to O'HARE (113.90) OBS=200 and NAV2 set to JOLIET (112.30) OBS=050. We start by flying on the O'HARE 200 radial after a while we will pass the point where the two radials meet. See the stages below.


Before passing the intersection point.	When passing the intersection point.	After passing the intersection point.

Example 3
Knowing what we now do we can navigate, using VORs and flying between them. So lets try another one. First lets plan a little: We will fly from Merrill C Miegs (KCGX) to Schertz field (KC34). We will use the following VORs: PEOTONE (113.20), ROBERTS (116.80), CHICAGO HEIGHTS (114.20) and KANKAKEE (111.60). But we won't fly entirely to and from the VORs, We will fly in between them. First let us calculate a couple of intersections points, we will use three. They will be between PEOTONE - CHICAGO HEIGHTS, KANKAKEE - PEOTONE and ROBERTS - KANKAKEE. So now we have three intersections, now we just make a line of flight. And so we have our plan (see below). The plan thereby consists of five legs:

Merrill C Miegs (KCGX) - Intersection 1 = [NAV1_113.20_OBS185] [NAV2_114.20_OBS270]
Intersection 1 - Intersection 2 = [NAV1_111.60_OBS185] [NAV2_113.20_OBS210]
Intersection 2 - Intersection 3 = [NAV1_116.80_OBS210] [NAV2_111.60_OBS220]
Intersection 3 - ROBERTS VOR = [NAV1_116.80_OBS210]
ROBERTS VOR - Schertz field (KC34) = [NAV1_116.80_OBS210]

Our flight plan from Miegs to Schertz. Intersections marked by
golden rings.

So lets go flying. We will start at Miegs, setting NAV radios as above. Since we don't have PEOTONE in range we will start flying heading 185 until we start receiving PEOTONE, then we will use NAV1 hold. Once we reach the first intersection we change the NAV radios to the new frequencies and OBS courses. And so on we continue until reaching Schertz.

Example 4
Finally I would just like to show you how to use the VORs to and from function, when using different radials to and from (see below). We simply fly toward the VOR, but then we turn right to 090 degrees and set our OBS course to the new 120. Then just before our needle passes the middle we turn right to 120 degrees and we have now intercepted the new radial from the VOR. Smart! Note that in this case we turn to 090 degrees, this isn't always so, it depends on which radial we are using and at which angle we want to fly towards the new radial.

Flying using different to and from radials.

Note that you don't have to fly using the autopilot. Actually any pilot calling himself a good pilot can easily fly the above examples not using the autopilot.

Good Luck!

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