REFLECTOR: Fusing distribution lines

Mon Jul 31 22:54:03 CDT 2006

Terry,

What are you using for your battery bus?  I'm using a fuse block, so all the
feeders coming off it are protected, including the e-bus alternate feed.

The decision regarding whether to protect the feeder to the e-bus depends on
whether there could realistically be a threat to that wire.  "Fat" feed
wires do not have to be protected, provided that great care is taken to
avoid any mechanical threat and they are large enough to support the maximum
amperage that could actually be fed through them.  That's why the main #2
battery and ground cables don't need protection.  Similarly, if the grand
total of all CBs or fuses coming OFF the e-bus is significantly less that
the amperage that the feed wire can sustain, there is no real electrical
threat to the e-bus wire.  That's because the other circuit protection would
open before the feed wire could get hot enough to be compromised.
Naturally, this assumes that there cannot be a short directly to the feed
wire itself, which is where the care to avoid any mechanical threat to that
wire comes in.

The fusible link in the alternator "B" lead is to protect the alternator
from the battery, not to protect wiring from the alternator output.  An
alternator is physically incapable of making significantly more amps than it
is rated for, and the "B" lead is sized to handle that comfortably.

How did you end up with a spare LASAR timing box?  I don't have one yet, so
I might well be interested.

Does anyone know whether there would be a problem using a separate starter
push button with a LASAR electronic ignition?  All of their documentation
shows the classic "OFF - LEFT - RIGHT - BOTH - START" keyswitch, but I would
rather have the option to get the engine turning before firing up the
ignition.  I don't know if the LASAR will be happy starting on only one
ignition, or coming alive when the engine is already moving.  I bought a
starter pushbutton form B&C a few years ago, before I was committed to the
LASAR ignition, and I'd still like to use it.

Keith Hallsten

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Terry Miles
Sent: Monday, July 31, 2006 2:45 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: REFLECTOR: Fusing distribution lines

Keith, Al,

Thanks both of you for all the advice.  Keith:  If you haven't yet, don't
buy a timing device for that Lasar ignition system.  I have one I will sell
you at half price.  

Did either of you fuse your battery-fed-to-essential distribution line--that
is the wire running from your battery hot bus to the emergency feed into
your essential bus.  I am doing this with a 700 series toggle switch that
will control a 30 amp relay.  I am just trying to decide whether to put a
say 40 amp fuse on the #10awg running from the Hot Batt bus to the relay #30
lug and out the 87 to the essential bus?  What did you guys do?  Obviously I
am fusing my alternator feed line with a fuseable link, but should I also
fuse my Batt Only bus feed lines in the event of a major component draw or
short to ground or whatever on the client bus?  

Thanks

Terry

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Keith Hallsten
Sent: Monday, July 17, 2006 9:38 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Bus, Battery & Back Order

Terry,

Everyone will have their specific requirements, based on their background
and the way they intend to use their plane.  Thus, what others have done is
a source of ideas, but ultimately not very relevant to your own decisions.

I have ordered my plug-n-play panel from Stein Bruch.  We are currently
exchanging drawings to get to final conclusions regarding exact locations of
equipment, switches, etc.  

I went with the dual-display, single AHRS, GRT "Horizon" EFIS.  I seriously
considered their "Sport" EFIS, but it was not actually shipping at the time
I placed my order (the last I heard it was to start shipping today), and it
isn't entirely clear that the way certain functions are implemented will
satisfy me.  There comes a point in every project when you have to "pull the
trigger" on the order and at that point you need to choose from equipment
that is actually available.

For in-panel backups, I have a mechanical airspeed and altimeter and the
TruTrak "ADI Pilot 2" autopilot which provides attitude and bearing
information, even when the autopilot is not in use.  I decided to put the
"handheld" G-396 backup GPS in a panel dock, which makes it a
"semi-panel-mount".  That way I don't have extra wires to get tangled in,
and I can actually wire it up to the EFIS as well.

For the handheld backup comm radio I'm installing a panel jack to connect to
the second comm antenna in the other winglet and a "cigarette lighter" style
of power receptacle.  This will back up the single SL-30 Nav/Comm in the
panel.

I'm going to put in two batteries, mostly so that the LASAR ignition and EIS
6000 engine monitor can run off a separate battery during starting.  I will
determine the battery size after I have done the weight and balance.  Once
the engine is running I will tie the batteries together, so it won't be a
true two-bus system.  I will have an "endurance" bus, though.  Since I will
have no vacuum system, I couldn't resist putting an SD-8 dynamo on the
vacuum pump pad.

I didn't like the design of the Velocity exhaust system that was available
at the time, so I got an exhaust system made to my specifications by Custom
Aircraft Parts of El Cajon, CA.  Clint Anderson shipped it to me less than a
week after I ordered it, so backorder was not an issue! 

