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tomhanaway

Joined: 12 Aug 2006
Posts: 111
Location: Murphy, NC

Posted: Sat Jul 12, 2014 1:15 pm Post subject: Dual master solenoids

Working my way through Nuckoll's Z-13 wiring diagram.

I'm building an 8-a VFR with single battery, single alternator.



I'm not excited about the use of his "always hot" main bus because of the additional wire runs it would create from the buss mounted close to the rear mounted battery and difficulty accessing fuses for those wires.



I'd like to run all electrical busses from the always hot side of the starter solenoid (always hot when master solenoid is hot).



Given this scenario, it seems that the really significant system weakness is the failure of the master solenoid. I was thinking that a second master solenoid, with a separate wire and switch, wired in parallel at the battery, would address this issue.



Does this make sense or am I missing something obvious (or not so obvious)?



Thanks, 

Tom H.



Sent from my iPad

_________________
RV-10. Built and sold
RV-8a. Building

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Jul 12, 2014 3:14 pm Post subject: Dual master solenoids

At 04:14 PM 7/12/2014, you wrote:

 	  Quote: 	
		  



Working my way through Nuckoll's Z-13 wiring diagram.

I'm building an 8-a VFR with single battery, single alternator.



I'm not excited about the use of his "always hot" main bus because 

of the additional wire runs it would create from the buss mounted 

close to the rear mounted battery and difficulty accessing fuses for 

those wires.


	


    That's not a "MAIN BUS" . . . it's the MAIN BATTERY

    always-hot with exceedingly limited but often important

    tasks in getting power distributed to your airplane.



    GA airplanes have had always-hot busses since the

    clock and hour-meter fuses were mounted right next

    to the battery master contactor in the tail . . . in

    Cessnas I worked on in 1965.



    Study Z-13 again (or perhaps Z-11 which is a single

    alternator version). Also the notes for the z-figures

    along with the chapter on system reliability.



 	  Quote: 	
		  I'd like to run all electrical busses from the always hot side of 

the starter solenoid (always hot when master solenoid is hot).


	


    Not sure what's driving this . . . The Z-figures are

    the culmination of over 45+ years experience in TC

    aviation enhanced by 25+ years in OBAM aviation exploiting

    the freedoms not enjoyed by TC aviation . . . to craft an

    architecture that meets YOUR mission requirements . . .

    not those of a bureaucracy most of whom do not build or

    fly airplanes.

 	  Quote: 	
		  Given this scenario, it seems that the really significant system 

weakness is the failure of the master solenoid. I was thinking that 

a second master solenoid, with a separate wire and switch, wired in 

parallel at the battery, would address this issue.



Does this make sense or am I missing something obvious (or not so obvious)?


	


    It's not clear that you understand the philosophy behind

    the various architectures and functionality of their

    several features.



    Suggest you PLAN for Z-13/8 by having all the WIRES

    in place to have a second alternator . . . unless you're

    going to have a vacuum pump, the consider NOT plugging

    a perfectly good source of mechanical energy with a

    cover plate.



    Print out copies of http://tinyurl.com/7jqypwj  one for

    each bus. It generally takes three.



    List each load services by the various busses along

    with their magnitudes and flight configurations that

    the loads are expected/necessary.



    You may not need a battery bus . . . but get all your

    loads defined first . . . then decide what bus

    structures are needed.



    Do you plan any sort of electronic ignition. The

    RV8 is low wing so you no doubt have electric

    fuel pumps. Does any of your proposed electrics

    need memory keep-alive power? I single alternator,

    what's your goal for battery-only endurance? The

    load analysis study will let you set necessary battery

    size based on predicted loads. There's lot of

    sifting of requirements that will drive what

    gets powered from which busses.



    Go with Z-13/8 with second 4-pound alternator

    and your alternator-out endurance deliberations

    get a WHOLE LOT easier.

   Bob . . .

bob.verwey(at)gmail.com
Guest

Posted: Sat Jul 12, 2014 9:54 pm Post subject: Dual master solenoids

TOM, 

  Then you may as well have two of everything.  

