Today's Message Index:
----------------------
1. 02:11 PM - Shut down (Jerry Painter)
2. 05:11 PM - Re: Shut down (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
3. 06:12 PM - Re: Engine/avionics shutdown procedure (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
4. 06:34 PM - Re: Engine/avionics shutdown procedure (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
5. 08:02 PM - Re: Engine/avionics shutdown procedure (Walter Lannon)
Message 1
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Gents--
I can tell you from sad, time consuming and expensive experience that if you
shut off the alternator/generator/master before the engine stops in your
Nanchang you run a very high risk of torching your voltage regulator. The
old vibrator style regulators will stand it, and maybe your avionics, too,
but the newer solid-state regulators will blow up immediately. Not "maybe,"
but absolutely, positively, you will burn it up, guaranteed. Do not "cycle"
the generator with the engine running, either, results ditto. Treat your
Yak or Nanchang just like that Cessna you learned to fly in: Electrical
loads off first (avionics, lights etc.) then kill the engine (mags).
Finally and only then, shut off the generator and master. You will save
yourself a great deal of trouble and expense. So far as I know this applies
to Yaks, too, and, no, I'm not going to "experiment" to test the hypothesis.
Slow, yes. Stupid, maybe. But once is enough.
Jerry Painter
Wild Blue Aviation
www.FlyWBA.com
JP@FlyWBA.com
425-876-0865
Message 2
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Jerry,
The suggestions was to shut off the Avionics Master, not the generator or alternator
control.
Mark
p.s. On the YAK models, the generator master switch controls the output to the
field winding.
________________________________
From: owner-yak-list-server@matronics.com on behalf of Jerry Painter
Sent: Mon 9/27/2010 5:04 PM
Subject: Yak-List: Shut down
Gents--
I can tell you from sad, time consuming and expensive experience that if you
shut off the alternator/generator/master before the engine stops in your
Nanchang you run a very high risk of torching your voltage regulator. The
old vibrator style regulators will stand it, and maybe your avionics, too,
but the newer solid-state regulators will blow up immediately. Not "maybe,"
but absolutely, positively, you will burn it up, guaranteed. Do not "cycle"
the generator with the engine running, either, results ditto. Treat your
Yak or Nanchang just like that Cessna you learned to fly in: Electrical
loads off first (avionics, lights etc.) then kill the engine (mags).
Finally and only then, shut off the generator and master. You will save
yourself a great deal of trouble and expense. So far as I know this applies
to Yaks, too, and, no, I'm not going to "experiment" to test the hypothesis.
Slow, yes. Stupid, maybe. But once is enough.
Jerry Painter
Wild Blue Aviation
www.FlyWBA.com
JP@FlyWBA.com
425-876-0865
Message 3
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| 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@matronics.com on behalf of Walter Lannon
Sent: Mon 9/27/2010 12:41 AM
: yak-list@matronics.com
Subject: Re: Yak-List: Engine/avionics shutdown procedure
Thanks Mark;
Great information. Do you have a recommendation for which Battery- Minder to
get?
Walt
----- Original Message -----
From: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E"
<mark.bitterlich@navy.mil>
Sent: Sunday, September 26, 2010 8:04 PM
Subject: RE: Yak-List: Engine/avionics shutdown procedure
> MALS-14 64E" <mark.bitterlich@navy.mil>
>
> 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@matronics.com on behalf of Steven Johnson
> Sent: Sun 9/26/2010 8:18 PM
> To: yak-list@matronics.com
> Subject: RE: Yak-List: Engine/avionics shutdown procedure
>
>
>
> Mark, how does one check the batteries properly?
