Today's Message Index:
----------------------
1. 06:31 AM - Which side of the firewall (klehman@albedo.net)
2. 07:32 AM - Pressure altitude and short sparks (Fergus Kyle)
3. 08:14 AM - Re: Circuit Breakers and OVPs (Eric M. Jones)
4. 09:07 AM - Re: Pressure altitude and short sparks (Brian Lloyd)
5. 09:07 AM - Re: Pressure altitude and short sparks (klehman@albedo.net)
6. 09:13 AM - Re: Pressure altitude and short sparks (echristley@nc.rr.com)
7. 10:15 AM - Re: Pressure altitude and short sparks (Bruce Gray)
8. 11:06 AM - Re: Pitot Static Sources and Ram sources (Eric M. Jones)
9. 11:27 AM - Re: Pressure altitude and short sparks (Matt Prather)
10. 11:55 AM - Re: Pressure altitude and short sparks (Brian Lloyd)
11. 12:54 PM - Re: Pressure altitude and short sparks (klehman@albedo.net)
12. 01:04 PM - Feedback for Bob - Roll your own crowbar module (Ralph Ketter)
13. 01:21 PM - Re: Pressure altitude and short sparks (klehman@albedo.net)
14. 02:13 PM - Re: Pressure altitude and short sparks (Matt Prather)
15. 02:25 PM - Re: Pressure altitude and short sparks (Bruce Gray)
16. 03:49 PM - Re: Re: Pitot Static Sources and Ram sources (Kevin Horton)
17. 03:50 PM - Re: Pressure altitude and short sparks (George Braly)
18. 04:04 PM - OT Re: Pressure altitude and short sparks (Matt Prather)
19. 07:36 PM - Z-12 Main Alternator Control (Richard Sipp)
20. 09:53 PM - Re: Pressure altitude and short sparks (Bruce Gray)
21. 10:35 PM - Re: Pressure altitude and short sparks (George Braly)
Message 1
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| Subject: | Which side of the firewall |
--> AeroElectric-List message posted by: klehman@albedo.net
How bad an idea is it to locate circuit breakers for my two alternator
output wires forward of the firewall beside the batteries? Some
breakers spec a 60 degree C. ambient but both my breakers would be rated
50% higher than the alternator outputs. I would guess there is not a
problem as far as the trip point goes. Used breakers are handy/cheap for
me but I'm willing to cough up the bucks for both an ANL and a Maxi fuse
holder if they are necessary or clearly a better idea.
I'm also wondering which side of the firewall to mount the voltage
regulator for a John Deere 20 amp PM alternator. I'd like to keep the AC
feed from the alternator forward of the firewall instead of bundling it
with the other wires coming through the firewall. I have a lot of efi
wiring coming through the firewall. OTOH the regulator might live longer
on the cool side of the firewall if there is no problem bundling all the
wires. Due to high ambient heat after shutdown, I've pretty much
dismissed the third option which would locate it on the forward side of
the engine.
thanks for any comments
Ken
Message 2
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| Subject: | Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "Fergus Kyle" <VE3LVO@rac.ca>
"As has been discussed on this list before, denser air (a composition of
non-conductive gasses) is a better insulator (higher dielectric breakdown
capability). As the air gets thinner, its propensity to conduct increases."
"You can see that Vacuum will break down at around 20kV with a 1" gap,
whereas dense air might hold up to 75kV over the same gap."
" A plug that works properly at atmospheric pressure may display shorts when
the gap is exposed to pressurized air (which has even higher dielectric
strength)."
How can it display shorts at higher pressure and still have higher
dielectric strength?
Ferg
Europa A064
Message 3
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| Subject: | Re: Circuit Breakers and OVPs |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
When an Over-Voltage Module crowbars the alternator field line to ground, it
is extremely important to have a fast blow circuit breaker for the
Alternator Field when using a crowbar. This fine point is easy to miss.
This really might be a good reason to use non-crowbar OVPs
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones@charter.net
" I would have made a good Pope."
-- Richard M. Nixon (1913-1994)
Message 4
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| Subject: | Re: Pressure altitude and short sparks |
--> AeroElectric-List message posted by: Brian Lloyd <brianl@lloyd.com>
Fergus Kyle wrote:
> " A plug that works properly at atmospheric pressure may display shorts when
> the gap is exposed to pressurized air (which has even higher dielectric
> strength)."
