Bombardier (Canadair) CL600 Challenger and RJ 100 Series - Service Difficulty Alert

AL 2003-01
9 January 2003

Aileron Quadrant / Feel Unit
P/N 600-91178-7

Transport Canada has recently received a Service Difficulty Report regarding the bearing failure in the Aileron Quadrant/Feel Unit on a CL600 2A12 (601) Challenger aircraft.

While performing a 600-hour inspection and after completing operational tests on the aileron system, personnel were exercising the ailerons bleeding off the hydraulic system pressure. When the pressure was released, a loud bang was heard while the controls were being moved. Troubleshooting to find the source started, and when the aileron controls were moved again, the bang was heard and the wheel well quadrant area was determined to be source of the noise. The quadrant was removed and disassembled. Quadrant bearing, P/N MS 27646-39 was found dry of grease and the balls had worn a groove deep into the inner race.

It is important to note the operator did not experience any symptoms that would have lead to the discovery of this failing part prior to its failure, i.e. stiff or ratcheting control wheel. This quadrant has a common part number throughout the Challenger and Regional Jet 100 fleet.


Transport Canada strongly recommends that an operational check be carried out on the aileron system similar to the text above. A visual inspection of the quadrant to ensure the presence of sufficient lubrication should be carried out at the operator's earliest convenience. If left undetected, aileron control operation could be compromised, possibly resulting in jamming or aileron control stiffness.

Any defects or further occurrences should be reported by sending a Service Difficulty Report to Transport Canada, Continuing Airworthiness, Ottawa.

For further information contact a Transport Canada TCC, or contact Mr. Steve Dudka, Continuing Airworthiness, Ottawa, telephone (613) 952-4361, facsimile (613) 996-9178 or email

For Director, National Aircraft Certification

B. Goyaniuk
Chief, Continuing Airworthiness