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Failure modes with Z14

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jpx(at)qenesis.com
Guest

Posted: Sat Feb 20, 2010 1:54 pm Post subject: Failure modes with Z14

I received lots of response to this, so rather than copy the text of  

four messages, I will continue with the pertinent pieces.  I  

appreciate the responses !



To start, I confused everyone, sorry.  It is Z14, not Z12 that I am  

considering (along with Z13/, so that messed up the discussion a  

lot, since my actual question was not directly addressed.



Also, I didn't mention which electronic ignitions I plan to use.  I  

intend to install E-Mag ignitions, not the Light Speed, but this  

choice does not really affect the design.



I currently fly a 40 year old Cessna.  longg(at)Pjm picked an excellent  

example, since each spring my wife and I fly it from Toronto to  

Bahamas to Sun n Fun and back, and other long trips as well.  No  

matter what design I select, it will be a far better system.  However,  

since I can do it better, I want to 



Joe described what I like about Z13/8 - pretty much any single  

electrical failure permits continuation of flight to intended  

destination.  Power from the second alternator can be applied to any  

chosen load in the airplane as needed, within the limits of the  

current produced.  I have spent quite a lot of times considering the  

effects of various failures.



The only single failure I can think of that would cause a significant  

problem is an over voltage event that the OV module didn't address in  

a timely fashion, and the electronics in both ignitions fried.  Bob,  

your experience indicates this is a very unlikely occurance.  Medical  

statistics are the same way.  I don't care how rare a disease is if I  

am the one that has it.  Then, in another post, you describe the  

in-flight fire in a Lancair IV-P due to the abused regulator/OV unit  

that I am planning on using 



An over voltage event is something I have no plan B for.  A battery  

operated radio is great, but there is no equivalent for the ignition.   

Unlike a regulator and alternator, that I can easily see are working  

throughout the flight, I have no way of knowing if the OV unit will  

function as intended in the rare case I need it to.  I do not have the  

resources to analyze and test the design to be convinced it is  

failure-proof.  Of course, like any component, it is not, so I need a  

plan B.



One way of addressing it, is two isolated systems running the  

ignitions.  So although I really like Z13/8, Z14 has possibilities.



Unlike Z13/8, Z14 has what seems to me to be a weakness.  There is no  

essential bus diode, so a single contactor failure leaves the battery  

bus unpowered, in spite of having two working alternators.  So if I  

have one electric fuel pump, and it happens to be on that battery bus,  

then my flight endurance is limited by battery capacity.



Perhaps what I am looking for, is a modification to Z14, that will  

provide an alternative path to a battery contactor that fails, without  

providing additional failure modes that take away the advantages of  

the isolated system.  Any ideas how to do this ?



Jeff Page

Dream Aircraft Tundra #10

klehman(at)albedo.net
Guest

Posted: Sat Feb 20, 2010 7:50 pm Post subject: Failure modes with Z14

Jeff



I have 320 hours on my Z-14 which is really two electrical systems. Each 

system powers an ignition and efi system directly from the battery and 

either system will run the engine. Both alternators have an OVP system 

that will disconnect the respective alternator.



So to damage one ignition or efi computer there must be two failures. 

The  regulator and then the OVP system. I don't worry about two failures 

but even then the second system will run the engine. As per Bob's 

directions for the OVP, it is easy to test the OVP module occasionally 

if I choose. The procedure is simply to bump the voltage a couple of 

volts with a couple of D cell flashlight batteries as I recall.



I guess my main point is that I do not route engine critical current 

through a contactor. Why put more things to fail in those current paths. 

I do run other systems, including starter current through a contactor.



The only time the crossfeed contactor closes is during engine cranking 

or if I decide to manually close it after an alternator fails. I also 

feed one cigarette lighter receptacle from a battery bus in case I ever 

need to power a handheld device from it. Also comes in handy when camping.



Ken



Jeff Page wrote:

 	  Quote: 	
		   

 

 I received lots of response to this, so rather than copy the text of 

 four messages, I will continue with the pertinent pieces.  I appreciate 

 the responses !

 

 To start, I confused everyone, sorry.  It is Z14, not Z12 that I am 

 considering (along with Z13/, so that messed up the discussion a lot, 

 since my actual question was not directly addressed.

 

 Also, I didn't mention which electronic ignitions I plan to use.  I 

 intend to install E-Mag ignitions, not the Light Speed, but this choice 

 does not really affect the design.

 

 I currently fly a 40 year old Cessna.  longg(at)Pjm picked an excellent 

 example, since each spring my wife and I fly it from Toronto to Bahamas 

 to Sun n Fun and back, and other long trips as well.  No matter what 

 design I select, it will be a far better system.  However, since I can 

 do it better, I want to 

 

 Joe described what I like about Z13/8 - pretty much any single 

 electrical failure permits continuation of flight to intended 

 destination.  Power from the second alternator can be applied to any 

 chosen load in the airplane as needed, within the limits of the current 

 produced.  I have spent quite a lot of times considering the effects of 

 various failures.

