VHF OmniRange (VOR) Flashcards
What does VOR stand for?
VHF OmniRange
The aviation industry uses three navigation systems that operate in VHF frequency band:
VOR, Localizer, and Marker Beacons
The VOR operates on what frequencies?
108.00MHz to 117.95MHz
A receiver on the aircraft receives the energy and demodulates the signal. That results in what?
A 30Hz sine wave called the Variable Signal
What is the varying energy transmitted as from a VOR station?
a Variable Signal
For the aircraft to determine the field direction:
the transmitted signal is Amplitude Modulated with a reference signal of varying frequency centered on 9.96KHz
What do Radials do?
Give imaginary lines on the ground that radiate in all directions from the VOR station
What depicts the VOR radials on Sectional Charts?
Compass Roses
What is the short range navigation system used throughout most of the world?
VOR
A well designed and installed VOR receiver can be accurate to within:
One compass degree
What does CDI stand for?
Course Directing Indicator
What does a CDI do?
Allows pilots to select and determine their relationship to the selected course
What does OBS stand for?
Omni Bearing Selector
What does the pilot use an OBS for?
to set the course
What was one of the early ways to indicate VOR bearings?
on a Radio Magnetic Indicator (RMI)
What does the RMI show?
the heading on the compass card and the bearing to the VOR station
What does RMI not have?
A CDI needle
Each dot on the CDI represents:
30 micro Amps and two degrees of course error
How else can VOR information be displayed?
on a Horizontal Situation Indicator (HSI)
Also known as a
Pictorial Navigation Indicator (PNI)
VHF navigation receivers are almost identical in appearance to VHF communication receivers. A key difference is that:
a Navigation Transceiver does not have a squelch control. They do have an extra output for the navigation signal and an identification filter
How are VOR stations identified?
a 1020 Hz Morse Code signal which makes the voice transmissions more understandable
What is the heart of the VOR system?
the receiver
What is a Localizer or LOC?
a system used to guide the aircraft down to the runway and is part of the ILS
What does ILS stand far?
Instrument Landing System
What is commonly used in light/smaller aircraft?
a transceiver. And in some systems is combined with VHF comm. Transceiver
What do many large aircraft use?
an Integrated Flight Management System that includes both navigation and communication functions
How many antennas does the VHF Nav system use?
two antennas typically mounted one to each side of the airframe
What type of aircraft is the Whip style antenna used on?
light or slower flying aircraft that have less of a drag loading on the antenna
What is the Whip style antenna normally mounted on?
the vertical stabilizer
The Towel Bar style antenna is mounted where?
to either sides of the vertical stabilizer or fuselage
What style type antenna is used on higher speed aircraft?
The V style
It has a larger footprint and more aerodynamic shape to reduce drag
Where is the optimum placement of the V antenna?
forward on top of the fuselage
What are Blade style antennas normally used for?
high speed aircraft and mounted to each side of the vertical stabilizer
What type of aircraft are Blade style antennas found on?
business type and transport category aircraft
VOR testing must be done how often and by whom are they usually performed and logged by?
within the last 30 days
usually performed and logged by the pilot
What does VOT mean?
VOR Test Facility
VOR test readings should not be greater than:
+/- 4 degrees from the desired heading
+/- 6 degrees is check is done in the air
If the needle moves erratically, darting left and right, this typically is due to:
an internal component (a resolver) that turns with the OBS
Anytime a VOR ground station is being worked on, what happens?
the technician turns off the audio ident which warns the pilot not to use the station for navigation
If the VOR needle is swinging side to side slowly it is called:
course bends
If the VOR needle is swinging side to side fast it is called:
course scalloping
What does NOTAM stand for?
Notice to Airmen
a notice stating that certain radials of a VOR are unusable
What causes both needles to move together like windshield wipers?
propeller or rotor modulation
What is propeller or rotor modulation?
the signal from the ground station passed thru the propeller and is “chopped” in the spinning blades
For propeller driven aircraft, be sure that the VOR antenna is mounted:
in the location suggested by the airframe manufacturer
Rotor modulation in helicopters is more troublesome because:
the rotor blades cover a larger area.
this problem is known and filters in radios are provided and intended for helicopter operation
