Airworthiness Directives; Boeing Model 747-400 Series Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 747-400 series airplanes. That AD currently requires replacement of the decompression panels that are located in the smoke barrier between the passenger and main deck cargo compartment with new panels of an improved design. This new AD requires modification of the decompression panels on the smoke barrier in the main deck cargo compartment, or replacement of the smoke barrier with an improved smoke barrier, as applicable. This new AD also requires repetitive inspections of the decompression (vent) panels on the smoke barrier and corrective actions if necessary. This new AD also adds airplanes to the applicability. This AD results from reports of decompression panels on the smoke barrier opening in flight and on the ground without a decompression event. We are issuing this AD to prevent inadvertent opening or tearing of decompression panels, which could result in degraded cargo fire detection and suppression capability, smoke penetration into an occupied compartment, and an uncontrolled cargo fire, if a fire occurs in the main deck cargo compartment.