>
> How can it display shorts at higher pressure and still have higher
> dielectric strength?
When the pressure in the cylinder is higher the increased dielectric strength of
the air at the electrodes might cause the plug, wire, or some other place in
the ignition chain to break down first.
--
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
http://www.lloyd.com St. Thomas, VI 00802
+1.340.998.9447 (voice) +1.360.838.9669 (fax)
There is a time to laud one's country and a time to protest.
A good citizen is prepared to do either as the need arises.
Message 5
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| Subject: | Re: Pressure altitude and short sparks |
--> AeroElectric-List message posted by: klehman@albedo.net
Ferg
I think they mean breakdown outside the combustion chamber. Sometimes
poor/wet ignition wires will run the engine fine at low power settings
but at high power and high compression the wires break down and the
engine misses. The voltage goes higher to fire the spark under higher
cylinder pressure.
Ken
Fergus Kyle wrote:
> --> AeroElectric-List message posted by: "Fergus Kyle" <VE3LVO@rac.ca>
>
> "As has been discussed on this list before, denser air (a composition of
> non-conductive gasses) is a better insulator (higher dielectric breakdown
> capability). As the air gets thinner, its propensity to conduct increases."
>
> "You can see that Vacuum will break down at around 20kV with a 1" gap,
> whereas dense air might hold up to 75kV over the same gap."
>
> " A plug that works properly at atmospheric pressure may display shorts when
> the gap is exposed to pressurized air (which has even higher dielectric
> strength)."
>
> How can it display shorts at higher pressure and still have higher
> dielectric strength?
> Ferg
> Europa A064
>
>
>
>
>
>
>
Message 6
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| Subject: | Re: Pressure altitude and short sparks |
--> AeroElectric-List message posted by: echristley@nc.rr.com
----- Original Message -----
From: Fergus Kyle <VE3LVO@rac.ca>
Subject: AeroElectric-List: Pressure altitude and
short sparks
> --> AeroElectric-List message posted by: "Fergus
Kyle" <VE3LVO@rac.ca>
>
> "As has been discussed on this list before, denser
air (a
> composition of
> non-conductive gasses) is a better insulator
(higher dielectric
> breakdowncapability). As the air gets thinner,
its propensity to
> conduct increases."
>
> "You can see that Vacuum will break down at around
20kV with a 1" gap,
> whereas dense air might hold up to 75kV over the
same gap."
>
> " A plug that works properly at atmospheric
pressure may display
> shorts when
> the gap is exposed to pressurized air (which has
even higher
> dielectricstrength)."
>
> How can it display shorts at higher pressure and
still have higher
> dielectric strength?
> Ferg
> Europa A064
>
I think the answer here is that pressurize air does
in fact conduct more than a vacuum, which is the
best insulator; however, rarified air is more
easily IONIZED. What you have with ionized air is a
substance is an very good conductor. The subtle
difference can have some profound implications. For
instance, get some air moving across those worn
wiring harnesses and see if they still arc.
Message 7
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| Subject: | Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
Hmmm.... I don't see how the cylinder pressure, before ignition,
increases with engine speed. Voltage might go up, as a result of magnito
RPM increasing. But these are some of the reasons why sparkplugs should
be tested in a pressure tester every time they are cleaned and gaped.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
klehman@albedo.net
Subject: Re: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: klehman@albedo.net
Ferg
I think they mean breakdown outside the combustion chamber. Sometimes
poor/wet ignition wires will run the engine fine at low power settings
but at high power and high compression the wires break down and the
engine misses. The voltage goes higher to fire the spark under higher
cylinder pressure.
Ken
Message 8
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| Subject: | Re: Pitot Static Sources and Ram sources |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
It would make a great science project for your high school student to
determine if there is a size tube that is unattractive to mud wasps (and
therefore best for pitot [after Henri Pitot (1695-1771), French physicist]
tubes).
For bees, it turns out that if a gap (and maybe a hole) is below a certain
size, the bee will fill it. If the gap is bigger, the bees will build comb
in it, but if it is a certain size (7.5mm +/-1.5 mm) the bees will simply
ignore it. Rev. Lorenzo Langstroth (Philadelphia in 1851) was the first
person to use the bee space in hive construction. How he determined that
bees used the metric system is truly one of the wonders of science.
You don't have to search the NTSB very hard to find "wasp-like creature in
pitot tube" accidents. And you don't have to talk to many pilots to find
hair-raising tales that thankfully didn't end up in an NTSB report. Usually
pitot tube clogs are discovered near flying speed, half-way down the runway.