 

 The only single failure I can think of that would cause a significant 

 problem is an over voltage event that the OV module didn't address in a 

 timely fashion, and the electronics in both ignitions fried.  Bob, your 

 experience indicates this is a very unlikely occurance.  Medical 

 statistics are the same way.  I don't care how rare a disease is if I am 

 the one that has it.  Then, in another post, you describe the in-flight 

 fire in a Lancair IV-P due to the abused regulator/OV unit that I am 

 planning on using 

 

 An over voltage event is something I have no plan B for.  A battery 

 operated radio is great, but there is no equivalent for the ignition.  

 Unlike a regulator and alternator, that I can easily see are working 

 throughout the flight, I have no way of knowing if the OV unit will 

 function as intended in the rare case I need it to.  I do not have the 

 resources to analyze and test the design to be convinced it is 

 failure-proof.  Of course, like any component, it is not, so I need a 

 plan B.

 

 One way of addressing it, is two isolated systems running the 

 ignitions.  So although I really like Z13/8, Z14 has possibilities.

 

 Unlike Z13/8, Z14 has what seems to me to be a weakness.  There is no 

 essential bus diode, so a single contactor failure leaves the battery 

 bus unpowered, in spite of having two working alternators.  So if I have 

 one electric fuel pump, and it happens to be on that battery bus, then 

 my flight endurance is limited by battery capacity.

 

 Perhaps what I am looking for, is a modification to Z14, that will 

 provide an alternative path to a battery contactor that fails, without 

 providing additional failure modes that take away the advantages of the 

 isolated system.  Any ideas how to do this ?

 

 Jeff Page

 Dream Aircraft Tundra #10

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Feb 20, 2010 9:47 pm Post subject: Failure modes with Z14

At 03:52 PM 2/20/2010, you wrote:

 	  Quote: 	
		  




	


   <snip>



 	  Quote: 	
		  The only single failure I can think of that would cause a significant

problem is an over voltage event that the OV module didn't address in

a timely fashion, and the electronics in both ignitions fried.


	


    But that's a DUAL failure. An OV protection scheme fails

    followed by a regulator running amok . . .



 	  Quote: 	
		  Bob, your experience indicates this is a very unlikely occurance.  Medical

statistics are the same way.  I don't care how rare a disease is if I

am the one that has it.


	


    How many dual failures do you intend to hypothesize and

    address as part of your FMEA?



 	  Quote: 	
		  Then, in another post, you describe the  in-flight fire in a Lancair

IV-P due to the abused regulator/OV unit that I am planning on using 


	


    That wasn't an electronics failure but an INSTALLATION failure.

    Similarly, you can't have a plan-b for loose prop bolts, thrown

    jugs, ailerons lost to high speed flutter, etc. These things

    are even more rare but offer exceedingly dire challenges to

    your survival skills.



 	  Quote: 	
		  An over voltage event is something I have no plan B for.


	


    A optimally managed OV event becomes an LV even in tens

    of milliseconds after onset of the failure. This is why

    we generally don't bother to install OV annunciators

    on the panel . . . but bulbs don't stay lit long enough

    for you to make much use of what they have to tell you.



    After the alternator is shut down, plan-b is the same

    as if you'd thrown a belt, broken a wire, etc.

 	  Quote: 	
		  A battery operated radio is great, but there is no equivalent for 

the ignition.

Unlike a regulator and alternator, that I can easily see are working

throughout the flight, I have no way of knowing if the OV unit will

function as intended in the rare case I need it to.  I do not have the

resources to analyze and test the design to be convinced it is

failure-proof.  Of course, like any component, it is not, so I need a

plan B.


	


     This is why instructions for installing our OV modules

     call for testing every annual along with instructions on

     how to do it. However, these devices have been installed

     on TC aircraft for over 40 years. I don't recall seeing

     any maintenance manual call for annual testing.



 	  Quote: 	
		  One way of addressing it, is two isolated systems running the

ignitions.  So although I really like Z13/8, Z14 has possibilities.

Unlike Z13/8, Z14 has what seems to me to be a weakness.  There is no

essential bus diode, so a single contactor failure leaves the battery

bus unpowered, in spite of having two working alternators.  So if I

have one electric fuel pump, and it happens to be on that battery bus,

then my flight endurance is limited by battery capacity.


	


    If a fuel pump is critical to sustained flight, then why

    don't you have two pumps? Z14 has no ENDURANCE bus because

    one bus becomes the endurance bus should the other one be

    taken down due to alternator failure. If the small alternator

    quits, then most likely both busses can be kept up using

    the larger alternator. If the big guy quits, then  shut

    the main bus down, reduce loads to get airport in sight using

    small alternator . . . then close the cross-feed contactor

    and use both batteries plus small alternator to terminate

    the flight.



