SDR 2025F00184

Service difficulty report · Switch · Beech C90A

Difficulty date
August 15, 2025
Submitted
August 15, 2025
Operation
General aviation
Aircraft
N135AA
Make and model
Beech C90A
Aircraft serial
LJ1112
Aircraft time
9,300 hours
Part
Switch
Part number
BZ7RW82255518T
Condition
Stuck
Location
Zone 600 Flaps
Part time
9,300 hours
Stage of operation
CL
How discovered
O
Nature of condition
F, A
Precautionary procedure
A

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

DURING TAKEOFF FROM BLUE GRASS AIRPORT (KLEX), THE PILOT REPORTED THAT UPON RETRACTING THE LANDING GEAR, THE LANDING GEAR LEVER RED UNSAFE LIGHT ILLUMINATED, ACCOMPANIED BY AN AURAL GEAR WARNING. THE PILOT EXTENDED THE LANDING GEAR, WHICH RESULTED IN THREE DOWN-AND-LOCKED INDICATIONS. HOWEVER, WHEN ATTEMPTING TO LOWER THE FLAPS, THE PILOT NOTED THAT THE FLAP MOTOR CIRCUIT BREAKER HAD POPPED. THE AIRCRAFT WAS PLACED ON JACKS FOR A GEAR RETRACTION TEST, DURING WHICH MAINTENANCE VERIFIED THE SAME GEAR UNSAFE WARNING LIGHT AND AURAL WARNING. THE FLAP MOTOR CIRCUIT BREAKER WAS OBSERVED TO POP APPROXIMATELY 20 SECONDS AFTER BEING RESET ON THE GROUND. TROUBLESHOOTING REVEALED THAT UNPLUGGING THE CANNON PLUG FROM THE FLAP SWITCH BOX IN THE RIGHT WING FLAP-WELL ELIMINATED THE WARNING AND PREVENTED THE CIRCUIT BREAKER FROM POPPING. IT WAS DETERMINED THAT THE FLAP WARNING POSITION SWITCH, WHICH ACTIVATES THE GEAR WARNING WHEN FLAPS ARE EXTENDED, WAS STUCK IN THE DOWN POSITION, CAUSING A FALSE GEAR UNSAFE INDICATION AND TRIPPING THE FLAP CIRCUIT BREAKER. NEW FLAP WARNING POSITION SWITCH (P/N: BZ7RW82255518T) AND FLAP MOTOR (P/N: 101-384040, S/N: 4221) WERE INSTALLED AND RIGGED. SUBSEQUENT TESTING CONFIRMED PROPER GEAR RETRACTION WITHOUT WARNINGS, AND THE FLAP MOTOR CIRCUIT BREAKER NO LONGER TRIPPED. THE AIRCRAFT WAS RETURNED TO SERVICE FOLLOWING SUCCESSFUL COMPLETION OF ALL TESTS AND VERIFICATION OF PROPER OPERATION.

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