Airworthiness Directives; Bombardier Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes

The FAA is superseding an existing airworthiness directive (AD) that applies to certain Bombardier Model CL-600-2B19 (Regional Jet Series 100 & 440) airplanes. The existing AD currently requires repetitive inspections of the left and right engine throttle control gearboxes for wear, and corrective action if necessary. The existing AD was prompted by numerous failures of the engine throttle control gearbox, some of which resulted in an in-flight engine shutdown. This AD adds airplanes to the applicability of the existing AD. We are issuing this AD to prevent excessive wear of the gearboxes and subsequent movement or jamming of the engine throttle; movement of the throttle towards the idle position brings it close to the fuel shut-off position, which could result in an in-flight engine shutdown.