This aerospace recommended practice provides guidance for the preparation of a Procurement Specification for an aircraft utility system linear hydraulic actuator. This document includes suggested Procurement Specification requirements, standards, processes and procedures for the design and qualification of the utility system actuator.
Rationale: 1.SAE does not have a specification for linear hydraulic actuators used in utility systems.
2. These actuators are the leading cause for hydraulic system removals which are related to dynamic seal leakage caused by seal selection, harsh operating environments (dirt and vibration) in combination with low operating pressure (return).
3. This type of actuator contains many unique functions, control elements and design concerns which are not covered by SAE ARP1281 Flight Control Servoactuator specification. For example, damping (dashpots), manual bleeding, anti-cavitation control, flow rate control (restrictors), zero leakage control (soft seats and elastomeric dynamic seals), lock sequencing, control valve sequencing, mechanical locking, hydraulic locking, back up power activation (shuttle valves), nitrogen actuation, dynamic load sensitivity, return pressure sensitivity and discrete position indication.