Model 560XL Appendix – Systems Description
Textron Aviation Citation 560XL 190-02313-03 Rev. 8
A-12
Underspeed Protection (Optional)
Underspeed Protection (USP) is an optional feature that provides a level of protection against the aircraft
stalling while the autopilot is engaged. If the autopilot is not engaged, Underspeed Protection will not
activate.
WARNING
UNDERSPEED PROTECTION RELIES ON STICK SHAKER ACTIVATION, AND
MAY NOT ACTIVATE AT SUFFICIENT AIRSPEED TO PREVENT
AERODYNAMIC STALL WHEN ABOVE 18,000 FT.
Installation of the Underspeed Protection option can be determined by viewing the Initialization page on
either GTC. If Underspeed Protection is installed, the text WITH UNDERSPEED PROTECTION will be
clearly displayed near the aircraft type.
When the stick shakers activate, USP will result in the following:
“AIRSPEED” aural alert.
UNDERSPEED PROT ACTIVE CAS message.
MINSPD visual alert displayed above the airspeed tape.
Existing Flight Director mode annunciations will turn white.
At stick shaker activation plus one second, USP commands the nose to lower and maintains wings level.
The pitch attitude is decreased to establish a one knot/second acceleration while shaker is activated.
When the stick shakers turn off, USP will pitch to maintain an airspeed two knots above the shaker OFF
speed. When the flight crew adds power to recover, if sufficient energy is available the airplane will
transition back to the original Flight Director command. Recovery should be initiated as soon as possible.
Underspeed protection is available only if the autopilot is engaged.
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