Figure 9-3.-Mode I landing sequence.
to fuel or safety status to determine landing priorities.
It is here that the aircraft is assigned a data link
channel for automatic landing. The pilot is cleared
for approach when the LDG CHK indicator
illuminates on the discrete message indicator. The
pilot prepares for landing by ensuring the APC is in
automatic and that all the other subsystems are on and
As the aircraft continues its approach and passes
through the acquisition radar window, the LCC radar
acquires the aircraft, and the ACL RDY lamp lights on
the discrete message indicator. The acquisition radar
window is located approximately 4 miles astern of the
ship. When the ACL RDY lamp lights, the CATCC
system begins sending vertical and lateral error
signals, which represent the actual displacement of
the aircraft from the approach path. These signals are
converted to a display on the VGI. At this time, the
pilot requests the approach mode desiredMode I for
fully automatic touchdown.
The LCC system transmits a COUPLE discrete
signal to the aircraft. This signal indicates that pitch
and bank commands may be coupled to the autopilot.
At this time, the pilot ensures that the APC is
engaged; the landing gear, flaps, and speed brakes are
extended; and the aircraft is near the approach speed
with wings level. With the autopilot turned ON and in
AUTO, the pilot then switches the ACL/OFF/PCD
switch to ACL. This couples the data link to the
autopilot. The pilot will then verbally acknowledge
engagement of the autopilot. The ground command
controller then sends the CMD CONT discrete signal
to the aircraft. At this time, the system begins sending
pitch and bank command signals to the aircraft. As
the aircraft continues down the approach path, and at
approximately 12.5 seconds from touchdown, the 10
SEC discrete message will be sent. This message
informs the pilot that deck motion compensation is
being added to the glide-path commands.
Compensation is in the form of a slight increase or
decrease in aircraft attitude as needed to adjust for the
movement of the touchdown point in response to the
carriers movement. At 1.5 seconds from touchdown,
the landing system freezes the pitch and bank
commands, and the autopilot holds the aircraft
attitude until touchdown.
The automatic carrier landing system has many
provisions to protect the pilot and the aircraft from
human errors or equipment failures. The monitor link
uses the ILS AN/SPN-41 to independently check the
LCCS flight path progress. This allows the pilot to
monitor position in relation to the safe glide path.
When the aircraft exceeds the Mode I flight path