Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to adopt a new airworthiness directive (AD) for certain Bombardier, Inc. Model CL-600-2A12 (CL-601 Variant), and CL- 600-2B16 (CL-601-3A, CL-601-3R, and CL-604 Variants) airplanes. This proposed AD was prompted by a report that a potential chafing condition exists between the negative-G fuel feed drain line of the auxiliary power unit (APU) and its surrounding structure and components. This proposed AD would require, for certain airplanes, a detailed inspection for chafing conditions of the negative-G fuel feed drain line of the APU, and corrective actions if necessary. For certain other airplanes, this proposed AD would require replacement of the APU negative-G fuel feed tube assembly and the drain line. We are proposing this AD to prevent a chafing condition in the negative-G fuel feed drain line, which can result in fuel leaking from the drain line. Leakage of the negative-G fuel feed drain line is a dormant failure. This condition, in combination with a nearby hot surface or other potential ignition source, could result in an uncontrolled fire in the aft equipment bay.