Definition
A turbine engine starter that can be driven by either of two power sources: high-pressure air directed onto a turbine wheel inside the starter, or hot gas produced by burning a solid-propellant cartridge inside a breech attached to the starter. Either source spins the starter turbine, which through a gear reduction turns the engine to starting speed.
Plain English
A starter motor for a jet engine that can be spun up two ways: by blowing high-pressure air through it, or by firing a small explosive cartridge that produces hot gas. Either method makes the starter turn fast enough to get the engine going.
Context Anchor
Seen in discussions of older or specialized aircraft engine starting systems, especially where electrical power or ground support equipment may not be available.
Derivation
Cartridge' comes from the French cartouche, meaning a rolled paper container holding a charge of powder — the same idea as a rifle cartridge. 'Pneumatic' is from the Greek pneuma, meaning breath or air. Together they describe a starter that can be powered by a small explosive charge or by air pressure.
Why Pilots Care
Enables engine starts in locations without ground support equipment or when batteries are insufficient for large engines.
Analogy
It is a little like using a one-time pressure canister to give the engine its first spin. Once the cartridge is used, it must be replaced before that starting source can be used again.
Intuition Check
Do not read pneumatic here as meaning it must be connected to an outside air hose. In this term, the pressure comes from the fired cartridge itself.
Example Sentence 1
Because the forward operating base had no ground support equipment, the crew used the cartridge-pneumatic starter to light off the engines.
Example Sentence 2
After the cartridge-pneumatic starter brought the turbine up to speed, fuel was introduced and ignition occurred.