REFLECTOR: Reflector Digest, Vol 100, Issue 10
Lawrence Epstein
ljepstein at hotmail.com
Thu Jul 4 12:51:57 CDT 2013
I strongly recommend the following reference for aircraft wiring/electrical
systems:
http://www.eaa.org/experimenter/articles/0903_aircraft_wiring.pdf
Granted, it is written by Greg Richter (BMA), but it goes through a logical
analysis of what sort of redundancy is necessary and where. He addresses
back up batteries (no need if you are 24 V) on page 5 and 2nd alternator
("overkill") on page 6.
Lots of good stuff here.
On Thu, Jul 4, 2013 at 11:15 AM, Patrick Sieders <pjsieders at comcast.net>wrote:
> Brooke and Dave,
>
> You all have a point in simplicity. On backup systems however, I disagree.
>
> Many production airplanes had backup systems : electrical and suction
> instruments.
>
> These days we are all leaning/using electrical EFIS screens etc. So to
> have another backup alternator in lieu of the old vacuumpump is just common
> sense.
>
> Take it from a guy flying an electric airliner, being told we always will
> have instruments(i.e. EFIS SCREENS) to look at.. I have met Murphy in IMC...
>
> Patrick sieders
>
>
>
> ------------------------------
> From: Dave T Nelson <dtnelson at us.ibm.com>
> Sent: July 04, 2013 10:09
> To: reflector at tvbf.org
> Subject: Re: REFLECTOR: Reflector Digest, Vol 100, Issue 10
>
> Brooke - well said, Sir!
>
> The comparison to other no redundancy systems (like your entire airframe)
> is spot on, and reinforces my philosophy - stay away from complexity, and
> build it really, really well - but just once. Adding all the stuff I hear
> about is adding extra weight, complexity, and failure modes.
>
> How many Cessnas, Pipers, Beechcrafts, Mooneys, etc., are lost due to the
> lack of an extra alternator? An extra battery? Where you see a store
> bought airplane accident due to an electrical failure, it's pretty much
> always due to smoke or fire in the cockpit... How much extra risk are you
> adding for that kind of problem with all of your additional redundant
> systems?
>
> Take great care in building, but build it once and keep it simple.
>
> Dave
>
> Dave T. Nelson
> T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
> Program Director, ISC ECAT NPI & Test Engineering
>
> ----- Message from Brooke Wolf <bwolf1 at tds.net> on Wed, 3 Jul 2013
> 21:32:32 -0400 -----
> *To:*
>
> reflector at tvbf.org
>
> *Subject:*
>
> REFLECTOR: Electrical system
>
> Reiff
>
> As we go through the mental gymnastics of 2 alternators or 2 batteries or
> primary busses or essential busses or main busses or emergency busses or
> battery busses and redundancy galore, let us not forget we have only one
> engine. Safety and associated redundancies should balance. Just food of
> thought.
>
> Brooke
>
> On Jul 3, 2013, at 4:11 PM, *reflector-request at tvbf.org*<reflector-request at tvbf.org>
> wrote:
>
>
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> Today's Topics:
>
> 1. Re: Electrical system (Jack Prock)
>
> *From: *"Jack Prock" <jackprock at wavecable.com>
> *Subject: Re: REFLECTOR: Electrical system*
> *Date: *July 3, 2013 4:10:30 PM EDT
> *To: *"Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> *Reply-To: *Velocity Aircraft Owners and Builders list <
> reflector at tvbf.org>
>
>
> Reiff,
>
> The only thing that I would add is that you start your engine using
> the battery, but fly using your alternator(s). If you were going
> to decide between having a duplicate of one OR the other, I would go
> with a duplicate alternator.
>
> If the battery goes out, you can’t start... get jumper cables, start
> the engine, you’re on your way... just like a car. (assuming 12 volt system
> )
>
> If your single alternator goes out, you run on your battery(s) until
> it/they die (while you look for a place to land)...
> at night... over mountains, not a good scenario!! Other backups will
> help... but the pucker factor goes way up when
> (almost) everything goes dark!
>
> The consequences of one, far outweigh the consequences of the other.
>
> That is just my opinion... and just like assholes, everyone has one!!
