Aviation spark plugs

[@aceroadholder2185]

I worked at Champion back in the 90s and we made aircraft engine spark plugs and jet engine igniters. In addition to the catalog listed spark plugs we also made specials. The rarest special spark plugs we made were for one specific engine. The engine was the power plant for the unlimited air racer "Rare Bear." The engine in the Bearcat was so souped up that it on one occasion blew a cylinder and head off the engine during a race.

[@jiyushugi1085]

How did those plugs differ from the stockers?

[@aceroadholder2185]

@@jiyushugi1085 The plugs were made in special heat ranges. The plug used depended on the ambient temperature, barometric pressure, and humidity. This sensitivity is seen on cars that run at Bonneville Salt Flats for example.

[@dukecraig2402]

I wouldn't brag about that, Champion's are the worst spark plug on the planet, I won't even run them in lawn mowers or weed wackers, they foul easier than any other plug and if by some miracle you do get them to light off they're never right after that. Here's a prime example, 30 years ago a friend of mine and myself rode across the state to see a friend of ours who we'd go spend a weekend with once a year and go to a local bike festival out there with him, this guy changed motorcycles like we change socks, every time you'd see him he had a different one, on this trip he had a 75 FLH Harley that had drag pipes, because it had an individual pipe coming off each cylinder you could tell the rear cylinder on that thing needed rebuild because it was puffing blue smoke out like a locomotive, he started the weekend with an 8 pack of Champion plugs for that application and every time it fouled one in the rear cylinder he'd just throw it away and replace it with a fresh one. We told him that when we left we'd leave my buddy's bike with him and take his bike back across the state with us and rebuild the top end of the engine for him and when we were done one day we'd meet him half way on the turnpike and trade bikes back, Monday morning when we went to leave the weather had turned miserable, it was fall and during the rest of the weekend we had beautiful 70 to 75° sunny weather, Monday morning was around 50° and raining, when we left there was 3 spark plugs left from that 8 pack, before we even got out of that town the 3rd one had fouled at the 3rd stop light we hit. After nursing it into a parking lot I took one of the plugs and rolled down the main street of the town looking for an auto parts store and came across a mom and pop place, walking inside dripping wet, cold and miserable I plopped down the plug on the counter and told the guy I needed an 8 pack of them, he told me he didn't have Champions but he did have the equivalent in Autolite, not caring what he had I got an 8 pack of the equivalent in Autolite, anything as long as I could get back to him and we could finally get on the highway to try getting out from under that rain. When I got back he put an Autolite in that thing and not only did it fire right up and not foul at the rest of the stop lights we hit on the way out of town and not only made it all the way back across the state but he rode that bike every day for 2 more weeks on that same plug in that rear cylinder that was smoking like a chimney everywhere we went before we rebuild that top end, the same plug all that time and it NEVER missed a beat. Well that was enough to make me a believer, ever since I've run nothing but Autolite's in everything I own, my kick start only Harley became much easier to get started, the difference was noticeable to say the least especially in the winter, every chainsaw I've ever taken into the woods has never let me down, every lawn mower, weed wacker and anything else that uses a spark plug has never caused me as spark plug related problem since I switched exclusively to Autolite, when I buy something brand new like a mower or chainsaw I stop at an auto parts store on the way home and buy a pack of Autolite plugs and put one in before I even start it, those things will fire in a bucket of oil, they'll even run in a Ford!!!

[@markthompson4885]

I use Champion "X" sparkplugs in my Tractor

[@DrFiero]

In the late 90's I started working as an AME. The 1954 Convair we were working on had 2 engines. 18 cyl's each. 2 plugs per cyl. - was about $5500 in parts back then to change the plugs! Can't imagine now. 200L of oil for each engine as well. Made for an expensive "tune up". ;) That cooking the gaskets thing was one of my first ever jobs as an apprentice! And cleaning the plugs. Only drop a plug twice. Once on the floor, then again into the can.

[@nickydoes]

Restoring vintage aircraft is definitely for the rich.

