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Chapter 3 - VOR. VOR = VHF Omni-directional Radio Range. Operates in frequency range 108.00 MHz - 117.95 MHz Ranges of up to 200NM Based on a system of “radials” determined by the phase relationship between two signals Usually co-located with DME. VOR Frequencies. 108.00 – 111.95 MHz.
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VOR = VHF Omni-directional Radio Range • Operates in frequency range 108.00 MHz - 117.95 MHz • Ranges of up to 200NM • Based on a system of “radials” determined by the phase relationship between two signals • Usually co-located with DME
VOR Frequencies 108.00 – 111.95 MHz 112.00 – 117.95MHz (Even & odd decimals & evens/odds + 50kHz) e.g. 112.00 112.05 112.10 112.15 112.20 112.25 …. 117.95 (Even decimals & evens + 50kHz) e.g. 108.00 108.05 108.20 108.25 108.40 108.45 …. 111.95 ILS LLZ frequencies = Odd decimals, e.g. 108.10 108.15
Conventional VOR ground station FM – 30Hz Omni-directional AM - 30Hz Rotating Clockwise
Phase Aligned with Magnetic North = 0° Radial W = 270° Radial E = 090° Radial S = 180° Radial
The VOR polar diagram shows the phase difference and variable signal at the cardinal points. Radio Navigation – Chapter 3
Radials MN • QDR = 245° • QDM = 065° 065° Which radial is the aircraft situated on? 245°
Note the position of the CDI needle as the indication in the TO/FROM window changes. Radio Navigation – Chapter 4
Horizontal Situation Indicator (HSI). Radio Navigation – Chapter 4
The Radio Magnetic Indicator (RMI), combines the information from the radio navigation instruments with the directional information from the slaved directional gyro. Change over switch Radio Navigation – Chapter 4
Tracking a desired track of 080, joining on radial 260. Radio Navigation – Chapter 4
Limitations & Accuracy • Line of sight – Maximum Theoretical Range • MTR (NM) = 1.25 (Ht VOR + Ht A/C) E.g. Height of VOR = 100 ft Height of aircraft = 10 000 ft • MTR = 1.25 (100 + 10 000) = 1.25 (10 + 100) = 1.25 x 110 = 137.5 NM
Limitations & Accuracy- Designated Operational Coverage –DOC Height Distance Distance VOR 1 VOR 2
Site & Propagation Errors • Ground station error: Maximum permitted ± 1° • Site error (scalloping) • Caused by multi-path reflections • Average error ± 3° • Airborne equipment error – up to ± 3° • Pilotage error ± 2.5° • Overall error ± 5° Site Monitor
VOR Test Transmitters-VOT- • Used for testing airborne equipment • Transmits an omni-directional radial of 000°M • If 360 is set with the OBS, then a ‘FROM’ flag should show • If 180 is set, then a ‘TO’ flag should show
Questions • What is the frequency range for VOR stations? • 108.00MHz to 117.95MHz • Which of the following is a valid VOR frequency? • 118.25MHz • 111.10MHz • 109.15MHz • 115.10MHz
Questions • Which way does the polar diagram of a Doppler VOR rotate and at what frequency? • Anti-clockwise, 30Hz • If you select a bearing with the OBS that equates to a QDM, what will the flag indicate? TO
Questions • If you have 200° selected on the CDI with the needle centred and a ‘TO’ indication, which radial is the aircraft situated on? • R020° • The height of a VOR is 900ft amsl; the aircraft is at FL225. What is the MTR? • MTR = 1.25 (900 + 22500) = 1.25 (30 + 150) = 1.25 x 180 = 225 NM
Questions • In a CVOR transmission, which element uses FM? • The reference signal • Apart from line of site limitations, what else limits the range of a VOR? • D.O.C. (Designated Operational Coverage) • What causes “scalloping” of the signal? • Multi-path reflections and site errors
