# Incident 19980311006709I: Boeing 737205, Anchorage, AK, March 11, 1998

- Type: FAA incident report (Accident/Incident Data System), as reported
- Date: March 11, 1998, 11:45 local time
- Place: Anchorage, AK
- Airport: Anchorage International
- Phase of flight: Other Ground Ops
- Operating rules: General operating rules (Part 91)
- Operator: SROM
- Location: 61.1602° N, 149.9900° W: From the FAA, an estimate near the named town, within about 3 miles
- Nearby events: https://openairdocs.org/map.md?lat=61.1602&lon=-149.9900&mi=10
- Aircraft: N733AR (not matched to a registry record)
- Reported make and model: BOEING 737205
- People aboard: 81
- Fatal injuries: 0
- NTSB investigation: [NTSB ANC98IA026](https://openairdocs.org/ntsb/ANC98IA026) (OpenAirDocs)
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/19980311006709I

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

NARRATIVE: ON MARCH 11, 1998, ABOUT 1145 ALASKA STANDARD TIME, A BOEING 737-205 AIRPLANE, N733AR, HAD AN UNCOMMANDED RUDDER MOVEMENT WHILE PARKING AT THE GATE AT ANCHORAGE INTERNATIONAL AIRPORT, ANCHORAGE, ALASKA. THE AIRPLANE WAS OPERATED BY ARCO ALASKA, INC., UNDER 14 CFR PART 91, BETWEEN PRUDHOE BAY, ALASKA, AND ANCHORAGE. THERE WERE NO INJURIES TO THE TWO PILOTS, THREE FLIGHT ATTENDANTS, OR THE 76 PASSENGERS ON BOARD. DURING A TELEPHONE CONVERSATION WITH THE NTSB INVESTIGATOR ON MARCH 11, THE CAPTAIN INDICATED THAT WHILE ON THE GROUND IN PRUDHOE BAY, THE CREW FELT A MOMENTARY AIRFRAME VIBRATION. THE AIRPLANE THEN DEPARTED PRUDHOE BAY EN-ROUTE TO ANCHORAGE. ON ARRIVAL IN ANCHORAGE, WHILE COMPLETING THE SHUT DOWN CHECK LIST, THE CREW AGAIN FELT A MODERATE VIBRATION. GROUND PERSONNEL OUTSIDE THE AIRPLANE NOTED THE 76 PASSENGERS ON BOARD. DURING MAINTENANCE TROUBLESHOOTING, WHILE ON GROUND POWER, APPLICATION OF RUDDER RESULTED IN A SEVERE AIRFRAME VIBRATION. GROUND PERSONNEL REPORTED THE RUDDER WAS MOVING AT A VERY HIGH RATE OF SPEED. FURTHER TESTS INVOLVING NTSB, FAA, BOEING AND ARCO ALASKA PERSONNEL, DETERMINED THAT THE YAW DAMPER COUPLER WAS PRODUCING OSCILLATORY INPUTS TO THE  RUDDER ACTUATOR. THE COUPLER HAS BEEN REMOVED FOR FURTHER TESTING.

## The NTSB's investigation of this event (1)

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.

- [NTSB ANC98IA026](https://openairdocs.org/ntsb/ANC98IA026), Mar 11, 1998: Boeing 737-205 (N733AR), Anchorage, AK, incident, no damage. Probable cause: The dynamic imbalance in the yaw rate gyro, which provided input to the yaw damper and rudder. A factor was the deteriorated grease in the gyro bearings.

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record.

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