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  #111  
Old 10-12-2017, 06:39 AM
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Quote:
Originally Posted by N941WR View Post
Dan, as always, you bring in good logic; however, once the P-mags are spinning, one or more of its wires can fail and it will keep the sparks flowing. (Unless the failure is in a plug wire.) How many wires can fail in a Distributed system before it stops producing sparks?
Fair point Bill.

Recall wires can fail open, or shorted. I typically make a list with each wire represented and think about both open and grounded failure modes, ignoring the probability of failure, and initially only considering what happens if it does fail. Example here: http://www.vansairforce.com/communit...8&postcount=63

A wire list for the CPI says shorting or opening almost any pin will shut it down. On the other hand, it does not appear any open or short can make it do strange things. Put another way, it works or it is dead.

In the case of the P-mag, the result of an open or short on a few of the wires is obvious. However, I don't know enough about the p-mag to be sure what happens when some of the wires are opened or shorted, notably software driven events.

Pin 1: I think you just stated the system works with this one open. If shorted is normal and open doesn't matter, the logical question becomes "Why is it there?" Back up for case ground to engine block?

Pins 2 and 3: Without an EIC, an open shifts timing aprox 5 degrees advanced. Field experience says that's probably not critical at WOT with 100LL fuel, just higher CHT. I have no idea what the result might be by shorting either 2 or 3 to ground, with or without the EIC. How does the EIC drive a timing shift with these wires?

Pin 4: Obviously a short kills the mag, like any mag.

Pin 5: An open above 800 RPM or so is no issue; that's the whole point of the internal generator. What about a short to ground?

Pin 6: Tach lead. Assumed to have no effect on the P-mag alone, open or shorted. Does the EIC use the tach signal for anything other than an RPM display?

Quote:
Originally Posted by N941WR View Post
No, but that's why you have two independent ignitions.
A perfectly reasonable answer. It's an extension of the above; list the possible failures, and consider the result of each. Here the result of all failures is the ignition doesn't work, but the flight continues, as we have two of them.
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  #112  
Old 10-12-2017, 08:18 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Captain Avgas View Post
SNIP

I have a LightSpeed Plasma 11 on one side (magneto on the other....I'm with Vic Syracuse on this). I'd have to think very seriously about publicly whinging about a fault in my EI on VansAirforce and then going cap in hand to Klaus at some time in the future for support. SNIP
I have recent personal experience on this. I'm helping a budding who has dual Lightspeed ignitions and he ordered (and paid for) a replacement coil from Klaus. Klaus would not mail the coil to me. He mailed it to my buddy and then he had to mail it to me.

The good news is both ignitions are working.

Carl
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  #113  
Old 10-12-2017, 09:48 AM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by DanH View Post
...Recall wires can fail open, or shorted. I typically make a list with each wire represented and think about both open and grounded failure modes, ignoring the probability of failure, and initially only considering what happens if it does fail...
You bring up a good point that this fault analysis is a great tool for uncovering vulnerabilities in a system. But it seems to me that many people don’t understand that this is but one step in the process. Many people think that vulnerable = unacceptable, and the preferred way to fix that is with redundancy. Many times, the “fix” is actually ensuring that the probability of failure is below the acceptable threshold through a robust installation. One grounded wire can take out a magneto, for example. So is it better to add another ignition or protect that wire from a short?

The point I’m trying to make is that we spend a lot of time on this forum searching for the perfect redundancy scheme, but not nearly enough time executing the basics of the system. Wiring, including connectors, are phenomenally reliable when designed and installed correctly. “Wiring” is significantly more reliable than the components they service, yet we see a lot of electrical issues in the E-AB world. Certainly much more so than in cars or spam cans. The problem, as it turns out, is “us”.

Talking about the latest magic scheme/gadget to ensure airliner levels of dispatch reliability may be sexy, but maybe we should spend some time learning how to terminate and route wires first?
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  #114  
Old 10-12-2017, 10:57 AM
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We get the redundancy/ reliability question often in our business during initial emails or phone calls with our customers. Some are wary of total electronic dependency, others are ready to ashcan all the legacy fuel/ ignition bits and step into the new world.

In the end, anything can fail and you're still in a single engined aircraft where the engine itself is a single point a failure. People seem to think that engine is infallibly reliable. It isn't. We all know or have heard of someone who's had one fail mechanically. Well designed electronics are many times more reliable than aircraft engines in my experience since there are no moving or wearing parts (remember our test ECU with 145,000 hours on it). I don't know of a single Lycoming engine which has gone even 1/20th that time without being touched.

As someone else posted here, there is always some risk on each flight and everyone has a different level of risk they will accept. Some happily fly single engined at night over the mountains, others would never accept that risk. If you can't accept ANY risk, best to stay home on the ground.

We can mitigate many risks by doing good work on our planes and making good decisions on the ground and in the air.
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  #115  
Old 10-12-2017, 06:35 PM
Chkaharyer99 Chkaharyer99 is online now
 
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Anyone out there running one Pmag and one SDS CPI EI?

Are these two devices compatible together on one lycoming engine?

