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Power Schematic for Review

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gordonrsmith921@yahoo.com

Joined: 06 Oct 2009
Posts: 24

Posted: Fri Jul 30, 2010 10:26 am Post subject: Power Schematic for Review

I have laid out a preliminary electrical system schematic for an all metal aircraft (Sonex) powered by a Jabiru 3300 engine.  I would appreciate Bob’s and other lister’s comments.  I have not yet done a complete Bus Load analysis so some of the wire sizes, fuse sizes and other options could change.  I have not included the ignition systems in that they are totally independent of the aircraft electrical system.  

   

In considering the possible Z figures, I found that Z20 (small Jabiru) and Z21 (J3300) did not quite offer what I was hoping to accomplish.  I believe that Z16 (Rotax 912/914) offered what I would like to have as a basis.  

   

Even though we have been cautioned about cherry picking the various Z figures, there are some features in other Z figures that I would like to incorporate.    First, I would like to      incorporate the soon to be available AEC9024 device for control of the      master contactor, the OV disconnect relay and as a LV warning device.  I cherry picked this      from Z09 and Z-Laury.  I might not have the pin-outs correct, but that can      be updated easily at a later time, when the specs are published.  I like      the idea of a “Breaker-less” panel.  
I would like to use the      JD101406 Rectifier/Regulator, as in Z09, in place of the Jabiru supplied      unit.  I understand that this might be a more robust option.  
I would like to have the      Alternator OV Disconnect Relay to Open one of the Dynamo leads as in Z16      instead of the +B lead as in Z21.  
There are two other major      options that I would like to consider:     BROWNOUT BATTERY       WITH B/O RELAY.  This as is illustrated in Z10-8.  I am considering a MGL       EFIS system.  They (and others, I believe) offer an option to use a       backup battery that is exclusive to powering the EFIS and its accessories.        I think that a well designed and crafted E-Bus system makes this       exclusive backup unnecessary and redundant.  The exclusive backup battery       cannot be kept charged unless turned “ON” during operation of       the EFIS from the main power source.  The Z-10-8 type of backup not only       offers a seamless full voltage for ALL E-Bus items, during cranking to       start, but adds to the alternator out E-Bus operating time capacity.  It       will also be topped off and maintained automatically when the main       battery is connected to a remote maintainer through the Aux. 12V. Power       plug in the panel.   
E-BUS ALTERNATE FEED RELAY.        This as in Z32.  In that I have not finalized the calculation of the       E-Bus loads, this may or may not be needed.  What is the continuous (and       intermittent) E-Bus amperage point at which the relay should be       implemented?  I have incorporated a LED light indicator to show that the       E-Bus feed is closed (ON) in any case.     

   

The other thing that needs to be reviewed is the use of FUSEABLELINKS.  We have also been cautioned to not incorporate them accept in special considerations so please comment:    Fuseablelink in the alternator      +B lead at the starter contactor as in Z16, Z18, Z20 and in the alt      alternator +B lead to the hot side of the main battery contactor of Z8.  
Fuseablelink in the E-Bus      alternate feed path at the connection to the E-Bus as in Z13-8 and Z13-8      E-Bus Feeders.  
Fuseablelink in the E-Bus      alternate feed from the hot side of the battery contactor as in Z16 and      Z18.  
Fuseablelink at the B/O battery      hot lead to the E-Bus alt. feed relay or switch.  In this use I could not      find illustration in the Z figures.  However I think that it might be      logical to assume that this use is OK if the use mentioned directly above      from the hot side of the main battery is OK.   

   

I have attached a four page illustration that shows all options.  The first page (D) shows the inclusion of both options.  Next (C) and (B) illustrate the two options implemented singly.  The last page (A) includes neither option.  

   

Gordon Smith

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nuckolls.bob(at)aeroelect
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Posted: Sat Jul 31, 2010 6:07 am Post subject: Power Schematic for Review

At 01:20 PM 7/30/2010, you wrote:

  	  Quote: 	
		    

 I have laid out a preliminary electrical system schematic for an all metal aircraft (Sonex) powered by a Jabiru 3300 engine.  I would appreciate Bob’s and other lister’s comments.  I have not yet done a complete Bus Load analysis so some of the wire sizes, fuse sizes and other options could change.  I have not included the ignition systems in that they are totally independent of the aircraft electrical system.

