TM 55-1510-222-10
Figure 3-13. Altitude Select Controller (AL-800)
(2) Altitude selector knob. Selects desired
altitude.
b. Altitude preselect. The altitude is selected by
turning the selector knob until the altitude display reads
the desired value. No further action is taken on the
controller. To initiate altitude preselect, the ALTSEL
button is selected on the flight director controller. The
pilot must initiate a maneuver to fly toward the
preselected altitude. Any of the following pitch modes
may be engaged: Pitch Hold, Airspeed Hold or Vertical
Speed Hold. Upon initiation of altitude preselect
capture,
the
previously
selected
pitch
mode
is
automatically reset.
3-22. RADIO ALTIMETER INDICATOR (RA-315).
a. Description. The radio altimeter indicator
(FIG. 3-14) displays radio altitude information from
2500 feet to touchdown with an expanded linear scale
below 500 feet.
b. Controls/Indicators and Functions.
(1) DH annunciator. Annunciator illuminates
to alert pilot that aircraft is at or below
selected DH.
(2) Decision height bug. Manually set by
knob to establish DH.
(3) Failure warning flag. When visible,
indicates that system information is
unreliable.
(4) Altitude pointer. Points to dial reading for
current radio altitude from 0 to '2500 feet.
(5) Decision height set knob. Used to
manually set DH.
(6) TEST pushbutton. Pressed to check
indicator R/T unit and flag operation.
Operating the test button causes the flag to come
into view and altitude pointer to indicate approximately
100 feet. Release of button causes pointer to return to
existing altitude, and flag to retract.
3-28