If the Pmag failed or misbehaved in flight as described in some posts would it/could it adversely effect the operation of the SDS CPI EI?

Anyone else notice that the CEO of SDS participated in this thread? I did. I appreciate hearing from the MFG of products I'm considering.

Anyone notice the conspicuous absence of representation from Pmag?

Nope, nada, nothing. Just saying.
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  #116  
Old 10-12-2017, 07:06 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by DanH View Post
...

Pin 1: I think you just stated the system works with this one open. If shorted is normal and open doesn't matter, the logical question becomes "Why is it there?" Back up for case ground to engine block?
I can't answer with certainty because I didn't design the P-mag but I believe you are correct that it is a backup ground. It is really needed for communication through the serial port.

Quote:
Originally Posted by DanH View Post
Pins 2 and 3: Without an EIC, an open shifts timing aprox 5 degrees advanced. Field experience says that's probably not critical at WOT with 100LL fuel, just higher CHT. I have no idea what the result might be by shorting either 2 or 3 to ground, with or without the EIC. How does the EIC drive a timing shift with these wires?
Since 2 and 3 are a serial port, I don't believe it would impact anything in flight. We have shorted them when developing the EICommander with no impact to out test P-mags.

As for what would happen if a break happened in flight, the P-mag only checks for the jumper upon startup, after that it never checks again. So, if you start up on the A memory location, it will continue on that configuration until shutdown.

If you have loaded a custom configuration via Emag's EICAD program or our EICommander, you are running off of the B memory location and when running without the EICommander, there is no jumper and when running with the EICommander, you can disconnect it and you will continue to run off of whatever configuration you have loaded, be it the A, B, or a custom configuration.

Quote:
Originally Posted by DanH View Post
Pin 4: Obviously a short kills the mag, like any mag.
Correct.

Quote:
Originally Posted by DanH View Post
Pin 5: An open above 800 RPM or so is no issue; that's the whole point of the internal generator. What about a short to ground?
An internal sort to ground would probably kill the generator; however, it would continue to fire, if ship's power is available.

Quote:
Originally Posted by DanH View Post
Pin 6: Tach lead. Assumed to have no effect on the P-mag alone, open or shorted. Does the EIC use the tach signal for anything other than an RPM display?
Correct and they list it as a "courtesy (optional) connection".


Quote:
Originally Posted by DanH View Post
A perfectly reasonable answer. It's an extension of the above; list the possible failures, and consider the result of each. Here the result of all failures is the ignition doesn't work, but the flight continues, as we have two of them.
This comes down to individual choice. How much control does one want of their ignition timing map and what type of back up system do they want.

As we have seen in this thread, there are many difference of opinion and risk tolerance. All good things.
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  #117  
Old 10-12-2017, 08:02 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Chkaharyer99 View Post
Anyone out there running one Pmag and one SDS CPI EI?

Are these two devices compatible together on one lycoming engine?

If the Pmag failed or misbehaved in flight as described in some posts would it/could it adversely effect the operation of the SDS CPI EI?

Anyone else notice that the CEO of SDS participated in this thread? I did. I appreciate hearing from the MFG of products I'm considering.

Anyone notice the conspicuous absence of representation from Pmag?

Nope, nada, nothing. Just saying.
We have a some people flying with one Pmag and one CPI if I recall. I see no issues with that. If the Pmag went down I don't see any reason it would affect the CPI or vice versa.

CEO? We're a small company, I double as the floor sweeper...
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http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #118  
Old 10-12-2017, 10:19 PM
gasman gasman is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
We have a some people flying with one Pmag and one CPI if I recall. I see no issues with that. If the Pmag went down I don't see any reason it would affect the CPI or vice versa.

CEO? We're a small company, I double as the floor sweeper...
Ross, you sure know how to jump in and take all the credit......
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  #119  
Old 10-12-2017, 10:20 PM
SHIPCHIEF SHIPCHIEF is offline
 
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Ross;
In Post #115, you referred to single point reliability. Those failures come in 2 kinds: Instant total failure, and progressive failure.
Although modern electronics have a reputation for reliability, they are also perceived to fail utterly and instantly.
A Kettering (points) ignition is less reliable, but has a reputation for slowly failing, giving fair warning so it can be repaired before dire consequences.
I don't need to heap additional cliche stories, and I have a personal experience where my 1988 Harley electronic ignition module failed softly, I changed it before being stranded.
I would be comforted to know that an electronic flight control would have a progressive failure mode.
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  #120  
Old 10-12-2017, 11:22 PM
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skylor skylor is offline
 
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Quote:
Originally Posted by Chkaharyer99 View Post
Anyone out there running one Pmag and one SDS CPI EI?

Are these two devices compatible together on one lycoming engine?

If the Pmag failed or misbehaved in flight as described in some posts would it/could it adversely effect the operation of the SDS CPI EI?

Anyone else notice that the CEO of SDS participated in this thread? I did. I appreciate hearing from the MFG of products I'm considering.

Anyone notice the conspicuous absence of representation from Pmag?

Nope, nada, nothing. Just saying.
Charlie,

Did you get the chance to meet the aforementioned CEO at Reno?

Skylor
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