Serious incident Fokker F-28 Fellowship 1000 C-GTAH, Sunday 21 June 1992

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Date:	Sunday 21 June 1992
Time:	20:30 LT
Type:	Fokker F-28 Fellowship 1000
Owner/operator:	Timeair Inc.
Registration:	C-GTAH
MSN:	11082
Year of manufacture:	1974
Total airframe hrs:	18527 hours
Engine model:	ROLLS-ROYCE R.B.183-2
Fatalities:	Fatalities: 0 / Occupants: 53
Other fatalities:	0
Aircraft damage:	None
Category:	Serious incident
Location:	Portland, OR - United States of America
Phase:	En route
Nature:	Unknown
Departure airport:	VANCOUVER BC (KYVR)
Destination airport:	Las Vegas, NV (KLAS)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
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.

Probable Cause: THE PARTIAL FAILURE OF THE HORIZONTAL STABILIZER TRIM DRIVE SYSTEM, THE RESTRICTED MOVEMENT OF THE STABILIZER, AND THE OVERTORQUE OF A SYSTEM COMPONENT.

Accident investigation: