TWENTYNINE PLMS, CA, USA
N125PS
CANADAIR CL600-2A12
THE WATER FILTER HOUSING LOWER SEAL WAS MIS-INSTALLED WHICH ALLOWED WATER TO SEEP OUT AND RUN DOWN THE HOUSING CASE. OVER TIME THE WATER DROPPED ONTO A LAVATORY DRAIN LINE, FOLLOWED THE LINE TO A LOW POINT & COLLECTED ON THE STAB AUG COMPUTER BOX. THE FLUID ACCUMULATION RESULTED IN CORROSION ON ONE OF THE CIRCUIT BOARDS WITHIN THE COMPUTER BOX CAUSING A POWER IMBALANCE WITHIN THE YAW DAMPER SYSTEM AND A SUBSEQUENT UNCOMMANDED RUDDER SIGNAL. DRG THE CLIMB TO CRUISE TRANSITION A MACH TRIM FAILURE OCCURRED WHICH WOULD HAVE NECESSITATED THE USE OF THE AUTOPILOT FOR SPEEDS IN EXCESS OF 0.7 MACH. OPERATION OF THE AUTOPILOT, HOWEVER, RESULTED IN OPERATION OF THE YAW DAMPER SYSTEM WHICH HAD BEEN DETERMINED TO HAVE BEEN PRODUCING UNCOMMANDED RUDDER INPUTS. AS THE ACFT WAS LEVELLED AT FL330 AND THE AIRSPD WAS ALLOWED TO EXCEED MACH 0.7 THE COPLT ACTIVATED THE AUTOPLT WHICH POWERED THE MALFUNCTIONING DAMPER SYSTEM AND A DUTCH ROLL MANEUVER ENSUED. PIC DISCONNECTED THE AUTOPLT, EXECUTED A DESCENT AND RECOVERY.
Source: NTSB Aviation Accident Database
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