Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to all Bombardier Model DHC-8-101, -102, - 103, -106, -201, -202, -301, -311, and -315 airplanes. The existing AD currently requires installation of a placard on the instrument panel of the cockpit to advise the flightcrew that positioning of the power levers below the flight idle stop during flight is prohibited. Additionally, the existing AD requires eventual installation of an FAA- approved system that would prevent such positioning of the power levers during flight. Installation of that system terminates the requirement for installation of a placard. This proposed AD would require operators who have incorporated a certain Bombardier service bulletin to perform repetitive operational checks of the beta lockout system and to revise the Airworthiness Limitations document. This proposed AD is prompted by in-service issues reported by operators who incorporated Bombardier Service Bulletin 8-76-24 as an alternative method of compliance to the existing AD. We are proposing this AD to prevent the inadvertent activation of ground beta mode during flight, which could lead to engine overspeed, engine damage or failure, and consequent reduced controllability of the airplane.