Airworthiness Directives; ATR-GIE Avions de Transport Régional Airplanes

The FAA is adopting a new airworthiness directive (AD) for all ATR--GIE Avions de Transport R[eacute]gional Model ATR42 and Model ATR72 airplanes. This AD was prompted by a design review that determined that the inspection interval of the pressure regulator and shut-off valve (PRSOV) functional test must be reduced to meet the design safety objectives, due to a risk of dormant failures. This AD requires repetitive functional tests of each PRSOV, and applicable corrective actions. The FAA is issuing this AD to address the unsafe condition on these products.