>
> Jack
>
> *From:* *Reiff Lorenz* <Reiff at lorenz.com>
> *Sent:* Wednesday, July 03, 2013 12:24 PM
> *To:* *Velocity Aircraft Owners and Builders list* <reflector at tvbf.org>
>
> *Subject:* Re: REFLECTOR: Electrical system
>
>
> Terry,
>
> Thank you for all the details. This is all very helpful. I like your
> suggestion about the heat-shrink labeling, even though it's expensive. For
> planning/drawing software I'm leaning toward Visio. (Turbo-CAD does have
> some good features, too.)
>
> I'm still working on the right tradeoff between redundancy and
> complexity. Lots of suggestions from other builders to do 2 batteries.
> Others say 1 battery and 2 alternators. Andy Millin sent me his diagram and
> he's got 3 batteries! The Vertical power system simplifies some of this.
> They have multiple configurations for dual batteries and/or dual
> alternators and/or ground power plugs, but it's still not as easy as
> connecting everything to one box.
>
> Builder Bill Stockman lives near me. He's retro-fitting his long-wing
> SE with a Vertical Power system and a Garmin G3X. I'm hoping to be able to
> help him and learn about wiring a VP system in the process.
>
> I may have similar W&B issues to what you describe. I'm a skinny guy
> and don't want to have trim issues, but I also want to take some of my
> larger friends in the front seat (6'3 & 260 lbs.) Maybe there's some
> middle ground between the two extremes?
>
> Looking forward to talking to you at Oshkosh!
>
> Reiff
>
>
> *From:* reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org<reflector-bounces at tvbf.org>]
> *On Behalf Of *Terry Miles*
> Sent:* Tuesday, July 2, 2013 11:46 PM*
> To:* Velocity Aircraft Owners and Builders list*
> Subject:* Re: REFLECTOR: Electrical system
>
> Wow. Dave, that is a very nice summary. I did all of my
> wiring...every inch, every connector, every everything. I would repeat a
> lot of what you offered, if asked, and that is: keep track of wire size to
> fit the current load, secure stuff properly so it cannot rub against
> anything, (I used that black wax lace stuff. Yank on every connector
> after you make it to test it. Check every BNC you make for continuity and
> twist it around a little before you declare it sound. If you make 25 pin
> connectors becareful with pin crimps, and especially the outboard most pins
> when you go to secure the entire bundle. (You can google how to tied the
> knots.) I read all the Nuckols stuff faithfully as I educated myself and
> choose against the double alternators, but I do have a pair of Odessey 925
> batteries located forward of the carnard bulkhead in the RG and have not
> had water issues so far. The main distribution is after of the carnard
> bulkhead. I did the 2 batts in part for wgt and bal since I am 150 pounds
> and heard stories of trim issues. While it is another discussion, the
> decision for one or two batts was and always will be debatable. It might
> have been better for me to use removable ballast since I cannot take
> anybody much over 200 lbs and put them in the front seat. My inflight draw
> is about 4 amps, much much different from days gone by. I will run out of
> gas before I every run out of batt power. I replace one batt every 18
> months to two years.
>
> Making wire streams (I like that term) would have been some good
> advice for me. I didn't do that and actually installed the wiring a little
> at a time and added a lot of after the fact stuff....and I do have a lot of
> loose single wires going hither and yon (sp?) back and forth from port to
> starboard behind the instrument panel. I used auto fusing mostly but do
> have about a dozen in view aircraft grade CB's for stuff I want to know
> about...ignition, transponder, hydro pump and gear control gizmo...stuff
> like that. There are also decisions about putting more than one component
> into a single fuse/breaker.
>
> I bought a $300 plus wire labeling system that uses heat shrink. The
> dam heat shrink refills were about 35 cents an inch, but I thought that was
> money well spent, as well as being able to work at a base level with
> turbo-cad to do the drawings since I experienced endless edits in that
> department from my first paper drawings.
>
> If you do your own wiring, I would call Dave first since he offered.
> I am only a Saturday afternoon electrician-avionics tech, but I can
> certainly add my name if you want an opinion about doing your own harness
> and/or tacking the job of installing all of the avionics and doing those 2
> gazillion settings on your own. Being able to buy both an AHRS and an
> autopilot from the same vendor is a big plus not available to me. I have
> GRT stuff and I like it. Besides buying mil spec wire, buying high grade
> teflon tape is a good idea too.
