PORTLAND, OR, USA
CGTAH
FOKKER F.28 MK 1000
WHILE CRUISING AT FLIGHT LEVEL 290, THE FOKKER F.28 MK 1000 EXPERIENCED AN UNCOMMANDED CLIMB OF APPROXIMATELY 3000 FEET. FULL FORWARD PRESSURE ON THE CONTROL COLUMN DID NOT ARREST THE CLIMB, AND THE ATTEMPTED USE OF THE ALTERNATE STABILIZER TRIM SWITCH RESULTED IN REPEATED POPPING OF THE CIRCUIT BREAKER. THE PILOT REGAINED PITCH CONTROL OF THE AIRCRAFT BY MOVING PASSENGERS FORWARD IN THE CABIN, AND BY ENLISTING THE PHYSICAL ASSISTANCE OF ONE FLIGHT ATTENDANT. BY ADJUSTING FLAP AND POWER SETTINGS A SUCCESSFUL LANDING WAS ULTIMATELY ACCOMPLISHED. THE INVESTIGATION REVEALED THAT THE ROD END BEARING ON THE STABILIZER SERVO SPOOL VALVE HAD BEEN OVERTORQUED, CAUSING THE FAILURE OF THE SPOOL, RESULTING IN A SLOW NOSE UP STABILIZER RUNAWAY.
THE PARTIAL FAILURE OF THE HORIZONTAL STABILIZER TRIM DRIVE SYSTEM, THE RESTRICTED MOVEMENT OF THE STABILIZER, AND THE OVERTORQUE OF A SYSTEM COMPONENT.
Source: NTSB Aviation Accident Database
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