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Viking Schematic

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user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Sun Jun 17, 2012 1:34 pm Post subject: Viking Schematic

I am helping a friend with a schematic for his Viking powered airplane.  See the attached pdf.  Is it safe to eliminate the Schottky diode in the lower left corner?  I want to remove the diode because it is one more failure point and I do not know if it can handle the full load of the main bus, perhaps as much as 25 or 30 amps.  The concern is a short in the alternator or starter circuit (Or is this a remote possibility?) with no way to isolate it without stopping the electrically dependent engine.  

Thanks for any advice.

Joe

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_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jun 19, 2012 6:43 am Post subject: Viking Schematic

At 04:34 PM 6/17/2012, you wrote:




I am helping a friend with a schematic for his Viking powered 

airplane.  See the attached pdf.  Is it safe to eliminate the 

Schottky diode in the lower left corner?  I want to remove the diode 

because it is one more failure point and I do not know if it can 

handle the full load of the main bus, perhaps as much as 25 or 30 

amps.  The concern is a short in the alternator or starter circuit 

(Or is this a remote possibility?) with no way to isolate it without 

stopping the electrically dependent engine.

Thanks for any advice.

Joe



--------

Joe Gores

    The rationale for this design is not clear just

    from the schematic. It appears to borrow nothing

    from the design philosophies for failure tolerance

    offered in the Z-figures. I'd have to know more about

    why it was all wired this way. What are the

    current demands for the two ignition systems?

   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Tue Jun 19, 2012 9:22 am Post subject: Re: Viking Schematic

Bob,

My friend is building an RV-12 with an automotive engine, the Viking, which is fuel injected and electrically dependent.  The power requirements for the ECU are not known but Viking uses 15 amp fuses.

http://www.vikingaircraftengines.com/Wiring%20page.html

 I do not like the electrical drawing on the Viking website because there are several possible points of failure all in series and supplying power to the engine through only one wire.

  I suggested to my friend that he use one of your drawings but he said they were too complicated.  I tried to simplify by removing the E-Bus and E-Bus diode, while still having a redundant power source for the ignition and fuel pumps without having always hot wires pass through the firewall.  The ignition and fuel pumps are located on the opposite side (aft) of the firewall from the engine.

  If the Alternate Feed Switch is turned on, the engine start circuit is disabled.   This will prevent starting current from flowing through the Alternate Feed Relay and damaging its contacts.  It is intended that the Alternate Feed Switch be turned on after starting and left on for the remainder of the flight.

 My friend prefers circuit breakers even though I recommended fuses.  He also wants to keep weight down by not having a starter contactor.

 The Main Bus receives power at each end of the bus.  If one connection should fail, the other will still provide power to the bus.

  The engine should keep running with power coming from only the Alternate Feed Relay or only from Master Contactor or only from the Alternator.

The Viking ECU has two independent (almost) units in one enclosure, although it only has one wire supplying power.  There is no pin-out available for the ECU 37-Pin D-Sub.  The only information comes from the Viking website.

The ECU has a SELECT wire that enables one of the two units, depending on whether the voltage on that wire is high or low.  At least that is what I deduced from the scant information on the Viking website.

  The major difference between your excellent drawings and my schematic is that I have eliminated the E-Bus diode and replaced it with part of the Alternate Feed switch to prevent starting current from flowing though the Alternate Feed Relay contacts.

  Now, without that E-Bus diode, I am having second thoughts about possible reverse current due to faults in the starter or alternator circuit.

Joe

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 21, 2012 2:39 pm Post subject: Viking Schematic

At 12:22 PM 6/19/2012, you wrote:

 	  Quote: 	
		  



Bob,

My friend is building an RV-12 with an automotive engine, the 

Viking, which is fuel injected and electrically dependent.  The 

power requirements for the ECU are not known but Viking uses 15 amp fuses.


	


   I've looked over the published instructions

   from Viking and the drawing you attached.

   The 'instructions' from Viking bear no demonstrable

   understanding of failure tolerant architecture

   for aircraft applications. There's a similar

   'disconnect' from legacy and modern processes

   and techniques for aircraft wiring.



   If your friend is willing to bring his project

   to "The List" and submit performance numbers

   to mission goals, I (and probably others) would

   be willing to help him sort the bits and pieces

   to arrive at the elegant solution.



   But the drawing taken together with abysmal

   instructions do not describe a 'sandbox'

   in which I would want to play. I would further

   advise you to distance yourself from this

   project. I've been made aware of several problem

   projects wherein the builders conversed with me

   but for reasons of their own, chose to do other

   things . . . yet they claim to have consulted

   me in the crafting of their system.



