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Engine/avionics shutdown procedure

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KingCJ6(at)aol.com
Guest

Posted: Sun Sep 26, 2010 2:01 pm Post subject: Engine/avionics shutdown procedure

Most  Nanchang checklists specify shutting the  engine down with mags prior to shutting off the electric switches which power  all of the avionics.  All  traditional GA checklists I've seen specify turning off the avionics master (or  individual components) prior to shutting down the engine to presumably prevent  damage from a potential power spike.   Any technical reason for the Nanchang to be  different? 

  

Dave

  [quote][b]

mark.bitterlich(at)navy.m
Guest

Posted: Sun Sep 26, 2010 2:44 pm Post subject: Engine/avionics shutdown procedure

Dave,  That is a very good point.  Again, I must caution anyone reading this that I have never worked on a CJ, though I am aware that they have two types of control systems for the generator.  

 

I believe there is a solid state controller and also a older more traditional style controller.  Whatever.  Let's just cut to the chase.  It would be much smarter to turn off your avionics before killing the mags (engine) if you have anything in there worth worrying about.  

 

Why?  Because on any engine that has a generator, when you kill the mags, the generator stops turning.  As it slows down, the generator voltage will drop below the battery voltage.  When this happens, current stops flowing from the generator to the battery, and instead flows from the battery to the generator.  This is called "Reverse Current".  In all aircraft with real generators, there is some device that is in there to prevent this.  

 

Or at least... normally the way it works is that as current STARTS flowing from the battery to the generator,  There is usually some kind of "set point" where this relay operates and then DISCONNECTS the generator from the aircrafts electrical bus.  

 

Here is the problem.  If your battery is not in just TIP TOP condition... which by the way, many of our batteries are not... because we fail to CHECK THEM PROPERLY.....  what will happen is that when the engine starts slowing down to a stop after you kill the mags, reverse current will start to flow.   If your batteries are not up to snuff, then the battery output voltage will drop as the current going to the generator increases.

 

Hopefully, eventually the current will rise high enough to where the reverse current RELAY operates and then disconnects the generator.  However, that does not HAVE to happen right away when it should.  If the batteries are WEAK, then this chain of events will happen much more SLOWYLY.  And that is a bad bad thing, because then your battery voltage will drop way down below 24 volts and maybe as low as 14-16 VDC.  Avionics systems really don't like voltage spikes like this.  Going down, or going up  They just don't like that kind of thing. Will it cause instant failure of your avionics?  NO.  Is it asking for a failure?  YES.   Shut off your avionics before killing the engine is the smart thing to do, regardless of what any check list currently says.  

 

Mark Bitterlich

 

p.s.  I do not bother to follow my own advice, but then I check my batteries carefully all the time, and I also am only powering one Russian radio.  But, I really should, and if I had any Avionics that cost more than a few hundred, I would be religious about it.  



________________________________



From: owner-yak-list-server(at)matronics.com on behalf of KingCJ6(at)aol.com

Sent: Sun 9/26/2010 5:58 PM

To: yak-list(at)matronics.com

Subject: Engine/avionics shutdown procedure



Most Nanchang checklists specify shutting the engine down with mags prior to shutting off the electric switches which power all of the avionics.  All traditional GA checklists I've seen specify turning off the avionics master (or individual components) prior to shutting down the engine to presumably prevent damage from a potential power spike.  Any technical reason for the Nanchang to be different?



 



Dave

sajdds(at)comcast.net
Guest

Posted: Sun Sep 26, 2010 4:38 pm Post subject: Engine/avionics shutdown procedure

Mark, how does one check the batteries properly?



Steve Johnson

Yak 52 N9900X 0B5

413 522-1130 Cell

--

N13472(at)aol.com
Guest

Posted: Sun Sep 26, 2010 5:04 pm Post subject: Engine/avionics shutdown procedure

Do you have a generator  or an Alternator ? With the Alt no issue, with the generator possibly depending  on your battery and reverse current relay. I have mostly

 turned off the master and  or avionics after engine shut down for many years and have had no  problems.

  

  

Tom Elliott

CJ-6A NX63727

702-595-2680  



 [quote]         From: owner-yak-list-server(at)matronics.com    [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of    KingCJ6(at)aol.com

Sent: Sunday, September 26, 2010 2:59    PM

To: yak-list(at)matronics.com

Subject: Yak-List:    Engine/avionics shutdown procedure

   

      

Most    Nanchang checklists specify shutting the    engine down with mags prior to shutting off the electric switches which power    all of the avionics.  All    traditional GA checklists I've seen specify turning off the avionics master    (or individual components) prior to shutting down the engine to presumably    prevent damage from a potential power spike.  Any technical reason for the    Nanchang to be    different?   

    

Dave

 	  Quote: 	
		  



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[b]

radiopicture

Joined: 23 Jun 2008
Posts: 263

Posted: Sun Sep 26, 2010 5:36 pm Post subject: Engine/avionics shutdown procedure

Im the Yak-52, I turn off all of the left side switches except engine instruments (which I never turn off) during the pre-shutdown run-up. 

On Sep 26, 2010, at 5:58 PM, KingCJ6(at)aol.com (KingCJ6(at)aol.com) wrote:

[quote]  Most Nanchang checklists specify shutting the engine down with mags prior to shutting off the electric switches which power all of the avionics.  All traditional GA checklists I've seen specify turning off the avionics master (or individual components) prior to shutting down the engine to presumably prevent damage from a potential power spike.  Any technical reason for the Nanchang to be different?

 

Dave



  	  Quote: 	
		  



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[b]

mark.bitterlich(at)navy.m
Guest

Posted: Sun Sep 26, 2010 7:08 pm Post subject: Engine/avionics shutdown procedure

Steve, that is yet another good question.    Most of us these days are using gell cell batteries so checking the specific gravity of the electrolyte is just not do-able.  