Remember the cardinal rule..." build in simplicity and lightness"Â   

BobÂ Â  Verwey On 12 Jul 2014 11:22 PM, "Tomhanaway" <tomhanaway1(at)gmail.com (tomhanaway1(at)gmail.com)> wrote:[quote] --> AeroElectric-List message posted by: Tomhanaway <tomhanaway1(at)gmail.com (tomhanaway1(at)gmail.com)>

 

 Working my way through Nuckoll's Z-13 wiring diagram.

 I'm building an 8-a VFR with single battery, single alternator.

 

 I'm not excited about the use of his "always hot" main bus because of the additional wire runs it would create from the buss mounted close to the rear mounted battery and difficulty accessing fuses for those wires.

  

 I'd like to run all electrical busses from the always hot side of the starter solenoid (always hot when master solenoid is hot).

 

 Given this scenario, it seems that the really significant system weakness is the failure of the master solenoid. I was thinking that a second master solenoid, with a separate wire and switch, wired in parallel at the battery, would address this issue.

  

 Does this make sense or am I missing something obvious (or not so obvious)?

 

 Thanks,

 Tom H.

 

 Sent from my iPad

 

 ===========

  -

 ric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ===========

 MS -

 k">http://forums.matronics.com

 ===========

 e -

  Â  Â  Â  Â  Â -Matt Dralle, List Admin.

 t="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 [b]

tomhanaway

Joined: 12 Aug 2006
Posts: 111
Location: Murphy, NC

Posted: Sun Jul 13, 2014 2:56 am Post subject: Dual master solenoids

I understand that but it doesn't answer my question.

Is there anything from an electrical point of view that keeps this from working. I.e., the backup master solenoid would have 12 vdc at both terminals whenever the primary master solenoid is turned on even if the aux master solenoid switch is not on.  My goal is to have the aux solenoid sitting idle unless activated by a switch.  

Tom



Sent from my iPad 



On Jul 13, 2014, at 1:50 AM, Bob Verwey <bob.verwey(at)gmail.com (bob.verwey(at)gmail.com)> wrote:

[quote]

 TOM, 

  Then you may as well have two of everything.  

Remember the cardinal rule..." build in simplicity and lightness"   

Bob   Verwey On 12 Jul 2014 11:22 PM, "Tomhanaway" <tomhanaway1(at)gmail.com (tomhanaway1(at)gmail.com)> wrote: 	  Quote: 	
		   --> AeroElectric-List message posted by: Tomhanaway <tomhanaway1(at)gmail.com (tomhanaway1(at)gmail.com)>

 

 Working my way through Nuckoll's Z-13 wiring diagram.

 I'm building an 8-a VFR with single battery, single alternator.

 

 I'm not excited about the use of his "always hot" main bus because of the additional wire runs it would create from the buss mounted close to the rear mounted battery and difficulty accessing fuses for those wires.

  

 I'd like to run all electrical busses from the always hot side of the starter solenoid (always hot when master solenoid is hot).

 

 Given this scenario, it seems that the really significant system weakness is the failure of the master solenoid. I was thinking that a second master solenoid, with a separate wire and switch, wired in parallel at the battery, would address this issue.

  

 Does this make sense or am I missing something obvious (or not so obvious)?

 

 Thanks,

 Tom H.

 

 Sent from my iPad

 

 ===========

  -

 ric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ===========

 MS -

 k">http://forums.matronics.com

 ===========

 e -

           -Matt Dralle, List Admin.

 t="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 

	


[b]

_________________
RV-10. Built and sold
RV-8a. Building

kleh(at)dialupatcost.ca
Guest

Posted: Sun Jul 13, 2014 3:47 am Post subject: Dual master solenoids

I don't see a problem with a dual master although I wonder if it really 

achieves your goal or achieves it as elegantly as one of the Z 

architectures. The failures of contactors that I've seen are failures to 

activate not failures during flight. I do agree that any truly essential 

system such as engine power should not be tied to a single contactor but 

the battery buss and/or essential buss concept seem like a better 

solution where applicable. Don't forget that a backup has little value 

unless tested regularly. For example, I test my backup EFI during taxi 

on every flight and it has always worked perfectly. I happened to test 

it in flight yesterday and discovered that it has started to miss at 

high power which pretty much means it has been useless dead weight for 

some undetermined length of time as I do not often test it at high power 

settings.