For static sources I am convinced (perhaps incorrectly) that too much fuss
is made of their position. And yes, you can tee off many instruments to the
same static source, and have multiple static sources. Classically static
sources have been taken from the supports for or just behind pitot ram
sources.
For pitot ram sources, you can also tee off many instruments, and
furthermore you can have multiple ram sources (several pitot tubes) leading
into one line. This seems never to have been done in EAA aircraft. Big
planes often use two or more pitot tubes but route them to their own
instrument banks.
I am designing a spare retractable pitot tube. The prototype will appear on
my website shortly. Comments are solicited.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones@charter.net
Ring the bells that still can ring
Forget your perfect offering
There is a crack in everything
That's how the light gets in
- - Leonard Cohen
Message 9
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| Subject: | Re: Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Hi Ken,
In addition to faults in the rest of the ignition system, spark plugs have a
fail mode that causes them to not spark at the electrode, but somewhere
within the body of the plug. Often, this kind of fail will only show up when
the electrode is exposed to the increased dielectric strength of a compressed
chamber - either in the sparkplug tester, or when being run in an engine.
I am not sure I understand your last comment about spark voltage. It sounds
like you are saying there is a mechanism that adjusts spark voltage based on
cylinder pressure - something I have never heard of.
Regards,
Matt-
N34RD
> --> AeroElectric-List message posted by: klehman@albedo.net
>
> Ferg
>
> I think they mean breakdown outside the combustion chamber. Sometimes
> poor/wet ignition wires will run the engine fine at low power settings
> but at high power and high compression the wires break down and the
> engine misses. The voltage goes higher to fire the spark under higher
> cylinder pressure.
>
> Ken
>
> Fergus Kyle wrote:
>> --> AeroElectric-List message posted by: "Fergus Kyle" <VE3LVO@rac.ca>
>>
>> "As has been discussed on this list before, denser air (a composition
>> of non-conductive gasses) is a better insulator (higher dielectric
>> breakdown capability). As the air gets thinner, its propensity to
>> conduct increases."
>>
>> "You can see that Vacuum will break down at around 20kV with a 1" gap,
>> whereas dense air might hold up to 75kV over the same gap."
>>
>> " A plug that works properly at atmospheric pressure may display
>> shorts when the gap is exposed to pressurized air (which has even
>> higher dielectric strength)."
>>
>> How can it display shorts at higher pressure and still have higher
>> dielectric strength?
>> Ferg
>> Europa A064
>>
>>
>>
>>
>>
>>
>>
>
>
Message 10
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| Subject: | Re: Pressure altitude and short sparks |
--> AeroElectric-List message posted by: Brian Lloyd <brianl@lloyd.com>
Bruce Gray wrote:
> --> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
>
> Hmmm.... I don't see how the cylinder pressure, before ignition,
> increases with engine speed.
It doesn't but it does increase with MAP. At low power settings the throttle is
mostly closed and the cylinder is sucking against the resistance of the throttle
valve. The MAP is low, probably 10" to 15" Hg, so the pressure in the cylinder
is correspondingly lower too. If the compression ratio is 10:1 (for ease
of calculation), the cylinder pressure at TDC with 10" of MAP will be 100"
Hg. With the throttle wide open the MAP will be close to 30" and the cylinder
pressure will be 300" Hg.
This is a simplistic calculation but hopefully it is understandable.
--
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
http://www.lloyd.com St. Thomas, VI 00802
+1.340.998.9447 (voice) +1.360.838.9669 (fax)
There is a time to laud one's country and a time to protest.
A good citizen is prepared to do either as the need arises.
Message 11
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| Subject: | Re: Pressure altitude and short sparks |
--> AeroElectric-List message posted by: klehman@albedo.net
Ferg
I think they mean breakdown outside the combustion chamber. Sometimes
poor/wet ignition wires will run the engine fine at low power settings
but at high power and high compression the wires break down and the
engine misses. The voltage goes higher to fire the spark with higher
cylinder pressure.
Ken
Fergus Kyle wrote:
> --> AeroElectric-List message posted by: "Fergus Kyle" <VE3LVO@rac.ca>
>
> "As has been discussed on this list before, denser air (a composition of
> non-conductive gasses) is a better insulator (higher dielectric breakdown
> capability). As the air gets thinner, its propensity to conduct increases."