Keith Hallsten, XLFG

N585V (reserved)

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Al Gietzen
Sent: Wednesday, June 15, 2005 10:36 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: RE: REFLECTOR: Bus, Battery & Back Order

Keith;

It sounds like we have taken a pretty similar approach to the panel.  Except
I have digital electronic backups and no gauges.

I just completed all electrical, and checkout of the things in the panel
(Well; still some wire 'dressing' to do.)  As far as I can check here on the
ground everything works (yippee!) - er, except the Trutrak AP.  

I expect I'm an isolated case, but I have not been happy with it from the
start.  Had to return the servo because it was sticking, and now the
programmer module isn't working.  They are assuring me that they will do
whatever is needed to make things right; which I appreciate, but if I were
doing it over I would opt for the Trio EZ pilot. One reason is the Trio
servo gears disengage when the unit is off - the Trutrak unit doesn't and
puts some unnecessary drag on the controls.

I also have the SL-30, and put in an I-COM panel mount for a COM 2.
Inexpensive; and from what I've heard, they work fine.  I think it is
basically a knockoff of an earlier King model.

Photo of panel attached.

Now to get busy on the interior.

Al (I'll probably run the engine tomorrow, haven't heard it for a few weeks
:-))

I have also been meditating on backup for the single-AHRS, two-display GRT

EFIS.  Although I may change my mind again, I am also settling on mechanical

airspeed and altimeter.  Therefore, I'll probably leave out the backup

airspeed and altimeter in the EIS - I'll talk to them at OSH next month

about the value of cross-check info to the EFIS.  The GRT EIS 6000 will be

the only source of engine instrumentation (loss of engine instruments is a

nuisance, not an emergency).  I plan to use either a TruTrak Pictorial Pilot

or their upcoming ADI Pilot as the

autopilot-and-combination-backup-attitude-indicator.  After that, the

backups come out of the flight bag!

I'm going with the internal GPS in the EFIS as the only panel-mount GPS for

the first couple of "VFR only" years.  I plan to leave a space for a GNS

430, but not install it until and unless I establish that I need the

additional capability the way I fly.  I'll have a handheld GPS with fresh

batteries up and running on cross-country flights.

I'm putting in a single SL-30 Nav/Com, and carrying a handheld comm radio as

backup.  I'm going to talk to the vendors at OSH about satellite weather

options - that seems like a pretty valuable capability in a cross-country

airplane.

Keith Hallsten

(I mounted my straight heated pitot out the nose of the XLFG this week.

Looks cool!) 

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

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On

Behalf Of Terrence Miles

Sent: Wednesday, June 15, 2005 12:27 PM

To: reflector at tvbf.org

Subject: REFLECTOR: Bus, Battery & Back Order

Hi to everyone but in particular to Brian, Keith, Al G, and Kurt who I think

are deep into wire issues.

Here's what I got.

For Electrics:  Here's my current plan and why.  Two big batts in the nose.

One stacked on top of the other.  For now I am going to slap the ground 

leads together and run them in parallel with B&C L60 alternator (60 amps) 

and the B&C external voltage regulator and the o'volt protection.

I may one day with not a lot of effort, put in a 2nd aux battery contactor, 

but I see its practical value as limited due to what follows next.

I have decided in favor of a single power bus.  I can't see a strong enuf 

reason to break things into separate buses to power up or shed in event of 

alternator problems.  I will instead pull out a checklist and do a load shed

procedure at each components control head/ panel switch/CB/whatever.  (Two 

mags, by the way until I have her in the air and de-bugged)

When I re-read the Nuckols stuff  on dual batt & single alt, I decided it 

wasn't for guys like me.  I can put two equal amphr batts right side by 

side...read no #2awg wires running all over hell.  I don't have dual EI's.  

Sure as sh--t the day I loss a alternator would be the day the #1 comm would

be TU and I have to repower the main load buss to access #2 comm and get 

myself confused say 2 years down the road by which time all the electron 

theory will be faded into dim memory.

GRT stuff:  Single AHRS system, 2 screens, EIS in the radio stack, no 

airspeed&Alt add-on to the EIS in favor of round dials below the GRT 

screeens.  Decided basically to abandon the two spare power leads.  I am 

told a solenoid controlled contact can draw an amp to 1.5 amps just to hold 

closed, and the diodes will cost you a volt in pressure.

Some of the above was driven by electrical abnormal checklist drafting.  

Some from the local tower operator/Cozy guy/ex USAF avionics tech.  For 

backup, his personal philos is a bag of external hand helds.

What do you four think of this?  Anybody else want to chime in?

I called Affordable panels this week.  He is an RV vendor...uses the 

Approach Hub stuff.  He is very backed up.  I am looking to make the major 

buy with Stein Air.  Anybody have any comments on him?

Where's everybody else on this topic.  Are you guys going to wire up your 

own intercomponents in the avionics rack?

Last but not least...anybody else waiting for engine mounts and exhaust 

systems besides me??

Regards,

Terry

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