During the start sequence, fuel is ignited by the igniter, which is energized by the ignition exciter. Once combustion becomes self-sustaining, the igniter is de-energized at _> 400º F.
Proper installation of the igniter plug on the combustor chamber is essential for long operating life. The igniter plug has a special distance ring that must be installed between the plug and the compressor rear frame. The correct distance of the plug in the rear frame is important, both for operation and cooling, and it can be adjusted with the distance ring. Cooling is achieved with compressor air flowing alongside the igniter plug tip. Also 12 holes in the plug tip are present for cooling purposes, and, finally 6 holes provide cooling air for the igniter plug shank.
To ensure a successful light off, the ignition system is comprised of two independent ignition systems. Due to already increased air temperature from compression through the compressor, and fuel atomization from the fuel nozzle, it is possible to achieve ignition with only one igniter. Running two independent systems ensures the ability to maintain normal operations even with the complete loss of one system.