 	  Quote: 	
		  Perhaps what I am looking for, is a modification to Z14, that will

provide an alternative path to a battery contactor that fails, without

providing additional failure modes that take away the advantages of

the isolated system.  Any ideas how to do this ?


	


    Your stacking failure on top of failure to the degree that

    you'll have plans B, C, D, etc. Worse yet, you risk becoming

    and electrical systems failure analyst when you should be

    concentrating on piloting instead of deducing the appropriate

    "plan".



    Make one of the Emags a self-powered version and wire

    as shown in Figure Z-13/8 . . . you've got redundancy

    to burn. If your engine is electrically dependent on

    fuel delivery, then you need two pumps. Run one from

    the main bus, the other from the battery bus.



    Run a 9011 multi-channel OV.LV monitor to annunciate

    contactor failure.



    Bob . . .

jpx(at)qenesis.com
Guest

Posted: Sun Feb 21, 2010 10:39 pm Post subject: Failure Modes with Z14

 	  Quote: 	
		   I guess my main point is that I do not route engine critical current

 through a contactor. Why put more things to fail in those current paths.

 I do run other systems, including starter current through a contactor.


	


Yes, I intend to power the ignitions and fuel pump directly from the  

battery bus (through fuses of course).



 	  Quote: 	
		   The only time the crossfeed contactor closes is during engine cranking

 or if I decide to manually close it after an alternator fails. I also

 feed one cigarette lighter receptacle from a battery bus in case I ever

 need to power a handheld device from it. Also comes in handy when camping.


	


I re-wired the cigarette lighter in my Cessna so I could charge my  

phone at Sun n fun and Oshkosh 



 	  Quote: 	
		   Ken


	


 	  Quote: 	
		  > The only single failure I can think of that would cause a significant

> problem is an over voltage event that the OV module didn't address in

> a timely fashion, and the electronics in both ignitions fried.



     But that's a DUAL failure. An OV protection scheme fails

     followed by a regulator running amok . . .

     How many dual failures do you intend to hypothesize and

     address as part of your FMEA?


	


Failure of any single part should cause little concern, and probably  

little notice by an oblivious passenger.  Probably most dual failures  

would mean full utilization of plan B, rather than a forced landing.   

The dual failure that merits my attention is both ignitions failing.   

With isolated electrical systems, that would be exceptionally  

unlikely.  With Z13/8 and a B&C LR3C-14 (or equivalent), that could  

potentially happen.  I don't plan on mounting it upside down so it can  

fill with water, but it is not impossible that I unknowingly make a  

similar mistake.



In the event of an OV situation, I have to count on the controller and  

the circuit breaker both doing what they are supposed to do.  Most of  

us have much confidence due to familiarity in the electrical items  

like alternators installed on our planes, because we have used them in  

cars etc. for years and have monitored their operation.  And we know  

they fail sometimes.  Who hasn't replaced an alternator ?  At best we  

can occasionally test the OV circuitry.  How many of us have extensive  

experience with the OV protection accomplishing its mission when it  

was needed ?  How do I compare the sensitivity of the OV module  

compared to the ignition module ?



If I install isolated systems to run the ignitions, I do not need to  

determine the potential for failure of the regulator, OV circuitry and  

circuit breaker.



I know it seems like I am overly concerned about a very unlikely  

possibility.  As ugly and maintenance prone as magentos are, they are  

unbelievably unlikely to both fail on the same flight.  I don't want  

to replace them with another system, for which I can identify a  

possible failure mode that takes them both out, while addressing it  

only with "well, that is very unlikely".  I need to either modify the  

design to eliminate the possibility, or be convinced that very  

unlikely is much more unlikely than, say, my prop coming off.  I have  

no practical way of quantifying "very unlikely", so I am trying to  

eliminate the possibility.  An isolated system is not excessively  

complex or expensive, I just need to determine the best way to do it.



 	  Quote: 	
		  > Then, in another post, you describe the  in-flight fire in a Lancair

> IV-P due to the abused regulator/OV unit that I am planning on using 

     That wasn't an electronics failure but an INSTALLATION failure.


	


Hopefully, due to the time spent learning from your book and this list  

(much appreciated !), together with my schooling and attention to  

detail, I won't make a similar error.



 	  Quote: 	
		       Similarly, you can't have a plan-b for loose prop bolts, thrown

     jugs, ailerons lost to high speed flutter, etc. These things

     are even more rare but offer exceedingly dire challenges to

     your survival skills.


	


The best I can do to mitigate some of these risks is to purchase  

quality parts and assemble them with mentors and mechanics checking my  

work, plus dual instruction in handling emergencies.



 	  Quote: 	
		  > An over voltage event is something I have no plan B for.

     A optimally managed OV event becomes an LV even in tens

     of milliseconds after onset of the failure. This is why

     we generally don't bother to install OV annunciators

     on the panel . . . but bulbs don't stay lit long enough

     for you to make much use of what they have to tell you.

