Skybrd Posted November 12, 2011 Report Posted November 12, 2011 Recently, I learned from a seasoned mechanic that if a person doesn't hold positive pressure on the key switch during starts, it can cause a broken starter. From what I understand, when you enable the key switch to start, the right magneto p lead is suppose to be grounded (turns off the mag) since it doesn't have an impluse coupling. If something interrupts this ground, the magneto is enable and it will fire too soon. It can backfire. The mechanic told me that it has broken some starters on planes he worked on.
triple8s Posted November 12, 2011 Report Posted November 12, 2011 Seen the very thing on a Piper Arrow, not sure about the "P" lead arrangement on the Arrow but the PIC did hit the starter and didnt keep it engaged and the engine popped about the time he made contact with the switch again and the nose broke right off the starter. The starter was a Skytec light weight starter, not sure if that made a difference or not but the owner thought the standard starter had a little more meat out there at the nose but who knows.
jetdriven Posted November 12, 2011 Report Posted November 12, 2011 I think it starts on the mag with the impulse coupler while grounding the normally timed mag. The impulse coupler retards timing and also causes the mag to jump forward making it fire at a lower cranking speed.
HopePilot Posted November 12, 2011 Report Posted November 12, 2011 By positive pressure, do you mean keep cranking until it has clearly started?
jetdriven Posted November 12, 2011 Report Posted November 12, 2011 I think they mean keep the key pushed in to keep the advanced mag from firing.
MARZ Posted November 14, 2011 Report Posted November 14, 2011 Was he talking specifically about the Mooney? I believe that Mooneys are the only ones that use the shower of sparks (SOS) ignition ??
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