Aircraft Systems & Structures Flashcards

What is the primary function of a hydraulic accumulator?

Answer: Store fluid under pressure to dampen surges and supplement pump output

An accumulator stores pressurized fluid to absorb pressure surges and provide extra flow during peak demand or a pump failure.

Which seal material is compatible with phosphate ester (Skydrol) hydraulic fluid?

Answer: Butyl rubber

Phosphate ester fluids attack petroleum-compatible seals, so butyl rubber or ethylene propylene seals are used.

MIL-H-5606 petroleum-based hydraulic fluid is dyed what color for identification?

Answer: Red

MIL-H-5606 is red, while Skydrol phosphate ester fluids are typically purple.

What is the purpose of a shimmy damper on a nose landing gear?

Answer: Prevent rapid oscillation of the nosewheel during ground roll

A shimmy damper resists rapid side-to-side oscillation of the nosewheel at speed.

When adding hydraulic fluid to an air/oil (oleo) shock strut, the strut should normally be in what condition?

Answer: Fully compressed with the air charge released

Servicing is done with the air released and the strut fully compressed so the correct fluid level can be established.

What is the function of a thermal relief valve in a hydraulic system?

Answer: Relieve pressure caused by expansion of trapped fluid as temperature rises

Thermal relief valves protect isolated lines from excessive pressure caused by thermal expansion of trapped fluid.

What is the purpose of fusible plugs installed in aircraft wheels?

Answer: Release tire pressure if the wheel overheats from excessive braking

Fusible plugs melt at a set temperature to deflate the tire and prevent an explosive tire failure.