6-3
Limitations and Performance
GENERAL PERFORMANCE
– CIRRUS AIRCRAFT
The input forces required for roll-axis control surface actuation
are demonstrably light and it is not difficult to force the servo (roll
trim spring cartridge) to drive to its limit. By design, reaching the
physical limit causes a micro-switch to be tripped which
effectively decouples the autopilot commands from the flight
control surfaces.
Pilot-induced inputs on the system including yoke input, rudder
input, p-factor, fuel imbalance, airspeed and general aircraft trim
alignment can all contribute to this condition.
In the event the DFC system believes the roll-axis servo limit has
been reached, a yellow
“
SERVO LIMIT
” text message is
displayed on the PFD.
WARNING
Reaching Servo Limits Can Cause
Uncommanded Rolls
If the roll servo limit is reached, the autopilot may
stop following lateral commands. This could appear
to the pilot as an uncommanded roll or a failure to
follow the commanded lateral target
.
As a result, it is highly recommended that a pilot avoid making
flight control inputs while in coupled autopilot mode operations
aside from minor rudder input to maintain coordinated flight.
Moderate rudder or any roll input may result in an inability of the
DFC90 autopilot to track the commanded targets.
It is also important to note that in aircraft equipped with only roll
trim motors (no roll servo), the maximum aileron deflection is ½
the total possible aileron throw.
Change 3
Limitations and Performance 6-5