How To Jumper A Dead Aircraft Battery

[Colonel]

Private aircraft hardly ever fly, and even
commercial aircraft despite checklists (gasp)
leave the master on.  Same result - a
dead battery.  What to do?

You can hand-bomb a piston engine.

You can give a jet a blowjob, to start.

And, you can jumper the battery of a
dead aircraft - flat piston, radial or jet.

It's nice when there's an external plug,
but you don't always have one (or the
plug, or cart, or APU).

I shake my head when I see people
jumpering an aircraft battery, because
they are always doing it wrong.

Most people don't think I'm very bright
compared to them, but you DON'T need
to pull the cap on the battery box, and
jump right to the dead battery terminals.

In fact, that really reduces the amps
available, because when you do that,
amps flow into the dead battery - it
sucks the (now parallel) DC volts down,
and reduces the amps available to the
starter.

So, when you jump an aircraft battery,
leave the battery box top on, and connect
your negative jumper to the airframe
ground (obvious) and your positive jumper
to the cold (non-battery) side of the master
solenoid.

If you take my advice, no current will flow
into the dead battery, and it will be as if
you turned the master switch on.  All of
the current from the good battery (cart,
car, whatever) is available for the starter.

After you get a start, master on and jumpers
off.  Make sure you have enough volts to
excite the alternator field, and get it producing
current.

Again, you probably think I'm stupid compared
to you, but try to remember this technique.  Or,
look at where the positive cable from the external
plug is connected - not to the frikken battery.

-- EDIT --

You can do this trick with a car, too.  The 996's
battery was totally flat - it has a phantom draw -
so I loosened the negative terminal, and after I
connected the jumper cables from the good battery
to the terminals of the totally dead battery, I lifted
the loose negative terminal of the dead battery,
and had an air gap between it and the post of the
dead battery.

All of the current from the good battery was flowing
into the car, and none into the dead battery.

After the Porsche started, I slid the negative terminal
back onto the post of the dead battery, and disconnected
the jumper cables, and it kept running on the alternator.

This stuff really isn't that complicated.  And since
I'm so stupid compared to you, you shouldn't be
doing it wrong.