Airworthiness Directives; Boeing Model 737-200, -300, -400, and -500 Series Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 737-200, -300, -400, and -500 series airplanes. This AD requires a one-time inspection of the frames between station 360 and station 907 to determine if a subject support bracket for the air conditioning outlet extrusion is installed, and related repetitive investigative actions and repair if necessary. This AD also provides an optional preventive modification that ends the repetitive investigative actions. This AD also requires a one-time post-modification/repair inspection for cracking of each repaired/modified frame. This AD results from numerous reports indicating that frame cracks have been found at the attachment holes for support brackets for the air conditioning outlet extrusion. We are issuing this AD to detect and correct such cracking, which, if the cracking were to continue to grow, could result in a severed frame. A severed frame, combined with existing multi-site damage at the stringer 10 lap splice, could result in rapid decompression of the airplane.