 

So, another method is easy and very simple but it is not something you can tape to a calibration table per se. 

 

Batteries that are in "good shape" (a very loose term) will hold their voltage for awhile when you put a load on them.  If you notice, most of those gell cells we stick in there have an amp/hour rating.  What this means is that you can draw that number of amps continuously for one hour.  You can do some math with this and interpolate accordingly.  You can get pretty fancy with this if you want to. 

 

But the plain and simple method is pretty straight forward.  Most YAK's and I believe CJ's, have a voltage and amp meter built into the aircraft.  Turn on the electrical master.  BEFORE you go flying.  Look at the voltage.  It should be around 24 volts or so, maybe as high as 25.  If it down around 22 vdc, your eyebrows should start going up in alarm.  At this point, start turning on anything that draws a lot of current.  Landing lights would be good.  So is Pitot Heat.  Radios, no.   As you turn this stuff on, look at that battery voltage.  Is it HOLDING?  Or is it dropping like a stone?   If you had 22-23 VDC and you turn on Pitot Heat and it drops to 20 vdc... HMMM!!!   If you then turn on a landing light.... and it drops to 16-18 volts OR LESS, then it is time to replace the batteries.  A much better way is to put a good digital meter on the battery terminals themselves when you do this by the way and read the voltage with that.  

 

Do not check them and come back and say: HEY, ONE IS 12 VOLTS AND ONE IS 6 VOLTS, SO I AM ONLY GOING TO REPLACE ONE!!!   Yeah, that will work, but it it is penny wise and dollar foolish.  You want all the cells in the two 12 volt batteries that you connect in series to get 24 volts to be BALANCED.  If they are NOT balanced, then the current to charge the WEAK cells has to flow through the GOOD cells to charge the weak ones.  This ends up over-charging the GOOD cells and causing them to vent gas.  Which makes them go bad.  Quickly.  

 

SO ... try to replace them in PAIRS.  

 

I don't want to sound like an advertisement, but I really am impressed with Battery-Minder battery chargers.  They not only have a temp. sensor that keeps from overheating charging batteries, but also, after the batteries are charged, they put a 3 Mhz blast pulse into the batteries that works to turn battery sulfate off the plates and put it back into solution, or.... "gell" that extends the life of the battery PLUS they check the status of the battery automatically.  They are not cheap.  But.... They are worth every cent in my opinion.   I own THREE of them.  

 

The YAK and CJ's aircraft for the most part do not use electrical starters (Some rare models excepted).  An electrical starter is a quick test for a battery.   I.E.  Think of your car when it gets cold.  Bad battery?  You don't start, so you replace it.  We do not have that huge electrical draw that the car starter represents... so our batteries kind of go bad in a sneaky way.  Leading to issues with the reverse current relay.   

 

Just had a nice person with a YAK-18T that this just happened to.  Hope this explains what is happening, and how to keep an eye out for it.  

 

Mark

 



________________________________



From: owner-yak-list-server(at)matronics.com on behalf of Steven Johnson

Sent: Sun 9/26/2010 8:18 PM

To: yak-list(at)matronics.com

Subject: RE: Engine/avionics shutdown procedure






Mark, how does one check the batteries properly?



Steve Johnson

Yak 52 N9900X 0B5

413 522-1130 Cell

--

wlannon(at)persona.ca
Guest

Posted: Sun Sep 26, 2010 9:01 pm Post subject: Engine/avionics shutdown procedure

Thanks Mark;



Great information. Do you have a recommendation for which Battery- Minder to 

get?



Walt

---

tigeryak18t

Joined: 26 Sep 2009
Posts: 233
Location: PARIS FRANCE

Posted: Sun Sep 26, 2010 9:55 pm Post subject: Engine/avionics shutdown procedure

Yeah

I also would like to have one or plus recommendation please



Regards



Didier Blouzard

+33 6 2424 3672



Le 27 sept. 2010 Ã  06:41, Walter Lannon <wlannon(at)persona.ca> a Ã©crit :



[quote] 

 

 Thanks Mark;

 

 Great information. Do you have a recommendation for which Battery- Minder to get?

 

 Walt

 ---

_________________
Didier Tiger YAK18T
Member of Commemorative Air Force
French Wing

mark.bitterlich(at)navy.m
Guest

Posted: Mon Sep 27, 2010 5:12 pm Post subject: Engine/avionics shutdown procedure

For 24 volt systems, I recommend one of two.  

 

For those that want to just plug it in and walk away, this one:

http://www.thebatteryminder.com/24vs3aircraftbatteryminder-p-83.html

 

For those that want more manual control, then this one: 

http://www.thebatteryminder.com/24vs2aircraftbatteryminder-p-79.html

 

Both are good.  Both cost around $180.  

 

There are other models for 220 volt applications for overseas.  Just check the web site.  

 

I use other models for 12 volt automobile systems.  I love these things.  They really work.  But, you need to form your own opinion.  That said, I can walk around the airport at New Bern these days and see them ALL over the place.   There are really not battery "chargers" per se.  They are battery MAINTAINERS.  You leave them plugged into the battery on your aircraft 24/7.  I have actually made an external cannon plug on my airplanes so that I can just plug them in and walk away after flying.  I don't like to influence others on what to buy commercially.  I do not like to put my name to things like that.  But... Walt... I would never steer you wrong Sir, and I think you will REALLY like these things.  If not.., I can always use another one.  If you are not happy with it, call me up and I will buy it from you at full price.  

 

Mark

 

 



________________________________



From: owner-yak-list-server(at)matronics.com on behalf of Walter Lannon

Sent: Mon 9/27/2010 12:41 AM

: yak-list(at)matronics.com

Subject: Re: Engine/avionics shutdown procedure






Thanks Mark;



Great information. Do you have a recommendation for which Battery- Minder to

get?



