Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 757 and 767 series airplanes. This proposal would require replacement of the hydraulic pressure transfer tube of the ram air turbine (RAT) system with a new hose assembly. This proposal is prompted by reports that, during flight tests, the hydraulic pressure transfer tube of the RAT cracked when the RAT was extended on a Model 767 series airplane. The actions specified by the proposed AD are intended to prevent such cracking, which could result in the loss of hydraulic fluid of the center system and the inability of the RAT to pressurize the center system; this situation could lead to loss of all hydraulic system power in the event that power is lost in both engines.