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Final Elect. System Review

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bcone1381

Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan

Posted: Fri Nov 18, 2022 8:52 am Post subject: Final Elect. System Review

Please help me finalize my electrical system.  It based off Bob’s Z101 and taylored to meet rather meager demands.   I am moving from the conceptual  phase to the fuselage as we speak, installing components today.  



My Bearhawk Patrol, like a Supercub, is VFR, with merely a Garmin G5, Engine Monitoring System, Surefly ignition, Comm, and Xpndr, and portable navigation.



I have done my load analysis, drawn all schematics for individual circuits.  My diagram is attached.   I transformed Bob’s Z101 Engine Bus to my Aux Bus (Essential Bus).  Continuous draw is 1.5A  (2.3A intermittent) plus a single USB charger max of 2.5A.  Please criticize me if the simple switch (Aux Bus - Aux Alt) is a risk that should fixed with a solenoid.  



The left side of the Battery Contactor has 12 AWG wire powering the Aux Bus through a switch (AUX BUS - AUX ALT) that is not protected.  Should I add protection to that circuit?  The length of the circuit is about 30 inches.  I have a 

B & C slow acting 23A midi fuse that might go well there.



Any other feedback?  Bob?

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_________________
Brooks Cone
Bearhawk Patrol Kit Build

user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Fri Nov 18, 2022 10:49 am Post subject: Re: Final Elect. System Review

In case of smoke in the cockpit or in case of an imminent forced landing, the pilot should have the ability to shut off all electrical power as close to the source(s) as possible.  Does your design meet that objective?  Relays can be used for remote control.

-

The surefly electronic ignition is powered by the battery bus and by the aux bus.  Are those two sources isolated with diodes?  If not, the aux bus will always be powered by the battery.

-

Long wires do not necessary have to be protected by a fuse or circuit breaker if physically protected against shorting.  Use your best judgement.

_________________
Joe Gores

bcone1381

Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan

Posted: Sat Nov 19, 2022 6:00 am Post subject: Re: Final Elect. System Review

 	  user9253 wrote: 	
		  In case of smoke in the cockpit or in case of an imminent forced landing, the pilot should have the ability to shut off all electrical power as close to the source(s) as possible.  Does your design meet that objective?  Relays can be used for remote control.

-

The surefly electronic ignition is powered by the battery bus and by the aux bus.  Are those two sources isolated with diodes?  If not, the aux bus will always be powered by the battery.

-

Long wires do not necessary have to be protected by a fuse or circuit breaker if physically protected against shorting.  Use your best judgement. 	




 User 9253, Thanks for this exercise!  I work alone.  I am an EAB builder. A is for Amateur.  My design skills are not good and you help me think.  The Z101 is so so helpful.



1)  Re: Shut off power close to the source.  It does not meet that objective and I see that a relay would.  How do we balance that objective with the objective of simplicity of a switch on a low Amp circuit?  My memory says that Bob in the past said 5A was the threshold.   What is Industry Best Practice...a relay or switch?



2) Re Surefly Ignition Module (SIM):  I am installing two SIM's.  The L. SIM source is the Battery Bus, the R. SIM source from the Aux Bus.   Good Catch.  I will update my diagrams.  Does this satisfy your concern?  I see no other bus bus power issues.



3) Thanks!



Like I said, you help me think.  If I explain my thinking it will not give me an industry best practice that experts know. Its  a debate.  My thinking is not an Industry Best Practice without "Your thinking can be improved, here is my concern, do it this way because...."

_________________
Brooks Cone
Bearhawk Patrol Kit Build

user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Sat Nov 19, 2022 7:48 am Post subject: Re: Final Elect. System Review

Sometimes there is no right or wrong answer, but rather a matter of personal preference.  I prefer simplicity: Just one bus.  But to each his own.

What is best practice, a relay controlled by a small switch or just a switch?

There is no right or wrong answer.  You will have to decide.  Consider the advantages and disadvantages.  If the relay fails, can you continue to fly safely?

_________________
Joe Gores

bcone1381

Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan

Posted: Sat Nov 19, 2022 12:44 pm Post subject: Re: Final Elect. System Review

8253;



I think of Art ....  I see now we are playing with "Industrial Arts."  Art has many answers.  Math is not art, is foundational for design, but it has one only one right answer.  You helped me see the Art side of electrical system design.

