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Rotax 912iS questions

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gilles.thesee(at)free.fr
Guest

Posted: Wed Jan 04, 2017 11:22 am Post subject: Rotax 912iS questions

Hi all,     

Presently considering the wiring of a Rotax 912iS in a friend's       composite project.     

The engine features a digital fuel injection with high pressure       fuel pumps, digital control "lanes", backup power circuit, dual       alternator with control box etc.     

The Rotax Installation manual calls for a certain number of panel       switches :      	  Quote: 	
		         

Pump A and B switches (permanent) : 10 A each       

Lane A & B switches (permanent) : 7.5 A each       

Engine Control Unit start power switch (momentary) : 20 A       

Backup battery switch (permanent) : 20 A     	
     

QUESTION : is it advisable to bring such heavy current carrying       wires to the panel, or would it be preferable to use relays to       control the system ?     

Any input appreciated,     

Thanks in advance,

          



          -- 

       Best regards,

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

ceengland7(at)gmail.com
Guest

Posted: Wed Jan 04, 2017 11:49 am Post subject: Rotax 912iS questions

On 1/4/2017 1:21 PM, GTH wrote:

     

      	  Quote: 	
		                

Hi all,       

Presently considering the wiring of a Rotax 912iS in a friend's         composite project.       

The engine features a digital fuel injection with high pressure         fuel pumps, digital control "lanes", backup power circuit, dual         alternator with control box etc.       

The Rotax Installation manual calls for a certain number of         panel switches :        	  Quote: 	
		           

Pump A and B switches (permanent) : 10 A each         

Lane A & B switches (permanent) : 7.5 A each         

Engine Control Unit start power switch (momentary) : 20 A         

Backup battery switch (permanent) : 20 A       	
       

QUESTION : is it advisable to bring such heavy current carrying         wires to the panel, or would it be preferable to use relays to         control the system ?       

Any input appreciated,       

Thanks in advance,

              



              -- 

         Best regards,

         Gilles

         http://contrails.free.fr

         http://lapierre.skunkworks.free.fr

     	
     For me, the decisions were based both on overall weight, and     complexity/reliabilityÂ  (yes, I know they aren't necessarily the     same thing, but can be related). 

     

     How much weight (length has a big influence) will using the heavier     gauge wire add, vs the added weight of the relay? How much     reliability will you sacrifice by adding a relay and all the extra     terminations required?

     

     Even 20 A is not that big a deal for the proper switch. Going bigger     than that, a relay starts to look more attractive, especially since     the automotive world now makes fairly light weight, high current     relays available for very reasonable prices. 

     

     Charlie

gilles.thesee(at)free.fr
Guest

Posted: Thu Jan 05, 2017 2:26 am Post subject: Rotax 912iS questions

Le 04/01/2017 Ã            20:49, Charlie England a Ã©critÂ :

         

      	  Quote: 	
		   

           

           Even 20 A is not that big a deal for the proper switch. Going           bigger than that, a relay starts to look more attractive,           especially since the automotive world now makes fairly light           weight, high current relays available for very reasonable           prices. 

                       

     	
     

     Charlie and all,

     

     Thank you to everyone who responded, on the list and in PM !

     Actually my concern is the high amperage in the fuel pumps and the     digital lanes wires. All those electrons flowing to and from the     panel just to keep the engine running, considering the avionics in     the vicinity...

     Maybe relays or contactors for the 20 amp circuits...

     Those injection engines are a bit complicated to manage : 5 switches     to fumble with in addition to the regular master and starter     switches just to start the engine.

     Lots of thinking to simplify the task of the pilot and avoid     forgetting something or manoeuvring the switches in the wrong     sequence...

     

     Thank you for your attention, and please keep giving advices, this     is a great help !

     

       -- 

       Best regards,

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jan 05, 2017 10:13 am Post subject: Rotax 912iS questions

At 04:25 AM 1/5/2017, you wrote:

  	  Quote: 	
		  Le 04/01/2017 Ã  20:49, Charlie England a Ã©critÂ :

  	  Quote: 	
		  



 Even 20 A is not that big a deal for the proper switch. Going bigger than that, a relay starts to look more attractive, especially since the automotive world now makes fairly light weight, high current relays available for very reasonable prices. 

