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Z-19RB clarification

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mrspudandcompany(at)veriz
Guest

Posted: Wed Jul 04, 2012 3:10 pm Post subject: Z-19RB clarification

I plan to use a slightly modified version of Z-19RB in my aircraft. It

appears to me that during an alternator failure you would want to deenergize

both the Main battery contactor and the Engine battery contactor, to

conserve battery power.  In doing this there is no power available from the

engine battery to the endurance bus.  The endurance bus alternate feed is

the only power feed path to this bus, with the contactors deenergized.



My question is, am I missing something, was this overlooked in the design

phase, or is there a specific reason for this design philosophy?



Thanks,



Roger

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Allen Fulmer

Joined: 10 Jan 2006
Posts: 79
Location: Alexander City, AL

Posted: Wed Jul 04, 2012 6:51 pm Post subject: Z-19RB clarification

Roger,

I am using Z-19RB in my Subaru H6 powered RV7.  My understanding as to why

the endurance bus alternate feed is from the Main Battery only is that the

engine bus and its battery are reserved for the running of the engine alone

just as long as possible.  I guess if you lose the main battery and thus the

endurance bus then you can still fly the airplane to a safe landing site as

long as the engine is running.  Whereas, if you lose the engine battery/bus

the endurance bus is not going to do you any good as you glide to a landing.



I am sure Bob will chime in with a more elegant explanation.

Allen Fulmer

RV7 Finishing wiring

Subaru hanging and run

N808AF reserved



--

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_________________
RV7 QB Fuselage
Eggenfellner H6 on orde
N808AF reserved
Alexander City, AL

mrspudandcompany(at)veriz
Guest

Posted: Thu Jul 05, 2012 5:17 am Post subject: Z-19RB clarification

Allen,



Thanks for your input, also thanks again for the use of your panel punch 

(best way to make nice clean instrument holes).



In my thinking, I was approaching this from a slightly different angle.  In 

IFR conditions if the main battery goes dead, because you had  a hard engine 

start and not sufficient time to recharge the main you have no avionics to 

get you to VFR conditions.  In this case a running engine does you no good. 

But, to put a little more logic into the situation, you should be seeking an 

out from IFR asap to improve your chances if something else does go wrong.



My slight mod, mentioned previously, to Z-19RB:

Since I have dual ignition and dual fuel pumps, I am eliminating the diodes 

and the 2-3 switches, to be replaced with 4ea. SPST, thus simplifying and 

also giving me full control of any combination of fuel pumps and ignition.



[quote] 

 <afulmer(at)charter.net>



 Roger,

 I am using Z-19RB in my Subaru H6 powered RV7.  My understanding as to why

 the endurance bus alternate feed is from the Main Battery only is that the

 engine bus and its battery are reserved for the running of the engine 

 alone

 just as long as possible.  I guess if you lose the main battery and thus 

 the

 endurance bus then you can still fly the airplane to a safe landing site 

 as

 long as the engine is running.  Whereas, if you lose the engine 

 battery/bus

 the endurance bus is not going to do you any good as you glide to a 

 landing.



 I am sure Bob will chime in with a more elegant explanation.

 Allen Fulmer

 RV7 Finishing wiring

 Subaru hanging and run

 N808AF reserved



 --

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Allen Fulmer

Joined: 10 Jan 2006
Posts: 79
Location: Alexander City, AL

Posted: Thu Jul 05, 2012 8:27 am Post subject: Z-19RB clarification

It will be interesting to see how long the Subaru will run on one battery if

the alternator goes out.



--

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_________________
RV7 QB Fuselage
Eggenfellner H6 on orde
N808AF reserved
Alexander City, AL

mrspudandcompany(at)veriz
Guest

Posted: Thu Jul 05, 2012 9:03 am Post subject: Z-19RB clarification

It will be interesting to see how long the Subaru will run on one battery if

the alternator goes out.