>
> "You can see that Vacuum will break down at around 20kV with a 1" gap,
> whereas dense air might hold up to 75kV over the same gap."
>
> " A plug that works properly at atmospheric pressure may display shorts when
> the gap is exposed to pressurized air (which has even higher dielectric
> strength)."
>
> How can it display shorts at higher pressure and still have higher
> dielectric strength?
> Ferg
> Europa A064
Message 12
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| Subject: | Feedback for Bob - Roll your own crowbar module |
--> AeroElectric-List message posted by: Ralph Ketter <arizonahikers@juno.com>
Original posting 4/12/04
>>
>>I build my own OV crowbar module and it functions correctly except that
>>it operated in the 10-11 volt range. I triple checked the components
and
>>wiring. I tested the 1N4742A diode and it regulates at 12V. I changed
>>the 1.62K ohm resistor specified for a 14 volt system to 6.04K and the
>>circuit operates in the correct voltage range of 15.5-17 volts. Has
>>anyone else found this?
***************************
> With the 1.62K resistor in place, adjust the potentiometer to
> approximately mid range. Adjust the power supply to a point just
> below the trip point and then measure voltage at (1) + end of
> capacitor and (2) junction of zener diode and the 392 ohm
> resistor and tell us what you get.
>
> Bob . . .
>
> -----------------------------------------
> ( Experience and common sense cannot be )
> ( replaced with policy and procedures. )
> ( R. L. Nuckolls III )
> -----------------------------------------
Thanks for the reply Bob,
Sorry I took so long with a response to your suggestion.
I did as you suggested. The pot is set to mid range for all of the
following voltage readings.
Designating Point (1) as the + end of the capacitor, and Point (2) as the
junction of the 392 ohm resistor, and GND as the negative lead, I got the
following readings:
1.62 K resistor in place for 14 volt operation. - Trip point = 10.4
volts.
Point (1) - Point (2) +0.436 volts
GND - Point (2) +7.6 volts
6.04K resistor replacing the 1.62K one. - Trip point = 16.22 volts.
Point (1) - Point (2) +0.538 volts
GND - Point (2) +7.36 volts
These readings made me realize the circuit was not letting the zener
regulate at 12 volts so I did the following checks.
First I disconnected the SCR trigger lead to prevent it from firing.
I reinstalled the original 1.62K resistor.
Measuring the Zener voltage from GND to Point (2):
As I increased the input voltage the voltage across the zener increases
linearly to about 8.25 volts and then starts to decrease. The input
voltage is about 9 volts when this knee occurs.
I then disconnected the 1N4148 diode and repeated the above test with
basically the same results.
With the 1N4148 diode still disconnected, I also disconnected the NPN
collector and PNP base (they remained connected together) from the Point
(2) junction. Now only the Zener and 392 ohm resistor are in series
across the supply. Again measuring the Zener voltage from GND to Point
(2):
The zener voltage tracks the input voltage up to about 11.3 volts at
which point the zener begins to regulate.
With the two transistors still disconnected, I reconnected the 1N4148
diode.
Now the voltage across the zener increases linearly up to 9 volts (input
voltage is 9.35) when suddenly the voltage drops to 1.87 volts.
When I made the statement in my original email that the zener regulates
at 12 volts, I neglected to say that I tested it out of the circuit.
Ralph Ketter
RV-6
Marysville, KS
***************************
Message 13
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| Subject: | Re: Pressure altitude and short sparks |
--> AeroElectric-List message posted by: klehman@albedo.net
Matt
I'm just saying that the voltage rises until the plug fires at which
point the voltage drops. With more cylinder pressure the voltage rises
higher before the plug fires. With defective ignition components it can
be that the spark gets out somewhere else before the plug fires.
Bruce
I am suggesting that cylinder pressure (and manifold pressure) rises
when one opens the throttle like it would in a manual transmission car.
Similarly with a propellor, cylinder pressure generally increases with
manifold pressure.
Ken
Message 14
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| Subject: | Re: Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Ken,
Thanks for the clarification. I hadn't thought about it in the terms you
described, but I agree with what you are saying.
Regards,
Matt-
> --> AeroElectric-List message posted by: klehman@albedo.net
>
> Matt
> I'm just saying that the voltage rises until the plug fires at which
> point the voltage drops. With more cylinder pressure the voltage rises
> higher before the plug fires. With defective ignition components it can
> be that the spark gets out somewhere else before the plug fires.