Ken



On 13/07/2014 6:55 AM, Tomhanaway wrote:

 	  Quote: 	
		   I understand that but it doesn't answer my question.



 Is there anything from an electrical point of view that keeps this from

 working. I.e., the backup master solenoid would have 12 vdc at both

 terminals whenever the primary master solenoid is turned on even if the

 aux master solenoid switch is not on.  My goal is to have the aux

 solenoid sitting idle unless activated by a switch.



 Tom



 Sent from my iPad



 On Jul 13, 2014, at 1:50 AM, Bob Verwey <bob.verwey(at)gmail.com

 <mailto:bob.verwey(at)gmail.com>> wrote:



> TOM,

> Then you may as well have two of everything.

>

> Remember the cardinal rule..." build in simplicity and lightness"

>

> Bob   Verwey

>

> On 12 Jul 2014 11:22 PM, "Tomhanaway" <tomhanaway1(at)gmail.com

> <mailto:tomhanaway1(at)gmail.com>> wrote:

>

>     

>     <tomhanaway1(at)gmail.com <mailto:tomhanaway1(at)gmail.com>>

>

>     Working my way through Nuckoll's Z-13 wiring diagram.

>     I'm building an 8-a VFR with single battery, single alternator.

>

>     I'm not excited about the use of his "always hot" main bus because

>     of the additional wire runs it would create from the buss mounted

>     close to the rear mounted battery and difficulty accessing fuses

>     for those wires.

>

>     I'd like to run all electrical busses from the always hot side of

>     the starter solenoid (always hot when master solenoid is hot).

>

>     Given this scenario, it seems that the really significant system

>     weakness is the failure of the master solenoid. I was thinking

>     that a second master solenoid, with a separate wire and switch,

>     wired in parallel at the battery, would address this issue.

>

>     Does this make sense or am I missing something obvious (or not so

>     obvious)?

>

>     Thanks,

>     Tom H.

>

kjashton(at)vnet.net
Guest

Posted: Sun Jul 13, 2014 3:48 am Post subject: Dual master solenoids

On Jul 13, 2014, at 6:55 AM, Tomhanaway wrote:



 	  Quote: 	
		   Is there anything from an electrical point of view that keeps this from working.


	


There is no electrical reason why your idea won't work but why do it?  Master solenoids don't typically fail in-flight.  They typically don't fail at all if installed as Bob suggests, unless the posts are tightened incorrectly and twist the internal contacts.  If one does fail, you can find a replacement at a FLAPS.  If your engine has magnetos, an inflight failure won't matter.  If you are using EIs, you'll probably have ignition power straight off the battery so it still won't matter.



Put the cost and the weight-cost of an additional heavy solenoid, additional foot or so of heavy AWG 2-4 wire, additional panel switch and wiring against the low chance you'll ever need it.

-Kent

Cozy IV

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jul 13, 2014 7:00 am Post subject: Dual master solenoids

At 06:47 AM 7/13/2014, you wrote:

 	  Quote: 	
		  

<kjashton(at)vnet.net>

On Jul 13, 2014, at 6:55 AM, Tomhanaway wrote:



 > Is there anything from an electrical point of view that keeps 

 this from working.



There is no electrical reason why your idea won't work but why do 

it?  Master solenoids don't typically fail in-flight.


	


   . . . and even if they did, the battery-bus/e-bus

   architectures are crafted to keep things comfortable

   in the cockpit even if it DID fail . . . in fact,

   the germinating idea behind the dual-feedpath e-bus

   was to facilitate a deliberate opening of the

   battery master contactor as part of load shedding

   protocol for battery-only operations.



   Suggest you do your own failure mode effects

   analysis where you consider the risks for a

   failure of any single component of your electrical

   system. If you discover a failure that puts

   comfortable termination of flight at risk,

   then let's talk about it. I'm certain

   that with judicious selection of accessories

   and distribution of power, you can craft

   a system where worries about the battery master

   contactor are at the bottom of the risk assessment

   list.



   Bob . . .

