SMT TKOF ABORTED WHEN UNABLE TO RAISE THE NOSE FOR LIFTOFF. STABILIZER TRIM INDICATOR IN COCKPIT INDICATED NORMAL TRIM BUT THE STABILIZER ITSELF FOUND TO BE IN THE FULL NOSE DOWN POS.

Date: 1992-11 · Aircraft: Small Transport; Low Wing; 2 Turboprop Eng

Anomalies: aircraft-equipment-problem-critical|inflight-event-encounter-loss-of-aircraft-control

Synopsis

SMT TKOF ABORTED WHEN UNABLE TO RAISE THE NOSE FOR LIFTOFF. STABILIZER TRIM INDICATOR IN COCKPIT INDICATED NORMAL TRIM BUT THE STABILIZER ITSELF FOUND TO BE IN THE FULL NOSE DOWN POS.

Narrative

WE ACCOMPLISHED A NORMAL PREFLT ACCORDING TO COMPANY PROCS. PAX LOADING; START-UP AND TAXI OUT WERE ALL ACCOMPLISHED WITHOUT INCIDENT. ALL PROCS WERE COMPLETED WITH USE OF COMPANY CHKLIST. ON THIS LEG; IT WAS THE FO'S TURN TO FLY. ON RWY 21C; CTL OF THE ACFT WAS TURNED OVER TO THE FO AFTER THE RWY ITEMS CHKLIST HAD BEEN COMPLETED AND A TKOF CLRNC RECEIVED. THE TKOF WAS INITIATED V1 SPD OBTAINED. VR SPD WAS THEN OBTAINED. ALL OF THESE SPDS ARE VERBALLY CALLED OUT BY THE PNF. WHEN I CALLED VR; THE FO MOVED THE CTL COLUMN AFT TO INITIATE ROTATION; NO ROTATION OCCURRED. THE CTL COLUMN WAS PULLED FURTHER AFT AND STILL NO ROTATION WAS EFFECTED. AT THIS POINT; I CALLED FOR THE FO TO ABORT THE TKOF. THE TKOF WAS ABORTED; THE ACFT BROUGHT TO TAXI SPD; AND WE TAXIED CLR OF THE RWY. WE STOPPED THE ACFT INVESTIGATED ALL TKOF SETTINGS BUT COULD FIND NOTHING OUT OF PROPER INDICATION RANGE. AT THIS POINT WE RETURNED TO THE GATE AND DEPLANED. ON MY POST-FLT INSPECTION I NOTED THE HORIZ STABILIZER WAS NEAR THE TOP OF ITS UP TRAVEL. THE COCKPIT TRIM INDICATOR INDICATED THE STABILIZER TRIM WAS MID- RANGE. THIS EXTREME UP TRAVEL OF THE STABILIZER WOULD HAVE CREATED THE DOWNWARD PITCH MOMENT TO PREVENT ROTATION. THIS DISCREPANCY WAS NOTED IN THE MAINT LOG AND THE ACFT TURNED OVER TO COMPANY MAINT FOR INSPECTION AND REPAIR. CONTRIBUTING FACTORS: LACK OF SYS REDUNDANCY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: VERY COOPERATIVE RPTR SAID THIS ACFT HAS A TKOF WARNING HORN. THE TRIM INDICATOR IS IN THE COCKPIT AND IS BIASED BY THE PITCH TRIM COMPUTER. HE IS NOT SURE HOW THE STABILIZER CAME TO BE FULL NOSE DOWN BUT HE SAID IT WAS NOT A RUNAWAY STABILIZER. THERE IS A 'BEEPER' THAT SOUNDS INTERMITTENTLY AS THE STABILIZER IS TRIMMED. HE PROBABLY WOULD HAVE HEARD THIS IF THE STABILIZER RAN AWAY. THE TRIM INDICATOR/PITCH TRIM COMPUTER TRIGGERS THE TKOF WARNING HORN INDEPENDENTLY OF THE STABILIZER ITSELF.

Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.