     After the alternator is shut down, plan-b is the same

     as if you'd thrown a belt, broken a wire, etc.


	


As long as my ignitions are still working, plan B works well,  

otherwise I am landing in a very undesirable place 



 	  Quote: 	
		  > One way of addressing it, is two isolated systems running the

> ignitions.  So although I really like Z13/8, Z14 has possibilities.

> Unlike Z13/8, Z14 has what seems to me to be a weakness.  There is no

> essential bus diode, so a single contactor failure leaves the battery

> bus unpowered, in spite of having two working alternators.  So if I

> have one electric fuel pump, and it happens to be on that battery bus,

> then my flight endurance is limited by battery capacity.



     If a fuel pump is critical to sustained flight, then why

     don't you have two pumps? Z14 has no ENDURANCE bus because

     one bus becomes the endurance bus should the other one be

     taken down due to alternator failure. If the small alternator

     quits, then most likely both busses can be kept up using

     the larger alternator. If the big guy quits, then  shut

     the main bus down, reduce loads to get airport in sight using

     small alternator . . . then close the cross-feed contactor

     and use both batteries plus small alternator to terminate

     the flight.


	


The electric fuel pump is only necessary to back up the mechanical  

pump.  It just seems odd that with the design of Z14, that with the  

single failure of a contactor, but two working alternators, there is  

no path to charge both batteries.  With Z13/8 there are dual charging  

paths, which is a very nice design.



 	  Quote: 	
		       Make one of the Emags a self-powered version and wire

     as shown in Figure Z-13/8 . . . you've got redundancy

     to burn.


	


Actually, I do intend to run one or two P-Mags.  I just need to ensure  

I will not fry both of them with an OV event.



 	  Quote: 	
		       Run a 9011 multi-channel OV.LV monitor to annunciate

     contactor failure.


	


I have designed, but not yet prototyped a LV monitor that will  

annunicate LV on either battery, and be activated by either battery  

contactor switch or the "clearance delivery" switch (the don't drain  

the battery by leaving the switch on idiot feature).



Some of the features of Z14 I probably don't need.  There has been  

some discussion that two smaller batteries cannot delivery the same  

starter current that a single large battery can.  Perhaps the solution  

is a modification to Z13/8, whereby the standby alternator is always  

in use to power the second ignition.  Isolate that with a cross feed  

relay and add a second small battery.  The cross feed relay would be  

only used to route power to the endurance bus after main alternator  

failure, but not to kick in the second battery during starting.



Jeff Page

Dream Aircraft Tundra #10

user9253

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

Posted: Mon Feb 22, 2010 8:04 am Post subject: Re: Failure modes with Z14

The battery is NOT the power source for electrical equipment on an aircraft.  The alternator is.  Z-13/8 has two alternators.  If the main one fails, the aux alternator will power the ignition.  If both alternators fail, the battery is a backup.  Once the engine is running, failure of the battery contactor will most likely not affect the operation of the alternators.  An ignition connected to the E-bus will keep working after the battery contactor fails, drawing its power from the alternator as usual.  Each ignition should be connected to separate points of the electrical system so that a bad connection will only affect one ignition.  In Z-13/8 after a battery contactor failure, the battery can be kept charged by the main alternator through the E-Bus relay or by the aux alternator.  Even if both alternators and the battery contactor fail, the battery still has enough stored energy to power one ignition for a couple of hours.  The length of time can be determined by doing a load test on the battery.  This is something that should be done periodically anyway.  If there are still concerns of contactor failure, a diode can be placed across the big terminals of the contactor with the arrow pointing towards the battery.  However, this is not needed or recommended.

  Many years ago I had a VW with a 6 volt battery.  The generator quit working (but I did not know it).  The engine barely cranked when I started it to go home after work at night.  After a couple of miles, the headlights got dimmer and dimmer, then the engine quit.  Before the car coasted to a stop, I shut off the headlights and the engine started to run again.  There was not much traffic that late at night.  Every time a car approached, I pulled off onto the shoulder and waited for it to go by.  It was hard to see without headlights.  I discovered that the engine would keep running with the turn signal on.  So I used that to see the road, driving very slowly.  It took me a couple of hours to get home, but I made it.  The point is that it doesn't take a fully charged battery to power the ignition.

  As for over voltage protection, two OV modules can be used.  Then the regulator would have to fail along with both OV modules before the electronics would be fried.  I do not think these extreme measures are necessary or desired.  If the voltage regulator fails, an alternator properly sized to just barely meet the expected load will not develop as high of a voltage as a larger alternator will.

  Many things can go wrong on an aircraft.  Perhaps a BRS is the answer.  But even those malfunction.

