In the photo below there are two Igniters, the one on the left shows that the spark is concentrated on one area of the igniter.
Hard to see in this picture is the center electrode is arcing from under the tip. When looking directly at the end of the igniter the tip looks to be normal in diameter but is being undercut.
This can cause the tip to come off in one piece and it’s only way out is through the turbine nozzle vanes and turbine blades. The one on the right shows a more normal wear of the tip but needed to be changed.
Helicopters land in the middle of nowhere on purpose and not starting is a bad thing.
There is not a scheduled inspection for the igniters, when the Engine doesn’t start you go looking. Also the more worn the igniters are the more resistance they create and the harder the exciter box has to work which may cause it to fail.
I recommend inspecting the Igniters every 300 hr. even this may be too long if you have numerous starts per flight hour.
Igniters are not cheap but neither is recovering an aircraft or repairing it in the field.
Also if igniters are not all functioning too much fuel on start can flood the igniters and they can’t fire. ( like in your lawnmower when the sparkplug gets flooded ) Let the aircraft set for at least 3 minutes before attempting an other start.
Helicopter Maintenance Manager
Sacramento Metro Fire District