   The engine is VERY experimental . . . which

   is not a singular cause for concern. But the

   entire electrical system is even more "experimental".

   Burt Rutan used to advise, "do your engine experiments

   on a TC aircraft and your airframe experiments with

   a TC engine." The overarching point is to drive

   risks to a minimum which must INCLUDE educating the

   owner/pilot on how the system works and what to do

   when things don't work.



   I suggest your worries over the bus isolation diode

   is but the tip of an iceberg in terms of having

   identified and crafted work-arounds for all perceived

   risks. Driving those risks up with decidedly untried

   or demonstrably unsuited techniques and materials.



   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Thu Jun 21, 2012 5:27 pm Post subject: Re: Viking Schematic

Bob,

Thanks for your words of wisdom so eloquently stated.



I think that the Viking powered aircraft can be wired, for the most part, using one of your drawings.  There is one item unique to the Viking that is not addressed: ECU SELECT.  The Viking website recommends using one DPDT switch wired in parallel to act as a SPDT switch.  This switch will select either a high or low voltage and send it to the dual ECUs to enable either ECU1 or ECU2.  My concern is that if this switch fails, the pilot will not be able to switch to the backup ECU if needed.  Or if the switch fails open, who knows which ECU will be enabled, if any.  It is unknown what bad things might happen if both ECUs are enabled at the same time, even for a second.

  Is it safe to use one switch to choose between ECUs?  If not, is there a better way than to use 2 mechanically interlocked switches?  Perhaps a solid state circuit powered by the aircraft supply so that it would not load down the ECU.

Joe

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Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jun 22, 2012 5:24 am Post subject: Viking Schematic

At 08:27 PM 6/21/2012, you wrote:




Bob,

Thanks for your words of wisdom so eloquently stated.



I think that the Viking powered aircraft can be wired, for the most 

part, using one of your drawings.



    The exact architecture is not so important as

    the overall philosophy for the design and materials

    being considered. The Viking instructions did not

    speak eloquently to wire insulation but did caution

    about leaving your cowl open with the engine exposed

    to the sun! They also suggested the use of screw-terminal

    barrier strips . . . never used in TC aircraft to my

    knowledge and certainly not on my watch. On those

    two points alone, I would be inclined to comb the document

    for fundamental points of fact for performance (which

    there are precious few) and then pitch the document.



    This builder needs to FIND OUT how much current each

    of the ECU power inputs need. Then size wires, breakers

    and ENERGY SOURCES accordingly. This is not much different

    than a Lightspeed dual ignition system. If he is

    truly interested in simplicity, then wire per C-150;

    no e-bus or avionics bus. Run all normal ops equipment

    from a single bus including #1 ECU. Then add an aux

    battery sized to meet THE BUILDER's alternator out

    endurance requirements and drive the #2 ECU from that

    battery through it's own switch . . . not unlike the Lightspeed

    recommendations.  Separate switch for each ECU.



There is one item unique to the Viking that is not addressed: ECU 

SELECT.  The Viking website recommends using one DPDT switch wired in 

parallel to act as a SPDT switch.  This switch will select either a 

high or low voltage and send it to the dual ECUs to enable either 

ECU1 or ECU2.  My concern is that if this switch fails, the pilot 

will not be able to switch to the backup ECU if needed.  Or if the 

switch fails open, who knows which ECU will be enabled, if any.  It 

is unknown what bad things might happen if both ECUs are enabled at 

the same time, even for a second.



    Then find this out. Anyone willing to launch into the blue

    without answers to such questions is an accident waiting

    to happen . . . either from ignorance of this specific

    question or others like it. There is a reason that flight

    test pilots are required to have engineering degrees. It

    is insufficient to simply be able to fly the airplane.

    The pilot needs to (1) have an intimate understanding

    of the airplane and (2) a well founded confidence in those

    who say, "trust me, this will work." If this guy is in

    the "trust me" mode of receiving data, then you and everyone

    contributing that data are assuming risk that goes beyond

    simple advise. An RV built per Van's instructions is a very

    low risk flight system even for the "trust-me-it-will-work"

    customer. A warm fuzzy to the FAA's utopian quest for spending

    how ever much money it takes to drive the accident rate to zero.



    Failure mode effects analysis takes an intimate understanding

    of how the device or system is built right down to the last

    resistor. Baring that kind of knowledge, you 'partition off'

    blocks of a system and treat them as unknowns to be accommodated

    with failure tolerant design. This is reminiscent of the philosophy

    I was applying some years back during the "great IR/ER alternator

    debates". Conversations which were in fact not debates but

    affirmations of faith buy individuals who had no intimate

    knowledge of the systems and devices which they were

    promoting as "trust me, this will work."