 	


 Charlie and all,



 Thank you to everyone who responded, on the list and in PM !

 Actually my concern is the high amperage in the fuel pumps and the digital lanes wires. All those electrons flowing to and from the panel just to keep the engine running, considering the avionics in the vicinity...

 Maybe relays or contactors for the 20 amp circuits...

 Those injection engines are a bit complicated to manage : 5 switches to fumble with in addition to the regular master and starter switches just to start the engine.

 Lots of thinking to simplify the task of the pilot and avoid forgetting something or manoeuvring the switches in the wrong sequence...

 	


   Is there a down-loadable copy of the installation manual

   for your system?  The REAL concerns have little to do

   with switch ratings, wire sizes or breakers/fuses.



   The elegant solution considers failure modes (including

   risk of pilot error) . . . this is a system integration

   issue . . . a skill seldom demonstrated by folks who

   manufacture and market airplane parts. 



   After FMEA is done, you NEED to know the ENERGY 

   requirements for each accessory and anticipate the

   combinations in which those accessories are needed

   after loss of a single accessory for any reason.



   This is called LOAD ANALYSIS and it sets the sizes

   of alternators, batteries, circuit protection, wires,

   and yes . . . switches. Switches are last on the list

   of concerns. Many individuals in the OBAM aviation

   community get wrapped around the axles of AC vs. DC

   ratings, slow vs. fast break mechanisms, etc. etc.



   The underlying motivation being "nothing is too

   good for my airplane . . . and after all . . .

   it IS an airplane . . . everybody knows that

   things breaking on airplanes comes with risks

   for spiraling out of the sky trailing smoke."



   The realities are not nearly so exciting. See



  http://tinyurl.com/jfr8zzu



   The bottom line demonstrates that IF your

   FMEA is artfully conducted and IF your energy

   budgets are KNOWN and MAINTAINED, likelihood of

   an electrically induced bad day in the cockpit

   is vanishingly low. 



   Let's pray over the manufacture's data a bit

   to see if there's enough data to move your

   deliberations forward with confidence.



 

   Bob . . .    	 		 			 				 			 		 		 			

 				This email has been checked for viruses by Avast antivirus software. 				

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rlborger(at)mac.com
Guest

Posted: Thu Jan 05, 2017 10:42 am Post subject: Rotax 912iS questions

Bob,

The 912iS installation manual (along with all other manuals for all Rotax engines) is available at:



http://www.rotax-owner.com/en/support-topmenu/engine-manuals



Blue skies & tailwinds,Bob BorgerEuropa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP3705 Lynchburg Dr.Corinth, TX  76208-5331Cel: 817-992-1117rlborger(at)mac.com (rlborger(at)mac.com)



On Jan 5, 2017, at 12:11 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

  At 04:25 AM 1/5/2017, you wrote:  	  Quote: 	
		  Le 04/01/2017 Ãƒ  20:49, Charlie England a ÃƒÂ©critÃ‚ :  	  Quote: 	
		   Even 20 A is not that big a deal for the proper switch. Going bigger than that, a relay starts to look more attractive, especially since the automotive world now makes fairly light weight, high current relays available for very reasonable prices.  	
 Charlie and all, Thank you to everyone who responded, on the list and in PM ! Actually my concern is the high amperage in the fuel pumps and the digital lanes wires. All those electrons flowing to and from the panel just to keep the engine running, considering the avionics in the vicinity... Maybe relays or contactors for the 20 amp circuits... Those injection engines are a bit complicated to manage : 5 switches to fumble with in addition to the regular master and starter switches just to start the engine. Lots of thinking to simplify the task of the pilot and avoid forgetting something or manoeuvring the switches in the wrong sequence... 	
   Is there a down-loadable copy of the installation manual   for your system?  The REAL concerns have little to do   with switch ratings, wire sizes or breakers/fuses.   The elegant solution considers failure modes (including   risk of pilot error) . . . this is a system integration   issue . . . a skill seldom demonstrated by folks who   manufacture and market airplane parts.    After FMEA is done, you NEED to know the ENERGY    requirements for each accessory and anticipate the   combinations in which those accessories are needed   after loss of a single accessory for any reason.   This is called LOAD ANALYSIS and it sets the sizes   of alternators, batteries, circuit protection, wires,   and yes . . . switches. Switches are last on the list   of concerns. Many individuals in the OBAM aviation   community get wrapped around the axles of AC vs. DC   ratings, slow vs. fast break mechanisms, etc. etc.   The underlying motivation being "nothing is too   good for my airplane . . . and after all . . .   it IS an airplane . . . everybody knows that   things breaking on airplanes comes with risks   for spiraling out of the sky trailing smoke."   The realities are not nearly so exciting. See  http://tinyurl.com/jfr8zzu   The bottom line demonstrates that IF your   FMEA is artfully conducted and IF your energy   budgets are KNOWN and MAINTAINED, likelihood of   an electrically induced bad day in the cockpit   is vanishingly low.    Let's pray over the manufacture's data a bit   to see if there's enough data to move your   deliberations forward with confidence. 