Joe

_________________
Joe Gores

klehman(at)albedo.net
Guest

Posted: Mon Feb 22, 2010 8:13 am Post subject: Failure Modes with Z14

Jeff



The 2 little Dekka 8 AH batteries on my Z-14 system are indeed 

equivalent to one 16AH battery except for being more expensive. They 

have large bolted lead terminals and one will start the subaru. Two are 

better when it is very cold. The batteries do what the manufacturer 

says. Small batteries with small terminals that are not designed to 

start engines will be a different story.



My system does indeed allow charging both batteries with any single 

contactor failure. Not a big deal but a consideration with small 

batteries. Both alternators feed through their OV contactors to the 

respective battery. No second contactor between them and the batteries. 

With appropriate component placement I believe that I have no additional 

always hot wiring risk with this setup. Because I feed non engine loads 

(and cranking current) through a contactor, a failure of that contactor 

will kill most other systems but it won't affect the engine. I have 

ample battery bus (the cigarette lighter and limited panel lighting), 

and handheld backup options for that. I do not have any IFR avionics at 

this time.



Your failure concerns do resonate with me. My design was heavily 

influenced by the knowledge that it was a one off system by a first time 

builder using components placed in a new environment that nullified 

previous failure data. That is why Bob's philosophy and Z-14 suited me 

so well with an electric dependent engine. Even though electric 

components can fail without warning, the engine electrical and EFI 

systems are the least of my engine reliability concerns now.



If it helps - yes I did spend some time testing the OV modules and yes 

they perform exactly as advertised and the current version simply does 

not trip unless there is a real OV event.



Don't overlook ergonomics. Keep your system as operationally simple as 

possible. Give some thought to what you actions you will take for 

failures and locate controls to make those actions simple and 

methodical. Ideally one procedure for all engine problems is ideal.



Ken



snip>

 	  Quote: 	
		   Some of the features of Z14 I probably don't need.  There has been some 

 discussion that two smaller batteries cannot delivery the same starter 

 current that a single large battery can.  Perhaps the solution is a 

 modification to Z13/8, whereby the standby alternator is always in use 

 to power the second ignition.  Isolate that with a cross feed relay and 

 add a second small battery.  The cross feed relay would be only used to 

 route power to the endurance bus after main alternator failure, but not 

 to kick in the second battery during starting.

 

 Jeff Page

 Dream Aircraft Tundra #10

klehman(at)albedo.net
Guest

Posted: Mon Feb 22, 2010 9:58 am Post subject: Failure modes with Z14

While I have also seen an electrical system function just fine with the

battery disconnected, such performance is not a certainty in all situations.



You raise a point that is dear to me though. Perhaps because I've seen 

the results of batteries fed by a runaway regulator, I am also a 

proponent of using a small alternator. ie. one that is adequate for 

normal ops rather than one that can put out twice the power that will 

ever be needed. Especially as we migrate to lower power electronics, 

lights, and smaller batteries. Years ago I also had an occasion to 

manually cycle a runaway generator with a melting battery while IFR and 

it would have been much less tense had it been a smaller unit.



I have confidence in the OV protection but my OV contactor still has to 

open for it to work and the less current going through it the better I 

think. Actually I had a different contactor fail to open this weekend 

but it worked on about 20 subsequent tries so I don't know yet whether 

it is the switch or the contactor. My OV contactors normally switch 

while unloaded so they will likely last forever.



Ken



user9253 wrote:

 	  Quote: 	
		   

 <fran4sew(at)banyanol.com>

 

 The battery is NOT the power source for electrical equipment on an

 aircraft.  The alternator is.  Z-13/8 has two alternators.  If the

 main one fails, the aux alternator will power the ignition.  If both

 alternators fail, the battery is a backup.  Once the engine is

 running, failure of the battery contactor will most likely not affect

 the operation of the alternators.  An ignition connected to the E-bus

 will keep working after the battery contactor fails, drawing its

 power from the alternator as usual.  Each ignition should be

 connected to separate points of the electrical system so that a bad

 connection will only affect one ignition.  In Z-13/8 after a battery

 contactor failure, the battery can be kept charged by the main

 alternator through the E-Bus relay or by the aux alternator.  Even if

 both alternators and the battery contactor fail, the battery still

 has enough stored energy to power one ignition for a couple of hours.

 The length of time can be determined by doing a l! oad test on the

 battery.  This is something that should be done periodically anyway.

