Today's Message Index:
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1. 06:54 AM - Re: Coiled ignition systems (user9253)
2. 11:03 AM - Re: Re: Coiled ignition systems (Robert L. Nuckolls, III)
3. 12:39 PM - Re: Re: Coiled ignition systems (C&K)
4. 01:54 PM - Re: Re: Coiled ignition systems (Charlie England)
5. 07:07 PM - Hourmeter / oil pressure switch (micreb)
Message 1
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| Subject: | Re: Coiled ignition systems |
If a forced landing is immanent, all electrical power should be shut off to prevent
ignition of leaking fuel. A master switch that shuts off everything including
the engine is good for that scenario. However, smoke in the cockpit is
an emergency that may require shutting off all electrical loads except the engine.
In that case, engine ignition needs to be independent of the master switch.
The most reliable ignition circuit is less complicated and has fewer components.
If it were my plane, I would power the ignition system from the battery,
independent of the master switch. The engine starter circuit should be disabled
when the master switch is off.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=461520#461520
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| Subject: | Re: Coiled ignition systems |
At 08:53 AM 10/22/2016, you wrote:
>
>If a forced landing is immanent, all electrical power should be shut
>off to prevent ignition of leaking fuel. A master switch that shuts
>off everything including the engine is good for that
>scenario. However, smoke in the cockpit is an emergency that may
>require shutting off all electrical loads except the engine. In
>that case, engine ignition needs to be independent of the master
>switch. The most reliable ignition circuit is less complicated and
>has fewer components. If it were my plane, I would power the
>ignition system from the battery, independent of the master
>switch. The engine starter circuit should be disabled when the
>master switch is off.
Agreed . . .
Since your ignition system will run nicely
on 7A or less, I too would recommend you
run the ignition directly from the battery
through a 7A fuse. Power the starter from
the bus powered through the master contactor.
The ignition circuit is low risk for post-crash
ignition source . . . so even if you don't
get the engine killed before anticipated
contact the primary risk is to the engine
having a powered prop strike.
Taking everything else through the battery
master is the conventional philosophy.
Bob . . .
Message 3
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| Subject: | Re: Coiled ignition systems |
A 7 amp CB seems reasonable but a 7 amp fuse makes me a bit nervous. I
seem to recall that when I looked at ignition currents I noted that they
went up at high rpm, at high temperatures, and in some rare cases when
the engine was not turning. I did not notice any automotive systems
that lightly fused the ignition circuits. So while I've never measured
over 5 amps on my soob units, my personal recommendation is a minimum 10
amp fuse on ignition circuits that feed multiple cylinders even if they
are solid state. It may be that the peak currents as seen on a scope
caught my attention or that I just like more headroom on critical fuses.
I think part of my thought process might have been that on my system if
one solid state coil driver shorted full on it would not necessarily
take out the system fuse. I don't have any idea what the tolerance is on
an ATC fuse. I have 700 hours on the original 10 amp fuses that feed the
4 cylinder soob. I've had two cases of one cylinder losing power due to
a partial coil failure. Once during initial ground testing and once at
around 500 hours. These are DIS coils that each feed two cylinders but
in both cases only one cylinder lost power.
Ken
On 22/10/2016 2:02 PM, Robert L. Nuckolls, III wrote:
> At 08:53 AM 10/22/2016, you wrote:
>>
>> If a forced landing is immanent, all electrical power should be shut
>> off to prevent ignition of leaking fuel. A master switch that shuts
>> off everything including the engine is good for that scenario.
>> However, smoke in the cockpit is an emergency that may require
>> shutting off all electrical loads except the engine. In that case,
>> engine ignition needs to be independent of the master switch. The
>> most reliable ignition circuit is less complicated and has fewer
>> components. If it were my plane, I would power the ignition system
>> from the battery, independent of the master switch. The engine
>> starter circuit should be disabled when the master switch is off.
>
> Agreed . . .
>
> Since your ignition system will run nicely
> on 7A or less, I too would recommend you
> run the ignition directly from the battery
> through a 7A fuse. Power the starter from
> the bus powered through the master contactor.
>
> The ignition circuit is low risk for post-crash
> ignition source . . . so even if you don't
> get the engine killed before anticipated
> contact the primary risk is to the engine
> having a powered prop strike.
>
> Taking everything else through the battery
> master is the conventional philosophy.
>
>
> Bob . . .
>
Message 4
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| Subject: | Re: Coiled ignition systems |
Ken brings up an easy redundancy opportunity. Some (most?) automotive
style engine controllers switch the ground side of the coils and the
injectors. To limit the impact of such failures, I chose to
independently fuse each coil. Might be worth a look if running an auto
style engine controller.
Charlie
On 10/22/2016 2:37 PM, C&K wrote:
>
> A 7 amp CB seems reasonable but a 7 amp fuse makes me a bit nervous. I
> seem to recall that when I looked at ignition currents I noted that
> they went up at high rpm, at high temperatures, and in some rare cases
> when the engine was not turning. I did not notice any automotive
> systems that lightly fused the ignition circuits. So while I've never
> measured over 5 amps on my soob units, my personal recommendation is a
> minimum 10 amp fuse on ignition circuits that feed multiple cylinders
> even if they are solid state. It may be that the peak currents as
> seen on a scope caught my attention or that I just like more headroom
> on critical fuses. I think part of my thought process might have been
> that on my system if one solid state coil driver shorted full on it
> would not necessarily take out the system fuse. I don't have any idea
> what the tolerance is on an ATC fuse. I have 700 hours on the original
> 10 amp fuses that feed the 4 cylinder soob. I've had two cases of one
> cylinder losing power due to a partial coil failure. Once during
> initial ground testing and once at around 500 hours. These are DIS
> coils that each feed two cylinders but in both cases only one cylinder
> lost power.
> Ken
>
> On 22/10/2016 2:02 PM, Robert L. Nuckolls, III wrote:
>> At 08:53 AM 10/22/2016, you wrote:
>>>
>>> If a forced landing is immanent, all electrical power should be shut
>>> off to prevent ignition of leaking fuel. A master switch that shuts
>>> off everything including the engine is good for that scenario.
>>> However, smoke in the cockpit is an emergency that may require
>>> shutting off all electrical loads except the engine. In that case,
>>> engine ignition needs to be independent of the master switch. The
>>> most reliable ignition circuit is less complicated and has fewer
>>> components. If it were my plane, I would power the ignition system
>>> from the battery, independent of the master switch. The engine
>>> starter circuit should be disabled when the master switch is off.
>>
>> Agreed . . .
>>
>> Since your ignition system will run nicely
>> on 7A or less, I too would recommend you
>> run the ignition directly from the battery
>> through a 7A fuse. Power the starter from
>> the bus powered through the master contactor.
>>
>> The ignition circuit is low risk for post-crash
>> ignition source . . . so even if you don't
>> get the engine killed before anticipated
>> contact the primary risk is to the engine
>> having a powered prop strike.
>>
>> Taking everything else through the battery
>> master is the conventional philosophy.
>>
>>
>>
>>
>> Bob . . .
>>
>
Message 5
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| Subject: | Hourmeter / oil pressure switch |
Hope someone might be able to help out here.
I have a three pin oil pressure switch that feeds my low oil pressure light and
turns on the Hobbs meter.
The reference I have is a wiring diagram from Aeroelectric somewhere along the
line but no figure or diagram number.
The only reference is on the part, D-86117. I can't seem to cross it to anything
useful to replace it.
Would someone have a good number to order a replacement?
Paul
--------
I'd rather be flying than building but there's an end to the means here (I hope).
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=461528#461528
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