	Allen,



You should do some tests to see what the electrical load is on each battery

with alternator off and endurance bus on.  Then check the capacity of your

batteries at these loads.  I plan to do a battery test as a part of my

annual inspection.



	Roger

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 05, 2012 3:57 pm Post subject: Z-19RB clarification

At 08:16 AM 7/5/2012, you wrote:

 	  Quote: 	
		  

<mrspudandcompany(at)verizon.net>



In my thinking, I was approaching this from a slightly different 

angle.  In IFR conditions if the main battery goes dead, because you 

had  a hard engine start and not sufficient time to recharge the 

main you have no avionics to get you to VFR conditions.  In this 

case a running engine does you no good. But, to put a little more 

logic into the situation, you should be seeking an out from IFR asap 

to improve your chances if something else does go wrong.


	


   How do you kill a main battery and not the engine

   battery too? Why would you launch into IFR after

   an anomalous engine start with knowledge that the

   battery(ies) are now less than optimal? How much 'avionics'

   do you 'need' to navigate to VMC? What's then energy

   budget? How would you position switches and reduce

   loads to maximize available resources . . . indeed,

   what policies and procedures will you put in place

   to always KNOW what your resources are?

 	  Quote: 	
		  My slight mod, mentioned previously, to Z-19RB:

Since I have dual ignition and dual fuel pumps, I am eliminating the 

diodes and the 2-3 switches, to be replaced with 4ea. SPST, thus 

simplifying and also giving me full control of any combination of 

fuel pumps and ignition.


	


   But 'full control' over what? Flying an airplane

   is like baking a cake. You cannot make useful changes

   to a recipe AFTER the batter is in the pan. Z-19

   was designed to deal comfortably with one annunciated

   failure. Launching into unfriendly conditions without

   KNOWING that your Plan-B energy budget can be met is

   the first failure . . . stacking a "dead battery" on

   top of that is a second failure . . . adding a dead

   alternator to that is a third failure. Sounds like

   the script to a Hollywood dark-n-stormy night movie.



   Sorry my friend, all the switches offering back-ups to

   back-ups is the very last thing you need in single-pilot

   IFR. Please review chapter 17 and apply the logic to your

   own cake recipe. The chapter is a bit dated given the

   much heavier e-bus loads but the principal for careful

   study of system loads, knowing limits to energy sources

   and insuring timely pilot awareness and SIMPLE response

   is critical to an effective Plan-B. When the LO VOLTS

   light comes on, you say 'oh fooey' and reposition a

   couple of switches at most then get on with the task

   of putting your wheels on the pavement without breaking

   a sweat.



   Adding plans C, D, E and F with lots of new options

   for total control is an invitation to an unhappy

   day in the cockpit. Launching with known deficiencies

   is performance or resources is like hitting the highway

   for a run to the mountains in a dust storm and 100 miles

   between towns knowing you're a quart low on oil, one tire

   is half inflated, or remembering you left your Dopp kit

   on the bed. Each deficiency adds its own level of

   uncertainty or risk to the trip. Stack them on top of each

   other and you may have created a situation that no

   amount of extra features in the flipping of switches

   is going to help.

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 05, 2012 3:57 pm Post subject: Z-19RB clarification

At 08:16 AM 7/5/2012, you wrote:




In my thinking, I was approaching this from a slightly different 

angle.  In IFR conditions if the main battery goes dead, because you 

had  a hard engine start and not sufficient time to recharge the main 

you have no avionics to get you to VFR conditions.  In this case a 

running engine does you no good. But, to put a little more logic into 

the situation, you should be seeking an out from IFR asap to improve 

your chances if something else does go wrong.



   How do you kill a main battery and not the engine

   battery too? Why would you launch into IFR after

   an anomalous engine start with knowledge that the

   battery(ies) are now less than optimal? How much 'avionics'

   do you 'need' to navigate to VMC? What's then energy

   budget? How would you position switches and reduce

   loads to maximize available resources . . . indeed,

   what policies and procedures will you put in place

   to always KNOW what your resources are?



