Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes. This proposal would require replacement of any brake system accumulator that has aluminum end caps with an accumulator that has stainless steel end caps. This proposal is prompted by reports of fractures of aluminum end caps on brake system accumulators. The actions specified by the proposed AD are intended to prevent high- velocity separation of a brake system accumulator barrel, piston, or end cap, which could result in injury to personnel in the wheel well area, loss of cabin pressurization, loss of certain hydraulic systems, or damage to the fuel line of the auxiliary power unit.