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#1
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an interesting in flight experiment
Next time you're at altitude and in cruise mode, switch from 'both' to
a single bank of spark plugs. It will remind you what happens should you have one side decide to go in/op when in flight. I had the engine (IO 360) go rough a couple of weeks ago, but rough was a lot better than the very smooth and silent effects the left mag only gave me. |
#2
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an interesting in flight experiment
"a" wrote in message
... Next time you're at altitude and in cruise mode, switch from 'both' to a single bank of spark plugs. It will remind you what happens should you have one side decide to go in/op when in flight. I had the engine (IO 360) go rough a couple of weeks ago, but rough was a lot better than the very smooth and silent effects the left mag only gave me. Sounds like at least two problems--unless the fault was in the switch. Peter Just a thought |
#3
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an interesting in flight experiment
On Oct 17, 3:01*pm, "Peter Dohm" wrote:
"a" wrote in message ... Next time you're at altitude and in cruise mode, switch from 'both' to a single bank of spark plugs. It will remind you what happens should you have one side decide to go in/op when in flight. I had the engine (IO 360) go rough a couple of weeks ago, but rough was a lot better than the very smooth and silent effects the left mag only gave me. Sounds like at least two problems--unless the fault was in the switch. Peter Just a thought Nope. Engine went rough, stayed just as rough on the right bank, too quiet on the left. After the repair all was well again. Even on run up you lose some RPMs when on a single bank of spark plugs. |
#4
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an interesting in flight experiment
"a" wrote in message
... ... Even on run up you lose some RPMs when on a single bank of spark plugs. If you don't get an rpm drop when running on a single mag, something's probably amiss. My engine has never run rough during a mag check, except when I forgot to lean aggressively before taxi and got lead fouling. |
#5
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an interesting in flight experiment
This test should be part of the run-up pre-flight check.
You are verifying that the P-lead correctly grounds the magneto (by observing the drop) and that the firing side is operational. You are also, of course, verifying that the engine will run on the ungrounded side (and that it is firing that entire bank of spark plugs by scrutinizing how well it runs). I am sure you know all of this (grin), I just chimed in becuase its a check best done on the run-up pad. Todd "Peter Dohm" wrote in message ... "a" wrote in message ... Next time you're at altitude and in cruise mode, switch from 'both' to a single bank of spark plugs. It will remind you what happens should you have one side decide to go in/op when in flight. I had the engine (IO 360) go rough a couple of weeks ago, but rough was a lot better than the very smooth and silent effects the left mag only gave me. Sounds like at least two problems--unless the fault was in the switch. Peter Just a thought |
#6
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an interesting in flight experiment
"twdeckard" wrote I am sure you know all of this (grin), I just chimed in becuase its a check best done on the run-up pad. He did not say you shouldn't do it at run-up. He was just pointing out that your engine could run very rough if you lose one side while cruising. -- Jim in NC |
#7
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an interesting in flight experiment
I didn't mean the post to sound too pedantic. I guess I reacted to the OP
phrasing it as a question or a suggestion. I am sure it was rhetorically so .... "Morgans" wrote in message ... "twdeckard" wrote I am sure you know all of this (grin), I just chimed in becuase its a check best done on the run-up pad. He did not say you shouldn't do it at run-up. He was just pointing out that your engine could run very rough if you lose one side while cruising. -- Jim in NC |
#8
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an interesting in flight experiment
"Morgans" wrote in message
... "twdeckard" wrote I am sure you know all of this (grin), I just chimed in becuase its a check best done on the run-up pad. He did not say you shouldn't do it at run-up. He was just pointing out that your engine could run very rough if you lose one side while cruising. -- Jim in NC I am really not sure exactly what he tried to say; but, in his initial post, it was clear that he had lost the use of all of one mag and a part of the other--or the plugs or wires attached to it. The problem with that is that mags have a couple of failure modes that are common to all breaker point ignition systems in addition to the failure modes that are peculiar to magnetos. As far as I know, it is still a common practice to simply set the timing and perform a runup type mag check as part of an annual and not open the mags to gap and visually check the points. That leaves the door a lot farther open for the failure modes involving erosion of the points--which is related to one of the two failure modes of the capacitor a/k/a condenser--and also to wear of the cam follower. Both of those failure modes usually make the engine harder to start long before they will fail in flight, or at runup test; but are masked sufficiently by electric starters that they can go virtually unnoticed--unless the pilot is so dilligent as to carefully prime and set the throttle and then count the blades on nearly every start. Peter |
#9
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an interesting in flight experiment
On Oct 18, 10:40*am, "Peter Dohm" wrote:
"Morgans" wrote in message ... "twdeckard" wrote I am sure you know all of this (grin), I just chimed in becuase its a check best done on the run-up pad. He did not say you shouldn't do it at run-up. *He was just pointing out that your engine could run very rough if you lose one side while cruising. -- Jim in NC I am really not sure exactly what he tried to say; but, in his initial post, it was clear that he had lost the use of all of one mag and a part of the other--or the plugs or wires attached to it. The problem with that is that mags have a couple of failure modes that are common to all breaker point ignition systems in addition to the failure modes that are peculiar to magnetos. As far as I know, it is still a common practice to simply set the timing and perform a runup type mag check as part of an annual and not open the mags to gap and visually check the points. *That leaves the door a lot farther open for the failure modes involving erosion of the points--which is related to one of the two failure modes of the capacitor a/k/a condenser--and also to wear of the cam follower. *Both of those failure modes usually make the engine harder to start long before they will fail in flight, or at runup test; but are masked sufficiently by electric starters that they can go virtually unnoticed--unless the pilot is so dilligent as to carefully prime and set the throttle and then count the blades on nearly every start. Peter To put several of your minds at ease, of course I did the conventional both-right-both-left mag check at runup, but at 1900 RPM. I had not had one bank of spark plugs go in/op ever until the in flight failure a little while ago, and my post was simply to suggest pilots go to one mag while at cruise rpm and engine loading to see what happens. In my case the engine ran a bit rougher -- rpms stayed where they were set, of course, because prop pitch changed to accommodate the reduction in power. I am sure I make lots of inadvertent errors when flying: missing a mag check is not one of them. |
#10
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an interesting in flight experiment
a wrote:
In my case the engine ran a bit rougher -- rpms stayed where they were set, of course, because prop pitch changed to accommodate the reduction in power. And if you were flying a 6 cylinder (or larger) engine, you may not have even noticed the roughness. (I once failed to get the switch back to "both" after a run-up. Managed to take-off and fly for ~15 minutes before I noticed it. The roughness became more pronounced when I started leaning it out). -- Frank Stutzman Bonanza N494B "Hula Girl" Boise, ID |
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