REFLECTOR: 24 volt electrical system

[John Dibble]

My RMI monitor and encoder are also on during start.  That is not a
problem during normal starts.  However on a cold day when the battery
was too weak and I had to jump it, I lost data in the encoder.  So if I
anticipate a difficult start, I turn the encoder and monitor off.

John

Dave Bertram wrote:

>
>
  I would like to make one comment about engine start.  I have a Blue Mtn. EFIS and it is on during engine
  start.  I have had no problems with losing any of my EFIS data.  This includes my engine indications.  I do
  have the Chevy v-8 which may start easier.  Dave BertramN350TX
  -------Original Message-------

  From: Velocity Aircraft Owners and Builders list
  Date: 09/27/06 12:06:53
  To: Velocity Aircraft Owners and Builders list
  Subject: Re: REFLECTOR: 24 volt electrical system
   I have a solution to change everything to 24 volt except the high amperage draw for the gear pump. Here are
  some of the reasons to go to 24 volt. This is from a booklet (Aircraft wiring for smart people) on the Blue
  Mountain web site written by Greg Richter at BM. BM also has a power board that has power regulation and
  control for all the 12 volt trim motors. I am considering using their power board on my install. This doesn't
  mandate that I have to go to 24 volt, just adds the option. As of mid-2004, just about everything you can buy
  in avionics will run on 10-32 volts DC and doesn't care either way. single voltage items like landing lights
  and strobes can be all be had at 24 volt versions now so this isn't a problem either. Since a given load
  draws half the current at 24 volts that it does at 12 you can use smaller wire with the same results. you can
  use wire that's only 1/4 the size, which is a pretty big deal when you're are running #18 and everyone else
  is running #14. Most small planes have nearly 50 pounds of wire in them. How would you like to save 10 pounds
  of dead weight? Engine start will drop a 12-volt system to around 9 volts causing EFIS systems to reboot,
  radios to loose presets and fuel totalizers to restart. A 24 volt system will only drop to about 18 volts
  during engine start, which is well above the 10.5 volt minimum for modern, digital avionics. No backup
  batteries, no switching, no relays, and no fiddly, complex systems to solve a non-problem. A 24 volt system
  also has a lot more reserve energy available for use than a 12 volt system. As a point #2, a failed
  alternator in a 12 volt system leaves you a 2 volts from shutdown. A 24 bolt system you've got a lot more
  reserve before your avionics and FADEC (If you have the money for FADAC) drop offline. Look at discharge
  curves, and you'll see that a 12 volt battery at 11 volts is only partially discharged. A 24 volt battery at
  11 volts is very close to dead. There are a lot more reasons these are just a few. Andy
  ----- Original Message -----
  From: Ron Brown
  To: Velocity Aircraft Owners and Builders list
  Sent: Wednesday, September 27, 2006 10:31 AM
  Subject: Re: REFLECTOR: 24 volt electrical system
   Andrew, Is there a particular reason you want to use 24 volts?  Since you are building your own airplane,
  you have lots more choices for equipping the airplane and lots more stuff is available for 12 volt systems
  from the automotive and marine worlds.  If you have to have 24 volts because of good deals on avionics, then
  you could go to
  http://www.parker.com/frameless/default.asp?substDivId=&FamID=715&DivID=&GID=&Type=2&ID=364&TechID=&PSID=3773
  and order a replacement 24 vdc motor for your hydraulic pump. I understand the elevator trim system is
  already 24 volt (slows down the trim action since the motor runs slower on 12 volts).  You could probably use
  a power resistor in series to slow the trim motor down. Ronnie
  ----- Original Message -----
  From: Andrew Ellzey
  To: Velocity Aircraft Owners and Builders list
  Sent: Wednesday, September 27, 2006 10:27 AM
  Subject: REFLECTOR: 24 volt electrical system
   I would have liked to use a 24 volt electrical system on my aircraft, the problem is the hydraulic gear pump
  system being 12 volt @ 30 amp. Has anyone flying an XLRG found a way around this issue? Andy Ellzey
  ------------------------------------------------------------------------

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