TM 11-5840-281-12-1
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COMPONENT PRINCIPLES OF OPERATION. (CONT)
DUAL BETA DISPLAY
The dual beta display is used for precision approach operation when operating in NORM, 35EL, 60AZ, or SIMULT
modes. When the aircraft is within 6 to 8 miles from touchdown, the operator switches to a precision mode in order to
guide the aircraft in for a landing. The mode selected depends on the azimuth and elevation of the aircraft as it
approaches the runway. The 35 EL mode is used to provide wide vertical coverage for steep glidepaths and the 60AZ
mode provides wide horizontal coverage when required. The NORM mode provides 30 degrees in azimuth and 11
degrees in elevation coverage and the SIMULT mode provides 360 degrees in azimuth and 11 degrees in elevation
coverage. The SIMULT mode utilizes two control-indicators: master and slave. The master has a dual beta display for
precision approaches and the slave a ppi display for search operation.
The dual beta display is a double display (elevation and azimuth) on the crt at the same time. The upper display is
elevation and the lower is azimuth and represents the area scanned by each antenna (elevation and azimuth). The time-
base sweep extends horizontally across the crt and moves up and down in step with the scanning action of each antenna.
There is a curved line (cursor) on both the elevation and azimuth displays. The cursors have been preset during
alinement to represent the glidepath (best angle of descent) on the elevation display and the courseline (bearing of the
runway) on the azimuth display. When the radar set is installed on the left side (facing landing aircraft) of the runway,
the azimuth cursor will curve up. When installed on the right side, it will curve down.
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