_________________
Brooks Cone
Bearhawk Patrol Kit Build

johnbright

Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA

Posted: Sat Nov 19, 2022 3:28 pm Post subject: Re: Final Elect. System Review

[quote="bcone1381"] 	  user9253 wrote: 	
		  ... 1)  Re: Shut off power close to the source.  It does not meet that objective and I see that a relay would... My memory says that Bob in the past said 5A was the threshold..." 	




Ref FAR 23.1361 "Master Switch Arrangement". FAR 23.1361 calls for protective device of 5A or less but Bob Nuckolls' advice is to allow 7-1/2 A fuses since fuses are faster than breakers, that's why the largest fuse you see on the battery bus in Z schematics is 7-1/2A.



https://www.risingup.com/fars/info/part23-1361-FAR.shtml



BTW, fuses are normally sized (max load) / (0.75) = fuse rating. Max load on a 7-1/2A fuse should be 5.6A.



As you can see, a 23A MIDI fuse does not meet FAR23.1361. Also it is considered bad practice to put two fuses in series even though the 10A fuses on your aux bus are smaller than a MIDI 23.



As mentioned, FAR 23.1361 is for fire-in-the-cockpit and off-field landing scenarios but it's also for service scenario, that's why auto service manuals say first thing disconnect the battery negative terminal.



Thoughts:

Z101 has the backup alternator B lead on the battery but you show it on the aux bus. Not necessarily a bad thing but IMO it's not correct to call it Z101.

Do you choose the PM backup alternator because it self-starts with no battery present? FYI there is the Monkworkz PM vacuum pad alternator available now that makes 30A at 1800 Lycoming RPM (its B lead cannot be connected directly to the battery because it presents a ~30mA passive load).

There's room for opinion but I would put a 20A or 40A automotive relay (like B&C sells) in the aux bus feed.

I can't imagine why the Surefly fuse on the battery bus can't be 7-1/2A. The four-cylinder Surefly draws 0.7 +/- 0.2A per the IM. OTOH the Surefly is proxim to the battery bus so the 10A fuse could be argued to meet FAR 23.1361.

_________________
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
N1921R links

bcone1381

Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan

Posted: Sat Nov 19, 2022 5:29 pm Post subject: Re: Final Elect. System Review

FAR23.1361  Thanks for this reference.  I will be adding the Solenoid now.  

I see my switch is not adjacent to the bus, whereas a solenoid is and it will eliminate the Midi Fuse. 



Fuse size.   I’ll search out more feedback regarding circuit protection.  I refer often to AC 43.13 table 11-3 titled DC Wire and Circuit Protection when manufacturers instructions are not available.   



Surefly Instructions call out 14 AWG with 10A circuit protection but I find no fault in your assessment.   



My choice is the SD-8 is due to me having it on hand.  I've read about the Monkworkz and think is numbers are impressive. I think it will be the GO TO alternator for EAB.  But the SD-8 is enough for my backup, is very light weight and may be one of the most proven reliable alternators on the market.  The Monkworkz is new and  It’s hard to get good data on component failure rates.

_________________
Brooks Cone
Bearhawk Patrol Kit Build

Peter(at)sportingaero.com
Guest

Posted: Sun Nov 20, 2022 12:54 am Post subject: Final Elect. System Review

Dear Brooks,



As you are VFR only, and I guess your G5 has a back-up battery, do you need more than one alternator and one bus? Its only more cost, weight and complexity that won't buy you much in terms of continued flight after a failure as the battery will do that with the simple system you are planning.

If the alternator fails figure out what must be switched off to extend battery endurance.

The G5 will provide 4 hours and the portable navigation must have an internal battery, so not that much left.

A typical 15Ah battery will keep your airplane flying until you are out of gas.

Keep everything as simple, and as low parts count, as possible. No point in adding solenoids if a switch can handle the expected load.

Your diagram came over fairly low res, with the text indistinct, but if you really want to cater for loss of the battery connector use the switch you already have to bypass directly to all the busses. If a DPDT switch is used disable the start button circuit so starter loads cannot be put through the switch.

Is circuit protection required on a 12G wire? Perhaps, if you have a large fuse it may be worth adding, the risk is low.

