REFLECTOR: Redundancy (was Compass)

Tue Apr 25 22:37:53 CDT 2006

I have a total electrical system.  The B&C SB1-A, the LR3 regulators and the D-20 and D-60 alternators.  During my IFR training my instructor asked;  What would happened if the battery failed.

I spent some time with B&C discussing this issue.  The response was that if the battery failed, which is very rare, both alternators would overload and fail leaving me without any electrical supply.  Not a nice thought when in IMC conditions.

So this are the alternatives:  a second battery to supply 12V to the alternator field or to shut down and use a backup computer with a rechargeable battery system with an electronic gyro and one of those inexpensive programs that offer all the instruments on a computer to get me down.  For those of us that are electric I would recommend a second battery or at every annual load test your battery and keep it always on a trickle charger.

Tim at B&C tech support advised me that some are doing the: two battery, two alternators and two bus thing as per Bob Nuckols Z-14 diagram.

When it comes to IMC no one knows what can happen up there.

Fred
  ----- Original Message ----- 
  From: Keith Hallsten 
  To: 'Velocity Aircraft Owners and Builders list' 
  Sent: Tuesday, April 25, 2006 11:13 PM
  Subject: RE: REFLECTOR: Redundancy (was Compass)

  Yes, I have not yet decided whether to use a little second battery or to use a twin of the "main" battery as the back-up battery.  It's likely to be determined by weight & balance considerations.  The main battery does not have to be particularly large or heavy if a sealed lead-acid battery is selected.  Since I'm not using a vacuum system, I put the B&C SD-8 PM alternator on the vacuum pump pad.  That provides quite a bit of redundancy in the electrical system.  The electrical system will also be divided into separate buses so that a fault can be isolated.  I will have a feed from each bus to the GRT EFIS.

  Keith

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  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Dave Dent
  Sent: Tuesday, April 25, 2006 9:57 AM
  To: Velocity Aircraft Owners and Builders list
  Subject: Re: REFLECTOR: Compass

  I would also install a back up for the GRT.  It can take two back ups.  I put in a 12V5Ahr li-ion battery as a back up.  But you can get a small 7Ahr lead acid and do the same.  It will just be a little heavier.  I turn mine on while doing test with just the ship's battery on.  When the gear pump cycles it drops my GRT/EFIS screen of line for a second.  So by turning on the back up, it keeps it on line.  I charge my EFIS battery every 50 hrs weather it needs it or not, normally it don't.  I keep it separate from all other systems, including the charging system.  

    ----- Original Message ----- 

    From: Keith Hallsten 

    To: 'Velocity Aircraft Owners and Builders list' 

    Sent: Monday, April 24, 2006 9:03 PM

    Subject: RE: REFLECTOR: Compass

    Whether or not it's strictly required, it seems like a pretty good idea, and doesn't cost much.  I'm putting in the GRT EFIS with a magnetometer, but I will definitely install an old-fashioned whiskey compass against that day when nothing in the panel works!  

    I will also keep a hand-held Comm radio with fresh batteries in the flight bag, and have a portable GPS up and running that will revert to its own batteries if the entire ship's electrical system goes out to lunch.  It's not that I have no confidence in my ability to install and maintain a reliable electrical system; I just believe it's prudent to have a workable "Plan B" for the failure of ANY component of the aircraft if at all possible.  When it comes to most aircraft systems, it's both possible and practical.

    Keith Hallsten

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    From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Joe Ewen
    Sent: Monday, April 24, 2006 6:10 PM
    To: Velocity Aircraft Owners and Builders list
    Subject: REFLECTOR: Compass

    A quick compass question.  If the AC is equipped with a glass panel that provides magnetic compass heading, is a mechanical compass still required?

    Thanks,

    Joe

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