Walt

---

mark.bitterlich(at)navy.m
Guest

Posted: Mon Sep 27, 2010 5:34 pm Post subject: Engine/avionics shutdown procedure

On second thought, to be absolutely sure you will be happy, get this one. 

 

http://www.thebatteryminder.com/24vs2aircraftbatteryminder-p-79.html

 

 

 

 

 

Mark

 

 

 

 

 



________________________________



From: owner-yak-list-server(at)matronics.com on behalf of Walter Lannon

Sent: Mon 9/27/2010 12:41 AM

To: yak-list(at)matronics.com

Subject: Re: Engine/avionics shutdown procedure






Thanks Mark;



Great information. Do you have a recommendation for which Battery- Minder to

get?



Walt

---

wlannon(at)persona.ca
Guest

Posted: Mon Sep 27, 2010 7:02 pm Post subject: Engine/avionics shutdown procedure

Thanks mark;



Thats the one I will get.

Don't have my batteries yet but leaning toward the Panasonic LC-X1228P (2 

ea.) which is valve regulated lead acid.

I used these in my last CJ restoration, at the customers's request and they 

are still going strong after at least 8 years. They are a bit heavy at 24 lb 

ea. (and pricey) but fit nicely into the CJ battery box.

This time it's my CJ so I would really appreciate your thoughts on the 

battery.



Cheers;

Walt

---

stephenmorrey(at)gmail.co
Guest

Posted: Tue Sep 28, 2010 12:25 am Post subject: Engine/avionics shutdown procedure

On a yak during low  idle the generator light will go on indicating

the generator is not operating (or at least not charging to some

level)  when the rpm is low.  Should I assume that stress to the

avionics can also happen just during idle when the generator cycles on

and off as indicated by the generator light or is the light just an

indication of the level of output of the generator and hence the same

effect as seen in shut down is not likely?  steve



On Sun, Sep 26, 2010 at 6:28 PM, Bitterlich, Mark G CIV Det Cherry

Point, MALS-14 64E <mark.bitterlich(at)navy.mil> wrote:

 	  Quote: 	
		   



 Dave,  That is a very good point.  Again, I must caution anyone reading this that I have never worked on a CJ, though I am aware that they have two types of control systems for the generator.



 I believe there is a solid state controller and also a older more traditional style controller.  Whatever.  Let's just cut to the chase.  It would be much smarter to turn off your avionics before killing the mags (engine) if you have anything in there worth worrying about.



 Why?  Because on any engine that has a generator, when you kill the mags, the generator stops turning.  As it slows down, the generator voltage will drop below the battery voltage.  When this happens, current stops flowing from the generator to the battery, and instead flows from the battery to the generator.  This is called "Reverse Current".  In all aircraft with real generators, there is some device that is in there to prevent this.



 Or at least... normally the way it works is that as current STARTS flowing from the battery to the generator,  There is usually some kind of "set point" where this relay operates and then DISCONNECTS the generator from the aircrafts electrical bus.



 Here is the problem.  If your battery is not in just TIP TOP condition... which by the way, many of our batteries are not... because we fail to CHECK THEM PROPERLY.....  what will happen is that when the engine starts slowing down to a stop after you kill the mags, reverse current will start to flow.   If your batteries are not up to snuff, then the battery output voltage will drop as the current going to the generator increases.



 Hopefully, eventually the current will rise high enough to where the reverse current RELAY operates and then disconnects the generator.  However, that does not HAVE to happen right away when it should.  If the batteries are WEAK, then this chain of events will happen much more SLOWYLY.  And that is a bad bad thing, because then your battery voltage will drop way down below 24 volts and maybe as low as 14-16 VDC.  Avionics systems really don't like voltage spikes like this.  Going down, or going up  They just don't like that kind of thing. Will it cause instant failure of your avionics?  NO.  Is it asking for a failure?  YES.   Shut off your avionics before killing the engine is the smart thing to do, regardless of what any check list currently says.



 Mark Bitterlich



 p.s.  I do not bother to follow my own advice, but then I check my batteries carefully all the time, and I also am only powering one Russian radio.  But, I really should, and if I had any Avionics that cost more than a few hundred, I would be religious about it.



 ________________________________



 From: owner-yak-list-server(at)matronics.com on behalf of KingCJ6(at)aol.com

 Sent: Sun 9/26/2010 5:58 PM

 To: yak-list(at)matronics.com

 Subject: Engine/avionics shutdown procedure



 Most Nanchang checklists specify shutting the engine down with mags prior to shutting off the electric switches which power all of the avionics.  All traditional GA checklists I've seen specify turning off the avionics master (or individual components) prior to shutting down the engine to presumably prevent damage from a potential power spike.  Any technical reason for the Nanchang to be different?



 Dave

yakplt(at)yahoo.com
Guest

Posted: Tue Sep 28, 2010 10:52 am Post subject: Engine/avionics shutdown procedure

I use those same batteries in my UTVA-66 and they work extremely well.  Yes, a pair of them are very heavy, but they ought to work extrememly well.  I use the battery charger you are looking at on them and it works perfectly.  Suggest installing the temp sensor and also making a way to connect the charger easily after flight.  



Mark

--- On Mon, 9/27/10, Walter Lannon <wlannon(at)persona.ca> wrote:



[quote] From: Walter Lannon <wlannon(at)persona.ca>

 Subject: Re: Engine/avionics shutdown procedure

 To: yak-list(at)matronics.com

 Date: Monday, September 27, 2010, 10:59 PM

 

 Walter Lannon <wlannon(at)persona.ca>

 

 Thanks mark;

 

 Thats the one I will get.

