Definition
A component on an aircraft engine that is powered by the flow of hot exhaust gases leaving the engine, rather than by mechanical linkage to the crankshaft. In turbocharging, the exhaust-driven device is the turbine wheel that spins as exhaust gas passes over it, which in turn drives a compressor to pressurize intake air.
Plain English
A part that is spun by the engine's hot exhaust gases on their way out, instead of being turned by a belt, gear, or shaft from the engine itself.
Context Anchor
Seen in turbocharging discussions when explaining how a turbocharger can boost engine intake air without being powered by a separate motor.
Derivation
"Exhaust-driven" simply means "powered by exhaust." The phrase highlights the source of energy: gases that would otherwise be wasted out the tailpipe are instead used to do useful work.
Why Pilots Care
It enables an engine to maintain sea-level manifold pressure well above the altitudes where a normally aspirated engine would lose power, expanding the aircraft’s useful operating envelope.
Analogy
It is like wind turning a small wheel, except the moving air is hot exhaust from the engine and the wheel is part of the engine system.
Intuition Check
Do not read “exhaust-driven” as meaning the device produces exhaust. Here it means the device is powered by exhaust gas coming from the engine.
Example Sentence 1
The turbocharger is an exhaust-driven device, so it adds manifold pressure without robbing power from the crankshaft.
Example Sentence 2
During the preflight, the instructor pointed out the wastegate that regulates the exhaust-driven device to prevent overboost.