What was found
ON MAY 18 2026, N999LR HAD A FLIGHT CONTROL MALFUNCTION HORIZOTAL STABILIZER ACTUATOR (HSTA) WHICH LED TO THE CREW DECLARING AN EMERGENCY. THE FLIGHT DEPARTED KHPN ENROUTE TO KBCT. DURING THE APPROACH INTO KBCT WHILE CONFIGURING FOR LANDING FLIGHT CREW SEES AN AMBER FLAP/STAB SYNC FAIL CASS MESSAGE. FLT CREW FOLLOWED THE QRH 03-12-10 FAILURE OF FLAP/STABILIZER SYNCHRONIZATION CHECKLIST AND DIVERTED TO KPBI DUE TO LONGER AVAILABLE RUNWAYS. FLIGHT CREW CHOOSE TO LAND AT A REDUCED FLAP SETTING (20) IN CASE OF GO AROUND. THE LANDING WAS UNEVENTFUL AND WE TAXIED INTO FBO. SUBSEQUENTLY MAINTENANCE CONFIRMED HSTA FAILED AND REMOVED AND REPLACED HSTA P/N 1159SCC500-9 S/N 2582. FAA PMI REQUESTED WITNESSED TEARDOWN OF THIS FAILED HSTA S/N 2582 AT THE HSTA MANUFACTURERS REPAIR STATION. TEARDOWN REPORT ISSUED FROM THE REPAIR STATION INDICATES FAILED HSTA CLUTCH MAY HAVE CAUSED THE LVDT'S IN THIS UNIT TO SHOW MISMATCH POSITIONS RESULTING IN CREW REPORTED CAS MESSAGE AND MAY HAVE LOCKED THE HORIZONTAL STAB. IN OTHER THAN NEUTRAL POSITION WHICH FLIGHT CREW WAS ABLE TO OVERCOME WITH USE OF ELEVATORS AND FLAP POSITION ON LANDING.