Definition
A turbine-driven engine starter used on most turbine-powered aircraft, in which a high-volume flow of compressed air spins a small turbine wheel. The turbine drives the engine's main shaft through a reduction gear and clutch, accelerating it to a speed at which fuel can be introduced and the engine can self-sustain. The compressed air is supplied by a ground air cart, an onboard auxiliary power unit (APU), or bleed air from another running engine.
Plain English
A device that uses a strong stream of compressed air to spin a turbine engine fast enough for it to start running on its own.
Context Anchor
Seen in turbine-engine starting systems, especially when starting an engine using air from a ground air cart, another engine, or an onboard air source.
Derivation
From 'turbine' (Latin turbo, a spinning thing) and 'starter.' The name reflects exactly how it works: air spins a small turbine, and that turbine starts the engine.
Why Pilots Care
Provides a reliable way to start large turbine engines when battery power alone is insufficient.
Intuition Check
Do not read this as “a starter for an air turbine.” It means a starter powered by air, used to turn an aircraft engine during start.
Example Sentence 1
The first engine was started using bleed air from the APU routed to the air turbine starter.
Example Sentence 2
During the preflight, the crew verified the air supply pressure to the air turbine starter.