Airframe IV | Hydraulics & Pneumatics Study Guide

What is the definition of viscosity?

Internal resistance to flow

Definition of chemical stability?

A liquids ability to resist oxidization

Definition of flashpoint?

Temperature at which a liquid gives off vapor in sufficient quantity to momentarily ignite or flash when a flame is applied

What hydraulic fluid category is the most flammable?

Mineral based fluids

What hydraulic fluid category is the least flammable?

Phosphate ester-based

What hydraulic fluid is in the polyalphaolefin category?

MIL-H-83282

What seal and o ring material is compatible with mineral hydraulic fluid?

Synthetic rubber seals

What seal and o ring material is compatible with phosphate ester hydraulic fluid?

Natural fibers and many synthetics

What/who controls hydraulic hydraulic system contamination (from outside sources)

Those who service/maintain equipment

Why is phosphate ester based hydraulic fluid a health and safety concern?

They dissolve fatty materials causing drying of the skin / dermatitis

What PPE must always be worn when working with hydraulic fluid?

Proper gloves & eye protection

What is the difference between open center and closed center hydraulics?

The selector or direction control valves are not operated in series in the closed center hydraulics

What is the advantage of a hydraulic power pack system?

No need for centralized power supply or long supply of hydraulic lines

What components in a hydraulic reservoir are used to control swirling and surging?

Baffles / fins

What are two means of pressurizing a hydraulic system reservoir?

Air pressurized, fluid pressurized

no

Will normal operation of a hydraulic system cause the fluid to become contaminated?

What happens if a hydraulic filter becomes clogged during system operation?

A filter bypass valve opens

Will hydraulic contaminants be found on the inside or outside of the filter elements?

Inside

How may a hydraulic pump be powered?

Engine driven, electric motor, air driven

How are hydraulic pumps classified?

Positive displacement, non-positive displacement

What do “flow control” valves do in a hydraulic system? Name flow control valves.

Controls the speed and / or direction of flow. Selector valve, check valve, sequence valve, pressure control sequence valve,

What valve is used to control the direction of fluid movement in a hydraulic system?

Selector valve

What valve is used to isolate the normal hydraulic system from the emergency system?

Check valve

What component is used to dampen pressure surges in a hydraulic system?

Accumulator

What are the two movements that actuators produce?

Forwards and backwards

How is a “RAT” utilized in a hydraulic system?

A “ram air turbine” is used as backup power if the primary sources are lost

What is the purpose of a hydraulic motor? Name a use of hydraulic motors

A backup source of energy in case of an electrical failure

What is a hydraulic motor driven generator?

A motor spun by hydraulics to generate electrical power in the case of an electrical failure

What is the difference between a gasket and a packing?

Gaskets are used as static seals and packings are used on sliding/moving parts

How must v-rings and u-rings be installed in a hydraulic system?

The open end must face the pressure

How does a high pressure emergency pneumatic system operate?

Pressurized nitrogen is applied to move hydraulic fluid to the actuator