 Don't have my batteries yet but leaning toward the

 Panasonic LC-X1228P (2 

 ea.) which is valve regulated lead acid.

 I used these in my last CJ restoration, at the customers's

 request and they 

 are still going strong after at least 8 years. They are a

 bit heavy at 24 lb 

 ea. (and pricey) but fit nicely into the CJ battery box.

 This time it's my CJ so I would really appreciate your

 thoughts on the 

 battery.

 

 Cheers;

 Walt

 ---

dougsappllc(at)gmail.com
Guest

Posted: Tue Sep 28, 2010 11:55 am Post subject: Engine/avionics shutdown procedure

Mark,I have been using the dry cell batteries for a few years now and like them, will the same "minder" work for the dry cell as the gel or led acid batteries?  

Doug



 On Mon, Sep 27, 2010 at 6:08 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)> wrote:

[quote] --> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>

 

 For 24 volt systems, I recommend one of two.

 

 For those that want to just plug it in and walk away, this one:

 http://www.thebatteryminder.com/24vs3aircraftbatteryminder-p-83.html

 

 For those that want more manual control, then this one:

 http://www.thebatteryminder.com/24vs2aircraftbatteryminder-p-79.html

 

 Both are good.  Both cost around $180.

 

 There are other models for 220 volt applications for overseas.  Just check the web site.

 

 I use other models for 12 volt automobile systems.  I love these things.  They really work.  But, you need to form your own opinion.  That said, I can walk around the airport at New Bern these days and see them ALL over the place.   There are really not battery "chargers" per se.  They are battery MAINTAINERS.  You leave them plugged into the battery on your aircraft 24/7.  I have actually made an external cannon plug on my airplanes so that I can just plug them in and walk away after flying.  I don't like to influence others on what to buy commercially.  I do not like to put my name to things like that.  But... Walt... I would never steer you wrong Sir, and I think you will REALLY like these things.  If not.., I can always use another one.  If you are not happy with it, call me up and I will buy it from you at full price.

  

 Mark

 

 

 

 ________________________________

 

 From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) on behalf of Walter Lannon

 Sent: Mon 9/27/2010 12:41 AM

 : yak-list(at)matronics.com (yak-list(at)matronics.com)

 Subject: Re: Engine/avionics shutdown procedure

 

 

 

 --> Yak-List message posted by: Walter Lannon <wlannon(at)persona.ca (wlannon(at)persona.ca)>

 

 Thanks Mark;

 

 Great information. Do you have a recommendation for which Battery- Minder to

 get?

 

 Walt

 ---

yakplt(at)yahoo.com
Guest

Posted: Tue Sep 28, 2010 11:55 am Post subject: Engine/avionics shutdown procedure

You are again correct. 

If everything is working absolutely perfectly and your batteries have good capacity, when the engine is brought down to idle, the generator output will go below 28 volts, reverse current will start to flow, the reverse current relay will sense this and the main generator contactor will disengage and the generator will no longer be connected to the aircraft electrical system.  So in reality ... this does not happen as you shut down the mags, it actually should happen when you bring the power back to idle.  

Again, if everything is working perfectly at this point, if you shut off the engine with the mag switch, at this point the generator is already disconnected and there should be no load change or voltage surge to the avionics.  

This may sound contrary to what I was saying before, but I tried to cover it in the other explanation.  

A gent with a YAK-18T recently had an issue where his generator light did not come on all the time at idle.  When he killed the engine with the mags, it then DID come on as the engine came to a stop.  In this case, the gent had weak batteries.  When he brought the engine down to idle, the batteries were so weak that they could not provide enough reverse current to cause the reverse current relay to do it's job.  The result was that the main contactor for the aircraft stayed closed, and kept the generator connected to the aircraft electrical bus. 

During this period of time, main bus electrical voltage sagged down to between 12 and 14 volts.  Eventually the generator came to a stop and there was enough current to cause the reverse current relay to open, thus disengaging the main contactor to the generator, and the load went away and battery voltage jumped back up to 20 volts or so. 

This is the kind of nonsense I was trying to talk about.  

However, if your aircraft battery is in good shape and every part in the aircraft is working properly, you should not see a really large voltage spike as the generator comes on and off line.  Basically, if everything is working just perfectly, the generator will be connected to the aircraft electrical bus when it's output is a few volts above that of the battery.  There will be a minor 2-3 volt jump in battery voltage as the thing connects, but that is usually not something to worry about.  

When the engine RPM is lowered and the generator voltage drops, current flow will increase going back to the generator.  This is where if your batteries are not working right that you will run into trouble.  

In the end, I just think it is a good idea to get any expensive avionics turned off as soon as possible to avoid any kind of voltage spikes or lags.  But as I said, if you keep your batteries in perfect working order and you have a good reverse current relay ... all should be well.  

Mark

--- On Tue, 9/28/10, Stephen Morrey <stephenmorrey(at)gmail.com> wrote:

 	  Quote: 	
		   From: Stephen Morrey <stephenmorrey(at)gmail.com>

 Subject: Re: Engine/avionics shutdown procedure

 To: yak-list(at)matronics.com

 Date: Tuesday, September 28, 2010, 4:16 AM

 Stephen Morrey <stephenmorrey(at)gmail.com>

 On a yak during low  idle the generator light will go

 on indicating

 the generator is not operating (or at least not charging to

 some

 level)  when the rpm is low.  Should I assume

 that stress to the

 avionics can also happen just during idle when the

 generator cycles on

 and off as indicated by the generator light or is the light

 just an

 indication of the level of output of the generator and

 hence the same

 effect as seen in shut down is not likely?  steve

 On Sun, Sep 26, 2010 at 6:28 PM, Bitterlich, Mark G CIV Det

 Cherry

 Point, MALS-14 64E <mark.bitterlich(at)navy.mil>

 wrote:

 > 

 CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>

 >

 > Dave,  That is a very good point.  Again, I must

 caution anyone reading this that I have never worked on a

 CJ, though I am aware that they have two types of control

 systems for the generator.