>
> Bruce
> I am suggesting that cylinder pressure (and manifold pressure) rises
> when one opens the throttle like it would in a manual transmission car.
> Similarly with a propellor, cylinder pressure generally increases with
> manifold pressure.
>
> Ken
>
>
Message 15
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| Subject: | Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
Sorry, the engine is just a constant volume air pump. Cylinder pressure
will not vary, regardless of RPM, MP, or a constant speed prop.
Now cylinder pressure after ignition is a different matter.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
klehman@albedo.net
Subject: Re: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: klehman@albedo.net
Matt
I'm just saying that the voltage rises until the plug fires at which
point the voltage drops. With more cylinder pressure the voltage rises
higher before the plug fires. With defective ignition components it can
be that the spark gets out somewhere else before the plug fires.
Bruce
I am suggesting that cylinder pressure (and manifold pressure) rises
when one opens the throttle like it would in a manual transmission car.
Similarly with a propellor, cylinder pressure generally increases with
manifold pressure.
Ken
==
==
==
==
Message 16
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| Subject: | Re: Pitot Static Sources and Ram sources |
--> AeroElectric-List message posted by: Kevin Horton <khorton01@rogers.com>
>--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
>
>For static sources I am convinced (perhaps incorrectly) that too much fuss
>is made of their position.
The ideal static source would be located where the pressure was the
same as the ambient air pressure. But, the aircraft forces the air
to flow around it, which causes the air to accelerate and decelerate.
Bernoulli's law tells us that the static pressure will change as the
air accelerates or decelerates. So it is quite hard to find a place
on the airframe where the static source will actually be seeing the
correct pressure. And even if you find a location that is good at a
particular angle of attack, flap angle, etc, the airflow pattern will
be different at other conditions.
So, if you want accurate altimeter and airspeed readings, then static
source location is important. If you think having an accurate static
source is only important if you fly IFR, remember that the static
source error affects the altitude reported by our transponder, and
that affects the response of TCAS equipped aircraft. If the error is
small, no problem, but if the error is large you could easily have a
TCAS equipped aircraft that would have missed you if he had just kept
flying level, instead climb or dive toward you, because your
transponder is reporting that you are at the wrong altitude.
The transponder checks that are done won't find a problem with static
source position error, as static source position error only exists
when you have air flowing around the aircraft. You need to do
careful flight tests to measure it:
http://members.rogers.com/khorton/rvlinks/ssec.html
--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
Message 17
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| Subject: | Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "George Braly" <gwbraly@gami.com>
Bruce,
The peak cylinder pressure does change with manifold pressure.
Regardless of whether or not there is a spark.
For a normal 8.5:1 CR engine, if no spark, peak cylinder pressure
happens at TDC, at somewhere between about 125PSI and 300 PSI,
depending on MP .
Regards, George
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bruce
Gray
Subject: RE: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: "Bruce Gray"
<Bruce@glasair.org>
Sorry, the engine is just a constant volume air pump. Cylinder pressure
will not vary, regardless of RPM, MP, or a constant speed prop.
Now cylinder pressure after ignition is a different matter.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
klehman@albedo.net
Subject: Re: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: klehman@albedo.net
Matt
I'm just saying that the voltage rises until the plug fires at which
point the voltage drops. With more cylinder pressure the voltage rises
higher before the plug fires. With defective ignition components it can
be that the spark gets out somewhere else before the plug fires.
Bruce
I am suggesting that cylinder pressure (and manifold pressure) rises
when one opens the throttle like it would in a manual transmission car.
Similarly with a propellor, cylinder pressure generally increases with
manifold pressure.
Ken
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Message 18
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| Subject: | Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Bruce,
I respectfully disagree.
I am not sure how an engine being a constant volume air pump has
any bearing on what the pre-ignition cylinder pressure is.... Air is
compressible. As the throttle position is varied, a varying mass of the
fuel-air mixture is allowed to enter the cylinder each time the intake
valve spends some time open. If the throttle is fully open, a larger mass
of fuel-air is drawn into the cylinder on the piston's intake stroke than
when the throttle is closed. This larger mass will cause a relatively higher
pressure to be generated when the piston reaches the top of its stroke,
achieving its fixed minimum volume. This is true whether fuel-air is ever
ignited or not.
