NTSB Identification: CHI97IA034.
The docket is stored in the Docket Management System (DMS). Please contact Records Management Division
Scheduled 14 CFR operation of NORTHWEST AIRLINES
Incident occurred Sunday, November 24, 1996 in ROMULUS, MI
Probable Cause Approval Date: 10/31/1997
Aircraft: Airbus Industrie A-320-211, registration: N310NW
Injuries: 147 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.

As the captain applied rudder over the runway threshold to compensate for a crosswind, he noted that the rudder pedals 'were locked in the neutral position.' He used slight banking to keep the airplane on runway centerline through touchdown, and differential braking and nosewheel steering to stay on runway centerline after touchdown. Shortly after exiting the runway, the rudder became free and moved normally. Examination of the rudder autopilot artificial feel unit revealed that the radial play of the autopilot mode engagement/disengagement lever was not sufficient. This introduced higher friction in the bearing of the lever, resulting in an increased operating force. In this case, the back driving force was not able to rotate the lever and disengage the autopilot mode. A review of all service bulletins (SBs) covering the A320 rudder system revealed an Airbus Industrie SB, dated March 21, 1992, which addressed this condition, and introduced a new modified lever with a larger radial play of the bearing to eliminate the problem. The A320, N310NW, did not have this modification at the time of the incident.

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

restricted movement of the autopilot mode engagement/disengagement lever bearing in the rudder artificial feel and trim unit. A factor relating to this incident was: company management not implementing the respective service bulletin.

Full narrative available

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