 If there are still concerns of contactor failure, a diode can be

 placed across the big terminals of the contactor with the arrow

 pointing towards the battery.  However, this is not needed or

 recommended. Many years ago I had a VW with a 6 volt battery.  The

 generator quit working (but I did not know it).  The engine barely

 cranked when I started it to go home after work at night.  After a

 couple of miles, the headlights got dimmer and dimmer, then the

 engine quit.  Before the car coasted to a stop, I shut off the

 headlights and the engine started to run again.  There was not much

 traffic that late at night.  Every time a car approached, I pulled

 off onto the shoulder and waited for it to go by.  It was hard to see

 without headlights.  I discovered that the engine would keep running

 with the turn signal on.  So I used that to see the road, driving

 very slowly.  It took me a couple of hours to get home, but I made

 it.  The point is that it doesn't take a fully charged battery to

 power the ignition. As for over voltage protection, two OV modules

 can be used.  Then the regulator would have to fail along with both

 OV modules before the electronics would be fried.  I do not think

 these extreme measures are necessary or desired.  If the voltage

 regulator fails, an alternator properly sized to just barely meet the

 expected load will not develop as high of a voltage as a larger

 alternator will. Many things can go wrong on an aircraft.  Perhaps a

 BRS is the answer.  But even those malfunction. Joe

 

 -------- Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Feb 23, 2010 8:19 am Post subject: Failure Modes with Z14

At 09:38 AM 2/22/2010, you wrote:

 	  Quote: 	
		  



Jeff



The 2 little Dekka 8 AH batteries on my Z-14 system are indeed 

equivalent to one 16AH battery except for being more expensive. They 

have large bolted lead terminals and one will start the subaru. Two 

are better when it is very cold. The batteries do what the 

manufacturer says. Small batteries with small terminals that are not 

designed to start engines will be a different story.


	


   Yes, the Dekka products are unique for their size.



 	  Quote: 	
		  My system does indeed allow charging both batteries with any single 

contactor failure. Not a big deal but a consideration with small 

batteries. Both alternators feed through their OV contactors to the 

respective battery. No second contactor between them and the batteries.


	


   Your words generate an interesting idea . . .



   Assume the builder chooses commercial off the shelf

   IR alternators and a variant on Z-24 for control and

   ov protection. In this instance, one COULD set the

   altenrator b-lead contactor next to a battery contactor

   and tie it's output directly to the battery.



   This configuration satisfies the legacy design goal

   of minimizing hot fat-wires when all switches are

   OFF. Now you can have your battery contactors feed

   a single main bus. No e-bus is needed since you're

   not likely to every need battery-only ops. Now you

   have two, independently alternator-supported batteries.

   Two battery busses to distribute loads for an electrically

   dependent engine. A main bus that's not subject to

   single-point-of-failure. Cool.



   I'll pray over this a bit. Perhaps a Figure Z-8 is

   being conceived . . .



   Bob . . .

klehman(at)albedo.net
Guest

Posted: Tue Feb 23, 2010 10:36 am Post subject: Failure Modes with Z14

Yes I was thinking that a small Bosch "40" amp relay and fuse would be 

quite adequate for turning my main bus into an E bus since my main bus 

loads are under 20 amps. Halogen landing lights and nav lights are the 

only things on it that draw significant power. With my key starter 

switch, it is not possible to crank the engine unless the main bus 

contactor is closed. Similar to a car, first key position closes the 

main bus contactor and then the spring loaded position cranks the 

engine. It has worked well for me.

Alternatively, with a 20 amp or larger second alternator, most folks 

could eliminate the crossfeed contactor and then dual main bus 

contactors would in fact be the crossfeed.

Ken

Robert L. Nuckolls, III wrote:

 	  Quote: 	

 <nuckolls.bob(at)aeroelectric.com>

 At 09:38 AM 2/22/2010, you wrote:

> 

>

> Jeff

>

> The 2 little Dekka 8 AH batteries on my Z-14 system are indeed 

> equivalent to one 16AH battery except for being more expensive. They 

> have large bolted lead terminals and one will start the subaru. Two 

> are better when it is very cold. The batteries do what the 

> manufacturer says. Small batteries with small terminals that are not 

> designed to start engines will be a different story.

   Yes, the Dekka products are unique for their size.

> My system does indeed allow charging both batteries with any single 

> contactor failure. Not a big deal but a consideration with small 

> batteries. Both alternators feed through their OV contactors to the 

> respective battery. No second contactor between them and the batteries.

   Your words generate an interesting idea . . .

   Assume the builder chooses commercial off the shelf

   IR alternators and a variant on Z-24 for control and

   ov protection. In this instance, one COULD set the

   altenrator b-lead contactor next to a battery contactor

   and tie it's output directly to the battery.

   This configuration satisfies the legacy design goal

   of minimizing hot fat-wires when all switches are

   OFF. Now you can have your battery contactors feed

   a single main bus. No e-bus is needed since you're

   not likely to every need battery-only ops. Now you

   have two, independently alternator-supported batteries.

   Two battery busses to distribute loads for an electrically

   dependent engine. A main bus that's not subject to

   single-point-of-failure. Cool.

   I'll pray over this a bit. Perhaps a Figure Z-8 is

   being conceived . . .

   Bob . . .

jpx(at)qenesis.com
Guest

Posted: Tue Feb 23, 2010 7:56 pm Post subject: Failure modes with Z14

Joe,



I am quite comfortable with the situation that would occur if any of  

the individual parts of Z13/8 should fail.  I don't expect a contactor  

failure is any more significant than other failures.  What I like  

about Z13/8 is that there are alternate feed paths so that the  

alternator(s) can continue to keep the batteries charged, and power  

can be supplied to the endurance bus.