  

 In considering the possible Z figures, I found that Z20 (small Jabiru) and Z21 (J3300) did not quite offer what I was hoping to accomplish.  I believe that Z16 (Rotax 912/914) offered what I would like to have as a basis.

  

 Even though we have been cautioned about cherry picking the various Z figures, there are some features in other Z figures that I would like to incorporate. 	


   "Cherry picking" refers to items that drive architecture,

   and failure mode effects analysis. Functional accessories

   like ov protection, lvwarn, ground power, etc. are add-on

   features that can be selected from a variety of styles. 	  Quote: 	
		    First, I would like to incorporate the soon to be available AEC9024 device for control of the master contactor, the OV disconnect relay and as a LV warning device.  I cherry picked this from Z09 and Z-Laury.  I might not have the pin-outs correct, but that can be updated easily at a later time, when the specs are published.  I like the idea of a “Breaker-less” panel. 	
 

   The the pinouts are driven by the etched circuit

   board layouts. Finished that last week and got boards

   in yesterday. The pinouts illustrated in Z-08

   are consistent with the boards. 	  Quote: 	
		    I would like to use the JD101406 Rectifier/Regulator, as in Z09, in place of the Jabiru supplied unit.  I understand that this might be a more robust option. 	
 

   John Deere has consistently offered a bit more

   heat-sink performance on their rectifier/regulators

   so your substitution is probably a good thing. Do

   you know anyone else who has made this substitution

   and is flying it? 	  Quote: 	
		    I would like to have the Alternator OV Disconnect Relay to Open one of the Dynamo leads as in Z16 instead of the +B lead as in Z2 	
   Okay 	  Quote: 	
		    There are two other major options that I would like to consider: 	
  	  Quote: 	
		     BROWNOUT BATTERY WITH B/O RELAY.  This as is illustrated in Z10-8.  I am considering a MGL EFIS system.  They (and others, I believe) offer an option to use a backup battery that is exclusive to powering the EFIS and its accessories.  I think that a well designed and crafted E-Bus system makes this exclusive backup unnecessary and redundant.  The exclusive backup battery cannot be kept charged unless turned “ON” during operation of the EFIS from the main power source.  The Z-10-8 type of backup not only offers a seamless full voltage for ALL E-Bus items, during cranking to start, but adds to the alternator out E-Bus operating time capacity.  It will also be topped off and maintained automatically when the main battery is connected to a remote maintainer through the Aux. 12V. Power plug in the panel. 	
  

    Are you aware that the alternator on this engine is good

    for 20A? What size battery are you planning for the

    main battery? How much weight/volume are you willing

    to dedicate to a brown-out mitigation system? Are you

    sure that it's necessary/useful? The devices on your

    e-bus may not need brownout protection if the internal

    resistance of the main battery combined with inrush

    characteristics of the starter don't depress the

    bus enough to cause re-sets. Finally, one could always

    start the engine before turning on devices that have

    re-set issues . . . or just let them re-set.



    You've got a LOT of electro-whizzies planned for this

    project. Is this a night or ifr cross-country machine?  	  Quote: 	
		     E-BUS ALTERNATE FEED RELAY.  This as in Z32.  In that I have not finalized the calculation of the E-Bus loads, this may or may not be needed.  What is the continuous (and intermittent) E-Bus amperage point at which the relay should be implemented?  I have incorporated a LED light indicator to show that the E-Bus feed is closed (ON) in any case. 	
  

   With a 20A main alternator and a limited size

   for a main battery (this isn't going to be a

   C-210!!), your e-bus loads should be cultivated

   down to those described in the original writings

   about an e-bus. If your e-bus loads are more than

   a few amps, then your demonstrated performance

   is going to be disappointing.



