Airworthiness Directives; Boeing Model 747 Airplanes

The FAA is superseding an existing airworthiness directive (AD) that applies to certain Boeing Model 747 airplanes. The existing AD currently requires modifying the inflation systems of the upper deck escape slides; single-piece off-wing escape ramps/slides; two-piece off-wing escape slides; and door 1, 2, 4, and 5 escape slides/rafts; as applicable. This AD expands the applicability to include an additional airplane. This AD results from a report of 30- to 60-second delays in the inflation of escape slides/rafts. We are issuing this AD to prevent actuation delays in the inflation systems of the escape slides/rafts, which could result in delayed or failed deployment of escape slides/ rafts during emergency evacuation of an airplane.