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Climb-out/Enroute
3-7
NOTE
Logical Combination of Commanded Targets
A logical combination of commanded autopilot
targets means a combination of the altitude bug and
either the vertical speed bug or indicated airspeed
bug that can be achieved. For example, an altitude
bug that is above current aircraft altitude and a
positive vertical speed bug is a logical combination.
In contrast, an altitude bug that is above current
aircraft altitude and a negative vertical speed bug is
NOT a logical combination.
To perform a vertical speed-based altitude capture, set both the
VS bug and the ALT bug to the desired values and press both the
“VS” and “ALT” buttons on the autopilot control panel at the same
time. The system will light up the VS button in green and turn the
VS bug solid and light up the ALT button in cyan and turn the ALT
bug solid. Assuming a logical combination of vertical speed and
altitude were selected, the aircraft will immediately start a pitch
change to seek the target vertical speed. If a logical combination
wasn’t already preset, the VS bug will jump to +/- 500 fpm and
then the aircraft will climb or descend as required. If, during a
vertical speed-based altitude capture, either the target vertical
speed or altitude are changed to become an illogical combination,
the aircraft will fly the target vertical speed. A pilot throttle input
may be required to sustain the target vertical speed.
In the case of an indicated airspeed-based altitude capture, if a
logical combination of speed and altitude were not selected, the
aircraft will maintain it’s current state (will not initiate the climb or
descent). For example, if a target altitude was selected above
current aircraft altitude but an IAS target that was faster than
current aircraft IAS was also selected, the airplane will NOT
descend to pick up airspeed and then start the climb. Instead, it
will hold position. The same is true if a descent were attempted
at a speed slower than current aircraft speed.
The desired means of mode entry is via a simultaneous push of
both the speed and altitude buttons on the autopilot control panel.
However, an alternative technique is to press and hold one of the
buttons, and while that button is still depressed, press the other