Airworthiness Directives; de Havilland Model DHC-7 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all de Havilland Model DHC-7 series airplanes, that requires performing a review of the airplane maintenance records to determine if any insulation blankets have been repaired or changed during service, and various follow-on actions, if necessary. This amendment is prompted by reports of corrosion forming on areas of the airplane structure where black film thermal insulation blankets are used. The actions specified by this AD are intended to prevent such corrosion, which could result in degradation of the structural capability of the airplane fuselage and consequent sudden loss of cabin pressure.