NTSB Identification: CHI88IA040.
The docket is stored on NTSB microfiche number 37737.
Scheduled 14 CFR operation of NORTHWEST AIRLINES
Incident occurred Saturday, January 09, 1988 in MINNEAPOLIS, MN
Probable Cause Approval Date: 01/25/1990
Aircraft: BOEING 747-251F, registration: N618US
Injuries: 3 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.

AIRCRAFT EXPERIENCED A LOSS OF AILERON CTL WHEN ICE FORMED AROUND AILERON CONTROL CABLES AND RESTRICTED THEIR MOVEMENT. WATER DRAINING THROUGH OPEN PLENUM DRAINS IN THE MAIN LANDING GEAR WHEEL WELL FROZE WHEN EXPOSED TO BELOW FREEZING TEMPERATURES AT 35,000 FT. THE FLIGHT CREW WAS ABLE TO REGAIN LIMITED CONTROL BY USING VERY HEAVY CONTROL INPUTS. THE ACFT WAS LANDED UNEVENTFULLY AFTER DIVERTING TO THE NEAREST SUITABLE AIRPORT. MAINTENANCE PERSONNEL REPORTED THAT THE DRAINS WERE INADVERTENTLY LEFT OPEN.

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

MISC EQPT/FURNISHINGS..NOT SECURED

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

FLT CONTROL SYST,AILERON CONTROL CABLE/ROD..MOVEMENT RESTRICTED

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

FLT CONTROL SYST,AILERON CONTROL CABLE/ROD..ICE


Contributing Factors

AIRCRAFT SERVICE..IMPROPER..OTHER MAINTENANCE PERSONNEL

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