[@jiyushugi1085]

Most aviation mechanics (and any good car/motorcycle repair outfit) will have a spark plug tester/cleaner. These combine a bead blaster (or sand blaster) for cleaning the plugs, plus a small pressure chamber into which you screw the plug, attach a high tension lead and watch, through a window, how the plug fires under pressure. The pressure test is needed because a faulty plug will often fire just fine under ambient air pressure but fail under combustion pressure. The amount of money people waste on new plugs when all they need to do is clean their old ones is simply mind-boggling. When I was flipping bikes to pay my way through school I would regularly source plugs from pick-your-part junkyards or auto-parts trash cans, and simply clean them.For my own cars/bikes I simply clean the plugs periodically.

[@nickydoes]

This is exactly my experience. I would bring my fouled plugs to the shop, and a junior aspiring A&P would clean and test them with a tester just like what @jiyushugi1085 described. That's why I had 3 sets. One in the engine, and 1-2 being cleaned & tested.

[@dukecraig2402]

Run valve stem seals in your engine's and keep your fuel system in good order and you won't need to do that, just run them until the electrode is no longer serviceable. I've been building Harley engine's for year's, all their mid '81 and earlier engine's that didn't originally have valve stem seals I absolutely refuse to rebuild without fitting them on, what a huge difference it makes, it takes 3,000 miles for oil to turn black instead of 500 miles, you can actually read the spark plugs and not just for fuel ratio but you can also read the timing on them like a modern engine because after 100 miles they're not black from oil deposits. I've helped a few buddies out with car cylinder head's, the old school V8's that used umbrella seals I've told them if they buy the cutter and mandrel (if it's a size that the old, and some new, Harley's didn't have, some are in which case I already have them) then I'll do all the work for free as long as I get to keep the tooling. There's nothing like the modern valve stem seals that press on the top of the guides, they keep all that oil out of the combustion chamber allowing you to lean out the mixture and run more timing without getting detonation. In this day and age running any engine without valve stem seals or even those old umbrella seals is insanity, the difference the modern press on seals make in an old engine is night and day, it's the single most effective update you can do to the older engine's.

[@bobbybishop5662]

My uncle had a sparkplug cleaner in the shop on his farm. My cousin was putting the plug wire on the tester on a plug and I turned that sucker on. He took about a dozen good zaps before he could let go of the plug. Lol We laughed out butts off.

[@jiyushugi1085]

@@bobbybishop5662 We hooked ours up to a metal table.....

[@johno9507]

First job as an apprentice aircraft mechanic in the 1990s was removing and cleaning 36 plugs from a DC-3, thank god I later got hired by a large airline! 🙂🇦🇺

[@nickydoes]

That's a lot of plugs. Those Wasp radials are amazing!

[@michaelsamson3276]

Couple of things. If you quench the gasket it ends up clean again. Another thing, neither part of the spark plug is a neutral. The magneto switches polarity every 1/2 revolution.

[@nickydoes]

Quenching - definitely.

[@incandescentwithrage]

The outside of the plug is attached to the engine and will remain at engine potential (neutral, ground whatever you prefer). Whether the magneto charges the inner electrode with positive or negative potential with respect to the engine is irrelevant, it's the outer that retains the neutral / ground potential.

[@michaelsamson3276]

@@incandescentwithrage Sorry, but electron theory is pretty much accepted. Positive to negative except in the source.

[@incandescentwithrage]

@@michaelsamson3276 I'm going to ignore anything further you have to say. First you make a pedantic and irrelevant point about spark plugs. Secondly you incorrectly assert that electrons flow positive to negative. They don't.

[@9traktor]

Thank`s for that fine explanation. Learned a lot.

[@gEtar87]

A copper washer only costs 1¢ if you can use a penny. Not advisable for aviation but it definitely worked on vintage lawn mowers. "The extra cost in aviation is purely mechanical redundancy and worth the up front cost." - a guy who couldn't afford a lawn mower

[@Psyrecx]

*My car has an upper and lower spark plug, as well...* Leading, trailing. Spark plugs are also a lil screwy in it, also.

[@robinsparkes-u1l]

Great to see I found it interesting.

[@richb419]

Hi Nicky. I think I have seen that type of plug in the military vehicles like the jeeps and 5/4's. I wondered what they were.

[@nickydoes]

That would make sense. If you are stocking plugs for wartime use, make them the same if possible.

