Brantel
Well Known Member
Why would someone who has not had an issue have any cause to complain? We know what you mean though.
I really need to proof read my phone postings! Thanks, I have edited my OP....
Why would someone who has not had an issue have any cause to complain? We know what you mean though.
I have two Pmags and two CPI . This tread has been extremely stimulating. That said, it appears the bottom line issue affecting CPI reliability is wiring termination failures ( ignoring errors ) , i.e. Corrosion, vibration etc. So, perhaps Ross or someone would start a separate thread on optimizing wiring termination from corrosion, vibration, etc ???
Is this entirely true, considering the apparently critical external wire connection to engine ground?
Do the sparks keep flowing when the coil wires (primary side) fail?
(No need to answer Bill, we know the answer)
No, but that's why you have two independent ignitions.
My impression is that you are more likely to see a public complaint from someone that has an issue than a positive post by someone who has not.
Perhaps we need a NASA form for suppliers....Brian, if you personally have a problem with one of your PMAGs, are you going to report that fault on VansAirforce...probably not if it's not in your personal interest to do so. I mean, there's no moral or legal duty of disclosure....
Brian, if you personally have a problem with one of your PMAGs, are you going to report that fault on VansAirforce...probably not if it's not in your personal interest to do so. I mean, there's no moral or legal duty of disclosure.
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?
No, but that's why you have two independent ignitions.
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
...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...
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....
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?
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.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?
Correct.Pin 4: Obviously a short kills the mag, like any mag.
An internal sort to ground would probably kill the generator; however, it would continue to fire, if ship's power is available.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?
Correct and they list it as a "courtesy (optional) connection".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?
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.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.
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...
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.
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.
...I would be comforted to know that an electronic flight control would have a progressive failure mode.
Charlie,
Did you get the chance to meet the aforementioned CEO at Reno?
Skylor
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.
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.
An internal sort to ground would probably kill the generator; however, it would continue to fire, if ship's power is available.
Seems like some bench testing would not take too much time and effort. I'd do it on one of mine but I'm in "get 'er done" mode, and I don't want to fry one of my p-mags. Anyone have any pull with the emagair guys?Returning to P-mag reliability....
...
Bill, I know these are hard questions, but one can't claim superiority based on immunity to external wire faults without clearly defining exactly what happens given wire faults in the competing system.
I am new to Experimentals. Have many hours flying behind regular magnetos. I have read this complete thread and others and still cannot find an explanation of what P-Mags are, how they work and what the advantages/disadvantages are. Or at least I cannot decipher this information. Can someone please explain in layman terms how P-mags differ from a regular Bendix mag, how they work and what the advantages/disadvantages are? I would just like to have an understanding of P-Mags. I am talking to a gentleman that has an airplane I have an interest in with dual P-Mags on an IO360 Superior Engine with Cold Air Induction.
Thank you
Returning to P-mag reliability....
(discussing Pin 1 ground) So what doesn't work if it is not connected...or connected somewhere other than a case bolt? You've been very specific in the past:
http://www.vansairforce.com/community/showpost.php?p=1080846&postcount=10
http://www.vansairforce.com/community/showpost.php?p=1072337&postcount=8
http://www.vansairforce.com/community/showpost.php?p=978738&postcount=3
http://www.vansairforce.com/community/showpost.php?p=979945&postcount=4
Returning to P-mag reliability....
(discussing Pin 1 ground) So what doesn't work if it is not connected...or connected somewhere other than a case bolt? You've been very specific in the past:
http://www.vansairforce.com/community/showpost.php?p=1080846&postcount=10
http://www.vansairforce.com/community/showpost.php?p=1072337&postcount=8
http://www.vansairforce.com/community/showpost.php?p=978738&postcount=3
http://www.vansairforce.com/community/showpost.php?p=979945&postcount=4
Jumper in = ignore B
Jumper out = use B info.
EIC connected to jumper terminals = use signals from EIC to modify B info, in flight or on the ground.
Recall the mystery below? Since both the EIC and the P-mags were found to be A-OK, the conclusion was it had to be something about Nigel's serial wiring...
