I was used to have in vintage aircraft, with reciprocating engines, the "Primer" and the "Start" switches. Now R4D also has a "Vibrator" switch.I presume it is some kind of "spark generator", to provide ignition before the magnetos come into action, but I would like to be sure.Does anyone know what exactly it is?Regards,

From memory, you're right. The system utilises a set of points on one of the magnetos that is set to fire at or after TDC and a vibrator system to generate multiple high-voltage sparks when this set of points is enabled. The vibrator generates an alternating current and effectively arcs to create the ignition. Very crude!But it has been a long time since I studied this, so I might be wrong!Allcott

Thank you for your clarification.Regards,

Following your clarification, I found a text in:http://www.enginehistory.org/DC-3%20Crew%20Chief%20Notes.pdfwhere in Ch 74.7 and Ch 80.4 you will find references to the vibrator, that confirm your information.Regards,