03 VOR

RMIT Aerospace Engineering

VORVery High Frequency

Omni-directional Radio range

Check the courseguide for references


Let’s look at The principles of VOR operation Identify the component parts Explain the operation of VOR to block

diagram Describe the operation of controls and

interpretation of indicators Identify specialised teast equipment to test

VOR


VOR system

the ground transmitting equipment

the airborne receiving equipment

the instrumentation used to present VOR deviation information to flight crews.


How VOR works?

– The VOR ground station transmits two VHF radio signals:

– The reference phase, which is omni-directional

– Beamed emission that changes phase as it rotates clockwise like beam of a light house.


Light House analogy

– Imagining a light house emits an omnidirectional flash of light every time the beam is pointing due north. If the speed of rotation is known, and if a distant observer could record the time interval between seeing omni-directional flash and seeing the beam, bearing of the light house can be calculated.


VOR purposes:

– Orientation and position fixing;– Tracking to or from a VOR ground station;– holding (for delaying or manoeuvring

action); and– instrument approaches to land


VOR –Very High FrequencyOmni-directional Radio range

Comprising of a ground based transmitters and an airborne installation

Automatically and continuously provides the operator with the magnetic bearing of the aircraft from the beacon

VOR ground station transmits on a specific frequency between 108.00 and 117.95 MHz.[50 kHz channels]

Short range navigation system


System


Two signals from ground station


Bearing to transmitting station


Relative bearing


VOR - Radials

VOR ground transmitter radiates signals in all directions

360 different tracks away from the VOR are used each separated by 1 deg called radials

Short range navigation systemVHF range in nm = (1.5 x altitude in feet)


The aerial of the VOR aircraft receiver picks up the signals, whose phase difference (between the wave peaks) is measured, this difference depending on the bearing of the aeroplane from the ground station.


VOR Signals

The demodulated output of the receiver contains:– 1020 Hz Audio signal– a Variable phase 30 Hz signal– a Reference 30 Hz signal in the form of

frequency modulation on a 9960 Hz.


VOR components

the antenna the receiver the control unit indicator/s.



Antenna


ReceiverThe receiver contains all the circuits necessary to receive, decode and provide outputs of aircraft bearing information from transmitted VOR signal.In addition, the receiver contains self-monitoring circuits which validate the signals received and the accuracy of the bearing information sent to the indicator.Most commercial aircraft carry two complete VOR/ILS receivers.Typically, receivers are black box units mounted in the aircraft radio equipment racks.


Control

The control unit provides all necessary control of frequency selection for VOR and ILS operation.


HIS Horizontal situation indicator


VOR Indicators

The output of VOR receiver:– Audio to headsets[1020 Hz]– Bearing information– Deviation from selected radial– TO/FROM signal– Flag or warning signal

Manual VOR requires the pilot to select a particular radial on which he wants to position his aircraft. The actual radial on which the aircraft is flying is compared with the desired radial.


Pilot selects 75 degree (magnetic) this is what he would see on the indicator


VOR block diagram


VOR controller


Monitoring and self test


Test equipmentVOR ramp test set

Used for installed testing


VOR ramp test setup


Questions From a pilot’s viewpoint, how does ADF differ from

VOR?

List the airborne components of a VOR system.

What is meant by the cone of confusion?

Explain the function of the TO/FROM flags in the HSI.

True or false? VOR ramp test sets must be connected to mains power. Explain you answer.


Reference

The Air Pilot’s Manual – Radio Navigation and Instrument Flying; Vol 5, Trevor Thom

Documents

03 VOR