T-45C TS INav-02
Introduction to INav and Voice Procedures
The reason why federal airways are limited to a
Sg 8, fr 5
maximum altitude of FL 450 is due to the
service volume of VORs. The 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.
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.
Identified by 3-letter aural Morse code identifier or
recorded automatic voice alternating with Morse
Most can be used to transmit voice communications
to aircraft as well as scheduled and/or urgent
There is a negligible cone of confusion over a VOR
antenna. Due to its size, station passage over a
VOR is a recognized fix. Therefore, over the station
holding can be conducted directly over a VOR
If you feel it necessary to again show the graphic depicting
VOR/TACAN Cones of Confusion, call up Seg 8/frame 4.