• Author / Uploaded
• Kashyap Sompura

Citation preview

VACUUM/PNEUMATIC

SYSTEM LAYOUT • Twin engine aircraft vacuum system contains engine drive vacuum pump on each engine. • Associated line & components are separate for both the engine act as wo separate vacuum systems. • The vacuum lines from both the pumps are routed through relief valve & check valve into four way selector valve. • From four way manifold flexible hoses connect vacuum supply to vacuum operated instruments such as turn & bank indicators, artificial horizon.

SYSTEM LAYOUT • As reduced vacuum supply required for turn & bank indicators, needle valve are installed in supply line of turn & bank indicators. • The valve has three position Main, Left T & B And right T & B. • In the main position the vacuum gauge indicate vacuum pressure in the line of artificial horizon & directional gyro. • In the other position , the lower vacuum pressure for T & B indicators.

PNEUMATICS SYSTEM

• High Pressure( 3000 Psi) Pneumatic systems are used for 1. Brakes 2. Opening & closing of doors 3. Driving hydraulic pumps, alternators, starters, water injection pumps 4. Operating emergency devices such as brakes & landing gear • Many high pressure pneumatic systems are installed for one time emergency or back-up use and are completely discharged when used • They use pressurized air or nitrogen containers with no on-board means provided to re-pressurize the system once deployed.

PNEUMATICS SYSTEM

• Other high pressure use systems pneumatic pressurized containers that are re-charged during flight of action the through compressors installed in the system. This type of installation allows the pneumatic system components operate to repeatedly rather than just once in a manner similar to a hydraulic system.

PNEUMATICS SYSTEM • Sources for high pressure pneumatic systems include enginedriven and other on-board compressors, ground air, and ground nitrogen sources. • some aircraft employ permanently installed air compressors which recharge air bottles whenever pressure is used for operation of a unit. • Several types of compressors are used for this purpose. Some have two stages of compression, while others have three, depending on the maximum desired operating pressure. • They are typically oil lubricated thus the system plumbing may contain an oil separator of some type as well as a means for removing moisture in the system.

PNEUMATICS SYSTEM • Alternately, air and nitrogen storage containers for pneumatic systems are filled on the ground with either a ground-based compressor or a high pressure bottle transfer for nitrogen. • For high-pressure systems, air is usually stored in metal bottles at pressures ranging from 1 000 to 3 000 psi, depending on the particular system. • Charging of high pressure bottles is done with either an onboard compressor or a ground source. The typical high-pressure storage bottle has two ports, one of which is equipped with a charging valve. • Ground-operated compressor or air bottle can be connected to this valve to add air. Nitrogen may also be introduce through this valve.

PNEUMATICS SYSTEM • For on-board charging, the charging valve is plumbed to the compressor outlet. The other valve on a typical high pressure pneumatic reservoir is a control valve. It acts as a shutoff valve, keeping air trapped inside the bottle until the system is operated. • Pneumatic power is distributed through high pressure steel or stainless steel lines. The use of check valves is common to prevent back flow. • In systems that operate one time and emergency systems, a shuttle valve is often used to close off the normal system flow and allow flow of high pressure pneumatic air to operate the component. • A pressure regulator maintains system pressure with a relief valve to limit pressure in case of regulator failure.

PNEUMATICS SYSTEM • Check valves are used to prevent back flow to the compressor. In addition to the use of a selector valve or control valve to direct the air to the portion of the system through which it must be distributed. • Isolation valves are often installed in the distribution system to isolate working components from those that are inoperative or to isolate part of the system that has a leak.

PNEUMATICS SYSTEM • All components in a high pressure system do not pneumatic necessarily operate at full system pressure. Pressure reducing valves are used to lower the system pressure to that require by a particular component or sub system. Restrictors and variable restrictors are use to control the speed of the by operated component(s) pneumatic.

PNEUMATICS SYSTEM • Many aircraft use a high-pressure pneumatic back-up source of power to extend the landing gear or actuate the brakes if the main hydraulic braking system fails. • High pressure nitrogen is not directly used to actuate the landing gear actuators or brake units but, instead, it applies the pressurized nitrogen to move hydraulic fluid to the actuator. This process is called Pneudraulics. • Nitrogen used for emergency landing gear extension is stored in two bottles, one bottle located on each side of the nose wheel well. Nitrogen from the bottles is released by actuation of an outlet valve. Once depleted, the bottles must be recharged by maintenance personnel. Fully serviced pressure is approximately 3 100 psi at 70 °F (21 °C) enough for only one extension of the landing gear

PNEUMATICS SYSTEM • The outlet valve is connected to a cable and handle assembly. The handle is located on the side of the copilot's console and is labeled EMER LDG GEAR. Pulling the handle fully upward opens the outlet valve, releasing compressed nitrogen into the landing gear extension system. • Pushing the handle fully downward closes the outlet valve and allows any nitrogen present in the emergency landing gear extension system to be vented overboard. ‘the venting process takes approximately 30 seconds.

PNEUMATICS SYSTEM • A medium pressure pneumatic system (35-150 psi) does not include an air bottle/storage reservoir. Instead, it draws air from the compressor section of a turbine engine. This is known as bleed air and is used to provide pneumatic power for engine starts, engine de-icing, wing de-icing, air conditioning and more. • In some cases, it provides hydraulic power to the aircraft systems (if the hydraulic system is equipped with an air driven hydraulic pump). Engine bleed air is also used to pressurize the aircraft's hydraulic reservoirs, anti-ice the TAT probe and other applications specific to particular aircraft.

PNEUMATICS SYSTEM • Ground sources of pneumatic air also are used. Fixed and portable cart type units containing engine-driven air supply compressors are connected into the pneumatic manifold to power the pneumatic system without running the engines. A ground air supply connector and check valve is provided in the manifold for the ductdiameter sized hose from the ground source.