Hardware Monitors - Honeywell BENDIX/KING KAP 140 Maintenance Manual

2.2.1 HARDWARE MONITORS

The following monitoring functions are implemented in the FCC hardware.
2.2.1.1 Acceleration Monitor (Pitch engaged):
Whenever the normal acceleration is invalid or outside of the range --0.4g to +0.4g for 0.4 seconds,
the pitch axis will be disengaged (i.e. engage clutch unpowered). The axis automatically
re--engages (if previously engaged) when the acceleration is valid and less than 0.2 g absolute
for 0.4 seconds. If the acceleration input is invalid or outside the above monitor limits for 1.0
seconds, the FCC disconnects the pitch axis and provides disconnect alerting. The AP mode can
be re--engaged after the excessive acceleration is removed. This monitor runs continuously
whether the AP is engaged or not.
For the --5101, --5302, and --7802 flavors: If the acceleration output is greater than +0.4 g's or --0.4
g's for 0.4 seconds, then the accelerometer monitor will fail and disengage the pitch, roll, and trim
clutches.
For the --5201, --54XX, --55XX, --77XX and --79XX flavors: If the acceleration output is greater than
+0.4 g's or --0.4 g's for 0.4 seconds and the pitch tachometer output (greater than +/--0.36 V) is
in the direction of the sensed acceleration, then the accelerometer monitor will fail and disengage
the pitch, roll, and trim clutches.
2.2.1.2 Autotrim Runaway Monitor (Pitch engaged):
In a two axis system with the autopilot pitch axis engaged, the trim runaway monitor detects if the
trim motor drive is in opposition to the pitch servo command (See below for details on thresholds
and time durations). If this condition is detected, the pitch trim is disabled until a subsequent
Preflight test is performed. Pitch modes are still allowed and manual trim indications made
available to the pilot. When a trim runaway is detected, a continuous audio tone is generated until
the AP DISC button is pressed. "PT" is displayed on the FCC and an external TRIM FAIL
annunciation is also illuminated.
For five seconds after a trim runaway is detected, the acceleration monitor (described above) is
disabled. This allows primary pitch servo authority to oppose a trim runaway. The trim modes (MET
and autotrim) can only be re--engaged by cycling AP power and successfully passing pre--flight
test. This monitor runs continuously when the pitch axis is engaged.
For the --5101, --5302, and --7802 flavors: If the trim voltage exceeds +/--2.7 V for 0.7 seconds and
the pitch command is greater than +/--0.61 V and is in opposition to the direction the trim servo
is running in the aircraft then the autotrim runaway monitor will fail and disengage the trim clutch.
For the --5201, --54XX, --55XX, --77XX and --79XX flavors: If the trim voltage exceeds +/--2.7 V
for 1.1 seconds and the pitch command is greater than +/--0.36V and is in opposition to the
direction the trim servo is running in the aircraft, then the autotrim runaway monitor will fail and
disengage the trim clutch.
Revision 2, Dec/2002
CS:15574F02.IDU
BENDIX/KING
KAP 140
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