Definition
Failures or abnormal conditions in an airplane's hydraulic system, which uses pressurized fluid to operate components such as landing gear, flaps, brakes, and flight controls. Malfunctions can include loss of fluid, loss of pump pressure, broken lines, or contamination, and may result in partial or complete loss of the systems the hydraulics power.
Plain English
Something has gone wrong with the system that uses pressurized fluid to move parts of the airplane like the landing gear, brakes, or flaps. Depending on the failure, those parts may work poorly or not at all.
Context Anchor
Encountered during emergency and abnormal procedures, especially when planning an approach or landing with possible gear, flap, brake, or control problems.
Derivation
Hydraulic comes from the Greek hydor, meaning water, and aulos, meaning pipe or tube. The original idea was moving water through pipes to do work. In airplanes, the fluid isn't water but a specialized oil — yet the principle is the same: pressurized fluid in lines doing the work of pushing and pulling parts.
Why Pilots Care
These malfunctions can prevent normal gear extension or flap operation, requiring pilots to use alternate procedures such as manual extension to land safely.
Grounding Statement
If the airplane cannot build or hold hydraulic pressure, the parts that depend on that pressure may not work normally.
Intuition Check
Do not assume a hydraulic system malfunction always means total failure. It may be a leak, low pressure, slow movement, partial operation, or complete loss, depending on the airplane and the affected part.
Example Sentence 1
After noticing the hydraulic pressure gauge reading zero, the pilot referred to the checklist for hydraulic system malfunctions and prepared to use the emergency gear extension.
Example Sentence 2
Simulated hydraulic system malfunctions help students practice landing without normal power to the landing gear.