   Bob . . .    	 		 			 				 			 		 		

 				This email has been checked for viruses by Avast antivirus software. 				www.avast.com

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jan 05, 2017 12:24 pm Post subject: Rotax 912iS questions

At 12:38 PM 1/5/2017, you wrote:

  	  Quote: 	
		  Bob,



 The 912iS installation manual (along with all other manuals for all Rotax engines) is available at:



  http://www.rotax-owner.com/en/support-topmenu/engine-manuals 	


   Thanks!



 

 

   Bob . . .    	 		 			 				 			 		 		 			

 				This email has been checked for viruses by Avast antivirus software. 				

www.avast.com

gilles.thesee(at)free.fr
Guest

Posted: Thu Jan 05, 2017 1:06 pm Post subject: Rotax 912iS questions

Le 05/01/2017 à 19:11, Robert L.       Nuckolls, III a écrit :

     

      	  Quote: 	
		  

           The elegant solution considers failure modes (including

           risk of pilot error) . . . this is a system integration

           issue . . . a skill seldom demonstrated by folks who

           manufacture and market airplane parts. 

         

           After FMEA is done, you NEED to know the ENERGY 

           requirements for each accessory and anticipate the

           combinations in which those accessories are needed

           after loss of a single accessory for any reason.

         

           This is called LOAD ANALYSIS and it sets the sizes

           of alternators, batteries, circuit protection, wires,

           and yes . . . switches. Switches are last on the list

           of concerns. 	
     Hi Bob,

     

     Thank you for responding.

     

     I tried to follow this approach of system integration, and after     some hard thinking we had a 2-day meeting with my partners playing     the "what if" game and establishing the corresponding load analysis.

     Thanks Bob B for the link. I would also suggest downloading the     Operator's Manual to have a look at the starting and holding point     sequences. Seems akin to rigging a nuclear sub for dive...

     Many opportunities to forget something or doing the wrong manoeuver.

     I have some ideas for combining some functions and rendering pilot     error less likely, though it implies more complexity than the     rudimentary circuit proposed by Rotax (with some errors in their     schematics).

     

     I would add that the Aeroelectric community is a tremendous help.     Peer review and critique of ideas or architectures are invaluable.

     Please Bob and everyone, keep up the good job !

     

     And BTW our two battery, Rotax 914 four-seater is still going strong     after 12 years !

     

     Thank you,

     -- 

       Best regards,

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jan 06, 2017 8:21 am Post subject: Rotax 912iS questions

At 02:22 PM 1/5/2017, you wrote:

  	  Quote: 	
		  At 12:38 PM 1/5/2017, you wrote:

  	  Quote: 	
		  Bob,



 The 912iS installation manual (along with all other manuals for all Rotax engines) is available at:



  http://www.rotax-owner.com/en/support-topmenu/engine-manuals 	


   Thanks! 	


    Oh . . . fooey. For all the skills, time and

    effort Rotax put into the rest of this product,

    the wiring diagrams are . . . well . . .



    My teachers held that a schematic should be

    all revealing. The architecture, functionality

    of each conductor, pin connection and component

    should just 'jump off the page' at you. This

    philosophy was practiced in every job I've

    ever held.



    I'm disappointed to find that the published

    drawings in the installation manual do not

    lend themselves well in this regard.



    It would take too much time and perhaps

    consultation for me to achieve a functional

    understanding of the Rotax system at the

    engineer/integrator level.



