NTSB Identification: CHI95IA138.
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Scheduled 14 CFR (D.B.A. NORTHWEST AIRLINES )
Incident occurred Thursday, April 27, 1995 in WASHINGTON, DC
Probable Cause Approval Date: 04/29/1996
Aircraft: Airbus Industrie A320-211, registration: N331NW
Injuries: 108 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.

THE PILOT REPORTED THAT DURING THE VISUAL APPROACH TO RUNWAY 18, THE AIRPLANE ENTERED UNCOMMANDED ROLLS. A GO-AROUND WAS PERFORMED. ACCORDING TO THE PILOT, ON THE SECOND APPROACH THE AIRPLANE ONCE AGAIN EXPERIENCED AN UNCOMMANDED ROLL. THE AIRPLANE WAS LANDED. FDR DATA SHOWS THE ROLL OSCILLATIONS WITH A MAX ROLL OF 15.5 DEGREES. DURING THIS TIME THE SIDE STICK WAS BEING MOVED BACK AND FORTH TO ITS FULL TRAVEL LIMITS. THE AIRPLANE MOVEMENTS AND THE PILOT'S ACTIONS ARE CONSISTENT WITH PILOT INDUCED OSCILLATIONS (PIO). THE AIRPLANE WAS BEING LANDED IN CONF 3 (20 DEGREES OF FLAPS) WHICH MAKES THE HANDLING CHARACTERISTICS OF THE AIRPLANE 'MORE CRISP'. IN 1993 AIRBUS PUBLISHED A TEMPORARY REVISION TO THE AIRPLANE'S FLIGHT CREW OPERATING MANUAL STATING THE AIRPLANE SHOULD NOT BE LANDED IN ADVERSE WEATHER CONDITIONS (GUSTY WINDS AND TURBULENCE) IN CONF 3 DUE TO THE POSSIBILITY OF PIO. NORTHWEST AIRLINES HAD NOT INCORPORATED THIS INFORMATION IN THEIR OPERATING MANUALS.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

the pilot's excessive use of the flight controls during the landing approach, the company's disregard of information provided by the airplane manufacturer, and the company's failure to identify a potentially hazardous conditions based on the information provided by the airplane manufacturer. Factors associated with the incident were the gusty wind conditions and the pilot's failure to land with full flaps.

Full narrative available

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