# NTSB SEA92IA136: Fokker F.28 MK 1000, Portland, OR, June 22, 1992

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: June 21, 1992, 19:30 local (Jun 22, 1992, 02:30 UTC)
- Place: Portland, OR
- Coordinates: 45.549873, -122.55902 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=45.5499&lon=-122.5590&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 53 uninjured
- Status: Completed, report June 30, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 41594
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA92IA136
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41594/pdf
- Page: https://openairdocs.org/ntsb/SEA92IA136

## 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.

## Analysis

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.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, cruise
  - flight control system - overtorque (cause)
  - flt control syst,horiz stab drive - failure,partial (cause)
- Altitude deviation,uncontrolled, cruise
  - flt control syst,horiz stab drive - movement restricted (cause)

## Aircraft

- Registration: CGTAH (not matched to a registry record)
- Reported make and model: FOKKER F.28 MK 1000 (F.28 MK 10)
- Category: Airplane
- Serial number: 11082
- Airframe hours: 18527
- Engines: ROLLS-ROYCE R.B.183-2 9900 lbs thrust turbo fan
- Damage: No damage
- Flight: Part 129
- Operator: Timeair Inc.
- Registered owner: Timeair Inc.
- Airworthiness certificate: Standard, Transport
- Last inspection: Unknown, June 19, 1992, 33 hours before
- Departed: YVR, VANCOUVER BC
- Destination: LAS, LAS VEGAS, NV
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; airline transport, foreign; airplane ratings: multi-engine land, single-engine land, multi-engine sea, single-engine sea; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 9,000 total

## Weather

- Conditions: Visual (VMC), Day
- Lowest ceiling: none

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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