AD NUMBER: 2011-12-06

MANUFACTURER: Bombardier, Inc. Model CL-600-2C10 (Regional Jet Series 700, 701, & 702), Model CL-600-2D15 (Regional Jet Series 705), and Model CL-600-2D24 (Regional Jet Series 900) Airplanes
SUBJECT: Airworthiness Directive 2011-12-06

SUMMARY: We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as: An inspection by the vendor revealed that a number of Rubber Bull Gears (RBG) in the Horizontal Stabilizer Trim Actuator (HSTA) of the CL-600-2C10, CL-600-2D15 and CL-600-2D24 aeroplanes were installed with a wheel material hardness out of specification. This non-conformity has a direct impact on the HSTA life limit. The teeth of the senon-conformant RBGs could break and in extreme cases, could lead to uncontrolled HSTA movement without the ability to re-trim the aeroplane. If not corrected, this condition could result in a difficulty to control the pitch and subsequent loss of the aeroplane.
* * * * * We are issuing this AD to require actions to correct the unsafe condition on these products.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/