Definition
Electrical devices in a gas turbine engine combustion chamber that produce a high-energy spark to ignite the fuel-air mixture during engine start. Once combustion is established and self-sustaining, the igniter plugs are switched off and play no further role in normal running.
Plain English
The spark makers that light the fuel in a jet engine when you start it. After the fire is going steadily, they turn off because the burning keeps itself going.
Context Anchor
Encountered when studying gas turbine engine starting, ignition, and engine relight procedures.
Derivation
From Latin ignire, 'to set on fire,' the same root behind 'ignite.' A 'plug' here is the threaded fitting that screws into the combustion chamber wall, similar in shape to a piston-engine spark plug but built for far higher energy and heat.
Why Pilots Care
Reliable igniter plugs are required for consistent engine starts, especially in cold weather or after shutdowns.
Analogy
An igniter plug is similar in purpose to a spark plug in a car engine: it provides the spark needed to begin combustion. In a turbine engine, it is mainly needed for starting, not for every power stroke.
Intuition Check
Do not assume igniter plugs keep firing all the time in normal operation. In many turbine engines, they are mainly used for starting and selected relight situations.
Example Sentence 1
After the starter spooled the engine to the correct speed, the pilot moved the fuel control to run and the igniter plugs lit the fuel-air mixture in the combustion chamber.
Example Sentence 2
After landing, the crew inspected the igniter plugs for erosion before the next flight.