 >

 > I believe there is a solid state controller and also a

 older more traditional style controller.  Whatever.  Let's

 just cut to the chase.  It would be much smarter to turn

 off your avionics before killing the mags (engine) if you

 have anything in there worth worrying about.

 >

 > Why?  Because on any engine that has a generator,

 when you kill the mags, the generator stops turning.  As it

 slows down, the generator voltage will drop below the

 battery voltage.  When this happens, current stops flowing

 from the generator to the battery, and instead flows from

 the battery to the generator.  This is called "Reverse

 Current".  In all aircraft with real generators, there is

 some device that is in there to prevent this.

 >

 > Or at least... normally the way it works is that as

 current STARTS flowing from the battery to the generator,

  There is usually some kind of "set point" where this relay

 operates and then DISCONNECTS the generator from the

 aircrafts electrical bus.

 >

 > Here is the problem.  If your battery is not in just

 TIP TOP condition... which by the way, many of our batteries

 are not... because we fail to CHECK THEM PROPERLY.....

  what will happen is that when the engine starts slowing

 down to a stop after you kill the mags, reverse current will

 start to flow.   If your batteries are not up to snuff,

 then the battery output voltage will drop as the current

 going to the generator increases.

 >

 > Hopefully, eventually the current will rise high

 enough to where the reverse current RELAY operates and then

 disconnects the generator.  However, that does not HAVE to

 happen right away when it should.  If the batteries are

 WEAK, then this chain of events will happen much more

 SLOWYLY.  And that is a bad bad thing, because then your

 battery voltage will drop way down below 24 volts and maybe

 as low as 14-16 VDC.  Avionics systems really don't like

 voltage spikes like this.  Going down, or going up  They

 just don't like that kind of thing. Will it cause instant

 failure of your avionics?  NO.  Is it asking for a

 failure?  YES.   Shut off your avionics before killing the

 engine is the smart thing to do, regardless of what any

 check list currently says.

 >

 > Mark Bitterlich

 >

 > p.s.  I do not bother to follow my own advice, but

 then I check my batteries carefully all the time, and I also

 am only powering one Russian radio.  But, I really should,

 and if I had any Avionics that cost more than a few hundred,

 I would be religious about it.

 >

 > ________________________________

 >

 > From: owner-yak-list-server(at)matronics.com

 on behalf of KingCJ6(at)aol.com

 > Sent: Sun 9/26/2010 5:58 PM

 > To: yak-list(at)matronics.com

 > Subject: Engine/avionics shutdown procedure

 >

 >

 >

 > Most Nanchang checklists specify shutting the engine

 down with mags prior to shutting off the electric switches

 which power all of the avionics.  All traditional GA

 checklists I've seen specify turning off the avionics master

 (or individual components) prior to shutting down the engine

 to presumably prevent damage from a potential power spike.

  Any technical reason for the Nanchang to be different?

 >

 >

 >

 > Dave

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tigeryak18t

Joined: 26 Sep 2009
Posts: 233
Location: PARIS FRANCE

Posted: Tue Sep 28, 2010 12:13 pm Post subject: Engine/avionics shutdown procedure

Hi gents,

for my point of view, it doesn't do anything bad to turn off all the unnecessary electrical loads after landing and that's just what I do.

When landing the engine is at low boost but not low RPM. I imagine  that's why we don't have the generator lamp coming on. After landing, I turn off all unnecessary electrical consumers like the gyros and the converter, the radio and transponder and all the rest.

  The only switches that are staying on are the five first : Battery, Generator, Ignition, Motor and landing instruments.

The rest is off as soon as the speed is controlled or just after having vacated the airstrip.

 I would enjoy any comments concerning this...way of doing.....is it good or bad for the system..???

Thanks a lot and fly safe

Didier 

2010/9/28 Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)>

   	  Quote: 	
		  --> Yak-List message posted by: Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)>

 You are again correct.

 If everything is working absolutely perfectly and your batteries have good capacity, when the engine is brought down to idle, the generator output will go below 28 volts, reverse current will start to flow, the reverse current relay will sense this and the main generator contactor will disengage and the generator will no longer be connected to the aircraft electrical system.  So in reality ... this does not happen as you shut down the mags, it actually should happen when you bring the power back to idle.

 Again, if everything is working perfectly at this point, if you shut off the engine with the mag switch, at this point the generator is already disconnected and there should be no load change or voltage surge to the avionics.

 This may sound contrary to what I was saying before, but I tried to cover it in the other explanation.

 A gent with a YAK-18T recently had an issue where his generator light did not come on all the time at idle.  When he killed the engine with the mags, it then DID come on as the engine came to a stop.  In this case, the gent had weak batteries.  When he brought the engine down to idle, the batteries were so weak that they could not provide enough reverse current to cause the reverse current relay to do it's job.  The result was that the main contactor for the aircraft stayed closed, and kept the generator connected to the aircraft electrical bus.

 During this period of time, main bus electrical voltage sagged down to between 12 and 14 volts.  Eventually the generator came to a stop and there was enough current to cause the reverse current relay to open, thus disengaging the main contactor to the generator, and the load went away and battery voltage jumped back up to 20 volts or so.

 This is the kind of nonsense I was trying to talk about.

 However, if your aircraft battery is in good shape and every part in the aircraft is working properly, you should not see a really large voltage spike as the generator comes on and off line.  Basically, if everything is working just perfectly, the generator will be connected to the aircraft electrical bus when it's output is a few volts above that of the battery.  There will be a minor 2-3 volt jump in battery voltage as the thing connects, but that is usually not something to worry about.

