TM 55-1510-215-10
cause an immediate command V-bar deflection on the
FDI directing a turn to the new course.
CAUTION
The NAV mode is cancelled by depressing the NAV
The APPR mode of operation will
button. by selecting HDG (when in NAV coupled) or
continue to provide aircraft control
APPR modes, or deselecting FD.
without a valid VOR/LOC signal (NAV
flag in view).
CAUTION
(7) Back course (BACK CRS) mode.
Whenever a LOC or ILS frequency is selected, the BC
The NAV mode of operation will
mode may be activated by depressing the BC button on
continue to provide aircraft control
the mode controller, after selecting APPR. When in BC
without a valid VOR/LOC signal (NAV
mode and localizer capture occurs, the system will turn
flag in view).
and track outbound on the front course or inbound on
the back course. The BC mode reverses the LOC
(6) Approach (APPR/ARM, APPR/CPLD and
deviation signal and course datum to permit the FDI
GS CPLD) mode. The APPR mode provides visual roll
steering command display to operate on a steer-to rather
and pitch commands on the FDI command V-bar to
than a steer-from basis on the reverse course. BACK
capture and track precision ILS beams. or non-precision
CRS will be displayed on the mode annunciator panel.
VOR radials. Lateral and vertical deviation is monitored
on the pilot's HSI.
(8) Go-around mode. The go-around mode is
The automatic APPR capture function will be
primarily designed to assist in establishing the proper
immediately armed. APPR/ARM will be displayed on the
pitch attitude under missed approach conditions.
mode annunciator panel. In APPR/ARM mode, prior to
However. it can also be used to establish a proper climb
capture, the heading select mode is retained.
attitude during takeoff. The go-around switch is located
on the left power lever. Depression of the go-around
The LOC beam or VOR capture point will vary,
switch cancels all flight director modes and, if the
depending on angle of intercept and rate of change of
autopilot is engaged, disengages the autopilot. A wings-
deviation indication. Upon capture, a bank command
level and 8-degree pitch-up command is displayed by
will be introduced on the FDI, the existing heading mode
the FDl. GO AROUND will be displayed on the mode
will be cancelled and APPR/ CPLD will be displayed on
annunciator panel.
the mode annunciator panel. The pilot may manually
bank the aircraft to satisfy the command display, which
Go-around is cancelled by use of vertical trim,
will command a rollout to level flight when the aircraft is
altitude hold mode, control wheel steering or by turning
on course. Automatic crosswind compensation will
off the flight director.
provide precise tracking. VOR/LOC deviation is shown
on the pilot's HSI. Actual crab angle will be indicated by
(9) Altitude select (ALT ARM) mode. This
offset of the course arrow from the lubber line.
mode allows for selection of an altitude, and upon
approaching that altitude obtain an automatic visual pitch
If the autopilot is engaged during operation in the
command on the FDI, to capture and hold this pre-
APPR mode, automatic steering response will follow the
selected altitude. As the aircraft reaches the selected
command display on the FDI.
altitude, ALT HOLD will automatically engage. ALT
The glideslope mode is armed for automatic capture
HOLD will display on the mode annunciator panel and
if LOC front course capture has occurred. Automatic
ALT ARM display will disappear. If the autopilot is
glideslope capture occurs as the aircraft passes through
engaged the system will automatically capture and hold
the glide path from above or below. Upon interception of
the selected altitude.
the glideslope, capture occurs and GS CPLD is
ALT ARM is disengaged by depressing the ALT
displayed on the mode annunciator panel. A capture
ARM button, by engaging ALT HOLD, by GS capture, or
pitch command is displayed by the command V-bar.
deselecting FD.
The pilot or autopilot (if engaged) controls the aircraft to
(10) Altitude hold (ALT HOLD) mode. This
satisfy the command V-bar. Upon GS capture, the ALT
mode will cause a computed visual pitch command on
HOLD mode (if active) is cancelled. However, ALT
the FDI command bars to hold the aircraft at the
HOLD may be manually reselected to maintain altitude
pressure altitude existing at the time the mode was
upon reaching MDA if visual contact is not established.
activated. The mode is activated either automatically by
APPR/CPLD mod is cancelled by selection of HDG.
the ALT ARM function, or manually by depressing the
NAV, or go-around modes or by deselecting FD or
ALT button on the mode controller. If the autopilot is
APPR.
engaged, it will automatically hold the aircraft at that
altitude.
3-30 Change 5