[@richb419]

@@nickydoes yea they apparently waterproof too

[@wendellsmith1349]

I never knew ... Thank you for making this.

[@michaelmurphy6869]

Now I see why those plugs are so expensive. I was told once by an A/P mechanic that the gap on the plugs had to be set at .012-.014 or the plugs won't fire because of the AC magnetos used on Aviation piston engines. Unlike in some vehicles where the gap can be set from .022 - .085* ( * Cadillac had that spec back in the 80's on some of their engines) those days the standard gap is .035 - .044 (1.1 mm). Thanks for informative video.

[@nickydoes]

The magnetos look like vintage tractor magnetos.

[@buttcrack7784]

.0.012-0.014 gap is not only a very tight range but under any gap setting specifications I’ve ever seen. My Lycoming O-360 and an O-320 I had previously had a gap spec of 0.016-0.022. I question that A/P’s advice and would check the engine manufacturers recommendations.

[@in4merATP]

Best single way to keep your plugs clean is to lean as aggressively as possible while on the ground, at idle.

[@UQRXD]

I had to laugh. If you can afford a plane what's 10 bucks for some washers. I mean really.

[@rkan2]

10$ washers could br 1000$ in an aviation application 😅

[@nickydoes]

@@rkan2 Aircraft owners are generally super cheap about operating expenses. Plug washers are a perfect example. Conversely, many refer to 'AMUs' where 1 AMU = $1000. "How much was your engine overhaul?" "65 AMUs"

[@nickydoes]

​@@rkan2 Spark plugs and washers are considered consumable items, and don't need the same rigor as other aircraft parts (PMA'd, 8130 'yellow tag' history, or even a serial number). You could cut your own washers out of a copper sheet if that's what you chose to do.

[@Goodkiwibloke]

Interesting video These spark plugs are more similar to outboard motor 2 stroke constant gap spark plugs

[@nickydoes]

I've never seen anything but common automotive style plugs in outboards. So you have a model or example that used different plug types? Seems like OMC tried a lot of crazy cool ideas.

[@Goodkiwibloke]

@@nickydoes Google "surface gap spark plug". There are several different types

[@michaelmurphy6869]

If recall Mercury or OMC was using in their outboard engines (2-stroke variants) what was labeled a "surface gap" which was a fixed gap. There wasn't a center electrode the plug fired diagonally across which they stated improved performance because of the more exposed spark. Even though that still occasionally fouled, I always thought because the center electrode length between the tip and the insulator was too short this allowed contaminants to build up on the insulator and short across to the plug housing. Once they were fouled they couldn't be cleaned and reused, because the insulator material was too porous. I don't know if they use that type of plug anymore. Mazda used a similiar type, twin ground electrode spark plug in some their rotary engines along with Toyota in their more conventional smaller 4 cyl engines.

[@garycarbonneau499]

Mercury Outboard was the first to use " gapless" plugs meaning they had no negative side electrode but used the whole threaded perimeter. It took their high energy Thunderbolt ignition to fire them at high rpm. Less chance of fouling but more importantly there was no welded on negative electrode to come off and eat the piston and bore. I still use them on my high rpm 2 stroke outboards that l drag race. One note... they are impossible to read for tuning so l use standard plugs of the same heat range for that. Gary RKG Outboard Drag Racing

[@BruinHerr-bj7uk]

And I thought my $20 OEM Honda iridium plugs made by NGK were expensive! (Beware of FAKE NGK iridium plugs)

[@nickydoes]

Everything 'airplane' is a different level of expensive. Engine overhaul (not a new one) is north of $50K for a 6 cylinder engine. They're often overhauled after 16-1800 hours of run time.

[@Mike40M]

One thing not explained is why the threaded top of the plug. To make a waterproof cable connection and secure the cable from coming loose. It also reduces emission of radio frequency noise. Car plugs nowadays has a built in resistor to reduce noise, don't mix well with magneto ignitions. Seen similar electrode layout in motorcycle race plugs where thermal load on the plugs are high. Seen similar plug design in old military vehicles for waterproofing. Twin plugs per cylinder both gives added safety and increased power.

[@nickydoes]

Good points. Thanks for sharing. These are resistor plugs as well.

