Above is a VORTAC station VORTAC stands for
Above is a VORTAC station. VORTAC stands for VOR + TACAN Stands for Tactical Air Navigation and it includes DME is Distance Measuring Equipment, and it’ll tell you how far your are from the station. The “counterpoise” is the base of the station and provides grounding of the station.
The VOR signal is comprised of a Reference Phase and a Variable Phase. The Reference Phase is broadcast in all directions. The Variable Phase is a rotating beam. The difference of phase between the Reference Phase and the Variable Phase is used by the VOR receiver in the airplane to calculate the bearing from the station.
Here is the VOR signal as it appears to the receiver. The carrier rises and falls in strength (AM). The signal is at max strength when the rotating beam is pointed directly at the airplane shown by the blue arrow. The red arrow shows the highest frequency of the subcarrier which occurs at N. The receiver compares the 2 signals by measuring the phase of each signal then calculates the difference as a magnetic course from the VOR.
Here is a VOR Indicator used in General Aviation. The VOR course is selected by turning the OBS (Omni Bearing Selector) knob to the desired course. The Course Deviation Indicator (CDI) displays steering commands.
Here is an HSI. The compass card is slaved to the compass system and shows the aircraft’s heading automatically. The course is selected by a knob located elsewhere and is displayed by digitally in the upper right corner and by the course needle, here it is 20°. The deviation bar shows that we are off course to the right.
The RMI displays both VOR and ADF (automatic direction finder) information. The compass card is slaved to the compass system.
Since the VOR’s have a relatively short range, using them to navigate would cause “doglegs”, flying a “connect-thedots” path. RNAV, or area navigation solves this problem by referencing VOR stations and computing a straight-line path.
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