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d_emond(at)mweb.co.za
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 Posted: Wed Apr 16, 2008 1:43 pm Post subject: Ground Power - Z31A |
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Bob
Please can you confirm the correct procedure for using the ground power on
Z31a architecture.
Is it imperative to first switch on the "ground power" switch, before
switching on the master switch?
Would I just switch ground power off, once the aircraft has started?
What would happen if ground power switch was inadvertantly left on for an
indefinite period, or turned on whilst the aircraft engine was running?
Your assistance as always is appreciated.
Dave Emond
RV10
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nuckolls.bob(at)cox.net
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| Posted: Thu Apr 17, 2008 3:49 am Post subject: Ground Power - Z31A |
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At 11:38 PM 4/16/2008 +0200, you wrote:
| Quote: |
Bob
Please can you confirm the correct procedure for using the ground power on
Z31a architecture.
Is it imperative to first switch on the "ground power" switch, before
switching on the master switch?
|
No. The ground power may be turned on at any time in the
starting sequence without regard to damage to the system.
The ground power circuits as depicted are reverse polarity
and ov protected . . .
| Quote: | Would I just switch ground power off, once the aircraft has started?
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Yes.
| Quote: | What would happen if ground power switch was inadvertantly left on for an
indefinite period, or turned on whilst the aircraft engine was running?
|
No big deal. IF the ground power source voltage was set
higher than your ship's regulator, your alternator
would not come on line and pick up system loads as long
as the ground power was connected. If you're getting a
start from a battery cart - as ship's systems came
alive, your ship's alternator would begin to charge/
re-charge ALL batteries in the system . . . including those
in a still connected ground power cart.
If you're using external power from an engine driven or
AC mains powered cart, then would would expect the external
voltage source to be set at "battery charging" voltage
levels (14.2 or 28.5). In this case, you could turn on
ground power long before closing the master switch and
let ground power replenish you ship's battery. After
15 minutes or so, your ship's battery may well contain
sufficient snort to start your engine and ground power
could be disconnected for the start an subsequent
pre-flight. If the ground power is a battery cart,
then no charging of the ship's battery can take place
and you're obligated to use ground power to get the
engine started. After starting, you'd want to turn
ground power off so that ALL of your ship's alternator
output was being used to replenish stored energy in
the ship's battery.
In cold weather, you may wish to use ground power
as a routine assist for getting the engine
started even if your battery is in good shape.
Aside from the possibility of too much ground power
voltage and/or reversed polarity, there are no risks to
your airplane's systems that warrant concern. Making
ground power managed from the pilot's seat
puts you in control of this resource for the purpose
of addressing the task at hand.
It's an energy management problem with solutions
determined by equipment available, condition of
your battery and immediate goals. I recall reading
a story many moons ago where a pilot used his ground
power jumper cables to get his car started using
his airplane's battery after returning from a trip
and finding the car battery was not up to the task.
| Quote: | Your assistance as always is appreciated.
|
Pleased to be of service sir!
Bob . . .
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