Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Model 747 series airplanes. This proposal would require a repetitive detailed inspection of the aft pressure bulkhead for indications of "oil cans" and previous "oil can" repairs, and corrective actions, if necessary. An "oil can" is an area on a pressure dome web that moves when pushed from the forward side. This action is necessary to detect and correct the propagation of fatigue cracks in the vicinity of "oil cans" on the web of the aft pressure bulkhead, which could result in rapid decompression and overpressurization of the tail section, and consequent loss of control of the airplane. This action is intended to address the identified unsafe condition.