TM 11-5840-281-12-1
1-15.
COMPONENT PRINCIPLES OF OPERATION. (CONT)
The position of the target on each display depends on the position of the time-base sweep at the instant an echo is
received. The position of the sweep will coincide with the scan angle of each antenna. By using the cursors as a
reference, the operator can tell whether or not the aircraft is on the proper glidepath and courseline. As in the ppi display,
the sweep ranges are the same with the exception that the range marks are vertical with range increasing to the right.
When the 5- or 10-mile range display Is selected, the time-base sweep is modified to expand the spacing of the range
marks nearer touchdown and thereby increase resolution of targets nearing touchdown.
HEIGHT FINDER DISPLAY
The height finder display is used during the precision approach operation to determine the altitude of an aircraft
approaching the runway. As in the dual beta display, the operator must select the mode of operation (NORM, 350EL,
600AZ or SIMULT) that best suits his or her needs.
The azimuth antenna is not used for height finder information. It continues to scan as in the precision approach
operation and the azimuth display remains on the lower half of the crt. During height finder operation, a different cursor
(called the height finder cursor) appears on the elevation display. The height finder cursor has been prealined, but it is
not fixed. It can be shifted to represent any line of constant altitude above the ground or mean sea level. Targets
appear on the elevation display the same as on the dual beta display. The operator shifts the height finder cursor so that
it intersects the target. At this point, the cursor represents a horizontal line drawn at the altitude of the target. The height
of the target is indicated in hundreds of feet on the ALTITUDE indicator. All range marks are the same as on the dual
beta display.
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