Serious incident Bombardier CRJ-100ER N709CA, Wednesday 8 May 2002
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Date:Wednesday 8 May 2002
Time:12:00 LT
Type:Silhouette image of generic CRJ1 model; specific model in this crash may look slightly different    
Bombardier CRJ-100ER
Owner/operator:Comair
Registration: N709CA
MSN: 7044
Engine model:General Electric CF-34
Fatalities:Fatalities: 0 / Occupants: 18
Other fatalities:0
Aircraft damage: None
Category:Serious incident
Location:Covington, KY -   United States of America
Phase: En route
Nature:Unknown
Departure airport:Cincinnati/Northern Kentucky Airport, KY (CVG/KCVG)
Destination airport:Omaha-Eppley Airfield, NE (OMA/KOMA)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The Bombardier CL600-2B19 regional jet experienced aileron control stiffness during cruise flight. The airplane was pushed back during a period of moderate to heavy rain. After pushback, the airplane was held on the taxiway for about 30 minutes while the rain continued. Takeoff also occurred during a period of heavy rain. After leveling off at flight level 280, while in cruise flight, the "AP TRIM IS LWD" caution annunciator illuminated. The first officer disconnected the autopilot, and found the aileron controls to be "stiff and binding." The captain then took control of the airplane, and also found the aileron controls to be stiff and binding. The captain applied "light to moderate" roll input and felt a snap. Aileron control then operated normally. The captain executed left and right turns with no additional problems or binding noted. The crew re-engaged the autopilot, and the flight continued to an uneventful landing. On the same date, two other CL600 regional jets from the same airline also experienced aileron stiffness after taking off at the same airport and in similar weather conditions. Both airplanes landed uneventfully. One of the airplanes diverted to an alternate airport. The investigation revealed that approximately 40 Bombardier CRJ CL-600-2B19 regional jets experienced in-flight aileron control stiffness after standing/taxiing in, or taking off during rainy conditions, then climbing to freezing temperatures. When the jets descended to above-freezing temperatures, the aileron control stiffness ceased. Testing revealed that aileron circuit binding occurred in the area of the Brake and Position Sensor Unit (BPSU) bay. Typically, within the bay, horizontally-oriented pulleys in the aileron control circuit would seize, and the aileron cable, after being subjected to water soaking, would freeze to the pulley. Water ingress to the bay most likely occurred via an aging self-contouring sealing pad on an access panel directly above the pulleys. The horizontal orientation of the pulleys, which had been used without difficulty in transport category aircraft for over 20 years, and the dished cross section of the pulley face allowed the retention of water when the airplane was parked. In addition, the drying of pulley grease over time, combined with water migration from rain, could temporarily allow the bearing to seize when the airplane reached altitude. A test on a dry-bearing pulley revealed that when water was applied to the pulley face, it remained pooled until the pulley was moved, when it flowed into the bearing. Prior to the incidents, the manufacturer had not issued specific instructions to inspect pulleys in the BPSU bay. Subsequent service letters and airworthiness directives to inspect the pulleys, grease the aileron cables and replace aging and seized pulleys, resulted in over 60 seized and deteriorating pulleys being found fleet wide. There have been no further aileron control stiffness events on aircraft which had undergone the new inspection/maintenance procedures.

Probable Cause: The manufacturer's failure to provide inspection criteria for the BPSU compartment aileron control pulleys, which resulted in eventual pulley corrosion, and subsequent control stiffness when seized pulleys and water-soaked aileron cables froze together at altitude. Factors included leaking BPSU bay access panel seals, precipitation, and freezing temperatures.

Accident investigation:
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Investigating agency: NTSB
Report number: NYC02IA097
Status: Investigation completed
Duration: 3 years and 2 months
Download report: Final report

Sources:

NTSB NYC02IA097

History of this aircraft

Other occurrences involving this aircraft

10 March 1998 N937CA Comair 0 Covington, KY sub

Location

Revision history:

Date/timeContributorUpdates
25-Mar-2024 10:47 ASN Update Bot Added

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