I would delete the always hot (endurance) bus on a simple VFR aircraft - it only runs down the battery. The load analysis always says it is good for several months but my experience is when you haven't made it out to the airport in a month or 6 weeks and have made an hour or two for a quick flight that plan will be sunk by a flat battery. 

Is the Surefly on the battery bus and aux bus? Would have thought it should be shut down on the master?

Check the wire gauges you have specified and go for the lightest possible, copper wire adds a lot of weight.



Regards, Peter

--

kenryan

Joined: 20 Oct 2009
Posts: 424

Posted: Sun Nov 20, 2022 5:08 am Post subject: Final Elect. System Review

Different path, but Viking Aircraft Engines, which supplies engines based on the Honda Fit, recommends an electrical system that utilizes one alternator and 2 batteries. They switch which battery gets charged each flight. Has Bob designed an architecture using one alternator and 2 batteries?



On Sat, Nov 19, 2022 at 11:56 PM Peter Pengilly <Peter(at)sportingaero.com (Peter(at)sportingaero.com)> wrote:



[quote]--> AeroElectric-List message posted by: "Peter Pengilly" <Peter(at)sportingaero.com (Peter(at)sportingaero.com)>

 

 Dear Brooks,

 

 As you are VFR only, and I guess your G5 has a back-up battery, do you need more than one alternator and one bus? Its only more cost, weight and complexity that won't buy you much in terms of continued flight after a failure as the battery will do that with the simple system you are planning.

 If the alternator fails figure out what must be switched off to extend battery endurance.

 The G5 will provide 4 hours and the portable navigation must have an internal battery, so not that much left.

 A typical 15Ah battery will keep your airplane flying until you are out of gas.

 Keep everything as simple, and as low parts count, as possible. No point in adding solenoids if a switch can handle the expected load.

 Your diagram came over fairly low res, with the text indistinct, but if you really want to cater for loss of the battery connector use the switch you already have to bypass directly to all the busses. If a DPDT switch is used disable the start button circuit so starter loads cannot be put through the switch.

 Is circuit protection required on a 12G wire? Perhaps, if you have a large fuse it may be worth adding, the risk is low.

 I would delete the always hot (endurance) bus on a simple VFR aircraft - it only runs down the battery. The load analysis always says it is good for several months but my experience is when you haven't made it out to the airport in a month or 6 weeks and have made an hour or two for a quick flight that plan will be sunk by a flat battery. 

 Is the Surefly on the battery bus and aux bus? Would have thought it should be shut down on the master?

 Check the wire gauges you have specified and go for the lightest possible, copper wire adds a lot of weight.

 

 Regards, Peter

 

 

 --

user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Sun Nov 20, 2022 6:49 am Post subject: Re: Final Elect. System Review

There was another discussion in 2014 on the AeroElectric list about aircraft electrical architecture which includes a schematic by me.

http://forum.matronics.com/viewtopic.php?p=416668

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Nov 20, 2022 12:48 pm Post subject: Final Elect. System Review

 	  Quote: 	
		  What is best practice, a relay controlled by a small switch or just a switch?

 	
   There is a train of thought to resolving this question.

    

    Generally speaking, relays are used to carry larger

    currents than one wishes to bring to the panel on

    a switch. Good examples include starter and battery

    contactors (although the Piper Pacer had battery

    under seat and both circuits were manual switches

    on the panel under occupants legs!). Minimizing length

    of the high current power path can be an important

    consideration. One might also choose to use relays

    to centrally locate power management tasks and simplify

    control wiring. For example: Z101 suggests only 2 relays

    which are best located adjacent to the busses

    and fat-wires they control. Pilot management of those

    relays is through two switches and itty-bitty wires

    remotely located on the panel.

  

  	  Quote: 	
		  Consider the advantages and disadvantages.  If the relay fails, can you continue to fly safely? 	


    This is called FAILURE MODE EFFECTS ANALYSIS (FMEA

    for short). It's a process that should be artfully applied

    to everything you do to configure and install your

    electrical system. Everything from bolting a

    Garmin G10000 to the panel down to crimping a

    terminal on a wire.

  

    (1) What are the ways this feature can fail?



    (2) How will that failure affect ability of

    the FLIGHT SYSTEM (pilot, airframe, circumstance)

    ability to comfortably terminate the flight?



