Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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 Posted: Wed Jun 03, 2015 4:37 pm Post subject: Engine roughness, as in stops. starts. stops. starts. |
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Okay, can the spear be removed now? In layman's terms the aged coil broke down under chronic heat load from who knows why and puked a high voltage discharge that resulted in a misfire somewhere in the bowels of the engine that consumed enough fuel charge to make the engine stop for a heartbeat puking black smoke out of somewhere under the chin of the engine cowl resulting in sucking of the seat pack up mine and Mongooses collective asses before the prop resumed making thrusties and we aborted the flight landing at the nearest paved Terra firma! For those that have never had the experience...it is fucking impressive! Not quit as impressive as a main bearing failure in a GE 100 though. Luckily that came on engine start. Shut that puppy down and we handed the keys back to chief and stepped to the spare.
Anyway as I said in my one liner early in this diatribe of a thread...change the fucking coil or both coils...it will fix the problem and you will sleep better knowing your little magnetos are again making voltage for your spark plugs in the normal firing order so you can break the bonds of Terra firma and look down on all the poor schmucks stuck on the interstates trudging along never knowing the pleasures of dancing with the wind and cloud chasing !
Nuf said.
Doc
Sent from my iPad
[quote] On Jun 3, 2015, at 10:16 AM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich(at)navy.mil> wrote:
Jan,
I never considered a corona in action. Just for the sake of discussion, I'll mention that I measured the heat rise in a MSD Blaster II coil using an infra-red gun and it is significant (and it is also oil filled), which is kind of why I started wondering if it really is just engine heat that is involved. No doubt heat is contributory, but while it might be an insignificant point, I question whether it is all engine heat and not just self-induced, or maybe a combination of both.
So I am trying to get my mind around this. Without creating an actual arc, the corona should rob energy from the coil correct? Not to mention if there is moist air...... there should be the formation of nitric acid, although since the premise is that there is such a small amount of air and water available, that might not be much ... but never-the-less there should be a chemical reaction that also would be contributory to insulation loss.
Another thought is that the high voltage potential necessary for a corona to form would not be present throughout the whole coil but instead only near a certain percentage near the end where the voltage becomes "high enough" voltage to create corona loss.
The problem I have with this explanation is understanding why it would make the engine run rough, cough, lug, etc., with the opposite mag operating properly? I can see where it could cause the engine to run rough or misfire on that one mag, but how would it do it with both operating?
Mark
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