 When the engine RPM is lowered and the generator voltage drops, current flow will increase going back to the generator.  This is where if your batteries are not working right that you will run into trouble.

 In the end, I just think it is a good idea to get any expensive avionics turned off as soon as possible to avoid any kind of voltage spikes or lags.  But as I said, if you keep your batteries in perfect working order and you have a good reverse current relay ... all should be well.

 Mark

 --- On Tue, 9/28/10, Stephen Morrey <stephenmorrey(at)gmail.com (stephenmorrey(at)gmail.com)> wrote:

 > From: Stephen Morrey <stephenmorrey(at)gmail.com (stephenmorrey(at)gmail.com)>

 > Subject: Re: Engine/avionics shutdown procedure

 > To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 > Date: Tuesday, September 28, 2010, 4:16 AM

 > --> Yak-List message posted by:

 > Stephen Morrey <stephenmorrey(at)gmail.com (stephenmorrey(at)gmail.com)>

 >

 > On a yak during low  idle the generator light will go

 > on indicating

 > the generator is not operating (or at least not charging to

 > some

 > level)  when the rpm is low.  Should I assume

 > that stress to the

 > avionics can also happen just during idle when the

 > generator cycles on

 > and off as indicated by the generator light or is the light

 > just an

 > indication of the level of output of the generator and

 > hence the same

 > effect as seen in shut down is not likely?  steve

 >

 > On Sun, Sep 26, 2010 at 6:28 PM, Bitterlich, Mark G CIV Det

 > Cherry

 > Point, MALS-14 64E <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>

 > wrote:

 > > --> Yak-List message posted by: "Bitterlich, Mark G

 > CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>

 > >

 > > Dave,  That is a very good point.  Again, I must

 > caution anyone reading this that I have never worked on a

 > CJ, though I am aware that they have two types of control

 > systems for the generator.

 > >

 > > I believe there is a solid state controller and also a

 > older more traditional style controller.  Whatever.  Let's

 > just cut to the chase.  It would be much smarter to turn

 > off your avionics before killing the mags (engine) if you

 > have anything in there worth worrying about.

 > >

 > > Why?  Because on any engine that has a generator,

 > when you kill the mags, the generator stops turning.  As it

 > slows down, the generator voltage will drop below the

 > battery voltage.  When this happens, current stops flowing

 > from the generator to the battery, and instead flows from

 > the battery to the generator.  This is called "Reverse

 > Current".  In all aircraft with real generators, there is

 > some device that is in there to prevent this.

 > >

 > > Or at least... normally the way it works is that as

 > current STARTS flowing from the battery to the generator,

 >  There is usually some kind of "set point" where this relay

 > operates and then DISCONNECTS the generator from the

 > aircrafts electrical bus.

 > >

 > > Here is the problem.  If your battery is not in just

 > TIP TOP condition... which by the way, many of our batteries

 > are not... because we fail to CHECK THEM PROPERLY.....

 >  what will happen is that when the engine starts slowing

 > down to a stop after you kill the mags, reverse current will

 > start to flow.   If your batteries are not up to snuff,

 > then the battery output voltage will drop as the current

 > going to the generator increases.

 > >

 > > Hopefully, eventually the current will rise high

 > enough to where the reverse current RELAY operates and then

 > disconnects the generator.  However, that does not HAVE to

 > happen right away when it should.  If the batteries are

 > WEAK, then this chain of events will happen much more

 > SLOWYLY.  And that is a bad bad thing, because then your

 > battery voltage will drop way down below 24 volts and maybe

 > as low as 14-16 VDC.  Avionics systems really don't like

 > voltage spikes like this.  Going down, or going up  They

 > just don't like that kind of thing. Will it cause instant

 > failure of your avionics?  NO.  Is it asking for a

 > failure?  YES.   Shut off your avionics before killing the

 > engine is the smart thing to do, regardless of what any

 > check list currently says.

 > >

 > > Mark Bitterlich

 > >

 > > p.s.  I do not bother to follow my own advice, but

 > then I check my batteries carefully all the time, and I also

 > am only powering one Russian radio.  But, I really should,

 > and if I had any Avionics that cost more than a few hundred,

 > I would be religious about it.

 > >

 > > ________________________________

 > >

 > > From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)

 > on behalf of KingCJ6(at)aol.com (KingCJ6(at)aol.com)

 > > Sent: Sun 9/26/2010 5:58 PM

 > > To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 > > Subject: Engine/avionics shutdown procedure

 > >

 > >

 > >

 > > Most Nanchang checklists specify shutting the engine

 > down with mags prior to shutting off the electric switches

 > which power all of the avionics.  All traditional GA

 > checklists I've seen specify turning off the avionics master

 > (or individual components) prior to shutting down the engine

 > to presumably prevent damage from a potential power spike.

 >  Any technical reason for the Nanchang to be different?

 > >

 > >

 > >

 > > Dave

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 >

 >

 > Forum -

 > FAQ,

 >    - MATRONICS WEB FORUMS -

 > List Contribution Web Site -

 >               -Matt

 > Dralle, List Admin.

 >

 >

 >

 >

 ===========

 rget="_blank">http://www.matronics.com/Navigator?Yak-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

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

 ===========

-- 

Didier BLOUZARD

didier.blouzard(at)gmail.com (didier.blouzard(at)gmail.com)

0624243672

  [quote][b]

_________________
Didier Tiger YAK18T
Member of Commemorative Air Force
French Wing

mark.bitterlich(at)navy.m
Guest

Posted: Tue Sep 28, 2010 2:22 pm Post subject: Engine/avionics shutdown procedure

Doug, 

 

Honestly, you caught me competely off guard.   I have no idea what a "dry cell" battery is, and thus I really can not answer your question.  Could you give me a make and model number please? 

