User's Manual

Model 1150A DVOR
3-52 Rev. - November, 2008
This document contains proprietary information and such information may not be disclosed
to others for any purposes without written permission from SELEX Sistemi Integrati Inc.
3.6.8.3.2 VOR Ground Check Data Screen
The 1150A DVOR provides the ability to perform a ground check. The Ground Check Data Screen is shown in
Figure 3-47. This screen is used to initiate a VOR Ground Check and display of the data from the ground check.
SAFETY CRITICAL NOTE
The DVOR Automatic Ground Check changes the radiated signal and a NOTAM SHALL
be issued to notify that the DVOR is not in service during this test. Per ICAO State letters,
conducting this type of DVOR ground check is an HMI event. (HMI = Hazardously
Misleading Information). When HMI is intentionally produced, ICAO requires that the
NOTAM text contain information that conveys to the flight crew that the signals are not only
“out of service”, but may be unsafe to use, even though they may appear normal.
The monitor controls the RS422 data to the Commutator Control CCA to rotate the position of the DVOR from the
normal position in 22.5 degree increments. At each of these positions the Monitor measures the signal and computes
the error for that position. When all 16 positions have been measured, a Fourier Analysis is computed and the
resulting errors are displayed. The outputs of the Fourier analysis, (FFT Errors), are Duantal, Quadrantal, Octantal
and Bias errors. Duantal error has one maximum and one minimum in 360 degrees around the DVOR. Similarly
Quadrantal error has two peaks and two minimums around the 360 degrees. The Octantal Error has four peaks and
four minimums around the DVOR. The Bias error is the average azimuth shift of the DVOR station.
By selecting one of the graph options the data appears on the graph along with the optional legend for that data set.
Pressing the advanced button will display the Advanced Ground Check screen which allows viewing a larger graph,
printing and copying the graph to a file.
The Station error is a plot of the errors from the data in the Station Error column of data. The FFT sum is the
summation of the FFT errors components. The FFT sum plot should look like the Station error plot for a normal
station.
Figure 3-47 Ground Check Data Screen