Summary
The FAA proposes to revise an existing airworthiness directive (AD) that applies to certain Bombardier Model CL-600-2C10 (Regional Jet series 700 & 701) series airplanes and Model CL-600-2D24 (Regional Jet series 900) series airplanes. The existing AD currently requires revising the Airworthiness Limitations section of the Instructions of Continued Airworthiness by incorporating new repetitive inspections and an optional terminating action for the repetitive inspections, and repairing any crack. This proposed AD would clarify the applicability of the existing AD. This proposed AD results from reports of hydraulic pressure loss in either the number 1 or number 2 hydraulic system due to breakage or leakage of hydraulic lines in the aft equipment bay and reports of cracks on the aft pressure bulkhead web around these feed- through holes. We are proposing this AD to prevent loss of hydraulic pressure, which could result in reduced controllability of the airplane, and to detect andcorrect cracks on the aft pressure bulkhead web, which could result in reduced structural integrity of the aft pressure bulkhead.