One thing leads to another...

David Lesher wrote:
writes:



Back in the "good old days" when I was an avionics tech, they HAD to
put things in the back; the equipment was just too big to fit it all
behind the panel.

The equipment rack in the back of your average Cessna/Piper is no
heaven for equipment. It vibrates just as much and it is actually
hotter than behind the panel. Remember, there are no vents back there
while up front you have cabin vents.

But you can easily have ventilation. You don't need outside
air; a few boxer fans will help a great deal. The big thing is you
have volume and *access*. The big issue I see is protecting against
cokes spilled on/through the seat.

Hmmm, more wires to run, more stuff to put in the plane.

The equipment didn't go under the rear seat; it went behind the panel
behind the bagage compartment.

Most of the problems with the old MK-12 solid state inverter power
supplies and the AT-5 transponders were due to the heat and vibration
in the back.

We're talking an order of magnitude more heat in a MK-12 inverter
than for a current whole stack, I bet... I seem to recall those even
used geranium transistors...

Probably slightly less heat, and yes, the transistors were germanium.

Can't see why vibration is worse under the rear seat; only that the
panel has mounts. So, put stuff on mounts.

The vibration is the same; if you wanted it to last you DID put it on
mounts.

Running cables of any kind from the back to behind the panel is also
highly labor intensive when done correctly.

Agreed. But one real plus is fiber, even mil-spec "tank-proof" fiber,
is tiny as compared to the ahem equine reproductive equipment it
replaces here. (I installed LOTS of those in police cars years ago..)

The diameter (up to a point) of a cable bundle isn't an issue; it's
having to run it at all.

And you end up running coax from each antenna, mike/headphone/etc
up into a very tight location where you work by feel....

Fiber all avoids ground loops as well. I could see a audio panel
with a front panel for control, a knee-level jack panel for
mikes/headphones/PTT/CD player in, and a 2nd in the rear for those
passengers.

You didn't have ground loops back then with wires either if you put
stuff in correctly.

While you could replace a lot of the wiring with a fiber optic data cable,
you still have to run power back there and you still have to keep the
cables protected and out of the workings. Plus splicing and putting
connectors correctly on fiber is a pain in the butt.

I'd buy connectorized flexible duplex jumpers. But yes, you'd need to
run power there. Good place for the avionics master contactor.

Hmmm, 3 more wires; power in, power out, and control or have 2 separate
contactors for the front and rear stuff and avoid the power out?

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

--
Jim Pennino

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writes:


Hmmm, more wires to run, more stuff to put in the plane.

More wires under back seat; fewer under panel. If most
antennas are on the belly...

The equipment didn't go under the rear seat; it went behind the panel
behind the bagage compartment.

Either way...the back seat comes to mind because you could pull the
seat and SEE what you are working on.

The diameter (up to a point) of a cable bundle isn't an issue; it's
having to run it at all.

But lots of wires is connectors with a bunch of pins to solder, and
when the unit does not work, you end up with a DVM and sharp probes
to test each pin to pin etc. {I used to hate that kind of work..}
And fiber weighs less.

Instead we install oh 5 pairs of fiber with ST connectors. Use one
pair for nav/com, another for GPS, etc. Suspect trouble? Swap both
ends w/ another pair.

Fiber all avoids ground loops as well. I could see a audio panel
with a front panel for control, a knee-level jack panel for
mikes/headphones/PTT/CD player in, and a 2nd in the rear for those
passengers.

You didn't have ground loops back then with wires either if you put
stuff in correctly.

Until this ground or that came loose, or....

I'd buy connectorized flexible duplex jumpers. But yes, you'd need to
run power there. Good place for the avionics master contactor.

Hmmm, 3 more wires; power in, power out, and control or have 2 separate
contactors for the front and rear stuff and avoid the power out?

Avionics master switch goes two places -- to run panel remotes;
and contactor at rear rack.
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433