    (3) How will I know failure has occurred?

  

    (4) Is that failure pre-flight detectable?

    (if so, put it on the check-list).



    (5) If loss of that feature has a deleterious

    effect under (2), what is your Plan-B

    for mitigating the loss and having an exciting

    tale to tell the grandchildren?



    I have often referred readers to my personal

    vaccination against the dreaded Dark Panel Syndrome:



  https://tinyurl.com/4xjhgly



    As a consistent renter of airplanes from a

    relatively diverse fleet, taking a personal approach

    to FMEA and preventative maintenance was a

    bit impractical. But with those three items

    in my flight bag (along with an AFD), my

    chances of getting on the ground comfortably

    even assuming total electrical system failure were

    pretty good.



    Your own recipe to comfortable arrivals with

    the earth need not be so Spartan. But they

    can be quite simple and BUILT IN to your

    ship's architecture. Z101 offers multiple-source,

    dual-path conduits of energy to various classes

    of appliance. The likelihood of total loss

    of any appliance is driven more by craftsmanship

    than failure of a component . . . near zero.



    Z101 switching philosophy covers all

    keep-it-lit-and-turning options with

    at most 3  and possibly 2 toggle switches.

    The only radical in flight risk is to

    switch them all OFF . . . and having them

    all ON represents no particular hazard.



    

    



 



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

bcone1381

Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan

Posted: Sun Nov 20, 2022 2:37 pm Post subject: Re: Final Elect. System Review

Thanks for your input on multiple back up batteries.  



I am installing one main battery with no backups.  Z101 has good FMEA that will minimize risk and cost of ownership.  Backup Batteries have risk that rise over time and cost.   The SD-8 alternator is light weight, reliable, requires no annual maintenance and is in my inventory.

_________________
Brooks Cone
Bearhawk Patrol Kit Build

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Nov 20, 2022 2:37 pm Post subject: Final Elect. System Review

 	  Quote: 	
		  Ref FAR 23.1361 "Master Switch Arrangement". FAR 23.1361 calls for protective device of 5A or less 	


   That goes to crash-safety. The rational is that an

   always hot wire soft-faulted as a result of mashing your

   airplane into a wad is less likely to start

   a fire if it's protected at 5A or less. This

   idea is a bit specios . . . give me a cup of

   gasoline, a battery, a 5a breaker and a hunk

   of wire and I can start fires all day.



   That 5A number was pulled from somewhere the sun

   don't shine . . . but when you think about it,

   there ARE certain needs for always hot wires

   that HAD to be protected as SOME level . . . okay,

   how about 5A?



   But that assertion doesn't speak to the huge

   differences in performance between fuses and

   circuit breakers. Fuses are MUCH faster than

   fuses. See:



  https://tinyurl.com/muefe6s4



   The demo only loaded the protective devices to

   2 times rated. Presumably, a hard-fault to a

   battery fed wire will be much stronger causing

   faster operation. The likelihood of a dribbling

   of fuel in the same time frame as the hard-fault

   is very low if not impossible. A soft-fault is

   another matter. The worry is for a dangling

   remnant of a protected but always hot circuit making

   intermittent contact with 'ground' for significant

   periods of time. Time that allows compromised

   fuel containment to spread about.



   But as you saw in the video above, a soft-fault

   (intermittent sparking) cannot be guaranteed

   'fire safe' at any size of protective device 

   . . . so fooey, let's call it 5A and

   forge ahead.



  	  Quote: 	
		  Bob Nuckolls' advice is to allow 7-1/2 A fuses since fuses are faster than

 breakers, that's why the largest fuse you see on the battery bus in Z schematics is 7-1/2A. 	


   Yeah, but if you really, Really, REALLY needed

   a 10A always-hot circuit, go ahead with the

   fuse. 



  	  Quote: 	
		  BTW, fuses are normally sized (max load) / (0.75) = fuse rating.

 Max load on a 7-1/2A fuse should be 5.6A. 	


   Excellent point . . . but that assumes a 'gentle'

   load (mostly resistive, little or no inrush).

