RADIO ALTITUDE INDICATORS
• RADIO ALTITUDE DIGITAL READOUT
A digital readout for radio altitude is displayed for altitudes less then
2500 ft. If the radio altitude tape is displayed, the digital readout is
incorporated into the tape pointer. The radio altitude information is
removed from view above 2500 ft AGL. If the tape is not present, the
digital readout is displayed below the triple tachometer display. Brown
shading of the RA tape is present below zero (0) ft. Gray shading is
present above zero (0) ft.
• RADIO ALTITUDE SOURCE SELECTION
The PFD automatically selects the source for the radio altitude data.
Each PFD displays radio altitude data from the on-side MAU, if that
data is valid. If the on-side radio altitude data is not valid, the radio
altitude data come from the off-side MAU.
NOTE
When one radio altimeter is installed, it is wired to both
MAU. When two radio altimeters are installed, each is
wired to the on-side MAU.
• RADIO ALTITUDE SOURCE ANNUNCIATOR
When two radio altimeters are installed and a PFD is displaying data
from the off-side radio altitude sensor, the sensor is annunciated as
either RAD1 or RAD2.
• RADIO ALTITUDE MISCOMPARE
When a radio altitude miscompare is detected by the monitoring
software, a RAD2 to RAD to RAD2 annunciator flashes for the first 6
seconds and then shows RAD steadily above the radio altitude tape.
Once the miscompare is no longer detected, the annunciator is
removed. The miscompare function is performed whether there are one
or two radio altimeters installed. When only one radio altimeter is
installed, the miscompare function compares the same data from the
two MAU.
CAUTION
IF RADIO ALTITUDE INFORMATION IS LOST, A
RAD
ANNUNCIATOR REPLACES THE RADIO ALTITUDE DIGITAL
READOUT IN THE CENTER OF THE RADIO ALTITUDE TAPE.
WARNING
THE RADIO ALTITUDE DISPLAY DURING THE RADIO ALTITUDE
TEST PROCEDURE IS RELIABLE.
THE RADIO ALTITUDE MEASURES ABSOLUTE ALTITUDE
ABOVE TERRAIN DIRECTLY BENEATH THE HELICOPTER. IT
DOES NOT MEASURE ABSOLUTE ALTITUDE ABOVE TERRAIN
IN FRONT OF THE HELICOPTER.
LOW HEIGHT ALERT DISPLAY
The Low Height Alert Display is a shaded brown area outlined in amber
displayed on the barometric altimeter scale when RAD ALT is less than 550
ft AGL.
The top amber line of the area represents the ground level.
The indicator is based on the on-side Radio Altimeter data.