BobsV35B(at)aol.com
Guest

Posted: Sun Jul 13, 2014 7:26 am Post subject: Dual master solenoids

Just a test .Please excuse my interruption.

  

 Old Bob

  

  Do Not Archive

  

  In a message dated 7/13/2014 10:01:58 A.M. Central Daylight Time,  nuckolls.bob(at)aeroelectric.com writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: "Robert L. Nuckolls, III"    <nuckolls.bob(at)aeroelectric.com>



At 06:47 AM 7/13/2014, you    wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: Kent or Jackie    Ashton 

<kjashton(at)vnet.net>

On Jul 13,    2014, at 6:55 AM, Tomhanaway wrote:



 > Is there anything    from an electrical point of view that keeps 

 this from    working.



There is no electrical reason why your idea won't work    but why do 

it?  Master solenoids don't typically fail    in-flight.


	


   . . . and even if they did, the    battery-bus/e-bus

   architectures are crafted to keep things    comfortable

   in the cockpit even if it DID fail . . . in    fact,

   the germinating idea behind the dual-feedpath    e-bus

   was to facilitate a deliberate opening of    the

   battery master contactor as part of load    shedding

   protocol for battery-only    operations.



   Suggest you do your own failure mode    effects

   analysis where you consider the risks for    a

   failure of any single component of your    electrical

   system. If you discover a failure that    puts

   comfortable termination of flight at    risk,

   then let's talk about it. I'm certain

      that with judicious selection of accessories

   and distribution    of power, you can craft

   a system where worries about the    battery master

   contactor are at the bottom of the risk    assessment

   list.



   Bob . . .  = Use  ilities  ay                 - MATRONICS WEB FORUMS               - List Contribution Web Site  p;                             



	


 [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jul 13, 2014 10:21 am Post subject: Dual master solenoids

At 10:24 AM 7/13/2014, you wrote:

  	  Quote: 	
		   Just a test .Please excuse my interruption.

  

 Old Bob

  

  Do Not Archive

  	


   Bob,



   I'm replying through the List and with a copy

   to you directly. Have you sorted your email

   marbles out?



 

 

   Bob . . .    [quote][b]

user9253

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

Posted: Sun Jul 13, 2014 6:10 pm Post subject: Re: Dual master solenoids

 	  Quote: 	
		  I'm not excited about the use of his "always hot" main bus because of the additional wire runs it would create from the buss mounted close to the rear mounted battery and difficulty accessing fuses for those wires. 

I'd like to run all electrical busses from the always hot side of the starter solenoid (always hot when master solenoid is hot). 	


Schematics do not indicate how wires are routed in an aircraft.  They show the logic of a circuit, not necessarily the physical layout.  The heavy wire that supplies power to the main power distribution bus can be connected to either end of the wire between the two contactors (main battery and start).  Your idea of connecting to the always hot side of the starter contactor is identical (electrically speaking) to Bob's schematic.

   	  Quote: 	
		  I was thinking that a second master solenoid, with a separate wire and switch, wired in parallel at the battery, would address this issue. 	


Like Bob said, the E-bus circuit addresses this issue.  If you would rather backup the main battery contactor, it can be done with an automotive 30 or 40 amp relay at a fraction of the weight.  The relay must be disabled during engine cranking, maybe like the attached circuit.

  But keep in mind that the more complicated and the more components , the more to go wrong.

Joe

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Joe Gores

tomhanaway

Joined: 12 Aug 2006
Posts: 111
Location: Murphy, NC

Posted: Mon Jul 14, 2014 3:15 am Post subject: Re: Dual master solenoids

Thanks Joe,

Once I started thinking in terms of a relay, this came pretty close to what I was looking for.  

Interesting use of a starter enable/disable switch to ensure no cranking current through relay.



Interesting question ( to me, anyway), are heavy duty continuous service relays any less reliable than mechanical relays?  If about the same 

reliability, what are the reasons that they aren't used more often for a

master solenoid?  As you stated, the weight differential is pretty significant.



Thanks again,

Tom

_________________
RV-10. Built and sold
RV-8a. Building

user9253

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

Posted: Mon Jul 14, 2014 4:06 am Post subject: Re: Dual master solenoids

 	  Quote: 	
		  are heavy duty continuous service relays any less reliable than mechanical relays? If about the same reliability, what are the reasons that they aren't used more often for a master solenoid? 	


