Abstract: The characteristics of an energizing voltage pulse and of the spark discharge in an ignition device for a gas turbine engine are monitored by providing a voltage whose magnitude and duration correspond to those of an electrical field in the ignition device. An output signal is provided only when the duration and magnitude of the energizing pulse are respectively not greater than and not less than predetermined values, and when the time integral over a preset period of spark discharges in the device is greater than a predetermined value.

Abstract: A monitoring arrangement for a gas turbine spark ignition system in which the spark discharge current oscillates at a known frequency includes a sonic sensor accoustically coupled to the spark igniter, a filter for passing only those signals from this sensor which have a frequency corresponding to that of the discharge current and indicating means responsive to the filter output for indicating that the spark igniter is operating. An additional optical sensor may provide a signal response to a spark gap in the ignition system, signals from both sensors being required to energize the indicating means.