SAE ARP1281

Description / Abstract: This aerospace recommended practice provides a framework and suggested procedures or values for requirements for the design, performance, and test of hydraulically powered servoactuators for use in aircraft flight control systems.

The original version of this document was intended for military usage: consequently, the requirements still often reflect such use. However, the basic requirements of this ARP may and should be applicable to commercial usage as well, provided that appropriate considerations are given for the applicable FAR/JAR 25 regulations, hydraulic fluids, and environmental conditions.

Purpose:

This recommended practice is a guide and surrogate specification for preparing a detail specification for a particular servoactuator application.

Product Classification:

Servoactuators covered by this recommended practice are of the following classes:

Class A - Power Actuators

Class B - Signal Conversion Actuators

Class C - Power and Signal Conversion Actuator Combination

For military aircraft, the servoactuators covered by this recommended practice include those in the following types of hydraulic systems:

a. Type I − 65 to +160 °F (−54 to +71 °C) fluid temperature range

b. Type II − 65 to +275 °F (−54 to +135 °C) fluid temperature range

c. Type III − 65 to +390 °F (−54 to +199 °C) fluid temperature range

For commercial aircraft, the servoactuators covered by this recommended practice include those suitable for use with type IV and type V phosphate ester fluids.

Field of Application:

A servoactuator in the flight control system positions an aerodynamic control surface or other force effector to produce forces and moments on the aircraft for stability and control of the vehicle. These servoactuators may be controlled by mechanical, electrical, photonic or fluidic inputs, or combinations thereof, and may be powered by one or more hydraulic systems. The complete actuator assembly may incorporate basic components such as servovalve, input linkage and electrical, optical, and/or mechanical position feedback systems, and redundancy logic in addition to the actuating cylinder. These components are usually designed as an integral package, but in some cases are physically separated. Additional components may also be included and configured integrally or separately such as bypass valves, filters, pressure switches, motor or solenoid operated shutoff valves, thermostatic control valves, hydraulic logic, mechanical locking devices and electrical transducers.