Airworthiness Directives; Bombardier, Inc. Airplanes

We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440) airplanes. This AD was prompted by reports that the horizontal stabilizer trim actuator (HSTA) spur gear bolts inside the gearbox were found loose, broken, or backed out due to incorrect bending of the anti-rotation tab washer and the improper application of Loctite glue during installation. This AD requires replacing certain HSTAs with a new HSTA. This AD also requires revising the airplane flight manual (AFM) and the maintenance or inspection program, as applicable. We are issuing this AD to prevent failure of the HSTA and subsequent loss of control of the airplane.