Note: This material is for reference purposes only.

VOR Testing

By: Jesse Landeryou

Ramp Testing


Test Frequencies
  • With Nav-401 test box- 108.00 MHz
  • Without test box- 114.800 MHz

Nav-401L Test Box

The Nav-401 test box is a unit that provides testing and calibration of VOR, LOC, G/S, MKR and COMM systems. It has a self contained signal generator for all the system previous mentioned. VOR sensitivity and audio functions can be tested using the Nav-401L.


nav401l.jpg
Figure 1. NAV-401 Test Box


Procedure w/ Test Box

  • To and From Indication
  1. Set the VOR bearing to 0 degrees on the test box and set the indicator to 0 degrees also.
  2. Verify needle centering is within +/- 3 degrees.
  3. Turn the OBS knob on the indicator until the TO/FROM indicator begins to change direction.
  4. Once TO/FROM flag changes continue rotating the OBS knob until the flag changes again, verifying that the TO/FROM flags are operational.

  • Needle Deflection/Needle Centering
  1. Set the VOR bearing to 0 degrees on the test box and the indicator course to 0 degrees.
  2. Note the deviation.
  3. Repeat steps 1 and 2 for every 30 degrees up to 360 degrees.
  4. Center the needle on the indicator and set +10 degrees for VOR bearing.
  5. Record percentage of deflection.
  6. Repeat steps 4 and 5 with the VOR bearing set to -10 degrees.

  • Audio/Sensitivity

  1. Set the VOR frequency to 108.00 MHz and set the test mode switch on the test box to VOR XTL.

  2. Set the VOR bearing to 0 degrees and set the indicator to 5 degrees for half scale deflection.
  3. Verify signal reception and that the flag is out of view.
  4. Increase the output attenuation on the test box until flag comes into view.
  5. On the test box set the MOD selector to 400 Hz.
  6. With the Nav audio on verify that a 400 Hz tone is received in the aircraft.
  7. Repeat steps 5 and 6 with the MOD selector set to 1020 Hz.

  • Flag Indication

  1. Set indicator to half scale deflection (5 degrees).
  2. Remove the 9960 Hz reference signal.
  3. Verify flag comes into view.
  4. Remove the 30 Hz variable signal.
  5. Verify flag comes into view.


Set the VOR frequency to 108.00 MHz and set the test mode switch on the test box to VOR XTL.

  1. Set the VOR frequency to 114.80 MHz to tune into YYC VOT.
  2. A morse code ident should be heard.
  3. Set the indicator to 180 degrees, the TO flag should appear.
  4. Set the indicator to 0 degrees, the FROM flag should appear.

Bench Testing


Procedure

All parameters are the same for bench testing as ramp testing except various different frequencies between 108.00-117.975 should be test for sensitivity.




References:
  1. http://www.austrocontrol.at/Images/TASKCARD%2040.1%20Avionic%20Test%20Procedure_tcm586-58943.pdf
  2. http://www.austrocontrol.at/Images/TASKCARD%2040.1%20Avionic%20Test%20Procedure_tcm586-58943.pdf

  3. http://en.wikipedia.org/wiki/VHF_omnidirectional_range