>
> Steve Johnson
> Yak 52 N9900X 0B5
> 413 522-1130 Cell
> -----Original Message-----
> From: owner-yak-list-server@matronics.com
> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Bitterlich, Mark
> G
> CIV Det Cherry Point, MALS-14 64E
> Sent: Sunday, September 26, 2010 6:29 PM
> To: yak-list@matronics.com
> Subject: RE: Yak-List: Engine/avionics shutdown procedure
>
> --> Point, MALS-14 64E" <mark.bitterlich@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@matronics.com on behalf of KingCJ6@aol.com
> Sent: Sun 9/26/2010 5:58 PM
> To: yak-list@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
>
>
Message 4
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| 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@matronics.com on behalf of Walter Lannon
Sent: Mon 9/27/2010 12:41 AM
Subject: Re: Yak-List: Engine/avionics shutdown procedure
Thanks Mark;
Great information. Do you have a recommendation for which Battery- Minder to
get?
Walt
----- Original Message -----
From: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E"
<mark.bitterlich@navy.mil>
Sent: Sunday, September 26, 2010 8:04 PM
Subject: RE: Yak-List: Engine/avionics shutdown procedure
> MALS-14 64E" <mark.bitterlich@navy.mil>
>
> 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@matronics.com on behalf of Steven Johnson
> Sent: Sun 9/26/2010 8:18 PM
> To: yak-list@matronics.com
> Subject: RE: Yak-List: Engine/avionics shutdown procedure
>
>
>
> Mark, how does one check the batteries properly?
>
> Steve Johnson
> Yak 52 N9900X 0B5
> 413 522-1130 Cell
> -----Original Message-----
> From: owner-yak-list-server@matronics.com
> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Bitterlich, Mark
> G
> CIV Det Cherry Point, MALS-14 64E
> Sent: Sunday, September 26, 2010 6:29 PM
> To: yak-list@matronics.com
> Subject: RE: Yak-List: Engine/avionics shutdown procedure
>
> --> Point, MALS-14 64E" <mark.bitterlich@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@matronics.com on behalf of KingCJ6@aol.com
> Sent: Sun 9/26/2010 5:58 PM
> To: yak-list@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
>
>
Message 5
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| Subject: | Re: 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
----- Original Message -----
From: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E"
<mark.bitterlich@navy.mil>
Sent: Monday, September 27, 2010 6:20 PM
Subject: RE: Yak-List: Engine/avionics shutdown procedure
> MALS-14 64E" <mark.bitterlich@navy.mil>
>
> 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@matronics.com on behalf of Walter Lannon
> Sent: Mon 9/27/2010 12:41 AM
> To: yak-list@matronics.com
> Subject: Re: Yak-List: Engine/avionics shutdown procedure
>
>
>
> Thanks Mark;
>
> Great information. Do you have a recommendation for which Battery- Minder
> to
> get?
>
> Walt
> ----- Original Message -----
> From: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E"
> <mark.bitterlich@navy.mil>
> To: <yak-list@matronics.com>
> Sent: Sunday, September 26, 2010 8:04 PM
> Subject: RE: Yak-List: Engine/avionics shutdown procedure
>
>
>> MALS-14 64E" <mark.bitterlich@navy.mil>
>>
>> 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@matronics.com on behalf of Steven Johnson
>> Sent: Sun 9/26/2010 8:18 PM
>> To: yak-list@matronics.com
>> Subject: RE: Yak-List: Engine/avionics shutdown procedure
>>
>>
>>
>>
>> Mark, how does one check the batteries properly?
>>
>> Steve Johnson
>> Yak 52 N9900X 0B5
>> 413 522-1130 Cell
>> -----Original Message-----
>> From: owner-yak-list-server@matronics.com
>> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Bitterlich,
>> Mark
>> G
>> CIV Det Cherry Point, MALS-14 64E
>> Sent: Sunday, September 26, 2010 6:29 PM
>> To: yak-list@matronics.com
>> Subject: RE: Yak-List: Engine/avionics shutdown procedure
>>
>> --> Point, MALS-14 64E" <mark.bitterlich@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@matronics.com on behalf of KingCJ6@aol.com
>> Sent: Sun 9/26/2010 5:58 PM
>> To: yak-list@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
>>
>>
>>
>>
>>
>>
>>
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