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.
Plain English
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.
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.