 

Mark

 



________________________________



From: owner-yak-list-server(at)matronics.com on behalf of doug sapp

Sent: Tue 9/28/2010 2:51 PM

To: yak-list(at)matronics.com

Subject: Re: Engine/avionics shutdown procedure

Mark, 

I have been using the dry cell batteries for a few years now and like them, will the same "minder" work for the dry cell as the gel or led acid batteries?  



Doug

On Mon, Sep 27, 2010 at 6:08 PM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E <mark.bitterlich(at)navy.mil> wrote:

	

	

	For 24 volt systems, I recommend one of two.

	

	For those that want to just plug it in and walk away, this one:

	http://www.thebatteryminder.com/24vs3aircraftbatteryminder-p-83.html

	

	For those that want more manual control, then this one:

	http://www.thebatteryminder.com/24vs2aircraftbatteryminder-p-79.html

	

	Both are good.  Both cost around $180.

	

	There are other models for 220 volt applications for overseas.  Just check the web site.

	

	I use other models for 12 volt automobile systems.  I love these things.  They really work.  But, you need to form your own opinion.  That said, I can walk around the airport at New Bern these days and see them ALL over the place.   There are really not battery "chargers" per se.  They are battery MAINTAINERS.  You leave them plugged into the battery on your aircraft 24/7.  I have actually made an external cannon plug on my airplanes so that I can just plug them in and walk away after flying.  I don't like to influence others on what to buy commercially.  I do not like to put my name to things like that.  But... Walt... I would never steer you wrong Sir, and I think you will REALLY like these things.  If not.., I can always use another one.  If you are not happy with it, call me up and I will buy it from you at full price.

	

	Mark

	

	

	

	________________________________

	

	From: owner-yak-list-server(at)matronics.com on behalf of Walter Lannon

	Sent: Mon 9/27/2010 12:41 AM

	: yak-list(at)matronics.com

	Subject: Re: Engine/avionics shutdown procedure

	

	

	

	

	

	Thanks Mark;

	

	Great information. Do you have a recommendation for which Battery- Minder to

	get?

	

	Walt

	---

radiopicture

Joined: 23 Jun 2008
Posts: 263

Posted: Tue Sep 28, 2010 6:40 pm Post subject: Engine/avionics shutdown procedure

For what it's worth, the procedure I use (discussing electrical only):

I have a pretty much stock Yak-52. The only two electrical additions are a transponder and a hard-wire for a Garmin 696. They are both wired right to the master switch 

with in-line fuses. 

I always leave the engine instrument switch on, as I pretty much always need those any time the master is on.	

I check mags off, usually on both cockpits. Before I charge the system side (left side primer on the 52), I turn on the master so I can see if fuel pressure is building. Then I turn master back off and do whatever priming (if any) I'm going to do before entering the cockpit.

I turn the rear cockpit mags to 1+2. After strapping in, I turn the master on again, and my GPS off (which turned on when I turned on the master). Then generator and ignition. After start, I check instruments and then turn on all (left panel) switches and press the gyro button (OK, so that's not electric). GPS on, transponder on via the standby button (will go to ALT on takeoff, which I think is a cool feature). 

(Fly)

When I am shutting down, I run it up to 70%, and while that's going on, I shut off all left panel switches, then GPS and transponder. Then retard to 40% for a second or so, then fully retarded, then mags off, then master-generator-ignition off. 

Re-check switches before leaving hangar.

On Sep 28, 2010, at 4:10 PM, Didier Blouzard wrote:

 	  Quote: 	
		  Hi gents,

for my point of view, it doesn't do anything bad to turn off all the unnecessary electrical loads after landing and that's just what I do.

When landing the engine is at low boost but not low RPM. I imagine  that's why we don't have the generator lamp coming on. After landing, I turn off all unnecessary electrical consumers like the gyros and the converter, the radio and transponder and all the rest.

 The only switches that are staying on are the five first : Battery, Generator, Ignition, Motor and landing instruments.

The rest is off as soon as the speed is controlled or just after having vacated the airstrip.

 I would enjoy any comments concerning this...way of doing.....is it good or bad for the system..???

Thanks a lot and fly safe

Didier 

2010/9/28 Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)>

  	  Quote: 	
		  --> Yak-List message posted by: Yak Pilot <yakplt(at)yahoo.com (yakplt(at)yahoo.com)>

 You are again correct.

 If everything is working absolutely perfectly and your batteries have good capacity, when the engine is brought down to idle, the generator output will go below 28 volts, reverse current will start to flow, the reverse current relay will sense this and the main generator contactor will disengage and the generator will no longer be connected to the aircraft electrical system.  So in reality ... this does not happen as you shut down the mags, it actually should happen when you bring the power back to idle.

 Again, if everything is working perfectly at this point, if you shut off the engine with the mag switch, at this point the generator is already disconnected and there should be no load change or voltage surge to the avionics.

 This may sound contrary to what I was saying before, but I tried to cover it in the other explanation.

 A gent with a YAK-18T recently had an issue where his generator light did not come on all the time at idle.  When he killed the engine with the mags, it then DID come on as the engine came to a stop.  In this case, the gent had weak batteries.  When he brought the engine down to idle, the batteries were so weak that they could not provide enough reverse current to cause the reverse current relay to do it's job.  The result was that the main contactor for the aircraft stayed closed, and kept the generator connected to the aircraft electrical bus.

 During this period of time, main bus electrical voltage sagged down to between 12 and 14 volts.  Eventually the generator came to a stop and there was enough current to cause the reverse current relay to open, thus disengaging the main contactor to the generator, and the load went away and battery voltage jumped back up to 20 volts or so.

 This is the kind of nonsense I was trying to talk about.

