Airworthiness Directives; Bombardier, Inc. Airplanes

We propose to adopt a new airworthiness directive (AD) for certain Bombardier, Inc. Model CL-600-2C10 (Regional Jet Series 700, 701, & 702), CL-600-2D15 (Regional Jet Series 705), CL-600-2D24 (Regional Jet Series 900) airplanes, and CL-600-2E25 (Regional Jet Series 1000) airplanes. This proposed AD was prompted by a determination that wear and possible leakage of the high-pressure seal in the cylinder of the No. 3 hydraulic system reservoir could occur and prevent the system from reaching normal operating pressure. This proposed AD would require repetitive operational checks for wear and leakage of the high-pressure seal in the cylinder of the reservoir of the No. 3 hydraulic system, and corrective actions if necessary. We are proposing this AD to detect and correct a malfunctioning temperature indication of the No. 3 hydraulic system. High hydraulic fluid temperature combined with a temperature transducer malfunction could result in un-annunciated overheating of the hydraulic system and consequent ignition sources inside the fuel tank, which, combined with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.