AD NUMBER: 2010-20-03

MANUFACTURER: Bombardier, Inc. Model CL-600-2B16 (CL- 604 Variants (Including CL-605 Marketing Variant)) Airplanes
SUBJECT: Airworthiness Directive 2010-20-03

SUMMARY: 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:

Following five reported cases of  balance washer screw failure on similar ADGs [air-driven generators]/ram air turbines installed on other aircraft types, investigation by Hamilton Sundstrand determined that a specific batch of the screws had a metallographic non-conformity that increased their susceptibility to brittle fracture. 

Failure of a balance washer screw can result in loss of the related balance washer, with consequent turbine imbalance. Such imbalance could potentially result in ADG structural failure (including blade failure), loss of ADG electrical power and structural damage to the aircraft and, if deployment was activated by a dual engine shutdown, could also result in loss of hydraulic power for the flight controls [and consequent reduced ability of the flightcrew to maintain the safe flight and landing of the airplane].

FMI: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/3CBB076DC4230D7E862577AB005816B3?OpenDocument