T-45A UJPT & E2-C2 INav-03
Use and Operation of TACAN, VOR, VOR/DME
8. Cone of Confusion - A “cone of confusion,” where TACAN azimuth
information is not available, exists over TACAN stations. The
“cone” varies from 60 degrees to 110 degrees wide. TACAN DME
and I.D. signal will be received and station passage will be noted
by minimum DME. Although narrow at low altitudes, this “cone”
expands to about 18 nm across at 30,000 ft. Because of the size
of the TACAN “cone of confusion,” TACAN holding patterns will
always be established using DME
B. VOR
1. Unaffected by weather
2. 360 radials emitted from station
3. Provides magnetic radial
4. Operates in the VHF band (108.0-117.95 MHz) - fifty-nine (59)
available frequencies
5. Limitations
a. Line of sight
b. Standard Service Volume (SSV)
NOTE: SSV defines the reception limits of unrestricted
NAVAIDs which are usable for random/unpublished route
navigation.
The reason why federal airways are limited to a maximum
Fig 3: VOR
altitude of FL 450 is due to the service volume of VORs. The
Frequency Overlap
service volume is predicated on the limited number of available
VOR frequencies for airway navigation (total of 59). Present
FCC and FAA standards permit as many as 20 VORs to use
the same frequency. The problem with this is that the usable
range of VOR decreases with altitude due to overlapping
signals from VORs using the same frequency.
c.
From 18,000 ft AGL up to and including 45,000 ft AGL at radial
distances out to 130 nm
NOTE: Standard Service Volume limitations do not apply to
published IFR routes or procedures.
6. Identified by 3-letter aural Morse code identifier or recorded
automatic voice alternating with Morse code identifier
(6-99) Original
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