NTSB Identification: DEN92IA005.
The docket is stored on NTSB microfiche number 46058.
Scheduled 14 CFR operation of UNITED AIRLINES
Incident occurred Thursday, October 24, 1991 in DENVER, CO
Probable Cause Approval Date: 05/05/1993
Aircraft: BOEING 747-122, registration: N4719U
Injuries: 280 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
DURING LEVEL OFF AT FLIGHT LEVEL 290, WHILE ON A SCHEDULED INTERNATIONAL PASSENGER FLIGHT FROM SAN FRANCISCO, CALIFORNIA, TO LONDON, ENGLAND, ELEVATOR PITCH CONTROL BECAME ERRATIC AND OSCILLATIONS OF UP TO 1,000 FEET EITHER SIDE OF THE BASE ALTITUDE OCCURRED. THE AUTO PILOT WAS DISCONNECTED, COMMUNICATIONS WITH MAINTENANCE CONTROL WAS HELD, AND THE FLIGHT PROCEEDED TO THE NEAREST AIRPORT WITH RUNWAYS EXCEEDING 10,000 FEET IN LENGTH. AN UNEVENTFUL PRECAUTIONARY LANDING WAS CONDUCTED IN DENVER, COLORADO. STABILIZER TRIM COMPONENTS WERE EXAMINED REVEALING DISCREPENCIES IN THE TRIM MODULE AND ELEVATOR FEEL COMPUTER, DUE TO NORMAL WEAR.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: A MALFUNCTION IN THE STABILIZER TRIM CONTROL MODULE.
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