FLIGHT GUIDANCE
HONEYWELL PRIMUS 1000 CONTROL DISPLAY SYSTEM
The Honeywell Primus 1000 Control Display System is an autopilot/flight director and electronic flight
instrument system (EFIS) which is integrated into one complete automatic flight control system. The
primary component of the system is the IC-615 Integrated Avionics Computer (IAC) which contains
the symbol generator, the flight director, and the autopilot computer (autopilot computer in pilot’s IC-
615 only). The entire system is comprised of the flight director, automatic pilot, pilot's and copilot’s
electronic attitude director indicators (ADIs) and electronic horizontal situation indicators (EHSI)
located in one single primary flight display (PFD) for each pilot, dual air data computers with
associated outputs, autopilot controller, altitude alert and altitude preselect, touch control steering,
and the autopilot servos. The air data system provides pressure altitude, true airspeed and
overspeed warning. The system may be flown manually or automatically.
The IC-615s are cooled by individual cooling fans. Failure of the fan(s) are annunciated in the upper
left hand corner of the multi-function display (IC1 FAN or IC2 FAN). Continued operation of the IC-
600s without a fan may produce even greater heat (especially on the ground or in hot ambient
conditions). If temperature rises to between 110°C and 140°C, the message IC1 HOT or IC2 HOT
will appear on the Primary Flight Display. If temperatures exceed 140°C, the respective IC-615(s) will
shut down.
Specific procedures for dealing with fan failure and computer overheat conditions can be found in the
AFM.
LCR-93 ATTITUDE AND HEADING REFERENCE SYSTEM
(AHRS)
The dual AHRS is the primary source of attitude and heading information on the Citation XLS. The
LCR-93 is a strapdown AHRS which uses fiber optic rate gyros and three micromechanical
accelerometers to provide a composite source of pitch, roll and heading information for the
Electronic Flight Information System (EFIS) and the Automatic Flight Control System (AFCS).
Attitude data is also supplied to the weather radar antenna and heading data to the standby
horizontal situation indicator (HSI). A flux valve provides long term heading references for the
system. A digital computer mathematically integrates the rate data to obtain the heading, pitch and
roll information. The micro air data computers provide true airspeed and barometric altitude inputs to
the AHRS. The key component of the AHRS is the attitude and heading reference unit (AHRU). It
comprises the inertial sensors and the computer boards for data processing and interfacing.
MODES OF OPERATION
After the system is powered on and completes its alignment, it begins to provide system information
from the Normal, Basic, Slaved, and DG modes. The attitude loop is controlled by the normal/basic
modes, and the heading loop is controlled by the slaved/DG modes.
In normal mode the AHRS uses valid true airspeed (TAS) from the air data computers, to improve
attitude accuracy. If the true airspeed data are not available or are invalid, the system will
automatically revert to the basic mode to operate autonomously. If true airspeed becomes valid
again during basic mode operation, the system will revert to normal mode. Transition between
normal and basic modes is controlled by the availability and validity of true airspeed data, and the
transition is performed automatically in both directions.
Cessna Citation XLS - Instrumentation & Avionics
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