My slight mod, mentioned previously, to Z-19RB:

Since I have dual ignition and dual fuel pumps, I am eliminating the 

diodes and the 2-3 switches, to be replaced with 4ea. SPST, thus 

simplifying and also giving me full control of any combination of 

fuel pumps and ignition.



   But 'full control' over what? Flying an airplane

   is like baking a cake. You cannot make useful changes

   to a recipe AFTER the batter is in the pan. Z-19

   was designed to deal comfortably with one annunciated

   failure. Launching into unfriendly conditions without

   KNOWING that your Plan-B energy budget can be met is

   the first failure . . . stacking a "dead battery" on

   top of that is a second failure . . . adding a dead

   alternator to that is a third failure. Sounds like

   the script to a Hollywood dark-n-stormy night movie.



   Sorry my friend, all the switches offering back-ups to

   back-ups is the very last thing you need in single-pilot

   IFR. Please review chapter 17 and apply the logic to your

   own cake recipe. The chapter is a bit dated given the

   much heavier e-bus loads but the principal for careful

   study of system loads, knowing limits to energy sources

   and insuring timely pilot awareness and SIMPLE response

   is critical to an effective Plan-B. When the LO VOLTS

   light comes on, you say 'oh fooey' and reposition a

   couple of switches at most then get on with the task

   of putting your wheels on the pavement without breaking

   a sweat.



   Adding plans C, D, E and F with lots of new options

   for total control is an invitation to an unhappy

   day in the cockpit. Launching with known deficiencies

   is performance or resources is like hitting the highway

   for a run to the mountains in a dust storm and 100 miles

   between towns knowing you're a quart low on oil, one tire

   is half inflated, or remembering you left your Dopp kit

   on the bed. Each deficiency adds its own level of

   uncertainty or risk to the trip. Stack them on top of each

   other and you may have created a situation that no

   amount of extra features in the flipping of switches

   is going to help.

   Bob . . .

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 05, 2012 4:12 pm Post subject: Z-19RB clarification

At 09:52 PM 7/4/2012, you wrote:




Roger,

I am using Z-19RB in my Subaru H6 powered RV7.  My understanding as to why

the endurance bus alternate feed is from the Main Battery only is that the

engine bus and its battery are reserved for the running of the engine alone

just as long as possible.  I guess if you lose the main battery and thus the

endurance bus then you can still fly the airplane to a safe landing site as

long as the engine is running.  Whereas, if you lose the engine battery/bus

the endurance bus is not going to do you any good as you glide to a landing.



I am sure Bob will chime in with a more elegant explanation.



    During normal operations, BOTH batteries are on

    line and behave as a single battery equal to their

    combined capacity.



    When the low volts warning light comes on, all you

    have to finish the flight is what ever is carried

    in the two batteries.



    At that point in time you drop to the ENDURANCE MODE.

    Run no piece of equipment that is not necessary for

    a no-sweat return to earth.



    Repeat after me: "I will KNOW what the capacity of

    my batteries is at all times by which I will KNOW

    what my endurance limits are in alternator-out

    conditions." This usually calls for getting the

    battery contactors out of the picture . . . turning

    off both battery switches, running the engine from

    the engine battery and minimum electro-whizzies on

    the endurance bus. Once you have the airport in sight

    and are cleared to land, you can turn the main battery

    back on and use what ever is left to make a grander

    entrance . . . but the idea is that you've kept

    the engine's power source fire-walled off in a

    separate energy bucket.



    Now, if you want to add a second failure to this

    scenario, then BOTH battery switches are placed to

    ON and you begin moves to expedite landing while

    watching bus voltage readings. When it gets down

    to 10.5 volts, your on-board battery energy is

    more than 95% used up. You need to be on short

    final before that time.



    Being able to switch the engine from one battery

    to the other is a hedge against contactor failure

    stacked on top of other failures . . . a statistical

    tiny dot on the great horizon of possibilities for

    one failure.

   Bob . . .

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