VOR Navigation

It had been quite some times back then when I was doing my aircraft's practical. Yesterday, while the rest of my colleagues were having their IELS English Exams, some of us were dispatched to the floor to do the practical. We were told to remove and re-install back the VOR antenna on the Cessna 172.

Cessna 172
The red arrow indicates the
location of the VOR antenna
College has bought an unused Cessna 172
from a flying club last month.
Although, it was left unused for a period of time,
nevertheless, it is still serviceable after all the
necessary maintenance work have been performed on it ...

The VOR antenna resembles the shape of V
which is fitted at the vertical stabilizer of the Cessna 172.
So, you may ask what is VOR?

VOR is an acronym for Very High Frequency (VHF) Omni-Directional Radio Range. Generally, VOR serves as a source of navigation aid to the aircraft, just as if, a "sign board" on roads. VOR Navigation provides a reliable line from the VOR station which can be selected and followed by the pilots. VOR operates in the region of VHF from 108 MHz to 117.95 MHz. The signal received from the VOR station will contain the VOR Station identifier code and the location signal.

Then, you may ask, what so good about VOR Navigation? Indeed, VOR Nav will suffer little intervention from the thunderstorm and less "course-bending" around the coastlines and earth terrains. As the nature of law says, "Every good, there is bad! " Same applies to the VOR. The disadvantage of VOR is that it depends on the "line of sight" - If the transmitting antenna could not seen on a perfect clear way from the receiving antenna, the useful signal cannot be received. In short, if the VOR antenna on the aircraft cannot "see" the VOR station on ground, then, the NAV signal will serve no purpose.

Typical VOR station on ground
The signal is transmitted in all direction,
360 degrees all around.
It is hence called "Omni-Directional".
How it works?
Basically, two signals are transmitted by this station;
the reference phase signal and the rotating phase signal.
These two signals are essential to decode the
location and direction of the VOR station.
The signals received by the aircraft will be
processed and computed to determine the phase angle,
by which, the phase angle will equal to the direction from the station
to the aircraft in degrees with
reference to Magnetic North.
Some VOR station may have the
Distance Measuring Equipment (DME)
which provides the slant distance
of the aircraft to the VOR station ...

An overview of the VOR Station in aiding the aircraft navigation ...
An indicator, known as Horizontal Situational Indicator (HSI)
in cockpit is used to indicate the aircraft's bearing
with respect to the VOR station on ground.
To use the VOR station,
the pilots will need to tune the frequency of that station
based on the Aeronautical Chart.
However, as Science and Technology is playing prominent role in aviation,
the use of VOR is soon to be exiled.
The Global Positional System (GPS) is now taking over the
modern navigation on board of the aircraft.

For more information, click here for VOR,
here for HSI and here for DME.


Best wishes,
Cheers,
KeithK :)