Unicom

March 2009 Issue

Cold Weather, Hot Mags

I enjoyed Decemberís article, "Cold-Weather Ops." I wanted to pass on a suggestion for virtually all pilots flying piston engine airplanes. The article states, "When you first get to the airplane, put the ignition key on the panel so people can see it...." The article goes on: "Checking to see if the engine is warm often involves rocking the propeller." The reason given is that "with the key out of the ignition and readily visible, you are reasonably assured that the mags are not hot." Wrong and possibly dead wrong! I was fortunate to be trained by a high-time 18,000-plus-hour flight instructor. He ingrained in me the importance of doing a mag check during shutdown, prior to pulling the mixture: Turn off one mag and then the other to see if the RPM dropped as it should. Although a mag check should be done during the pre-takeoff run-up, there is no guarantee that a wire might not come loose during flight. If that were to happen, the mags would still be hot and rocking the propeller could be catastrophic!

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