  	  Quote: 	
		    

 The other thing that needs to be reviewed is the use of FUSEABLELINKS.  We have also been cautioned to not incorporate them accept in special considerations so please comment:  Fuseablelink in the alternator +B lead at the starter contactor as in Z16, Z18, Z20 and in the alt alternator +B lead to the hot side of the main battery contactor of Z8.  
Fuseablelink in the E-Bus alternate feed path at the connection to the E-Bus as in Z13-8 and Z13-8 E-Bus Feeders.  
Fuseablelink in the E-Bus alternate feed from the hot side of the battery contactor as in Z16 and Z18.  
Fuseablelink at the B/O battery hot lead to the E-Bus alt. feed relay or switch.  In this use I could not find illustration in the Z figures.  However I think that it might be logical to assume that this use is OK if the use mentioned directly above from the hot side of the main battery is OK. 	
 

   Fusible links are fine where shown in z-figures, no

   where else. Further, the alternator b-lead link can be replaced

   with a MAX in-line fuse holder and in the case of your

   Jab3300 alternator, a 30A fuse.



  	  Quote: 	
		  I have attached a four page illustration that shows all options.  The first page (D) shows the inclusion of both options.  Next (C) and (B) illustrate the two options implemented singly.  The last page (A) includes neither option. 	


   Suggest you get your load analysis done first

   and know exactly what you CAN run in this system

   and under what anticipated flight conditions. The

   forms for doing a load analysis are available

   at:



  http://www.aeroelectric.com/PPS/Load_Analysis/



   There are printed forms for a paper analysis

   and sample Excel files for a paperless analysis.

   

   You've spent a lot of time producing the

   drawings but it's not clear that you've 

   sized the system and planned accessories to

   the engine's alternator or to the airplane's

   missions. 



   You've expressed some concerns for keeping an

   EFIS system up and running . . . do you

   anticipate deliberate IFR ops? If so, what's

   your backup plan for the EFIS going south?

   Needle-ball-airspeed? Are you planning LOC/GS

   capability? What radios instruments are needed

   to support that activity?



   I can suggest that in 1000 hrs and 30 years

   of flying, much of that time at night, that

   I've never had or even desired the ability

   to bore holes in clouds under the watchful

   eyes of guys on the ground. I was ready to

   take my check-ride for an instrument ticket

   and the flight examiner gigged the airplane

   I had rented because there was no radio

   station license on board. My credit for

   the written was running out in a few days

   and my work schedule was going to hose a

   rescheduled ride. I also considered the $time$

   necessary to keep the ticket current. I decided

   that the design goal was to be able to bail my

   buns out of a poor visibility situation. The

   investment of time, talent and resources to

   be worthy of the benevolence and permission

   of others to practice a good and necessary

   skill did not add value to the goal.



   After that I kept my skills up to my own satisfaction

   knowing that should I do something stupid for

   being there in the first place, the hazards

   against saving the day were no worse whether or

   not I had the right piece of paper in my wallet

   or in the ship's documents.



   The point is that your airplane's electrical

   power supply, space on the panel, volume and

   weight limits are a finite resource. As with

   our automobiles, it's really easy to stack

   lots of bells and whistles into the mix . . .

   but they have their own cost of ownership

   issues. My son is having a several hundred

   dollar repair done to his electronically

   controlled a/c in his 2000 van . . . my 1987

   GMC has ON/OFF switch and some manually

   positioned flapper valves that have not missed

   a lick in 23 years.



   Depending on how you KNOW you're going to

   use the airplane, you may well find yourself

   lacking some functionality because hammers

   and saws were substituted with more expensive,

   more complex and less reliable nail guns

   and laser cutters.



   Keep in mind too that this is an opportunity

   to do something BETTER than what's handed to

   you in a C-172 over which you have no control.

   At the same time, you'll probably find that

   should you need to rent a C-172 because your

   airplane is down for maintenance, that you

   won't be climbing into the Cessna with

   trepidation growing out of some knowledge that

   YOUR airplane has electrical system features

   that the Cessna doesn't have.



   Suggest you nail down a mission statement

   for the airplane along with a load-analysis

   that is serviceable with the alternator and

   battery combination. Then take the Z-16

   as published and nit-pick it for potential

   operational failures that beg adjustment

   by adding features or changes to architecture.



 

   Bob . . .    [quote][b]

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