There are several ways that a relay or contactor can fail.  The contacts can develop a high resistance, the coil can burn open, springs or other mechanical parts can break, and etc.  I do not know which type is more likely to fail.  The current carrying capability determines which relay or contactor to use.  Starters can draw a few hundred amps initially to get the engine rotating.  A 30 amp automotive relay would not last very long carrying that much current.

  So why have the starter current go though the master contactor?  The starter contactor could be wired directly to the battery.  I think the reason is that contactors have been known to fail closed.  Having two contactors in series makes sure that the circuit can be opened.

Joe

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 14, 2014 6:45 am Post subject: Dual master solenoids

At 07:06 AM 7/14/2014, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>



 

 > are heavy duty continuous service relays any less reliable than mechanical relays? If about the same reliability, what are the reasons that they aren't used more often for a master solenoid? 	


    "Reliability" is a rather soggy concept.

    It can mean different things to most speakers

    in a group of conversants. If you

    write to Stancore/White-Rogers and ask,

    just HOW reliable is your 70-110 contactor?

    . . . they MIGHT fire back with a laboratory

    study that cites cycle-life of the contactor

    under various loads and perhaps environmental

    conditions. Write to Tyco about reliability

    of their Kilovac contactors and you MIGHT

    get another report.



    Okay, Tyco's numbers are better than S/W-R

    numbers . . . now what?



    As I've been explaining in my writing and

    presentations for the past 30 years, the

    elegant design has little, if any, interest

    in those numbers. Lessons-learned in over

    a century of building airplanes have demonstrated

    that the designer's prime directive is to

    reduce risk for a bad day in the cockpit.



    To be sure, if money, weight, $time$

    to market and cost of ownership were

    of no concern, then there are virtually

    limitless ways that hedges against risk

    can be applied to the system. But applied

    without the confidence that comes from

    understanding there is a larger risk that

    the end-product is burdened with "safety

    features" that degrade performance to

    far greater degrees than protecting the

    airframe and crew.

 [img]cid:7.1.0.9.0.20140714094258.04cc69a8(at)aeroelectric.com.2[/img] 

   



 

    My teachers would ask, "Okay, you've selected a 

    whiz-bang part for that location in the airplane,

    make your case for the decision." Had I whipped

    out the reliability data sheets for the constellation

    of choices and said, "See here, look at THOSE numbers!"

    they might have banished me to purchasing support

    or perhaps the EMC lab.



    The first bit of guidance germane to your decision

    resides in lessons-learned. Question: How many

    times have pilots experienced a bad day in the

    cockpit due to in-flight failure of the battery

    master contactor?



    I haven't a clue . . . because the incidents have

    been so few in numbers and so benign as to become

    completely buried in COMPONENT failures that

    put the whole SYSTEM at risk . . . The aviation

    journals are replete with what I have called

    "dark n stormy night" stories . . . most of

    which are so lacking in data as to defy understanding

    of root cause . . . or more illustrative of human

    weaknesses than those of the airplane.



    Consider that EVERY contactor is RATED and

    TESTED in the lab to perform as advertised

    for tens of thousands of cycles at rated lioad.

    YOUR battery contactor is going to close/open

    once per flight cycle . . . perhaps 100 times

    per YEAR and under nearly zero-load conditions.



    Were you to conduct laboratory reliability

    testing for conditions in YOUR airplane, it's

    unlikely that you would ever see a failure.

    We HAVE seen some failures here on the List.

    Detailed analysis revealed failure due to

    a variety of reasons including manufacturing

    defects 



 [img]cid:7.1.0.9.0.20140714094258.04cc69a8(at)aeroelectric.com.3[/img] 



   moisture ingress, and installation error . . . but in no

   case were the failures first detected in flight.



   Carrying lessons-learned a step further we can conduct

   a failure effects study. You do this by ASSUMING that every

   part will fail at some point in time. You then analyze

   how that failure will affect system performance. For

   failures that pose unacceptable risk, you make some

   design changes.  Except for things like wing struts

   and prop bolts, the elegant design drives more toward

   failure TOLERANCE than failure PROOF.



