nuckolls.bob(at)aeroelect
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 Posted: Mon Feb 24, 2014 7:15 am Post subject: Shower of Sparks question |
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At 02:47 AM 2/23/2014, you wrote:
Hi Bob
I have recently bought an FK131, which is a retro
build of the Bücker Jungmann a, a wonderful
little plane with a Walter Micron 3 motor (also a
rebuild of the original Hirth motor), the Czech
motor company who builds it chose the "Buzzer" as
a start assistance and I found the wonderful
little article you wrote which helped me
understand how the system works a little better.
I'm pleased that you found it useful . . .
I have 2 questions, how is switch for the "Shower
of Sparks" or Buzzer labeled in the cockpit?
No differently than for a system without shower of sparks.
The existence of shower of sparks is transparent to the
pilot . . . except that the engine starts better . . .
can the system be used in an emergency if one of
the magnetos were to fail?? or would the failed
magneto not give it the impulse to make a difference?
Usually, the electro-mechanical, shower of sparks
is applied to only one of the two magnetos . . . and
the accessorized mag will be fitted with a second
set of delayed-timing points. If that mag fails,
you're stuck. I think there are modern incarnations
of the shower-of-sparks that can be adapted to any
magneto with our without impulse coupling. The
spark augmentation energy is piped into the magneto
p-lead based on some electronic determination of
timing.
If your 'buzzer' is a solid state device and
the supported magneto has only one set of points,
then the device can be switched between the two
magnetos with impunity.
If your spark is mechanically timed (second set of
points) the SOS system CAN be very useful for propping the
engine by hand. But you need appropriate switching
to make sure the starter is not engaged while your
'organic starter' has their hands on the prop.
After priming the engine and pulling the prop around
to the start of a compression stroke, you hold
the shower of sparks system in the 'cranking'
mode while the prop is pulled sedately through
the opening of the retarded timing points. The
engine will start right up.
This probably won't work with electronically
retarded systems that expect to see cranking
on the order of 100-200 rpm.
So the short answer is that the system will
work for either magneto only if it's electronically
retarded -OR- both mags are fitted with retard
points.
Bob . . .
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