VOR Flashcards
What does VOR stand for, and what is it used for?
VHF omnidirectional range.
It allows A/C with VHF nav receiver and appropriate display equipment to locate an A/C and/or to fly along a desired track using the network of ground based systems.
Where is variation applied with VORs?
As signal is transmitted from the VOR, the variation is applied at the station.
What is the frequency band for VOR?
108mHz to 117.95mHz.
What are the ILS frequencies?
As VOR shares freq with ILS,
ILS is 108-112mHz but the odd no.s
What are the 2 types of VOR and what are the freq bands?
Enroute: 112 - 117.95mHz
Terminal: (TVOR): 108-112mHz
Bearings from a VOR are known as?
Radials.
VORs can be used to transmit ATIS info.
What is a conventional VOR?
A VOR which uses FM as a ref phase and AM as the variable phase. The rotation of the AM signal is at 1800RPM (30Hz) CW.
Signal is strongest when pointing straight at the A/C, thus weaker as A/C moves away from radial.
What is a Doppler VOR?
Doppler VOR is used to provide a more accurate bearing because as you move away from a radial in a CVOR, the signal becomes weaker.
Doppler VOR adopts the Doppler system to provide more accurate bearings and uses AM as it’s reference phase and FM as the variable phase. AM phases is transmitted via a rotor spinning anti-CW.
DVOR spins anti-CW so the aircraft receiver can separate it from the CVOR and distinguish which is the signal is the reference phase.
Why is the DVOR preferred?
• because more accurate
• less susceptible to siting areas (i.e. Uses less space as
smaller equipment unit)
How does the VOR self check?
A pick up antenna is placed on a given radial and this will sense drift. The system self checks that:
- the bearing info remains within +/- 1˚
- signal strength no less than 85%
- the monitor itself is working
If any of the above is not satisfied then the monitoring circuits will remove the ident or shut down the transmitter
VOR has a cone of confusion, what is the formula for a VOR and what is the ICAO requirement for the COC?
Diameter of COC = (height above the NDB x tan 50x 2)÷ 6080ft/nm
ICAO requires the COC to be no > 50˚ either side.
If want radius then do not ‘x2’
What would happen if a VOR RMI fails?
The needle will still point at the VOR (QDR given) as the signal comes from the VOR. The only difference is you cannot reply on the compass card to tell you the RB to the VOR as the RMI now acts like a fixed card RBI.
What equipment is required to use the VOR?
A/C equipment will need to comprise of (the same as an NDB unit):
- An antenna
- A VOR receiver and control unit
- An indicator (e.g RMI, OBI or HSI)
What is scalloping?
This is when, due to refraction and reflection of a signal, the signal oscillates on between both side of a radial.
The autopilot may disconnect if it’s not capable of following the rapidly changing flight path.
Scalloping is normally for a short period of time therefore select reasonable HDG and wait for deflections to stop.
ICAO annex 10 has a requirement that VORs must be received how many ˚ above the horizon?
40˚ above the horizon, hence the cone of confusion is measured 50˚ on either side of the vertical antenna.
