1. Aircraft Hydraulic Systems
AIAA Design Group II

2. Basic Hydraulic System
A valve is opened, the hydraulic flows into the actuator and presses against the piston, causing it to move and in turn move the attached control surface
Reference:

3. General Uses
Used for flight control, actuation of flaps, slats, weapons bays, landing gear, breaks
Provides the extra force required to move large control surfaces in heavy aerodynamic loads.

4. General Specifications
Several different Fluids
MIL-H-5606,   MIL-H-83282,   and MIL-H-81019
General Temperature Ranges : -65°F to 295°F
Pressures:
Airbus A380 has 5000psi hydraulic system
Typical commercial airline pressure is 3000 psi

5. Problems with Hydraulics
Heavy
High maintenance
Adds cost and creates a logistics problem
Requires space (pumps, hydraulic lines, etc.)

6. Possible Improvements
Electric Actuators
Consists of a small electric motor, pump and actuator ram requiring about 1 pint of hydraulic fluid
Flight tested by NASA’s Dryden Flight Research Center on a modified F-18.
Provides significant weight savings by eliminating pumps and hydraulic lines
Also could decrease required maintenance
Reference: NASA Dryden Flight Research Center. News Release 98-84

7. Electro – Mechanical Actuator
Reference: Air Force Research Laboratory

8. Impact on Design
Need to allow sufficient space for required hydraulic systems
Weight of the system must be accounted for