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• Instrument taxi checks to be completed
• Always refer to the ERSA for specific aid
information and Limitations
RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 1
VOR OPERATIONS
Aim: To learn the principles behind the operation of the VOR navigation system.
Application:
- orientation (where am I?)
- supplementary navigation information
- IFR instrument approaches
Definitions:
VOR
- VHF Omni-directional Radio Range
Radial
- is a magnetic track emitted FROM a VOR station. There are 360 of them,
hence omni.
Principles: operates on frequencies between 112.1 and 117.9MHz
(VHF radio band - line of sight transmissions)
Ground Station
- transmits two VHF signals:
The reference phase signal, which is omni-directional (ie: same in all
directions)
The variable phase signal, which rotates uniformly at a rate of 1800RPM,
with its phase varying at a constant rate throughout the 360
Two signals transmitted are:
- in phase at magnetic North
- 90 out of phase at magnetic East
- 180 out of phase at South
- 270 out of phase at magnetic West
- 360 out of phase (back in phase) at magnetic North
RMIT Flight Training VOR Operations
Brief 19
RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 2
- morse code identifier signal is transmitted every 10sec at 1020MHz,
allowing positive identification of station.
- since VHF signals are line of sight, range depends upon altitude. Rated
coverage found in AIP GEN.
Altitude (ft) Range (Nm)
< 5000 60
5000 to 10000 90
10000 to 15000 120
15000 to 20000 150
> 20000 180
- details found in ERSA and ERC.
Airborne Equipment
- consists of three main components:
Antenna
- usually a twin blade, V-shaped antenna mounted on horizontal
tail
Reciever
- the reciever and associated control panel are used to tune
VOR and ILS stations. Usually combined with a VHF-COM set
Indicator
- Indication is regardless of HDG
Brief 19
RMIT Flight Training VOR Operations
RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 3
Considerations:
Limitations
- various limitations effect the readings of the VOR:
a) Vertical Polarization
- VOR stations emit radio waves, which are orientated horizontally. ie:
waves oscillate parallel to Earth’s surface. Detected by horizontal antenna.
When aircraft banks, antenna no longer horizontal and picks up errors.
b) Terrain Effect
- bearing information contained in VOR signals may be spurious signals
reflected from terrain. This interference causes oscillations on the CDI.
Rapid oscillations is scalloping. Slow oscillations known as course
bending.
c) Airborne Equipment
- bearing errors arising from imperfections in indicator.
d) Ground Site
- signal accuracy is affected by ground station equipment (transmitter,
aerial, etc).
e) Site Effect
- propagation of VHF signals is affected by physical obstacles or irregular
terrain features near the VOR site. Minimised using Doppler VOR.
f) Aggregate Error
- algebraic sum of all errors mentioned. Rarely exceeds 5
Station Passage
- passage overhead a VOR station is indicated by; needle becoming more
and more sensitive, and oscillating; red, unserviceable flag appearing; TO
flag becomes FROM flag; then needle becomes more stable as station
departs.
Brief 19
RMIT Flight Training VOR Operations
RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 4
Air Exercise:
T - Tune to VOR using reciever
I - Identify using Morse code
T - Test by rotating OBS through 360
Airmanship:
- Always use VOR within its rated coverage
- TIT checks before use
- Always use as a “command instrument.”
Brief 19
RMIT Flight Training VAODRFOInpteerracteiopntss
RMIT Flight Training Night Circuits
RMIT Mass Brief Night Circuits 1/2004 1
NIGHT CIRCUITS
Aim: To take-off safely, complete a circuit and land correctly at night.
Application: Night flying
Revision: Main instrument in our scan is the AH
Instrument Scans
- Selective radial scan.
Definitions:
Last Light
- is the End of Daylight (EoD) and is found in the AIP’s. Without a night
rating, must be on ground 10min beforehand.
Principles:
Aerodrome Lighting
- Taxiway lighting is either green centreline or blue sideline lights.
- Holding point is amber lighting.
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