>
> Terry
> ------------------------------
> To: *reflector at tvbf.org* <reflector at tvbf.org>
> From: *dtnelson at us.ibm.com* <dtnelson at us.ibm.com>
> Date: Sun, 30 Jun 2013 10:36:59 -0500
> Subject: Re: REFLECTOR: Electrical system
>
> Hi Reiff,
>
> The power and ground bus bars I'm talking about is behind the canard
> bulkhead in the area behind the panel - not forward of the bulkhead and
> exposed.
>
> In general, for exposed connections, the worry wouldn't be failure due
> to shorting from the water, it'd be corrosion. In general, galvanic
> corrosion should be considered, but can be easily controlled with HW store
> electrician's grease. The relays and connections that I do have on the
> forward (exposed) side of my bulkhead all have a dab of that stuff (main
> contactor, hydraulic pump relays, battery connections, etc.).
>
> I've never seen galvanic corrosion on my homemade brass bus bars & the
> bimetal ring connectors I've used.
>
> I've seen the other comments re. use of two alternators, etc. I agree
> with the guidance from Richard Gentil - if you've got an electrical problem
> you're going to want to land and fix it anyway. Keeping your system as
> simple as possible and building your simple system with reliability in mind
> makes much more sense to me than trying to add all kinds of redundancy...
> which just gives Murphy more opportunities to ruin your day. I'd think
> really hard before installing a system with two alternators, two batteries,
> all kinds of switching relays, lots of extra wiring... failure points...
> and things to go wrong.
>
> My two cents.
>
> Dave
>
> Dave T. Nelson
> T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
> Program Director, ISC ECAT NPI & Test Engineering
>
> Dave,
>
> Terrific advice! Thanks for all the help.
>
> Did you cover the power buss with anything? Is there any concern of
> having a "naked" power buss in the nose? I have an RG, so I'm imagining the
> entire inside of the nose will get wet if I take off or land in the rain.
>
> I really appreciate all the info!
>
> Reiff
>
> *
> From:* *reflector-bounces at tvbf.org* <reflector-bounces at tvbf.org> [*
> mailto:reflector-bounces at tvbf.org* <reflector-bounces at tvbf.org>] *On
> Behalf Of *Dave T Nelson*
> Sent:* Saturday, June 29, 2013 1:12 PM*
> To:* *reflector at tvbf.org* <reflector at tvbf.org>*
> Subject:* Re: REFLECTOR: Electrical system
>
> This is an excellent area for KISS.... Keep It SIMPLE!
>
> In my installation, I used two connection blocks in the area behind
> the instrument panel for both 12V and ground (4 total), one of each flavor
> on the left and on the right. I made them myself by soldering brass screws
> into a brass plate. I then used ring terminals on the wire ends. The
> terminals are then held tight with MS21042 nuts. The idea is to avoid
> having to have wires seeking 12V or ground from having to cross the whole
> panel from the left side to the right (or vise-versa). The ground system
> should be simple - everything has only one grounding point (to avoid ground
> loops). On both power and ground, the buss bars are powered (or grounded)
> via two wires for redundancy.
>
> I used switch circuit breakers instead of switches with separate
> circuit breakers (or fuses). I wouldn't recommend that... I've had a
> couple of them fail.
>
> I used circuit breakers instead of fuses. My reasoning was that I
> want to be able to see at a glance if one had popped (hard to do with a
> fuse). I wish I'd used the type that allow you to pull the end of the
> circuit breaker to switch a circuit off.
>
> Don't buy used circuit breakers!
>
> Use real aviation grade wire, not Radioshack junk.
>
> I used, carefully and religiously, a wire size chart. I've seen many,
> many installations where folks use wire of way to low of a gauge (too thick
> and heavy). You'll be surprised how often you can use 20 or even 22 gauge
> based on the current requirements. Make sure the wiring chart you use is
> for bundled wire, not single strand. Make sure you use the right size
> terminal for each wire.
>
> I sized the circuit breakers for the load, not for the wire carrying
> capacity. There has been some debate on this, as Nuckolls would size the
> fuse/circuit breaker for the wire, not the load. IMHO I'm trying to
> protect the expensive load (radio), and the wire will always
>
>
>
> [The entire original message is not included]
>
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