Originally Posted by nigelspeedy
Approximately 1 in 20 times I have experienced a fault after sending a new ignition setting. I cant say where the root cause of the problem lies but the symptoms are as follows. After you press the send button the engine begins to run very roughly and lose power. Like a very LOP mag check. Unlike the brief firing suspension that is normal this roughness does not go away. On the EICommander one of the PMags will constantly display the correct new timing value you have just sent (this is normal). The other PMag display will vary between the new value and 19.6 deg about every 5 seconds (this is not normal). The CHT will rise at a rate of about 20F per minute and the engine oil temperature will do the same. I have found two ways of fixing this fault. First, you can reload a new ignition setting, (just repeating the one you just sent has worked for me) but this takes a few button pushes and about 30 seconds all the while you will be distracted by your engine which feels like it is under great duress. Second, you can take the P Lead for the misbehaving ignition and turn it off then back on. This is quicker but be very careful to properly identify the correct ignition. I normally associate top with 1 or left and bottom with 2 or right. On the EICommander display the upper timing advance number is associated with the right ignition. It is labeled as such but the display is quite small and you could easily make a mistake in haste. Although the faulty ignition 'display' is alternating between the correct value and 19.6 deg I don't think this is when the ignition is actually firing as the level of roughness and CHT rise are counter to this. After seeing this fault I checked the PMag timing and they were both at TDC so I don't think timing was lost, as the odds of it being subsequently found perfectly are pretty low. I also sent the PMags back for an overhaul and they were both within spec. They have always run the latest firmware version. I have seen the error on both the left and right ignition, not simultaneously though. My EICommander was also returned and it had one of the comm boards replaced but I have seen this fault a couple of times since. I have never experienced this fault except immediately after sending a change. I never had this fault with just the PMags before I installed the EICommander. I have never used the PMag proprietary software to make changes to the settings.
Next time you are at SnF or OSH, stop by the Emag display. Their 114 P-mag is wired to four sparkplugs and no ground wire connects the plugs to the P-mag.(discussing a short to ground on the Pin 5 wire) Ship's power would not be available; it's a grounded power lead. Right after it grounded, the breaker opened. So, the system is on internal generator power, with the external power lead shorted to ground. Does it provide a path to ground for the internal generator?
Bill, I know these are hard questions, but one can't claim superiority based on immunity to external wire faults without clearly defining exactly what happens given wire faults in the competing system.
I tried but the SDS CEO was in high demand and the line was long. Didn't want to be pushy. Besides, he was multi tasking what with all that floor sweeping and such.
I did speak with other SDS users and many who are considering SDS. Got many questions answered.
It was great watching you race at Reno. You had quite the cheering section and it was good meeting your very dedicated support team.
Are you considering EI? I think I remember you're running mags. Is that correct?
We spoke with Nigel after he experienced this and struggled to reproduce it in our lab. In fact, we couldn't reproduce it at all. This was the first time we had been informed of such an issue.
Next time you are at SnF or OSH, stop by the Emag display. Their 114 P-mag is wired to four sparkplugs and no ground wire connects the plugs to the P-mag.
When I asked Brad about this, he said they use the second plug as the primary return path. Remember they fire two plugs at the same time (wasted spark), that was a convenient way to always have an adequate electrical return path. So, they have three return paths; the P-mag body, the ground wire, and the other sparkplug.
One other design feature of the P-mag is that once they are spinning and producing power, there is no way to shut them down. All the P-lead does is stop the plugs from firing but the internal electronics are still alive.
....So why is it relevant to this particular exercise? The P-mag is unique, in that it's the only ignition which allows the user to insert the body and mesh the drive gear at random, then write a TDC position reference electronically...
...The architecture which allows random timing reset due to outside factors has nothing to do with the P-mag's significant benefit, its internal power supply. A system with a hard TDC reference and internal power generation would be a heck of an ignition...but that's not what we have here...
All other ignitions physically reference crankshaft TDC to the ignition. As such, installation requires physical alignment of trigger and crankshaft position. Losing that reference requires outright mechanical failure. It is slightly more difficult to install, but more reliable in service.
You know folks, there is a huge amount of useful (and some not so useful - you can sort that out...) data in this thread, but very little of it has to do with "PMAG Reliability in 2017". So most of the really good info will be lost because people aren't going to be able to search for it (let's all admit that the search function is pretty basic here), and they won't look under this title to find info on SDS equipment (for instance).
And there is absolutely no way a Moderator can (or will) sort this mess out.
Think about that folks - if you have presented good, new information here - think about going and starting a new thread. Or it is all lost for posterity.