 However, if your aircraft battery is in good shape and every part in the aircraft is working properly, you should not see a really large voltage spike as the generator comes on and off line.  Basically, if everything is working just perfectly, the generator will be connected to the aircraft electrical bus when it's output is a few volts above that of the battery.  There will be a minor 2-3 volt jump in battery voltage as the thing connects, but that is usually not something to worry about.

 When the engine RPM is lowered and the generator voltage drops, current flow will increase going back to the generator.  This is where if your batteries are not working right that you will run into trouble.

 In the end, I just think it is a good idea to get any expensive avionics turned off as soon as possible to avoid any kind of voltage spikes or lags.  But as I said, if you keep your batteries in perfect working order and you have a good reverse current relay ... all should be well.

 Mark

 --- On Tue, 9/28/10, Stephen Morrey <stephenmorrey(at)gmail.com (stephenmorrey(at)gmail.com)> wrote:

 > From: Stephen Morrey <stephenmorrey(at)gmail.com (stephenmorrey(at)gmail.com)>

 > Subject: Re: Engine/avionics shutdown procedure

 > To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 > Date: Tuesday, September 28, 2010, 4:16 AM

 > --> Yak-List message posted by:

 > Stephen Morrey <stephenmorrey(at)gmail.com (stephenmorrey(at)gmail.com)>

 >

 > On a yak during low  idle the generator light will go

 > on indicating

 > the generator is not operating (or at least not charging to

 > some

 > level)  when the rpm is low.  Should I assume

 > that stress to the

 > avionics can also happen just during idle when the

 > generator cycles on

 > and off as indicated by the generator light or is the light

 > just an

 > indication of the level of output of the generator and

 > hence the same

 > effect as seen in shut down is not likely?  steve

 >

 > On Sun, Sep 26, 2010 at 6:28 PM, Bitterlich, Mark G CIV Det

 > Cherry

 > Point, MALS-14 64E <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>

 > wrote:

 > > --> Yak-List message posted by: "Bitterlich, Mark G

 > CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>

 > >

 > > Dave,  That is a very good point.  Again, I must

 > caution anyone reading this that I have never worked on a

 > CJ, though I am aware that they have two types of control

 > systems for the generator.

 > >

 > > I believe there is a solid state controller and also a

 > older more traditional style controller.  Whatever.  Let's

 > just cut to the chase.  It would be much smarter to turn

 > off your avionics before killing the mags (engine) if you

 > have anything in there worth worrying about.

 > >

 > > Why?  Because on any engine that has a generator,

 > when you kill the mags, the generator stops turning.  As it

 > slows down, the generator voltage will drop below the

 > battery voltage.  When this happens, current stops flowing

 > from the generator to the battery, and instead flows from

 > the battery to the generator.  This is called "Reverse

 > Current".  In all aircraft with real generators, there is

 > some device that is in there to prevent this.

 > >

 > > Or at least... normally the way it works is that as

 > current STARTS flowing from the battery to the generator,

 >  There is usually some kind of "set point" where this relay

 > operates and then DISCONNECTS the generator from the

 > aircrafts electrical bus.

 > >

 > > Here is the problem.  If your battery is not in just

 > TIP TOP condition... which by the way, many of our batteries

 > are not... because we fail to CHECK THEM PROPERLY.....

 >  what will happen is that when the engine starts slowing

 > down to a stop after you kill the mags, reverse current will

 > start to flow.   If your batteries are not up to snuff,

 > then the battery output voltage will drop as the current

 > going to the generator increases.

 > >

 > > Hopefully, eventually the current will rise high

 > enough to where the reverse current RELAY operates and then

 > disconnects the generator.  However, that does not HAVE to

 > happen right away when it should.  If the batteries are

 > WEAK, then this chain of events will happen much more

 > SLOWYLY.  And that is a bad bad thing, because then your

 > battery voltage will drop way down below 24 volts and maybe

 > as low as 14-16 VDC.  Avionics systems really don't like

 > voltage spikes like this.  Going down, or going up  They

 > just don't like that kind of thing. Will it cause instant

 > failure of your avionics?  NO.  Is it asking for a

 > failure?  YES.   Shut off your avionics before killing the

 > engine is the smart thing to do, regardless of what any

 > check list currently says.

 > >

 > > Mark Bitterlich

 > >

 > > p.s.  I do not bother to follow my own advice, but

 > then I check my batteries carefully all the time, and I also

 > am only powering one Russian radio.  But, I really should,

 > and if I had any Avionics that cost more than a few hundred,

 > I would be religious about it.

 > >

 > > ________________________________

 > >

 > > From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)

 > on behalf of KingCJ6(at)aol.com (KingCJ6(at)aol.com)

 > > Sent: Sun 9/26/2010 5:58 PM

 > > To: yak-list(at)matronics.com (yak-list(at)matronics.com)

 > > Subject: Engine/avionics shutdown procedure

 > >

 > >

 > >

 > > Most Nanchang checklists specify shutting the engine

 > down with mags prior to shutting off the electric switches

 > which power all of the avionics.  All traditional GA

 > checklists I've seen specify turning off the avionics master

 > (or individual components) prior to shutting down the engine

 > to presumably prevent damage from a potential power spike.

 >  Any technical reason for the Nanchang to be different?

 > >

 > >

 > >

 > > Dave

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 > >

 >

 >

 > Forum -

 > FAQ,

 >    - MATRONICS WEB FORUMS -

 > List Contribution Web Site -

 >               -Matt

 > Dralle, List Admin.

 >

 >

 >

 >

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 rget="_blank">http://www.matronics.com/Navigator?Yak-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

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

 ===========

-- 

Didier BLOUZARD

didier.blouzard(at)gmail.com (didier.blouzard(at)gmail.com)

0624243672

  	  Quote: 	

href="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List

href="http://forums.matronics.com">http://forums.matronics.com

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