REFLECTOR: Bus, Battery & Back Order

Al Gietzen ALVentures at cox.net
Thu Jun 16 00:10:41 CDT 2005


Hi; Terry;

 

My electrical design was driven by a different set of needs - like having
all electronically controlled ignition and fuel injection - so the design is
quite different.  I needed redundancy in the electrical, including allowing
separation of the batteries to independently power flight critical loads.  I
have two contactors, but normal operation will be with only one on.  And the
plane will continue to fly with both contactors off.

 

I would only question the need for two big batteries tied together, unless
you know you need extra weight in the nose anyway.  A single battery of 30
amp hrs, or so, will give you plenty of time to decide where to go and time
to get there in the event of alternator failure.

 

I also have the GRT with single AHRS and two displays.  I have backup, but
no gauges.  Airspeed, altitude, and vertical speed are included on my engine
monitor display, I have a digital compass, and roll attitude on the TruTrak
Pictorial pilot.  

 

Not that it is 'essential', but I don't think you would find it very
complicated to split buses between essential and non-essential loads, with
the ability to dump all non-essentials with a single switch.  Then you have
time to decide which essentials really are critical to your situation. 

 

Al

 

 

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

 

Regards,

Terry

 

 

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