Hydraulic Systems

What are some possible signs of air in a hydraulic system?

Spongy actuation, chattering sounds.

How do you clear air in a hydraulic system?

Turn the system on and move the flight controls to work the air out of the system into the reservoir where it is not an issue.

Why is bleed air used in hydraulic reservoirs?

To pressurize the system to prevent cavitation and maintain performance.

What is a characteristic of petroleum based hydraulic fluids?

Readily flammable.

What might cause a hydraulic system to have no pressure?

Sheared pump shaft, unloading valve stuck in "kickout", lack of fluid, check valve installed backwards, anything that may cause free flow of fluid to the reservoir or overboard.

What would cause rapid fluctuation in a hydraulic pressure gauge?

Air in the gauge line. To fix this carefully

Where can you find troubleshooting information on the hydraulic system?

AMM

What may cause high system pressure?

Unloading valve (pressure regulator) failing to unload pump. Relief valve maintaining pressure. Contaminants clogging the line may also do this.

What may cause low systems pressure?

Unloading valve (pressure regulator) leaking, Relief valve leaking, Check valve leaking, faulty pump.

What may cause slow actuation?

Internal leakage.

What may cause a banging sound?

Improper accumulator action.

What is the purpose of an accumulator?

Supplies an emergency amount of fluid and pressure to essential systems. Its also filled with Nitrogen to dampen pressure surges.

How do you service an accumulator?

First step is to relieve system pressure

What hydraulic source does the RAT power?

Emergency fluid resovior

How are the hydraulic systems operated in a "ScareBus A-320"?

The ECAM (Electronic Centralized Aircraft Monitor), the pilot does however have an overhead panel to operate the systems with buttons.

What is the difference between the PTU and Engine/Electric Pump buttons compared to the RAT button?

The switch it guarded so it does not deploy accidentally because it causes lots of drag and is not undeployable.

What enables the "Blue" and "Yellow" Airbus hydraulic systems to pressurize each other automatically?

The PTU

What is the pressure at which the hydraulic fluid is at in an Airbus A-320 and is it a constant or variable pressure.

3,000 PSI and it is constantly at that pressure.

Where are the fire shutoff valves normally located in a hydraulic system?

Between the reservoirs and the engine driven pumps.

When system demand is high on a Boeing 777 what will aid the engine driven pumps?

The electrical pumps

If you see a yellow streak of dry fluid leaking from a fluid line what was it filled with?

Shydrol, purple in color but dries yellow.

What is a hydraulic mule?

Similar to an EPU but supplies high hydraulic pressure without turning the planes engine on or electrical pumps.

What is the purpose of a hydraulic pressure regulator?

One purpose of the pressure regulator is to manage the output of the pump to maintain system operating pressure within a predetermined range.

What is a hydraulic fuse?

The fuse is intended primarily to protect the system from loss of reservoir fluid in the event of a ruptured tube, hose or component.

What position are hydraulic fuses normally in?

NO (Normally open)

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