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Old 19th Aug 2018, 04:01
  #88 (permalink)  
jonkster
 
Join Date: Feb 2017
Location: Sydney
Posts: 429
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Originally Posted by Richard_Richard
Forgive me if this is a stupid question but how exactly can I check that the ignition key/mag switches have actually grounded both mags in the off position?

I recently acquired a share in a light aircraft and one of the requirements where the aircraft is based is that the prop is left in the horizontal position (for the purposes of the ground handlers moving the aircraft - who refuse to touch the aircraft other than connecting the tow to the nosewheel). This therefore means there's a 50/50 chance that I have to move the prop round 90 degrees..... which I absolutely hate doing! - now I've always been taught to make sure that when I shut a piston aircraft down that I turn the key to the OFF position and make sure the keys are out of the ignition.... but the last two posts on here suggest this might not be sufficient? maybe pulling a circuit breaker would ensure there's no mishaps? (type is a Beagle Pup 150)
magnetos are turned "off" by shorting them. This means if a wire or the switch breaks, the engine will keep running, what you want when flying. On the ground though if a wire comes loose or a switch breaks etc, you may have a live mag, even if the switch is off. There is no circuit breaker or anything else to disable the mags. They are designed so that failures in any switch, wiring etc are unlikely to stop the engine.

It is worth learning how to do a mag check prior to engine shutdown (and get into the habit of doing it each shutdown). If that ever indicates you may have a live prop, get someone to inspect the mags and avoid handling the prop (even put a sign on the prop indicating it is live).

Always treat props as live, always move the prop only if you are in a position to pull your hands away and never leave any part of your body in the arc of the prop when rotating it.
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