   The disadvantage of fuses is that they can be

   'hammered' by short but repetitive transient

   above their nameplate rating. The N811HB

   accident



  https://tinyurl.com/3h8vb3aj



   was the result of fuse operations delayed for

   HOURS of normal operations sprinkled

   with transient excursions into a range

   of currents that 'soften' the fuse element.



   This hammering causes a slow DEPRESSION

   of the fuse's operating current. N811HB had

   to hammer TWO fuses events where the second 

   precipitating rough arrival with the rocks.



  	  Quote: 	
		  As you can see, a 23A MIDI fuse does not meet FAR23.1361. Also it is

 considered bad practice to put two fuses in series even though the 10A

 fuses on your aux bus are smaller than a MIDI 23. 	


   I sort wish that there was a different symbol

   for fusible links vs. fuses. Fusible links are

   so very slow that they can be reliably incorporated

   to protect fat-wire feeders to bus bars that

   distribute power to downstream arrays of breakers or

   fuses.



   The MIDI devices are not generally used as

   protection to appliance feeders. They are

   robust and slow like the legacy ANL current

   limiters. See:



  https://tinyurl.com/pm54y2ye



   Note that a MIDI30 will carry 40 amps almost

   forever, 60A for about 8 seconds, 200A for

   200 mS. This device could be used to protect

   the fat-wire supplying a bus with a 5A breaker

   feeding a crowbar ov management module. Typical

   crowbar currents are on the order of 200A. A

   5A breaker opens in about 10 mS, 20x faster than

   any MIDI device protecting that bus upstream.



   But then, MIDI devices are kinda clumsy in that

   they need holders and hardware to mount them.

   a 10AWG feeder with a 14AWG fusible link wire

   would be a fine alternative to a MIDI30 limiter.



  	  Quote: 	
		  As mentioned, FAR 23.1361 is for fire-in-the-cockpit and

 off-field landing scenarios but it's also for service scenario,

 that's why auto service manuals say first thing disconnect

 the battery negative terminal. 	


   Good idea . . . watched a very well done youtube

   presentation by a fellow that was taking lots

   of wires loose and laying tools on top of his

   battery with all the fat-wires still hooked up.

   I'm assuming he edited out the scene with

   sparks and smoke . . .



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Nov 20, 2022 8:36 pm Post subject: Final Elect. System Review

At 04:37 PM 11/20/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "bcone1381" <bcone1964(at)gmail.com>



 Thanks for your input on multiple back up batteries.  



 I am installing one main battery with no backups. 	


   Tell us also that you plan periodic capacity

   checks along with a "replace at less-than-xx-percent"

   maintenance philosophy.



   Most light aircraft batteries get replaced

   when they don't crank the engine any more.

   By this time, capacity is probably much

   smaller than a practical, battery-only endurance

   mark.



   In 50+ years of reading 'dark-n-stormy-night'

   tales in the aviation rags, I cannot recall

   a single narrative where the writer cites

   battery failure in spite of satisfactory, 

   periodic maintenance tests.



   Batteries are a commodity. Like tires,

   oil, fuel, alternator belts, etc. they

   are CONSUMED starting at hour-one. Avoid

   your own dark-n-stormy night story by

   not consuming past hour-too-many.



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

bcone1381

Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan

Posted: Tue Nov 22, 2022 1:47 pm Post subject: Re: Final Elect. System Review

Bob;



Battery Condition will be checked every annual with a Lawn Mower destination when 80% capacity is reached.  I believe that is an Industry Best Practice.  



Fusible Link Question.  You have a Cartoon titled "How to Fabricate Fusible Links."  In block one you say 



THIS TECHNIQUE IS SUITED FOR 24 AND 22AWG FUSE LINKS ONLY (USE

TO PROTECT 20 AND 8AW G WIRES RESEPCTIVELY). CONTACT US FOR

SITUATIONS WHERE YOU MAY NEED LARGER FUSE LINKS.



What should I know about a 14 AWG fusible Link?



NOTE OF GRATITUDE:

I cant tell you how much I appreciated your reply.  My concerns include fear that I will build in a hidden failure point, or a single point of failure like N811HB.    A few days ago I stated reviewing past archive of my questions dating back 5 years to fabricate a list of industry best practices.  I'm humbled at your patience and a lot of time with me on this forum.  More than I deserve.

_________________
Brooks Cone
Bearhawk Patrol Kit Build

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