aircraft hydraulic system

There are basically three sources of power used to operate and manage a modern aircraft. They are:

- the electrical power

- hydraulic power

- the pneumatic power.

When high force and high speed are required, then the choice is to use the hydraulic power.

Just like in a car, the hydraulic power is used to assist in moving the steering. In an aircraft, the hydraulic power is used to move the flight control which will steer the aircraft. It is also used for move the landing gear and power the brake.

The source of hydraulic power.

The power come from engine driven pumps and electrical pumps. Electrical pumps are normally a back-up

The Control

The control in the cockpit are from the hydraulic panel on the overhead. You can switch off the engine pumps and on/off the electrical pumps.

The control of the flight control is done either by steering columns or the joy-sticks.

The Usage

- Flight controls like flaps,slat or ailerons.

- Landing gear and its braking system.

- the operating of cargo doors.

aircraft pneumatic system for Cabin Crew

To provide additional knowledge of the aircraft systems for cabin crews, we had include some information which we feel are important.

These information provide some background and appreciate of the aircraft. The knowledge can be useful in answering some of the queries from curious passengers.

About Pneumatic System

The pneumatic system is the system to supply, control and make the compressed air available for different application for the aircraft, both in the air or on ground.

Take note of the keywords, supply, control and make available of the compressed air. The actual usage of the pneumatic is included in the other section. Example, the use of pneumatic for air conditioning is put under the topic of air conditioning.

Applications (uses) of the compressed air.

1. Compressed are is mainly used to pressurize the aircraft. As the modern aircraft can fly to as high as 37,000 feet, the air is too thin at that altitude. As such the aircraft cabin pressure has to be maintained high for the safety of the passengers.

The function to maintain the pressure and the comfortable air condition is handle in different system.

2. Pneumatic is used to start a jet engine.

Most jet engines are started using a pneumatic starter. Pneumatic starter had a better power to weight ratio.

3. Use for anti-icing anf deicing.

These involve 2 functions, deicing is removing the ice after it had already formed. Anti-icing is the action taken to prevent the formation of ice.

The hot air is used to heat up the leading edge of the aircraft's wing to prevent the formation of the ice.

Where air comes from.
The pneumatic are from:

1. The engines : As air is being compressed by the engine, it gets hotter, the combination of cold and hot compressed are is being regulated to give the system the correct temperature and pressure.

2. The auxiliary power (APU) unit is a small jet engine designed to provide the compressed air as well as the electrical power.

3. Ground Power Unit: On ground, the aircraft can be connected to a ground power unit.

Control and Indication.

A simple switches and indication lights are provided in the cockpit to control the system. The system also has protection against over temperature. You can see the panel is a representative of the system, the sources are at the bottom. The users are on top.

Aircraft Electrical System

As a cabin crew or air hostess you may receive questions on aircraft electrical system fitted on the aircraft. This can come out of curiosity or the needs of the travelling passengers. The passengers may need to charge up their hand phones or computers.

If you are a cabin crew for a jetliner, the main system is ac and the secondary system is DC. The data are as follows:

A. Primary system
-115/200 volts 400 hertz 3 phases
- provided by the generator in the engines and in the auxiliary power unit.

B. The secondary system
- 28 V direct current, derived from the AC system. It has a battery for emergency.


Currently the aircraft can be fitted with special outlet to give the standard home power, which can be 240 or 115 volt.


note: APU - or auxiliary power unit is a small jet engine installed to provide the electrical power and pneumatic for the ground operation. It can also be operated in flight below a specific height. The pneumatic is used for engine start or airconditioning.

The aircraft electrical system is complex for most passengers, unless they are engineers by background. The power of the aircraft is big enough to service a small town.