T7 - Hydraulic Systems

What is the purpose of a hydraulic system?

To transform, distribute, and utilize mechanical energy using incompressible fluids at high pressure​.

What devices generate pressure?

Pumps/Valves
Hydro-accumulators

Why would you use hydraulic systems?

• High efficiency in power transmission

• Installation flexibility.

• Overload protection.

• reliability.

• Reduced maintenance requirements.

• Low mass => high frequency response (typically higher the better).

• Ease of control.

What aircraft systems are powered by hydraulics?

• Extraction/retraction of landing gear.

• Airbrakes.

• Wheel brakes.

• Wheel steering system.

• Flight control surface operation.

• Wings, ailerons, flaps, rudders, etc.

• Thrust reversers.

• Doors.

• Etc.

What are the advantages of higher pressure

• Smaller actuators and tubing for the same force.

• Reduced overall system weight.

• Higher power density​

What are disadvantages of a higher pressure

• Components may become too small

• More difficult to achieve - leak proof

What are the 2 main types of pump? Examples?

Positive Displacement - Piston, gear, membrane, screw

Fixed displacement pumps - Centrifugal, axial, magnetofluid-dynamics

How many pistons are needed for smooth operation of piston pump?

An odd number of pistons (e.g., 7 or 9) ensures smoother flow, better balance, and reduced vibration

What are the methods to maintain constant pressure?

• Method 1: Constant delivery pump with a regulator valve to return excess fluid to the reservoir.

• Method 2: Variable flow delivery to meet pressure requirements​