FlyingSafely.Com   Check Your Mags

 We all have "check mags" predominantly on the check list, and doing so becomes part of our routine, but improperly checking the mags can hurt you. Here are a couple of ways in which this can happen and has happened. Proper mag control can go a long way in enhancing aviation safety.

The first time I realized I made a mistake on my mag check was when I was departing a short grass strip in southeastern Illinois. It was a warm summer day and I needed all the thrust my Lycoming O320 could deliver. The end of the runway got very close before I was able to finally get airborne. "What is the matter with this thing?" I asked on climb out. It was obvious to me by then that I was not getting full power from the engine. (see our article about aborted takeoffs). Then, I saw the mag switch one click to the left of "both." I was running on one mag! I quickly switched the switch to the "both" position and the engine immediately gained full power.

I rehearsed in my mind how this had happened. I checked the mags, but I didn't ensure that the switch was returned to the "both" position. From that time on, I have always done mag checks as follows. Maybe it will help someone else to avoid my mistake. (Two clicks to the left, note RPM drop, two clicks to the right--say the word, "both". Then one click to the left, note RPM drop, then one click to the right--say the word "both". I have never made the mistake again. "Both" is a very important word to include in your run up. Say "both".

The other mag problem came to our attention recently at a nearby airport, when an experienced pilot moved a prop blade and the engine fired injuring him. Of course, we know this can be deadly. In this case he was lucky. How did it happen? The mag switch was defintely in the "off" position. But something was wrong, you guessed it, the grounding wire to one of the mags was broken, making the mag "hot".

The way to test for this is to include in your checklist a place to turn your mags off when the engine is in idle. If it starts to die, your mag ground wires have continuity to ground. If it keeps running, you have a dangerous problem -- a mag wire that is not grounded. If you don't do this check, you cannot know that the condition exists and you are ripe for an accident with a prop. As someone once observed, "That thing on the front of your airplane is a very mean thing, and he has never lost a fight."

Lesson -- be sure yours mags are "on" and be sure they are "off".