System Basics
This core law governs the distribution of pressure equally in all directions within a confined liquid.
What is Pascal's Law?
This term describes a fluid's internal resistance to flow and is considered one of its most important properties.
What is viscosity?
This component stores hydraulic fluid, replenishes lost fluid, and acts as an overflow basin.
What is a reservoir?
This type of valve allows fluid to flow in one direction but blocks it from flowing in the opposite direction.
What is a check valve?
The Boeing 737 has this many total hydraulic systems.
What is three (Systems A, B, and Standby)?
Aircraft hydraulic systems typically operate within this wide pressure range (in psi).
What is 200 to 5,000 psi?
This specific instrument measures fluid viscosity by timing how long it takes for 60 mL of fluid to pass through a standard orifice at 100 °F.
What is a Saybolt Viscometer?
This specific component dampens pressure surges, maintains system pressure, and provides emergency power.
What is an accumulator?
This specific valve ensures that hydraulic components operate in a strict, preset chronological order.
What is a sequence valve?
This emergency component powers the Boeing 777 center hydraulic system during critical failures.
What is a Ram Air Turbine (RAT)?
This type of hydraulic system maintains continuous fluid pressure when the power pump operates and arranges its actuators in parallel.
What is a closed-center hydraulic system?
This property is the temperature at which a hydraulic fluid vapor momentarily ignites when exposed to a flame.
What is the flash point?
These aluminum finned tube devices are placed inside aircraft fuel tanks to cool hot hydraulic fluid.
What is a heat exchanger?
This safety device automatically shuts off fluid flow if it senses a sudden, excessive flow rate.
What is a hydraulic fuse?
This specific mechanism supplies additional fluid for autoslats and leading-edge flaps on a 737 when the system B EDP fails.
What is the Power Transfer Unit (PTU)?
This type of hydraulic system features no system pressure when idle, circulating fluid freely from the reservoir through selector valves and back.
What is an open-center hydraulic system?
Combining fire-resistant MIL-H-83282 fluid with mineral-based MIL-H-5606 fluid results in the loss of this critical characteristic.
What is fire resistance?
These types of filters are explicitly designed to prevent particles greater than 10 microns from contaminating the system.
What are micron filters?
This valve directs fluid to essential systems first and restricts flow to non-essential systems until enough pressure builds.
What is a priority valve?
This dedicated isolation system protects the Boeing 777 from engine bursts and preserves critical brakes and steering.
What is the Center Hydraulic Isolation System (CHIS)?
Modern aircraft reduce overall weight by utilizing this type of electronic input control coupled with smaller power packs.
What is fly-by-wire?
Phosphate ester-based fluids (such as Skydrol) require seals made out of this specific type of material
What is butyl rubber (or ethylene-propylene elastomers)?
These specific pumps provide a constant, fixed amount of fluid per revolution regardless of the system pressure.
What are positive-displacement (or constant-displacement) pumps?
This automatic selector valve directs emergency backup pressure to critical components if the normal pressure side fails.
What is a shuttle valve?
Main system pumps draw fluid from this higher point in a reservoir to prevent complete fluid loss during an external line leak.
What is a standpipe?