   See:   http://tinyurl.com/ozum5u9



   If your studies for optimal design are driving you

   toward the purchase of high-dollar hardware -OR-

   adding backup components, then perhaps your confidence

   born of lessons-learned and artful conduct of

   failure analysis is shaky. I suggest that crafting

   any of the Z-Figures chosen to match your mission

   profiles and hardware will produce an exceedingly

   failure tolerant system. I suggest further that

   Z13/8 has more bang for the buck/pound/volume than

   systems flying in some pretty sophisticated airplanes.



   The very first example of Z13-8 flying in an OBAM

   aircraft was in an RV-8 in Connecticut about 25

   years ago . . . the father-son build team were

   delighted with its performance and confidence

   levels.



   They could loose a battery master contactor

   every few months and not suffer a bad day in

   the cockpit . . . but I'll bet that the Model

   70 contactor installed day-on is still flying.



   Bob . . .

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uuccio(at)gmail.com
Guest

Posted: Tue Jul 15, 2014 5:59 am Post subject: Dual master solenoids

It's also a safety issue with some starter configurations. For instance if you had a momentary push button for the starter instead of a key switch, even with the master off you would still be able to push the button and turn the prop.  



I have this configuration and as an added safety while the aircraft is stopped and the master needs to be on,  I always pull the starter CB. 



Sacha



 	  Quote: 	
		   On 14 Jul 2014, at 14:06, "user9253" <fransew(at)gmail.com> wrote:

 

 Having two contactors in series makes sure that the circuit can be opened.

stein(at)steinair.com
Guest

Posted: Tue Jul 15, 2014 6:53 am Post subject: Dual master solenoids

Aside from some anecdotal references that are oft repeated at hangar flying

sessions and on the interwebs, have you or do you know of a specific

instance where a master contactor/solenoid of standard design failed

repeatedly?  All mechanical things have "been known to fail", but we build

airplanes around the 99th percentile, not the 1th percentile.  If you built

a perfectly safe airplane, it would be one that wouldn't leave the

ground....so to that end you design in for the 99th, but also take into

account the 1th percentiles without doing crazy things like putting in two

master contactors or two tachometers (unless of course you have two

batteries, or two busses, etc..).  If you are going to put in two of those,

why not two starter buttons, or two circuit breakers for each circuit, or

two throttle cables, or two rudders, or two elevator pushrods,  (after all,

those have also been known to fail)?  You still do only have one camshaft

and one propeller and one crankshaft and one carb/fuel injector, one brain,

etc..



My point is that the probability of failure of that specific components is

likely less than the probability of other equally as important mechanical

things in your plane.  There is no reason to randomly pick one particular

component and focus on it over another when it has not proven to be a weak

point in the entire aerospace vehicle system design.



Just my 2 cents as usual, but one could come up with all sorts of 1th

percentile "possibilities" that are really not worth expending energy, time,

money, weight or complexity on as the return on all of that in actuality

becomes a negative. Remember, adding things for "redundancy" does not

necessarily and automatically translate into reliability - many times it has

the inverse effect (increased complexity = decreased reliability).



Cheers, 



Stein 





--

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jul 15, 2014 10:56 am Post subject: Dual master solenoids

At 08:57 AM 7/15/2014, you wrote:

 	  Quote: 	
		  



It's also a safety issue with some starter configurations. For 

instance if you had a momentary push button for the starter instead 

of a key switch, even with the master off you would still be able to 

push the button and turn the prop.


	




    Irrespective of the kind of switch that energizes

    the starter, I'm aware of no TC aircraft, or any

    OBAM aircraft wired per a Z-figure where this is

    the cased. The general rule of thumb for all

    airplanes is that opening the battery master

    contactor removes ALL power from the aircraft

    except for those items wired to a battery bus.

    Starters should be dead-in-place with the

    battery master off.



 	  Quote: 	
		  I have this configuration and as an added safety while the aircraft 

is stopped and the master needs to be on,  I always pull the starter CB.


	


    How was it that you came to wire your airplane

    this way?