I once drove a car all winter without a functioning alternator.  It  

was mounted on the bottom of the engine and I didn't want to lie in  

the snow to fix it.  I knew how many starts and how long I could drive  

with and without the headlights.  I only got caught needing a boost  

once all winter 



So the only thing that I would like to do is ensure that an  

overvoltage condition cannot damage both ignitions.  Perhaps two OV  

modules would do it, but I would feel more comfortable with an  

isolated system.



Ken,



 	  Quote: 	
		   The 2 little Dekka 8 AH batteries on my Z-14 system are indeed

 equivalent to one 16AH battery except for being more expensive.


	


This is good to know.



 	  Quote: 	
		   My system does indeed allow charging both batteries with any

 single contactor failure.


	


How did you change the circuit to accomplish this ?



 	  Quote: 	
		   If it helps - yes I did spend some time testing the OV modules and yes

 they perform exactly as advertised and the current version simply does

 not trip unless there is a real OV event.


	


Also useful to know.  How did you test them ?  I expect that applying  

16V to the sense lead would result in the field breaker tripping.  My  

concern would be duplicating the shorted regulator scenario, that is,  

applying 12V directly to the field terminal.  This should result in  

the alternator producing possibly 80-120V ?  Does the breaker trip in  

time to protect some cheap auto headlamps ?  I don't think I want to  

do this test with my expensive ignitions.



 	  Quote: 	
		   Don't overlook ergonomics. Keep your system as operationally simple as

 possible. Give some thought to what you actions you will take for

 failures and locate controls to make those actions simple and

 methodical. Ideally one procedure for all engine problems is ideal.


	


This I have thought a lot about.  In the end, I came up with a color  

coded system.  If this LV light illuminates, flip the switches joined  

with the same color line.  Easy to do in flight without a checklist  

(although I would use one anyway).  No troubleshooting in flight.



I would like opinions on the feasibility of modifying Z13/8 by  

isolating the aux alternator path with a cross feed relay that would  

be open in flight except after alternator failure.  I would add a  

small battery to ensure the SD-8 produces power.



Jeff Page

Dream Aircraft Tundra #10

raymondj(at)frontiernet.n
Guest

Posted: Tue Feb 23, 2010 9:28 pm Post subject: Failure modes with Z14

Jeff,

I would be interested in seeing your "Light/line" switch layout on your 

panel. Sounds like a good idea.  Are there any pictures posted anywhere 

I can look at?

Raymond Julian

Kettle River, MN.

Jeff Page wrote:

 	  Quote: 	

 Joe,

 I am quite comfortable with the situation that would occur if any of the 

 individual parts of Z13/8 should fail.  I don't expect a contactor 

 failure is any more significant than other failures.  What I like about 

 Z13/8 is that there are alternate feed paths so that the alternator(s) 

 can continue to keep the batteries charged, and power can be supplied to 

 the endurance bus.

 I once drove a car all winter without a functioning alternator.  It was 

 mounted on the bottom of the engine and I didn't want to lie in the snow 

 to fix it.  I knew how many starts and how long I could drive with and 

 without the headlights.  I only got caught needing a boost once all 

 winter 

 So the only thing that I would like to do is ensure that an overvoltage 

 condition cannot damage both ignitions.  Perhaps two OV modules would do 

 it, but I would feel more comfortable with an isolated system.

 Ken,

> The 2 little Dekka 8 AH batteries on my Z-14 system are indeed

> equivalent to one 16AH battery except for being more expensive.

 This is good to know.

> My system does indeed allow charging both batteries with any

> single contactor failure.

 How did you change the circuit to accomplish this ?

> If it helps - yes I did spend some time testing the OV modules and yes

> they perform exactly as advertised and the current version simply does

> not trip unless there is a real OV event.

 Also useful to know.  How did you test them ?  I expect that applying 

 16V to the sense lead would result in the field breaker tripping.  My 

 concern would be duplicating the shorted regulator scenario, that is, 

 applying 12V directly to the field terminal.  This should result in the 

 alternator producing possibly 80-120V ?  Does the breaker trip in time 

 to protect some cheap auto headlamps ?  I don't think I want to do this 

 test with my expensive ignitions.

> Don't overlook ergonomics. Keep your system as operationally simple as

> possible. Give some thought to what you actions you will take for

> failures and locate controls to make those actions simple and

> methodical. Ideally one procedure for all engine problems is ideal.

 This I have thought a lot about.  In the end, I came up with a color 

 coded system.  If this LV light illuminates, flip the switches joined 

 with the same color line.  Easy to do in flight without a checklist 

 (although I would use one anyway).  No troubleshooting in flight.

 I would like opinions on the feasibility of modifying Z13/8 by isolating 

 the aux alternator path with a cross feed relay that would be open in 

 flight except after alternator failure.  I would add a small battery to 

 ensure the SD-8 produces power.

