NTSB Identification: SEA88IA028.
The docket is stored on NTSB microfiche number 35038.
Incident occurred Sunday, December 06, 1987 in TWENTYNINE PLMS, CA
Probable Cause Approval Date: 07/10/1989
Aircraft: CANADAIR CL600-2A12, registration: N125PS
Injuries: 2 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

WATER AND WASTE SYSTEM..LEAK

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

IN-FLIGHT PLANNING/DECISION..IMPROPER..COPILOT/SECOND PILOT

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

OPERATION WITH KNOWN DEFICIENCIES IN EQUIPMENT..ATTEMPTED..COPILOT/SECOND PILOT

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

MAINTENANCE,INSTALLATION..IMPROPER..UNKNOWN

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

AUTOPILOT/FLIGHT DIRECTOR..ENGAGED


Contributing Factors

AUTOPILOT/FLIGHT DIRECTOR,AMPLIFIER AND COMPUTER..CORRODED


Contributing Factors

FLT CONTROL SYST,RUDDER CONTROL..ERRATIC

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