Plain English Meaning
A curved metal tube inside a pressure gauge that uncurls slightly when pressure pushes against the inside of it. That small uncurling movement turns a needle on the gauge face, so the pilot can read the pressure.
Full Definition
A pressure-sensing element consisting of a curved or coiled metal tube, sealed at one end, that tends to straighten when internal pressure increases. The movement of the sealed end is mechanically linked to a pointer on a gauge, providing a direct mechanical readout of pressure. Bourdon tubes are commonly used in aircraft instruments to measure oil pressure, hydraulic pressure, fuel pressure, and similar high-pressure systems.
Context Anchor
Seen in aircraft maintenance and instrument discussions, especially when learning how pressure gauges show oil, fuel, hydraulic, or air pressure.
Derivation
Named after Eugene Bourdon, a French engineer who patented the design in 1849. Knowing it is a person's name (not a technical adjective) helps the term stop feeling mysterious -- 'Bourdon' is just who invented it.
Why Pilots Care
Delivers reliable, non-electric pressure readings critical for altitude, airspeed, and engine monitoring when electrical systems fail.
Analogy
Think of a party blower -- the paper tube that uncurls when you blow into it. A Bourdon tube does the same thing on a tiny scale with metal and oil pressure instead of paper and breath.
Intuition Check
Do not read “tube” as just a pipe that carries fluid from one place to another. In this context, the tube is also the sensing part that turns pressure into gauge movement.
Example Sentence 1
The oil pressure gauge uses a Bourdon tube that flexes as engine oil pressure rises, moving the needle across the dial.
Example Sentence 2
Static pressure changes cause the Bourdon tube in the altimeter to flex and drive the altitude pointer.