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rotorwrench · 12-01-2020, 11:31 AM

[QUOTE=Mister Moose;1958006]Is this a round engine thing? All the Lycomings and Continentals I've flown didn't have anything like that cockpit controllable.

None of them are controllable other than operating the starter. Some of the smaller aircraft engines used impulse couplings that delay the spark during cranking then become non functional after start up due to flyweight action.

The electrical types used in older large engines, including many large radial engines and many newer and more modern opposed engines, produce a shower of sparks through the magneto coil until the opererator lets off the starter at which time the magnetos start to operate at full advance. The TCM/Bendix shower of sparks and the Slickstart starting aids only function when the starter is engaged.

No aircraft magnetoes that I'm aware of, have any mechanical spark control adjustment since it would require that the whole magneto be rotated to make it work. This type of set up is not practical from a reliability standpoint. Aviation systems must be as reliable as possible or they would never be approved for use. Magnetos have to be firmly affixed or the vibration would cause premature wear on the mounting parts.

A battery ignition system doesn't have to rely on the internal timing of the rotating magnet to the opening of the breaker points like a magneto does.

12-01-2020, 11:31 AM	#13
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,445	Re: Starter Mechanism [QUOTE=Mister Moose;1958006]Is this a round engine thing? All the Lycomings and Continentals I've flown didn't have anything like that cockpit controllable. None of them are controllable other than operating the starter. Some of the smaller aircraft engines used impulse couplings that delay the spark during cranking then become non functional after start up due to flyweight action. The electrical types used in older large engines, including many large radial engines and many newer and more modern opposed engines, produce a shower of sparks through the magneto coil until the opererator lets off the starter at which time the magnetos start to operate at full advance. The TCM/Bendix shower of sparks and the Slickstart starting aids only function when the starter is engaged. No aircraft magnetoes that I'm aware of, have any mechanical spark control adjustment since it would require that the whole magneto be rotated to make it work. This type of set up is not practical from a reliability standpoint. Aviation systems must be as reliable as possible or they would never be approved for use. Magnetos have to be firmly affixed or the vibration would cause premature wear on the mounting parts. A battery ignition system doesn't have to rely on the internal timing of the rotating magnet to the opening of the breaker points like a magneto does.