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Loss of Pitch Control on Fokker F.28 Due to Stabilizer Servo Valve Failure (CGTAH)

Portland, OR, US

On June 22, 1992, a Fokker F.28 MK 1000 (registration CGTAH) operated by Timeair Inc. was involved in an aviation accident near Portland, OR. No fatalities were reported. Investigators recorded the probable cause as: 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. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

While cruising at FL290, a Fokker F.28 Mk 1000 experienced an uncommanded climb of about 3000 feet. The pilot regained pitch control by moving passengers forward and with flight attendant assistance, then landed successfully.

Incident Description

During cruise at Flight Level 290, a Fokker F.28 Mk 1000 aircraft experienced an uncommanded climb of approximately 3000 feet. Applying full forward pressure on the control column did not arrest the climb. The flight crew attempted to use the alternate stabilizer trim switch, but this repeatedly caused the associated circuit breaker to pop.

To regain pitch control, the pilot moved passengers forward in the cabin and enlisted the physical assistance of one flight attendant. By adjusting flap and power settings, the crew was ultimately able to accomplish a successful landing.

Investigation Findings

The investigation revealed that the rod end bearing on the stabilizer servo spool valve had been overtorqued. This overtorquing caused the failure of the spool, which resulted in a slow nose-up stabilizer runaway.

Outcome

The aircraft landed successfully. No further details about injuries or damage were specified in the investigation report.

Probable cause

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.

Frequently asked questions

What happened in the 22 Jun 1992 Fokker F.28 MK 1000 accident near Portland, OR?

While cruising at FL290, a Fokker F.28 Mk 1000 experienced an uncommanded climb of about 3000 feet. The pilot regained pitch control by moving passengers forward and with flight attendant assistance, then landed successfully.

Were there any fatalities in the 22 Jun 1992 Fokker F.28 MK 1000 accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 22 Jun 1992 involved a Fokker F.28 MK 1000, registration CGTAH, operated by Timeair Inc., at Portland, OR.

What was the probable cause of the accident?

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.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X14994. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.