    So, getting back to the original questions

    on switches . . . ANYTHING B&C sells in the

    way of switches is entirely adequate to

    the task. Some of the 12AWG wire called out

    is 'overkill' but not harmful.



    I wish I could be more helpful but getting

    conversant with the designer's intent

    using only these drawings is like

    looking for a black cat in a coal mine with

    a candle. 



 

 

   Bob . . .     	 		 			 				 			 		 		 			

 				This email has been checked for viruses by Avast antivirus software. 				

www.avast.com

gilles.thesee(at)free.fr
Guest

Posted: Fri Jan 06, 2017 3:11 pm Post subject: Rotax 912iS questions

Le 06/01/2017 à 17:19, Robert L.       Nuckolls, III a écrit 

        	  Quote: 	
		   Oh . . . fooey. For all           the skills, time and

              effort Rotax put into the rest of this product,

              the wiring diagrams are . . . well . . .

         	
       

       ))

         They were not good at making diagrams back in the 914 days, but         it seems they didn't improve since then...

         I'll try to re-draw a simplified version of their proposed         architecture to help clarify some of my future questions.

         

               	  Quote: 	
		  

           

              So, getting back to the original questions

              on switches . . . ANYTHING B&C sells in the

              way of switches is entirely adequate to

              the task. 

         	
       

       So can we consider there is no problem bringing the         two permanent 10 amp pump wires and the two 7.5 amp "lane" wires         to the panel ?

         

         Thank you for your help, no doubt I'll have many more wiring         questions about this very peculiar engine.

              -- 

         Best regards,

         Gilles

         http://contrails.free.fr

         http://lapierre.skunkworks.free.fr

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Fri Jan 06, 2017 8:45 pm Post subject: Re: Rotax 912iS questions

 	  Quote: 	
		  So can we consider there is no problem bringing the two permanent 10 amp pump wires and the two 7.5 amp "lane" wires to the panel ? 

	
Designing an aircraft is full of compromises.  Running always hot wires to the instrument panel makes the engine circuits more reliable and simpler.  On the other hand, if one of those wires starts smoking or if a forced landing is imminent, they can not be disconnect from the battery.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Jan 07, 2017 5:52 am Post subject: Rotax 912iS questions

 	  Quote: 	
		    	  Quote: 	
		     So, getting back to the original questions

    on switches . . . ANYTHING B&C sells in the

    way of switches is entirely adequate to

    the task. 	


 So can we consider there is no problem bringing the two permanent 10 amp pump wires and the two 7.5 amp "lane" wires to the panel ?

 	


   Sure . . . I wouldn't add relays to the

   system to keep panel currents low. This

   just drives up parts count and offers

   little if any benefit.



 

 

   Bob . . .    	 		 			 				 			 		 		 			

 				This email has been checked for viruses by Avast antivirus software. 				

www.avast.com

gilles.thesee(at)free.fr
Guest

Posted: Sat Jan 07, 2017 11:31 am Post subject: Rotax 912iS questions

Le 07/01/2017 à           14:49, Robert L. Nuckolls, III a écrit :

         

      	  Quote: 	
		          	  Quote: 	
		           

             So can we consider there is no problem bringing the two             permanent 10 amp             pump wires and the two 7.5 amp "lane" wires to the panel ?

           	
       

             Sure . . . I wouldn't add relays to the

             system to keep panel currents low. This

             just drives up parts count and offers

             little if any benefit. 	
     

     Bob and all,

     

     Thank you.

     Attached is a drawing of how I understand the Rotax schematics. Hope     it'll get through.

     At least it helps me better understand the starting sequence (5     switches in addition to the master switches and start button).

     Please feel free to comment and point me to errors.

     Thanks for everything,

     -- 

       Best regards,

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

Rotax_wiring_redraw_01.pdf

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gilles.thesee(at)free.fr
Guest

Posted: Sat Jan 07, 2017 5:18 pm Post subject: Rotax 912iS questions

Le 07/01/2017 à           20:29, GTH a écrit :

         

      	  Quote: 	
		                

           Please feel free to comment and point me to errors. 	
     

     Hi all,

     

     Sorry, I just found a mistake : the starter contactor was misplaced     ;-(

     Here is a more correct version.

     

     -- 

       Best regards,

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

Rotax_wiring_redraw_02.pdf

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