VOR

Question 1

VOR stands for what and what’s the frequency range?

Answer 1

VHF omnidirectional range

111.975 MHz and 117.975

Question 2

Explain the basic operating principles of a VOR ground station, including the:
(a) reference phase signal;

Answer 2

Omni-directional signal, FM sign all modulated at 30Hz

Question 3

Explain the basic operating principles of a VOR ground station, including the:
(a) variable phase signal;

Answer 3

Directional signal rotated in azimuth uniformly at 1800rpm (at 30Hz)

Question 4

Explain the basic operating principles of a VOR ground station, including the: measurement of phase difference

Answer 4

The phase difference between the variable phase and the reference phase (when recovered from the carrier frequency at the aircraft receiver) provides position information of the aircraft relative to the VOR ground station.

Question 5

Discuss the factors affecting range and accuracy of VOR, including:
(a) maximum range, published route operating limitations

Answer 5

MRA - The minimum reception altitude is the lowest altitude the aircraft will receive sufficient VOR signal to navigate safely.

Terrain can block the VOR signal, meaning that the MRA can change along different sections of a route.

ROL - These can be found printed on enroute charts. They describe any limitations pertaining to aircraft flying along a particular segment of airway.

Question 6

What is the VORSEC chart?

Answer 6

The VOR/DME MRA Sector (or VORSEC) chart shows the higher of MRA or minimum altitude for terrain clearance for the VOR terminal area.

The sectors are divided up by radials and DME distances from the VOR.

Question 7

errors, particularly terrain effect error with “scalloping” and “radial bending” and roughness

Answer 7

Roughness -when they appear as relatively fast irregular course deviations

Scalloping -which appear as relatively smooth course deviations for short distances

Bending -which appear as slow deviations of the course, each deviation persisting for at least 2 NM

Such aberrations must be limited to +/- 3.5º. Unlike roughness and scalloping, bends can be unconsciously flown by pilots and hence are specified separately from roughness and scallops.