Ok....I think it's time to clear up this cock and bull story about the magneto. First, let
me say that I have rebuilt personally and Professionally hundreds of magneto's in my
lifetime as a journeyman mechanic....don't try to B.S. me about a magneto.

(everything in quotes " is from Member bassfisher's post)

"Yes, the engine is leaned out"

Once the engine is leaned out and the engines dies from total lack of fuel, there in nothing left in
the intake manifolds and cylinders, so there will not be any firing of the cylinders, until the engine
is primed, and fuel is supplied to the cylinders. This is a simple fact.

"and the mags turned to off"

When the mags are turned "off" they are grounded, and will not produce a spark...period.

"However, after working at a local airport throughout college"

Doing what ?

"A piston engine can start with the mags "off".

No it cannot, because the Magneto swith also cuts off power to the starter solenoid, and there fore
the starter cannot be engaged.

"If a magneto has an internal short"

If the Magneto has an internal "short" is will not produce a spark ever becuase it is not
functional....and is need of repair.

"the impulse coupler can produce a current to the spark plugs".

This is the crux of this BS story. The "impulse coupler" does not produce any electrical
current, ever. Impulse coupler is a fancy word for a mechanical ignition advance mechanism,
of which I am very familiar. This mechanism uses bob wieghts to advance the timing after the
engine is started. It's function is to retard the timing when the engine is not running, so
when you crank the engine...the engine will not backfire, and break the starter gears.


"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".

Oh, really ?

"The can happen especially on older engines that have lower compression in the cylinders".

An older engine would be even less likely to fire from a resting position, simply because
the comperssion will leak down after it has been stopped for a minute. A cylinder with no
compression will not fire at rest ever.


"I've had planes start on me as I pulled the prop through to prime the engine".

Really ? Why don't you try the prime function of the carburator and the elcetric srarter on the
engine next time. What are you "propping", WWI biplanes ?

"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".

This is another load of bull. The impulse coupler (advance unit) is keyed to the magneto shaft,
and is engaged all the time. It cannot be disengaged ever.

"It's best not to even touch the prop on a full size unless you know what you are doing."

That's why the mechanic told you not to lean on the prop....just keepin' the record straight.

Here's a factoid for those keeping score at home....a magneto has to be spun over rather briskly
for it to produce any spark. First the magnets have to spin around the field coils fast enough to
produce enough current to then supply the secondary windings enough current to produce a
spark of 20,000 volts or so to the apark plugs.

Trust me, this does not happen by "leaning against a propeller".

FBD.