Some problems in aircraft magneto development

Following a brief review of present-day ignition requirements, the elementary principles of magneto operation, including low-speed performance, are discussed, and arguments are given to explain the discrepancy which is found between theory and practice in the magnetic circuit. Development and progress in regard to the mechanical operation of contact-breakers is described, and a review of their electrical limitations leads to explanations why this component imposes a practical upper limit on the output voltages and sparking speeds of magnetos. Interesting phenomena associated with high-voltage distribution are included, particular referencebeing made to distributor operation at high altitudes. Some developments are discussed, including special circuit and transformer design, which aim at increasing the output beyond that possible with conventional design, and the paper concludes with a brief reference to capacitor-discharge ignition systems of the contactmake and high-frequency types.