I think the throttle works by changing the volumetric efficiency of the
engine - ie, how much volume of atmospheric pressure fuel-air is drawn
into the cylinder as compared to the actual cylinder volume.
Maybe I am missing something in your explanation...
Regards,
Matt-
> --> AeroElectric-List message posted by: "Bruce Gray"
> <Bruce@glasair.org>
>
> Sorry, the engine is just a constant volume air pump. Cylinder pressure
> will not vary, regardless of RPM, MP, or a constant speed prop.
>
> Now cylinder pressure after ignition is a different matter.
>
> Bruce
> www.glasair.org
>
> snip
>
> Bruce
> I am suggesting that cylinder pressure (and manifold pressure) rises
> when one opens the throttle like it would in a manual transmission car.
> Similarly with a propellor, cylinder pressure generally increases with
> manifold pressure.
>
> Ken
>
>
> ==
Message 19
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| Subject: | Z-12 Main Alternator Control |
--> AeroElectric-List message posted by: "Richard Sipp" <rsipp@earthlink.net>
Bob:
With respect to Z-12 (Single Battery, Dual Alternator) the main alternator appears
to be controlled by the main battery master switch while the aux alternator
has a separate on/off switch.
Is there a reason for not having a separate main alternator switch as well? I
plan on this system for the RV-10 I have under construction.
The aircraft is designed with a battery location aft of the passenger compartment.
With an aluminum airframe is the 4AWG ground cable to the instrument panel
ground bus still the preferred grounding method?
Many thanks.
Dick Sipp
RV10 #65
Message 20
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| Subject: | Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
I stand corrected. My recognized expert on the subject has spoken. I'll
just slink back into my corner.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
George Braly
Subject: RE: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: "George Braly"
<gwbraly@gami.com>
Bruce,
The peak cylinder pressure does change with manifold pressure.
Regardless of whether or not there is a spark.
For a normal 8.5:1 CR engine, if no spark, peak cylinder pressure
happens at TDC, at somewhere between about 125PSI and 300 PSI,
depending on MP .
Regards, George
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bruce
Gray
Subject: RE: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: "Bruce Gray"
<Bruce@glasair.org>
Sorry, the engine is just a constant volume air pump. Cylinder pressure
will not vary, regardless of RPM, MP, or a constant speed prop.
Now cylinder pressure after ignition is a different matter.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
klehman@albedo.net
Subject: Re: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: klehman@albedo.net
Matt
I'm just saying that the voltage rises until the plug fires at which
point the voltage drops. With more cylinder pressure the voltage rises
higher before the plug fires. With defective ignition components it can
be that the spark gets out somewhere else before the plug fires.
Bruce
I am suggesting that cylinder pressure (and manifold pressure) rises
when one opens the throttle like it would in a manual transmission car.
Similarly with a propellor, cylinder pressure generally increases with
manifold pressure.
Ken
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Message 21
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| Subject: | Pressure altitude and short sparks |
--> AeroElectric-List message posted by: "George Braly" <gwbraly@gami.com>
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bruce
Gray
Subject: RE: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: "Bruce Gray"
<Bruce@glasair.org>
I stand corrected. My recognized expert on the subject has spoken. I'll
just slink back into my corner.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
George Braly
Subject: RE: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: "George Braly"
<gwbraly@gami.com>
Bruce,
The peak cylinder pressure does change with manifold pressure.
Regardless of whether or not there is a spark.
For a normal 8.5:1 CR engine, if no spark, peak cylinder pressure
happens at TDC, at somewhere between about 125PSI and 300 PSI,
depending on MP .
Regards, George
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bruce
Gray
Subject: RE: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: "Bruce Gray"
<Bruce@glasair.org>
Sorry, the engine is just a constant volume air pump. Cylinder pressure
will not vary, regardless of RPM, MP, or a constant speed prop.
Now cylinder pressure after ignition is a different matter.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
klehman@albedo.net
Subject: Re: AeroElectric-List: Pressure altitude and short sparks
--> AeroElectric-List message posted by: klehman@albedo.net
Matt
I'm just saying that the voltage rises until the plug fires at which
point the voltage drops. With more cylinder pressure the voltage rises
higher before the plug fires. With defective ignition components it can
be that the spark gets out somewhere else before the plug fires.
Bruce
I am suggesting that cylinder pressure (and manifold pressure) rises
when one opens the throttle like it would in a manual transmission car.
Similarly with a propellor, cylinder pressure generally increases with
manifold pressure.
Ken
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