Frequencies in use for VOR and ILS?
VORs transmit in the VHF frequency band, between 108.00–117.975 MHz.
Between 108.00–111.975 MHz, the instrument landing system (ILS) uses frequencies with an ODD number after the decimal point.
VORs include?
- Conventional VOR (CVOR).
- Doppler VOR (DVOR).
- En-route VOR. - Use for IFR trafic along ATS routes at higher altitude.
- Terminal VOR (TVOR). - Low powered used for ILS. used as part of approach and departure procedures. Usually 108-112MHz
- Test VOR (VOT). - V low power to test AC equioment.
CVOR
Clockwise 30Hz
Contains moving parts.
DVOR
- 30Hz variphase trasnmitted from a number of antennas
- 30Hz refernece signal from a dipole.
- FM vari-phase signal rotates anti-clockwise at 30Hz.
- no moving parts.
Operating principle of a VOR?
VORs transmit reference (FM) and variable phase navigation (AM) signals. The phase difference between the two signals determines the magnetic bearing (radial) from the VOR.
Produces a 1800rpm rotating cardiod limacon with one null representing the phase differnece.
VOR Identification?
VORs are identified using a three letter Morse code and/or plain voice communications. Every 10 seconds at 1020Hz
Ground monitoring?
VORs have an automatic ground monitoring station. Failure to remain within accuracy limits will remove the transmitted navigation and identification signals.
Ground transmitter error shall be within +/-2 degrees.
When may the ground transmittor be shut down?
The ground transmitter error shall be within +/- 2°.
- However, the transmitter should transmit a warning to the self-monitoring control unit, and either remove the identification and navigation components from the carrier wave if:
- The bearing information transmitted by the VOR changes by > 1°
- The modulated components voltage level reduces by 15%
The following may also contribute to the accuracy at the receiver:
- Propagation error (disturbance of the signal as it travels)
- Airborne equipment error.
ATIS frequency?
ATIS (automatic terminal information service) information is often transmitted on a VOR frequency.”
Airborne equipment includes:
- Antenna - 1/4 wavelength horizontally polarised, often on the tailfin.
- VHF NAV receiver.
- Cockpit display indicator.
Where can VOR info be found?
A Course Deviation Indicator (CDI), Horizontal Situation Indicator (HSI) and/or Radio Magnetic Indicator (RMI) (feat. moving compass card) is used to determine VOR information.
Maximum angular displacement?
The angular displacement from a selected radial is read on a CDI or HSI. The maximum displacement is ±10°.
Flags?
The TO/FROM flags on the CDI/HSI are used to indicate the aircraft position relative to the VOR, considering the selected radial.
An RMI is used to indicate a radial from a VOR:
Arrow head and tail?
Radial FROM (QDR) – at the tail of the needle.
TO (QDM) – at the point of the needle.
VOR uses?
A VOR is used for en-route navigation, procedural turns, holding patterns and instrument approach procedures, along selected radials.
VOR tracking accuracy must be within half-scale deflection (±5°), taking wind effect into account.”
VOR Scalloping?
Scalloping is a fluctuation of the navigation signal and occurs when signals are reflected by terrain, buildings or vehicles.”
Scalloping is a fucntion of VHF frequencies.
VOR/DME?
DME ident frequency 1350Hz, with same letters as VOR transmitted after every 3 VOR idents. Higher pitch.
VOR/DME in terminal area?
In a terminal area VOR and DME trasnmitters must not be mre theen 100ft apart
All other VOR types must be within 2000ft (600m)
A DME more than 2000ft but within 6nm may be given a similar ident to VOR but last better will be a zulu.
OBI?
Omni bearing indicator / CDI. Used to track radials onto and away from bearings.
Not slaved to the compass.
Max +/- 10 degrees. Each dot is 2 degrees.
HSI
Compass rose with an OBI in the middle.
To/from flags do not relfect aircraft heading but instead point with respect to the beacon and the course selected to it.
VOR cone of confusion?
Tan(50) for VOR
Tan(40) for NDB
TSE?
VOR total system error. The accuracy of the VOR system is 5 degrees.
In order to enter a VOR into an RNAV route should be in range when?
Not when entered, but should be in range when used.
Issues with using VORs outside the desired range?
May lead to interfering signals from other VORs.
