Definition
A principle of fluid dynamics stating that as the speed of a moving fluid (liquid or gas) increases, the pressure within that fluid decreases. In aviation, this relationship between velocity and pressure helps explain how airflow over a wing produces lift and how venturi-style devices generate suction for pneumatic instruments.
Plain English
When air or any fluid speeds up, its pressure drops. When it slows down, its pressure rises.
Context Anchor
Seen in pneumatic system discussions, especially when explaining how airflow or a venturi-type passage can create the pressure difference used by gyroscopic instruments.
Derivation
Named after Daniel Bernoulli, an 18th-century Swiss mathematician who described the relationship between fluid speed and pressure. Knowing it is a person's name (not a technical word) helps avoid trying to decode the term itself.
Why Pilots Care
It explains how venturis generate the vacuum that spins attitude and heading indicators when engine-driven pumps are unavailable.
Analogy
Think of a garden hose. When you squeeze the nozzle, the water speeds up as it passes through the narrow opening. In the same way, air speeding up over a curved wing surface has lower pressure than the slower air beneath it.
Grounding Statement
Faster-moving air pushes sideways with less force than slower-moving air.
Intuition Check
Do not think “faster air” means “more pressure” in this context. Here, faster airflow means lower static pressure, which can create a useful pressure difference.
Example Sentence 1
Bernoulli's principle helps explain why the lower pressure above a wing, where air moves faster, produces lift.
Example Sentence 2
During preflight the pilot checks that the suction gauge shows proper vacuum created by Bernoulli's principle in the pneumatic system.