On 11/23/2021 8:58 AM, Flesner wrote:
Other concerns on electric pumps only came to mind during my morning
shower but I'll have to wait till this evening when I have more time
to post them.
Larry Flesner
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
On my "not to scale" drawing on an earlier post you may have noticed
that my fuel pressure gauge is after the pumps but before the
regulator. That's because I grew concerned that I'd need a regulator
after I had the system complete. The regulator fit nicely after the
gauge so I went with it. Result is I know if pumps are working but must
rely on regulator to maintain correct pressure. If they were reversed
I'd know exactly what pressure the carb is seeing.
Here is a photo of my batteries on the firewall.
https://www.dropbox.com/s/3h27f5jtqitz7yx/IMG_8083.JPG?dl=0
I weighed a 5 AH battery at the shop today and it was 3 pounds exactly.
Even if you double that for the rest of a backup system, switches,
wires, circuit breakers, etc., it's still a small price to pay to keep
you in the air and out of a corn field as mine did for me.
Here is a closeup of my "emergency" panel. Yellow switch hooks
alternator output to backup battery. The switch to the left of the
radio (Radio / GPS) has been replaced with a single pole / double throw
(up on / down on / center off) that is now "up = avionics on main buss"
"down = avionics on backup battery" "center = off".
https://www.dropbox.com/s/u39owy7asnll1b2/100_0169.jpg?dl=0
Better photo showing both fuel valves (down past the stick) and
"emergency" panel in red. Fuel line is on left firewall in the white
spiral braid. It makes a 90 degree about level with the panel bottom
and goes forward, through the regulator, firewall, and to the gas collator.
Anyone running a VW or Corvair should think twice before just running a
standard ignition with all electrical running off the master buss. If
you loose the master buss as I did (think turning off the master switch)
or a battery failure that draws voltage down below the level to power
components you have no way to recover. With a small backup battery you
can flip a switch and bring the ignition and fuel pumps back on line.
Mark Langford had posted some schematics to accomplish the task. If
your engine will not "windmill" make sure the backup includes the
ability to turn the starter. It shouldn't take much for the starter to
turn the engine if you still have flying speed to unload the prop. A
standard alternator will need the "field" backed up also to have
alternator output. Each aircraft is different so just make a list. If
I lose my master buss or battery, I need this to happen and then design
/ wire accordingly. Mark Langford and I have both had electrical
failures that required a backup to stay in the air. It's not an
uncommon occurrence. Anyone running magnetos simply need to keep the
fuel pumps running for the simplest possible backup.
Larry Flesner
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