Trio Avionics EZ Altitude Control - Manual (Page 10)

10
SERVO
FAULT
3.5.5 Servo Fault
This red message can be due to several factors
based on sensors within the servo and will always
cause an immediate disconnect and power down of
the servo.
System Response - In all cases the servo will be
immediately disconnected from the system, servo
power will be automatically removed and a red error message will be
displayed
Pilot Action - If the SERVO FAULT closely followed an extreme out of
trim condition, CLUTCH SLIP or G FORCE LIMIT alarm , press LCD
switch and continue normal operation. If the cause is unknown, or
occurs in conditions other than described above, perform ground tests of
the system paying particular attention to the wiring from the servo to the
electronics module and the mechanical linkage. If the problem persists,
contact Trio Avionics for assistance.
4.0 System Safety Features
The EZ altitude control system incorporates many safety features to ensure the system
cannot force the airplane into an un-commanded, unsafe flight regime. The following items
are implemented to ensure flight safety.
4.1 Aircraft G-load sensing. The AH module contains an accelerometer interfaced to
the main processor that is used to detect unusual positive or negative flight loads.
Software algorithms prevent unnecessary detection due to turbulence, but allow
shutdown of the servo if the flight loads exceed preset g-force limits. The intent of this
implementation is to prevent aircraft structural failure caused by an un-commanded
excursion of the servo or trim actuators. The fault condition is annunciated on the LCD
switch with the G FORCE LIMIT message
4.2 Servo Electronics monitoring . The servo and trim motor drive circuits are
instrumented and monitored by the servo main processor (SMP). The SMP commands
the magnitude and direction of the servo motor drive output. Any error in the
commanded state of these signals is reported back to the AH module via a digital data
link and results in a SERVO FAULT message on the LCD.
4.3 Clutch Slip Detection . Circuitry and software is provided that detects any slipping of
the safety clutch in the servo. Normally, this condition would only exist in the event the
pilot manually forced the control system into a position that exceeded the commanded
drive position of the servo. This event is reported to the AH module for resolution. The
amber CLUTCH SLIP message is displayed for a momentary slip condition.
4.4
Rotation Limit Detection . Under normal conditions the servo arm moves less than
20 degrees in either direction from the neutral (servo zero) position. If, for any reason
(commanded, un-commanded or pilot manual override), the crank arm transitions
approximately + / - 10 degrees outside of this range servo power is disconnected and a
red error message (CW or CCW LIMIT) is displayed.
4.5 Supervisory processor monitoring . The Servo Main Processor (SMP) is
continuously monitored by an independent supervisory processor to ensure it is
executing its program as designed. This is implemented via a “heartbeat” signal from
the SMP each 10 milliseconds. If for any reason the processor does not provide a