    This airplane and it's prospective pilot would benefit

    from a top-down review not only of the engine and it's

    requirements/idiosyncrasies but the materials, power

    sources, distribution, and in particular developing

    the Plan-B, C and D that can be called upon with

    CONFIDENCE to deal with specific failures. This data

    needs to be combined with mission profiles . . . day

    VFR only?



Is it safe to use one switch to choose between ECUs?



    No airplane is safe . . . every airplane ever built will

    terminate your existence in a heartbeat. Some more

    easily than others. The BD-5 comes to mind. Each comes

    with varying levels of risk that are dependent as much

    upon pilot knowledge and skill as system reliability.



If not, is there a better way than to use 2 mechanically interlocked 

switches?  Perhaps a solid state circuit powered by the aircraft 

supply so that it would not load down the ECU.



    FIND OUT if the operating the two ECUs in tandem

    presents a risk. FIND OUT also how much current these

    systems demand in cruising flight. If dual ECU ops presents

    risk and assuming that the builder is driven by the

    ultimate in simplicity, then use two separate switches

    with the #2 being annunciated with a really annoying

    light and taking power from a separate battery. Might

    even space the #2 switch off in it's own corner of the

    panel.



    The point being that if all this modern equipment

    operates true to history in its automotive applications,

    then it's unlikely that #2 ECU will ever be needed

    in flight. The only time #2 is ever turned on is in

    pre-flight, on the ground and in accordance with

    check-list procedure. As you've already perceived,

    this "keep me from throwing the wrong switch" interlock

    philosophy may add more risk than simply having each

    system stand alone.



    The answers to the questions you've posed are stone

    simple. They require no more information than any other

    system integrator would DEMAND in the design of any

    other machine that poses risks to people and property.

    It matters not whether it's an airplane or a 10-story

    tall construction crane.



    The biggest question in my mind is to determine if

    your friend is a cognizant beneficiary of your efforts

    or whether you're simply putting band-aids onto a system

    with more risk-issues (yet unidentified) than the choice

    of an ECU select switches.

   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Fri Jun 22, 2012 2:41 pm Post subject: Re: Viking Schematic

 	  Quote: 	
		  This builder needs to FIND OUT how much current each 

of the ECU power inputs need. 	


Unfortunately there is only ONE power input to the Dual ECU.  I find it hard to believe that the ECU manufacturer would provide only one power input to their dual ECUs.  I suspect that the Viking Engine developer, Jan Eggenfellner , has elected NOT to use a second available power input.  I do not know this to be a fact.  It is just speculation on my part.  

 	  Quote: 	
		  Then find this out. Anyone willing to launch into the blue 

without answers to such questions is an accident waiting 

to happen . . . either from ignorance of this specific 

question or others like it. 	


Unfortunately, Mr Eggenfellner has not answered such questions, probably because he does not know the answers.  He is a good mechanic but might lack electrical knowledge.

 	  Quote: 	
		  FIND OUT if the operating the two ECUs in tandem 

presents a risk. FIND OUT also how much current these 

systems demand in cruising flight. 	


This question has been asked on the Viking website with no response from Mr Eggenfellner.  If my assumption is correct that a high signal enables ECU1 and a low signal enables ECU2, then it would be impossible to operate both at once.  No one knows the consequences of the simultaneous application of both high and low signals to the SELECT wire or the consequences of an open floating input.

  My friend is making the final decisions on wiring his airplane.  He has accepted some of my recommendations and rejected some.

  From my point of view, it is hard to design a fool proof system without knowing the requirements or answers to above questions.  All I can do is ensure that power is always available to the lone ECU power wire, regardless of the failure of any one component.  And ensure that there is either a high or low signal on the SELECT wire, but never both at once.

  I think that we agree that the electrical system for the Viking engine has not been designed with a backup plan in the event of failure of key components.

  I am happy with my Rotax 912 engine.

Joe

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jun 22, 2012 5:16 pm Post subject: Viking Schematic

<snip>



 From my point of view, it is hard to design a fool proof system 

without knowing the requirements or answers to above questions.  All 

I can do is ensure that power is always available to the lone ECU 

power wire, regardless of the failure of any one component.  And 

ensure that there is either a high or low signal on the SELECT wire, 

but never both at once.



    I think you're right . . .



I think that we agree that the electrical system for the Viking 

engine has not been designed with a backup plan in the event of 

failure of key components.



    Hmmmm . . . I think this is a system I'd like to

    steer clear of . . .



    Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jun 24, 2012 7:03 am Post subject: Viking Schematic

 	  Quote: 	
		   From my point of view, it is hard to design a fool proof system 

 without knowing the requirements or answers to above 

 questions.  All I can do is ensure that power is always available 

 to the lone ECU power wire, regardless of the failure of any one 

 component.  And ensure that there is either a high or low signal on 

 the SELECT wire, but never both at once.


	


 	  Quote: 	
		  I think that we agree that the electrical system for the Viking 

engine has not been designed with a backup plan in the event of 

failure of key components.


	




   Joe,



   I don't know your friend . . . and I hope that my

   worst concerns for how his project is going together

   are unfounded. You're in the best position to add

   to his knowledge pool for making sure that his

   airplane goes together with a minimum of built-in

   risks.



   I recall having tried to converse with Eggenfellner

   some years back. Very uncooperative to the extent that

   I was concerned about his knowledge and attitudes for

   offering critical systems to aircraft.



   If your friend has not already read and studied the

   hindsight available on line surrounding the Dan

   Lloyd, RV-10, Eggenfellner accident, please encourage

   him to do so. The postings in part are available

   here:



http://tinyurl.com/7292l3z



http://tinyurl.com/6lqzab2



http://tinyurl.com/7ho2w57



   Maybe he's already 'plugged in' . . . without

   having engaged him in conversation and observed

   his work, we cannot know. I am particularly

   miffed with the Eggenfellner design in that

   supposedly dual, independent engine critical

   systems are not fitted with independent power

   and control paths. I don't recall the engine

   being considered when Z-19 was being crafted,

   it might have been the Eggenfellner product.



   It suggests steering diodes mounted close to

   the single-power input connection to one-of

   power plant accessories. If I had no other

   choices but to install a Viking engine I

   would take a similar approach.



   Normal and Alternate engine control switches.

   One taking power from the Main Battery Bus,

   one taking power from an Aux Battery Bus.



   If the numbers of switches is to be kept

   low, then use #1 switch to activate both

   power and command to the ECU for Normal

   Ops, the #2 switch to activate both power

   and command for Survivable Failure Ops.



   They have a moral, ethical, professional and

   even perhaps legal duty to make such data

   available to customers. Alternatively,

   they should offer their own iteration of Z-19

   to provide failure tolerant functionality.

   One or the other. If Dan Lloyd's engine

   quit due to the disconnect of one wire and

   could not be restarted by selection of

   Plan-B . . . then somewhere along the line,

   too many balls were fumbled . . . and not

   for subtle, esoteric reasons. My perceptions

   of risk for the Viking engine versus Eggenfellner

   are disturbingly similar.



   A discussion that really needs to be

   conducted for mounting a concentrated

   effort to acquire system integration data

   from Viking Engines as to current demands and

   consequences of having both ECU active at the

   same time. This is simple data, easy to acquire

   and absolutely necessary for competent

   system integration.



   Get me a name of a person that your friend

   is working with at Viking and I'll make the

   call.

   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Sun Jun 24, 2012 9:10 am Post subject: Re: Viking Schematic

Bob,

My friend sent me a CC email today that he also sent to others who are installing a Viking engine.  Here is a copy of that message:

  	  Quote: 	
		  Joe introduced me to the Matronics forum, sponsored by Bob Nuckolls.  There is an RV 12 section, and Joe submitted our concerns for public comments.  Suggest you read the exchange and join the list. 	


And so, my friend and others are aware of the inadequate electrical system illustrated on the Viking website.

 	  Quote: 	
		  Get me a name of a person that your friend 

is working with at Viking and I'll make the call. 	


I am not aware of anyone at Viking giving electrical advice beside Jan E.

I think that it would benefit Jan Eggenfellner to make available all information about the electrical system, especially the ECU.  Helping to prevent crashes of Viking powered aircraft will help his business.  Even if Jan E is electrically challenged, others can use information that he provides to come up with an electrical system that will keep the engine running despite the failure of any one component.

  Bob, I appreciate your concern.  There may be some builders blindly following the Viking electrical drawings.  But the builders that I am in contact with know the dangers and risks.  Unfortunately the risks can not be mitigated without more knowledge of the ECU requirements and capabilities.

Joe

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jun 24, 2012 6:05 pm Post subject: Viking Schematic

I am not aware of anyone at Viking giving electrical advice

beside Jan E. I think that it would benefit Jan Eggenfellner

to make available all information about the electrical system,

especially the ECU.



   My face is red . . . I didn't realize that Viking was

   direct descendant from the original Eggenfellner Subaru

   operations.



   Okay, I'll drop a note to Jan and see what, if any, information

   he can share toward the goal of crafting a more failure tolerant

   design



   Bob . . .

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