DME & VOR Flashcards
What is DME?
Distance Measuring Equipment
How does DME Work?
Distance is calculated by measuring the elapsed time between the transmission and reception of a pulse pair.
Why are two DME frequencies used?
To avoid aircraft interrogating each other.
What waveband does DME operate in?
UHF
DME is accurate to within…
1nm
What is the major error associated with DME?
Slant Error
What are some uses for DME?
Co-location with VOR to provide range and bearing
Provides positive ranges for aircraft flying the same track on the same DME
Co-location with precision approach aid to provide range from touchdown
Enhances holding pattern accuracy
Accurate area Navigation if coupled with a suitable computer
Military use for Tanking
What is a VOR?
VHF Omni-Directional Radio Range
Describe a VOR
System that automatically and continuously provides an aircraft with an accurate magnetic bearing from a beacon, using the principle ‘bearing by phase comparison’.
What two signals does a VOR use?
Reference Signal - transmitted Omni-directionally.
Variable Signal -Transmitted by a circular array of aerials around the Reference Signal antenna, simulating a revolving antenna.
They are transmitted simultaneously but the simulated rotation causes a phase difference.
What is the dark spot of a VOR known as?
Cone of Confusion or
Cone of Silence
What is OBS?
Omni-Bearing Selector
Describe an Earlier Form OBS
Displays only VOR information.
Shows deflection left or right of pre-selected QDM.
Shows whether the aircraft is generally heading to or from the beacon.
Describe a Later Form OBS
Shows all the same information as earlier form, but for the purposes of the Instrument Landing System as well as VOR.
Includes a Fail Flag when no signal is being received.
When flying inbound and outbound to a VOR, when are you flying the radial?
When flying inbound to the beacon, the magnetic course will be the reciprocal of the radial.
When flying outbound from the beacon, the magnetic course will be the same as the radial.
What is VOR limited to?
Line of Sight
What are some VOR Errors?
Site Errors
Propagation Errors
Equipment Errors
Interference Errors
What is a Site Error of a VOR?
Poor beacon siting can produce reflected signals from high ground and buildings that can cause bearing errors.
What is the Propagation Error of a VOR?
Caused by uneven propagation over long distance or irregular terrain.
What is the Equipment Error of a VOR?
Caused by incorrect tuning or calibration.
What is the Interference Error of a VOR?
The narrow operating bands limits the number of channels available, and high flying aircraft run the risk of receiving signals from more than one VOR on the same frequency when at or near the protected range of a beacon.
What are some uses for VOR?
Homing to a Station
Maintaining track along an airway centreline
Obtaining a Position line
Flying Instrument Approaches
Obtaining a fix with two or more VORs
Broadcast ATIS and other information
What is the maximum allowed aggregate errors of VOR?
A total of +/- 5 Degrees
Does the range of reliable VOR operation increase or decrease with height?
Reliable VOR Range increases with Height
