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Old 04-21-2007 | 01:45 AM
  #28  
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Flyboy Dave
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From: Pinon Hills, CA
Default RE: Beware of Surprise engine start

....you know, Tom....heh heh, after reading our friend bassfisher's post again....

....it looks like one of those "hook, line, and sinker" post's.

" Yes, the engine is leaned out and the mags turned to off. However, after working at a local airport throughout college, I developed a healthy respect for 100% scale engines. A piston engine can start with the mags "off". If a magneto has an internal short, the impulse coupler can produce a current to the spark plugs. The reason for two mags is to produce redundancy for the spark plugs. If one is not working, the other is there to pick up the load. It is not for safety on the ground. I have personally seen a plane start when someone leaned a little too hard on a prop. The stars where aligned, gravity was in place, and everything was perfect. Luckly for that person, they got out of the prop arc before they got hurt. The can happen especially on older engines that have lower compression in the cylinders. A good pilot or lineboy "proping" a plane is already ready for it to start no matter how long it has sat on the ground. After propping planes hundreds of times, my insurance policy was someone was always in the seat with the brakes applied. "Brakes On, Mags cold" was always the way to do it, but even with "cold" mags, I've had planes start on me as I pulled the prop through to prime the engine. If you ever have the notion to pull a prop through on a full size, always do it backwards so the impuse coupler will not engage. It's best not to even touch the prop on a full size unless you know what you are doing."

FBD.