Electrical measurements on aircraft-engine ignition circuits

A method of measuring ignition voltages with a cathode-ray oscillograph is described. Magneto and spark-plug voltage oscillograms covering several consecutive firing pulses were taken on a complete aircraft magneto ignition system under several engine operating conditions. Oscillograms taken with spark plugs firing in air show differences when compared with engine tests. An improved electronic oscillograph has been developed which is well adapted for ignition measurements.