Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747-400 series airplanes. The existing 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 proposed AD would require 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 proposed AD would also require repetitive inspections of the decompression (vent) panels on the smoke barrier and corrective actions if necessary. This proposed AD also adds airplanes to the applicability. This proposed AD results from reports of decompression panels on the smoke barrier opening in flight and on the ground without a decompression event. We are proposing 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.