wireweinie
FOUNDER
Palmer, AK
100% agree. I'm just expressing my exasperation with a large chunk of the human race.
Web
Web
100% agree. I'm just expressing my exasperation with a large chunk of the human race.
Web
and the AD or SB issued number was???
or was it just internet theory ???? I don't follow/pay attention to much internet theory...
not saying i don't appreciate the heads up... it makes sense!!
Yes, there was no continuity in the plug from the center electrode to where the plug wire contacts. If there is only a minute break, it will still jump a spark and pass a pressure test but does not meet the mil-spec for proper resistance.astjp2, what do you mean by "open circuit"? No current going through them at all? How did the engine run?
Jim
aircraft magneto service claims that it hurts the coils.I took apart a Champion plug that showed "open" with Fluke ohm meter. The resistor was pretty well burned, which is equivalent to a increased gap at the sparking end. At the same time my Bendix mags had their 500 hour check, and there was some tracking. I can't help but wonder if the increased effective gap could have contributed to that.
With an all cylinder EGT instrument installed in the airplane, a faulty plug can be found in less time than it takes to read your post without removing the cowl.
No EGT necessary. Just run it a bit on the bad mag and spit on each exhaust stack,bad plug will be obvious.
I find that a lot of owners think the massives' are cheaper and in the long run, its all the sameUsing the rotation sequence Champion and probably Tempest recommends the fine wires should last to TBO and not foul. Massive electrodes normally wear beyond my no go gauge in 500 hours and do seem to foul more. In my opinion it is a pay now or pay later.
that is why the DC-6's had an oscilloscope at the flight engineers station, lost of plugs on those pigsYou might be able to do that easily enough but I can't do that while flying.
No EGT necessary. Just run it a bit on the bad mag and spit on each exhaust stack,bad plug will be obvious.
The ohm test does not work on the old carbon pile spark plugs. Joe Logie at Champion told me the ohm test is a marketing thing from Tempest. He said if the plug passes a pressure test it is good. I have always used my pressure tester and never had an issue. I believe with so many customers with engine monitors if there was an issue it would have happened already. I use Tempest plugs myself, can't see paying so much more money for a name. I have ohmed plugs with my Fluke meter and seems the results are all over the place. I will continue to use my spark plug pressure tester until it is proved to me a plug can pass that test and fail an ohm test and not work in the engine.
Steve, I have had the experience of plugs (Champions) in a Husky that ran a bit rough...still ran, but just wasn't as smooth as desired. Resistances were upwards of 50Kohms on several of the plugs. They all passed testing with pressure tester. I replaced them with Tempests, and the roughness went away. (perhaps of interest, the EGTs had slight variance with the Champions).
In discussion with George Braly of GAMI, they have found a lot of problems with high resistance in plugs that pressure tested okay, but would misfire at altitude. (see https://taturbo.com/frames.html).
It makes sense in the context of Ohm's law....P=EI, I=E/R. As Resistance goes up, the amount of voltage required to generate enough power for the spark to jump the gap of the plug goes up as well. (exactly why the guy you helped had a problem....at low engine rpm, the mags weren't generating enough voltage for the spark to jump the (larger than normal) gap. A plug that has increased resistance demands more from the mag, which, in marginal conditions, can generate a misfire.
I've seen it several times in Barons/Bonanzas at altitude...a plug will start misfiring, but down low will be okay, and will be okay on pressure testing. Often it has high resistance, and when replaced the problem goes away.
(just my dumb country boy understanding, at any rate)
The best aircraft spark plugs are automotive spark plugs.
View attachment 47129
Sent from my iPhone using SuperCub.Org mobile app
The best aircraft spark plugs are automotive spark plugs.
View attachment 47129
Sent from my iPhone using SuperCub.Org mobile app