I understand that others with 0360 A1A engines have had similar issues especially with shaft and bearing problems.
I have an RV7 with an 0360 A1A which has been converted to Precision Airmotive FI and dual Pmags with firmware 36. At. 98.2 hours the R mag failed and L mag had lateral an axial play in the shaft. Brad at Pmag rebuilt the bearings in L mag and added firmware? 41 in both. I just reinstalled and they appear to operate fine for first few hours.
The engine was overhauled at engine shop in Florida to zero time.
I understand that others with 0360 A1A engines have had similar issues especially with shaft and bearing problems. If so, please let me know. [email protected]
I have an RV7 with an 0360 A1A which has been converted to Precision Airmotive FI and dual Pmags with firmware 36. At. 98.2 hours the R mag failed and L mag had lateral an axial play in the shaft. Brad at Pmag rebuilt the bearings in L mag and added firmware? 41 in both. I just reinstalled and they appear to operate fine for first few hours.
The engine was overhauled at engine shop in Florida to zero time.
I understand that others with 0360 A1A engines have had similar issues especially with shaft and bearing problems. If so, please let me know. [email protected]
Ok, discard Nigel's report, and consider timing loss with a known cause, the arcing alternator B-lead.
http://www.vansairforce.com/community/showthread.php?t=144336
At first, it was claimed that V40 would have prevented the issue, but that was obvious nonsense, as noted by this gentleman...
http://www.vansairforce.com/community/showpost.php?p=1130130&postcount=31
...and recognized by the manufacturer:
http://www.vansairforce.com/community/showpost.php?p=1131165&postcount=49
So why is it relevant to this particular exercise? The P-mag is unique, in that it's the only ignition which allows the user to insert the body and mesh the drive gear at random, then write a TDC position reference electronically. It's a wonderful feature as it relates to installation and inspection, as it makes timing a P-mag dirt simple. However, all design is the art of compromise. The same feature is an Achilles heel; the easy-to-set TDC position can also be reset. V-40 (and I suspect other patches too) is a example of an attempt to prevent unintended reset given a specific condition. The case of the arcing B-lead is an example of timing reset caused by a less predictable input, so it's not likely to be fixed with a software patch.
All other ignitions physically reference crankshaft TDC to the ignition. As such, installation requires physical alignment of trigger and crankshaft position. Losing that reference requires outright mechanical failure. It is slightly more difficult to install, but more reliable in service.
I've attempted to run though some basic "what if" analysis, which as Mike pointed out, would be followed by an estimate of probability. It does not appear we're going to be able to complete that examination due to lack of information. Frankly, it makes no personal difference to me. I'm just trying to lead the conversation back toward a logical estimation of reliability.
I will say this, based on reported field experience. The major P-mag risk is random timing reset. The major risk with other systems is simply no spark. Random timing can take out an engine. No spark merely means soldiering on with the other ignition.
The architecture which allows random timing reset due to outside factors has nothing to do with the P-mag's significant benefit, its internal power supply. A system with a hard TDC reference and internal power generation would be a heck of an ignition...but that's not what we have here.
Two things, and I'm outta here. One, it is easy to make sparks. The issue is the timing of those sparks. Two, all waste spark systems use the other plug in the paired coil as the return path for the secondary; that's why there is a wasted spark. It is very unlikely that the high voltage secondary is part of the ground path for control electronics.
I understand that others with 0360 A1A engines have had similar issues especially with shaft and bearing problems. If so, please let me know. [email protected]
What is the source of this information?
Thanks,
Erich
What i am curious about is what would cause the bearing to wear out or fail? The only thing I can think of is a side loading caused by improper gear clearance or something out of balance on the end of the shaft. As an example, when I had my slicks rebuilt the impulse mag was sloppy and looked in terrible shape but the non impulse one was in good shape. The mechanic said it was due to the big chunk of unbalanced iron spinning around inducing loads on the shaft. It made sense to me but P mags don't have that issue.
Mid 1990s. A big mfgr made a 2 blade composite prototype prop and I believe a friend had the first if not only on a pumped up 4 Cyl Pitts S1T, angle valve, 9:1 or greater compression.
It repeated interacted vibrations to the Slick mags that caused failures of the mags. I believe twice in under 50 hours.
I assume this interaction is still a challenge.