Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Bombardier Model DHC-8-400 series airplanes. This proposed AD would require revising the Limitations section of the airplane flight manual to include procedures for pulling the "HYD PWR XFER'' circuit breaker in the event of the loss of all hydraulic fluid in the No. 1 or No. 2 hydraulic system. This proposed AD results from reports of fluid loss in the No. 2 hydraulic system, causing the power transfer unit to overspeed, increasing the fluid flow within the No. 1 hydraulic system. We are proposing this AD to prevent possible loss of both the No. 1 and No. 2 hydraulic systems, resulting in the potential loss of several functions essential for safe flight and landing of the airplane.