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jul 15, 2014 11:35 am Post subject: Dual master solenoids

My point is that the probability of failure of that specific components is

likely less than the probability of other equally as important mechanical

things in your plane.  There is no reason to randomly pick one particular

component and focus on it over another when it has not proven to be a weak

point in the entire aerospace vehicle system design.



    Precisely . . .



    When opening the seminar segment on

    reliability, I like to put a z-figure

    up on the screen, point to a component

    and ask, "What do you need to do if THIS

    part malfunctions?"



    At least one participant will suggest

    that it be replaced with a 'better part'.

    That's the segment where I pose the notion

    that the flight SYSTEM consists of an airframe,

    pilot, environment and expendable resources.

    From the time the wheels break ground until

    you're parked at the destination, the design

    goal is not break a sweat . . . irrespective

    of any component failure.



    The last few ideas offered at the end of

    the segment suggests that it doesn't matter

    if you buy electrical parts from Autozone,  $high$

    parts from Honeywell or TC aircraft parts from

    the Cessna warehouse . . . it is possible to

    ARCHITECTURE the electrical system such that

    no single component failure will induce an

    in-flight sweat.



    In the final analysis, you're more likely

    to have a bad day in the cockpit driven by

    events and conditions far removed from

    things electrical. #1 cause of engine

    stoppage is fuel starvation. #1 cause

    for unplanned arrivals with the earth

    are most often based on human factors for dealing

    with environment: weather, mountains,

    night ops, etc.) As we have studied many

    times here on the List . . . mishaps

    that included electrical issues were

    FIRST driven by lapses in assembly skills,

    failure tolerant design or poor maintenance.



    See: http://tinyurl.com/ky7szec



    In other words, "two parts" or a "better

    part" would not have produced a better

    outcome.

   Bob . . .

uuccio(at)gmail.com
Guest

Posted: Tue Jul 15, 2014 12:34 pm Post subject: Dual master solenoids

 	  Quote: 	
		  It's also a safety issue with some starter configurations. For instance 

if you had a momentary push button for the starter instead of a key 

switch, even with the master off you would still be able to push the 

button and turn the prop.


	




    Irrespective of the kind of switch that energizes

    the starter, I'm aware of no TC aircraft, or any

    OBAM aircraft wired per a Z-figure where this is

    the cased. The general rule of thumb for all

    airplanes is that opening the battery master

    contactor removes ALL power from the aircraft

    except for those items wired to a battery bus.

    Starters should be dead-in-place with the

    battery master off.



Hi Bob, I was referring to the hypothetical situation that Joe brought up

where the starter contactor would be always hot, i.e. wired to the battery

bus.



 	  Quote: 	
		  I have this configuration and as an added safety while the aircraft is 

stopped and the master needs to be on,  I always pull the starter CB.


	


    How was it that you came to wire your airplane

    this way?



My apologies, I wasn't very clear...  My electrical setup is essentially

Z-16, but the starter button is a push button.  So whenever I am tinkering

around on the ground and the master needs to be on, I pull the starter CB

just to be safe.  Another situation is when my three year old wants to sit

next to me in the a/c and see the panel light up and pretend he's flying the

aircraft...

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jul 15, 2014 3:11 pm Post subject: Dual master solenoids

My apologies, I wasn't very clear...  My electrical setup is essentially

Z-16, but the starter button is a push button.  So whenever I am tinkering

around on the ground and the master needs to be on, I pull the starter CB

just to be safe.  Another situation is when my three year old wants to sit

next to me in the a/c and see the panel light up and pretend he's flying the

aircraft... 



    Understand . . . thanks!



   Bob . . .

user9253

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

Posted: Tue Jul 15, 2014 5:57 pm Post subject: Re: Dual master solenoids

 	  Quote: 	
		  I was referring to the hypothetical situation that Joe brought up 

where the starter contactor would be always hot, i.e. wired to the battery 

bus. 	


I did not bring that up.  I was referring to tomhanaway's post where he wrote, "the always hot side of the starter solenoid (always hot when master solenoid is hot)".

  It is much easier to understand each other when talking face to face compared to email or forum postings.  

Joe

_________________
Joe Gores

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