New Member
What could be the cause of one set of magnetos that show no drop in RPM during an engine run-up? From what I remember, no drop means that that set is not grounding properly right? If that's the case, what could cause this and would you consider it a safety issue in flight? It seems to me that it would only be an issue on the ground, where the engine could turn over if the prop was turned by hand.
Correct, if you get no mag drop, then that mag is not grounding out. This is most often caused by a broken 'p-lead'. If you look at the magneto, it is the little white wire. It could also be caused by a faulty ignition switch. It can be dangerous on the ground for the reason you mentioned, but you should not fly an aircraft in this condition if you can help it. If you have a magneto malfunction in flight causing the timing to be off, or the magneto starts to cross fire, you will not be able to turn the bad magneto off. This could cause engine damage or a loss of power. If your aircraft is operating correctly you could just turn off the bad mag and continue on one magneto.