 Jeff Page

 Dream Aircraft Tundra #10

user9253

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

Posted: Wed Feb 24, 2010 8:06 am Post subject: Re: Failure modes with Z14

Jeff,

 	  Quote: 	
		  Perhaps two OV modules would do it, but I would feel more comfortable with an isolated system. 	


The advantage of building your own plane is that you can design it to meet your goals.

 	  Quote: 	
		  How did you test them? I expect that applying 16V to the sense lead would result in the field breaker tripping. My concern would be duplicating the shorted regulator scenario, that is, applying 12V directly to the field terminal.

	


Testing is accomplished by applying a high voltage directly to the OV module and not to the rest of the electrical system.  Do this by disconnecting the wire to the OV module and inserting 2 D-Cells in series with the wire.  The test can be conducted with the engine not running.  See this circuit: http://tinyurl.com/ydpjzkl

This document also describes testing the over voltage protection, but it does not test the circuit breaker: http://www.aeroelectric.com/DIY/DIY_Crowbar_OVP_F.pdf

 	  Quote: 	
		  I would add a small battery to ensure the SD-8 produces power. 	


The SD-8 is a permanent magnet alternator.  It does not require any battery power to excite the field windings because there are none.



Bob N offers very good philosophy on the subject of backup systems:

http://tinyurl.com/ybbdffj

Joe

_________________
Joe Gores

jpx(at)qenesis.com
Guest

Posted: Wed Feb 24, 2010 11:47 am Post subject: Failure Modes with Z14

Ray,



My circuit diagram and the switch panel layout are available here:

http://www.qenesis.com/tundra/Electrical



Jeff Page

Dream Aircraft Tundra #10



Re: Failure Modes with Z14



 	  Quote: 	
		   I would be interested in seeing your "Light/line" switch layout on your

 panel. Sounds like a good idea.  Are there any pictures posted anywhere

 I can look at?



 Raymond Julian

raymondj(at)frontiernet.n
Guest

Posted: Wed Feb 24, 2010 1:04 pm Post subject: Failure Modes with Z14

Jeff,



	Thanks for the link.  Your layout looks like a good way to aid in 

decision making during high stress events.  I will definitely include 

that feature in my panel planning.

Raymond Julian

Kettle River, MN.



Jeff Page wrote:

 	  Quote: 	
		   

 

 Ray,

 

 My circuit diagram and the switch panel layout are available here:

 http://www.qenesis.com/tundra/Electrical

 

 Jeff Page

 Dream Aircraft Tundra #10

 

 Re: Failure Modes with Z14

 

> I would be interested in seeing your "Light/line" switch layout on your

> panel. Sounds like a good idea.  Are there any pictures posted anywhere

> I can look at?

>

> Raymond Julian

user9253

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

Posted: Wed Feb 24, 2010 1:14 pm Post subject: Re: Failure modes with Z14

Jeff,

I looked over your schematic at http://www.qenesis.com/tundra/Electrical/Tundra_Power_Wiring.pdf and it looks very good.  It would be interesting to see the internal schematic for the low voltage module and the purpose of the wires connected to it from switches.  I am not saying that anything is wrong, only that I do not know what is inside of that box and how it works.

Good job.

Joe

_________________
Joe Gores

jpx(at)qenesis.com
Guest

Posted: Wed Mar 10, 2010 7:04 am Post subject: Failure modes with Z14

Joe,



Thanks for taking the time to look at my diagram.  It is comforting to  

know that someone else doesn't see any obvious goofs.



I have finished the diagram of the low voltage monitor.  Its link is  

now available at the same page:

http://www.qenesis.com/tundra/Electrical



Note that I have drawn the diagram, but not yet breadboarded it, so it  

may not function as intended.



I would be particularly interested in any changes that would make the  

design better handle the DO-160 nasties.



Jeff Page

Dream Aircraft Tundra #10



 	  Quote: 	
		   I looked over your schematic at   

 http://www.qenesis.com/tundra/Electrical/Tundra_Power_Wiring.pdf and  

  it looks very good.  It would be interesting to see the internal   

 schematic for the low voltage module and the purpose of the wires   

 connected to it from switches.  I am not saying that anything is   

 wrong, only that I do not know what is inside of that box and how it  

  works.

 Good job.

 Joe

user9253

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

Posted: Wed Mar 10, 2010 2:57 pm Post subject: Re: Failure modes with Z14

Jeff,

If wire 2223 or its connections fail, power will be lost to the essential bus.  Wire 2222 should be connected directly to the E-Bus.

   Now I see what those 4 wires are for that connect between the low voltage module and grounded switches.  Any one of the switches can enable the low voltage module.  The diodes isolate the 4 switches from each other.  Did you design the low voltage warning module yourself?  Are you an electrical engineer?  Let us know how it works.

Joe

_________________
Joe Gores

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