T-6A INSTRUMENT NAVIGATION
Normal service ranges for the various classes of VORs are given in
NAVAID Service Volumes, paragraph G.
Most VORs are equipped for voice transmission. VORs without voice capability are indicated
on enroute and sectional charts by underlining the VOR frequency or by the designation VHF
Omnidirectional Range Without (Voice) (VORW) in the IFR Supplement. Since a large portion
of the frequencies available on the VOR control panel may overlap the VHF communication
The only positive method of identifying a VOR is by its Morse Code identifier or by the
recorded automatic voice identification which is always indicated by use of the word "VOR"
following the range's name. Reliance on determining the identification of a VOR should never
be placed on listening to voice transmissions by the Flight Service Station (FSS) (or approach
control facility) involved. Many FSSs remotely operate several VORs with different names. In
some cases, none of the VORs have the name of the "parent" FSS. During periods of
maintenance, the facility may radiate a T-E-S-T code (-●●●●-) or the code may be removed.
Voice identification has been added to numerous VORs. The transmission consists of a voice
announcement, "AIRVILLE VOR" alternating with the usual Morse Code identification.
The effectiveness of the VOR depends upon proper use and adjustment of both ground and
The accuracy of course alignment of the VOR is excellent, being generally within + 1°.
2. On some VORs, minor course roughness may be observed as evidenced by course needle
or brief flag alarm activity (some receivers are more susceptible to these irregularities than
others). At a few stations, usually in mountainous terrain, the aircrews may occasionally observe
a brief course needle oscillation, similar to the indication of "approaching station." Aircrews
flying over unfamiliar routes are cautioned to be on the alert for these vagaries, and in particular,
to use the "to/from" indicator to determine positive station passage.
VOR RECEIVER CHECK
FARs provide for certain VOR equipment accuracy checks prior to flight under IFR. To comply
with this requirement and to ensure satisfactory operation of the airborne system, the FAA has
provided aircrews with the following means of checking VOR receiver accuracy:
Certified airborne checkpoints.
Certified ground checkpoints on the airport surface.
INTRODUCTION TO NAVIGATION SYSTEMS 1-3