Swap Spark Plug Locations To Equalize Wear

brien23

brien23

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Champion Aviation Technical Bulletin 70-9 shows the recommended locations to switch plugs top to bottom. This will equalize electrode wear caused by constant polarity and capacitance and also keep lead accumulation down to a minimum.
 
brien23 said:
Champion Aviation Technical Bulletin 70-9 shows the recommended locations to switch plugs top to bottom. This will equalize electrode wear caused by constant polarity and capacitance and also keep lead accumulation down to a minimum.
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I don't have a clue what you mean by "capacitance" in this statement but proper rotation does tend to reduce erosion of the center electrode on massive electrode spark plugs. FWIW, I don't think it has much effect on lead accumulation unless there's a reason that bottom plugs run considerably hotter or cooler the top plug in the same cylinder.

Also, rotation doesn't seem to have much effect on the life of fine wire plugs IME but it doesn't hurt anything either.

But the absolutely most important thing to remember about aircraft spark plugs is DON'T DROP THEM. And if you do, don't put it back in the engine.
 
Geico266 said:
Good advice, a little spark plug thread lubricant will save you $$$ also. ALWAYS start your plugs with your fingers, never with the socket.
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I think a more accurate statement would be to make the first few tightening turns using your fingers on the plug or socket rather than using a wrench. That said, it's not all that difficult to limit the torque of a wrench if you're careful and can tell the difference between normal friction and crossed threads.

I often use a socket to start plugs, but I'm turning the socket by hand so I can tell if it's going in straight or cross threaded. I've found that since the socket limits the angle a plug can have relative to the threaded hole, using a socket actually makes it less likely that a plug will start with the threads crossed.

As to the "spark plug lubricant" I think it's worth mentioning that you're supposed to use "anti-seize compound" which is usually conductive and will stain almost anything it gets on. Therefore it's important to keep it away from the first few threads of a plug (so it doesn't get near the electrodes) and anything you don't want stained.
 
Swapping the plug to reverse the polarity adds about 10 minutes to run life of a plug. IAW Champion lecture at renewal siminar.

It ain't worth the time to bother. the plug will be replaced at 500 hours anyway.

Plugs are replaced due to the size of the total circumfrance of the 2 neg electrodes and the center electrode when gapped properly. using the tool to measure them.

It doesn't matter which electrode has been erroded, it will be replaced away anyway.
 
otoh - it doesn't take any more time to swap top/bottom each time the plugs
are cleaned, does it?
 
Tom-D said:
It ain't worth the time to bother. the plug will be replaced at 500 hours anyway.

So Tom what you are saying is that the people that wrote Champion Aviation Technical Bulletin 70-9 don"t know what they are talking about.
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OK, help me out here. As a non-owner pilot, I'm trying to understand the costs of ownership as I hope to be there in a year or so.

Are aviation spark plugs expensive? For my tractor and other engines that I use, they are a couple of bucks. So, I just swap them out each year or two, even if not totally gunked up. That way I know there's no accumulated carbon around that area of the engine. Is it a more difficult or expensive proposition for an aircraft engine?
 
brien23 said:
Tom-D said:
It ain't worth the time to bother. the plug will be replaced at 500 hours anyway.

So Tom what you are saying is that the people that wrote Champion Aviation Technical Bulletin 70-9 don"t know what they are talking about.
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Good theory, it sells plugs.
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nddons said:
OK, help me out here. As a non-owner pilot, I'm trying to understand the costs of ownership as I hope to be there in a year or so.

Are aviation spark plugs expensive? For my tractor and other engines that I use, they are a couple of bucks. So, I just swap them out each year or two, even if not totally gunked up. That way I know there's no accumulated carbon around that area of the engine. Is it a more difficult or expensive proposition for an aircraft engine?
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Aviation plugs run anywhere from about $20/ea to $80/ea...


Trapper John
 
nddons said:
Are aviation spark plugs expensive? For my tractor and other engines that I use, they are a couple of bucks. So, I just swap them out each year or two, even if not totally gunked up. That way I know there's no accumulated carbon around that area of the engine. Is it a more difficult or expensive proposition for an aircraft engine?
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From Aircraft Spruce, regular spark plugs are about $25 each, fine wire about $75 each. You have 8 for a 4cyl engine, 12 for a 6cyl engine, so yes, they are much more expensive than automotive plugs. Many (most?) people clean and regap them until the center electrodes are out of tolerance. Have your A&P show you how to clean and regap them. Lead balls and bridges in the lower plugs seems to be one of the big problems but can be helped by proper leaning on the ground.

Replacing them is not difficult.
 
Trapper John said:
Aviation plugs run anywhere from about $20/ea to $80/ea...


Trapper John
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tparsons said:
From Aircraft Spruce, regular spark plugs are about $25 each, fine wire about $75 each. You have 8 for a 4cyl engine, 12 for a 6cyl engine, so yes, they are much more expensive than automotive plugs. Many (most?) people clean and regap them until the center electrodes are out of tolerance. Have your A&P show you how to clean and regap them. Lead balls and bridges in the lower plugs seems to be one of the big problems but can be helped by proper leaning on the ground.

Replacing them is not difficult.
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WOW! Thanks, I never knew that.
 
tparsons said:
Lead balls and bridges in the lower plugs seems to be one of the big problems but can be helped by proper leaning on the ground.
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Circuit work will foul plugs, too. In the flight training aircraft we clean them every 50 hours, and rotate them. The Citabria's O-235 is a notoriously cool-running engine and lead deposits will sometimes foul the bottom plugs even before 50 hours. I got fed up with that and replaced the REM38/40 plugs with the REM 37BY jobs; they just won't foul up.

rem37byelectrode.jpg


The picture, unfortunately, is comparing an REM 37BY to a long-reach RHM plug, but you get the idea. The BY's well is shallow, and with the spark gap farther out it can't fill up and short the plug.

The BY fits many engines. Champion has a list of eligible installations for it. See
http://www.championaerospace.com/pdf/64552_Champion_ElecL.pdf


The best plug I ever used was the Auburn. Champion bought up Auburn about five years ago and shut them down, one of aviation's minor tragedies. Champion plug life is far inferior to the Auburn's. Unison now claims the same construction as the old Auburn for their plugs (monolithic resistor instead of the loose, spring-loaded thing Champ uses) but they fail even sooner than Champs, which is saying something. I've had brand-new Champs fail on the test stand, right out of the box.

Dan
 
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nddons said:
WOW! Thanks, I never knew that.
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Even though I managed to pay only $60 each for the fine wire plugs in my B55, the cost of one complete set (24 plugs) is a mere $1440, installation not included.
 
gismo said:
Even though I managed to pay only $60 each for the fine wire plugs in my B55, the cost of one complete set (24 plugs) is a mere $1440, installation not included.
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That's what you get for having 2 engines. :D
 
Besides a lot of paperwork, what else makes an aviation plug sell for $60?
 
vontresc said:
Besides a lot of paperwork, what else makes an aviation plug sell for $60?
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The market and a lack of competition. I don't know if Champion has ever been successfully sued for an airplane crash but I'm sure they pay a hefty insurance premium to cover the potential for that. I suspect that each spark plug type has to be certified by the FAA for each engine it can go in and chances are there's some testing involved. Then there's the quantity issue, there are probably more plugs made each year for lawn mowers than for airplane engines.
 
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