[@michaelbartholomew1038]

REM37BY plugs used in O-235 and others have an extended electrode like automotive plugs. Gaskets cost about 25 cents and not all engines foul spark plugs that bad.

[@louisesamchapman6428]

Do you sand blast your used plugs to clean the insulators? In the early 70s I did tuneups on leaded gas vehicles and if they were driven too hard right away (test drive) the insulators would glaze over and surface short /track to ground inside and misfire, had to clean or replace...! So Don't run them too hard, too soon !

[@fastinradfordable]

That’s bs Running your engine harder will have cleaner plugs unless you’re burning oil and low on compression.

[@louisesamchapman6428]

@@fastinradfordable Why then does he need so many spark plugs ?

[@nickydoes]

avgas lead builds up regardless. Aviation engines run most of their life at or above 80% power.

[@nickydoes]

Yes, it's either a pneumatic thingy, or a motor-driven wheel that slings 600 grit abrasive at the plugs. Or - you pick the lead out with a dental pick.

[@louisesamchapman6428]

@@nickydoes Carbon is probably from oil drawn past the intake valve stem seals (steady vacuum there). Try a quality umbrella style or replace the stock ones that may be baked and leaking .

[@UQRXD]

I have seen marine spark plug applications with the ignition cable nutted to the plug.

[@nickydoes]

A few have replied about this, and I wasn't aware. It makes sense. Thanks all for sharing this!

[@RS-vu3df]

Interesting, about the multi mass-electrodes, in Europe a lot of cars run on multispark plugs, upto 4 electrodes.

[@davidoickle1778]

When you own a 500k Cessna 172, what's $10 for new washers?

[@nickydoes]

It's $10, same as if you don't own a 172.

[@rusty358]

These plugs look very obsolete compared to modern iridium plugs. The whole ignition system looks obsolete as well. Don't know if leaded gas and iridium are compatible.

[@nickydoes]

Many aircraft engines are now certified for fine wire plugs.

[@servicetrucker5564]

When reliability is key single failure points and electronics are the enemy

[@jarikinnunen1718]

I did watch Congress hearing about why USAF pay $10000 for $10 worth bag of bushings?

[@nickydoes]

Wait! These are for the military? We'll run materials tests, x-ray tests, and document the origins, and charge $10,000 each!

[@mickvonbornemann3824]

Well I can now see the demand for diesel aero engines

[@nickydoes]

Today's diesels tear apart propellers. Unleaded fuel is here, though.

[@MarcelEnglmaier_1]

how do you gap those spark plugs?

[@nickydoes]

A gapping tool threads over the plug, then a lever pushes the electrode in or out. www.aircraftspruce.com/menus/ep/sparkplugs_tools_gapping.html

[@fluke196c]

saving $10 for a spark plug change? doesnt sound worth it to me, especially considering the cost of maintenance

[@richardbroussard857]

two plugs or for performce faa test question I got it rong I answered safety on air boats with aircraft engines they use car plugs auto. aircraft plugs or made like that to keep down radio noise

[@ormtheelder2657]

Don't see my comment that you should quench the red hot washer in cold water to make it soft. You are trying to temper the washer. If you let it air cool you are annealing ithe washer that makes it harder

[@nickydoes]

Copper is face-centered cubic, and can't be quench hardened. Quench or air cool - same results.

[@mannypuerta5086]

@ormtheelder The annealing process is actually softening the copper, not hardening it. You want the copper washer to soften for reuse.

[@jiyushugi1085]

I just put a bunch on a length of coat hanger get em changing color then drop 'em in a pan of water. It'd be nice to make a washer holding tool (on a lathe) that would hold the washer just proud of its surface so you could flatten it on a piece of wet/dry on a surface plate.

[@jetwrench2854]

They are cleaned and softened by quenching in white vinegar.

[@gb123-ej8wh]

I hate to break it to you but you are wrong. You stated that automotive spark plugs are just the one style of 1 electrode over hanging and gapped. That’s 1 kind, but not at all the only kind used in production automobiles. In fact there are what was colloquially called lawnmower plugs used in rotary engines where you had 3 sides coming in similar to your little 2 sides and basically making a path should 95% of that (not sure if it would be anode or cathode but the central pole in the plug that’s common to all the types I’m personally aware of) could be carbines up from arching and still have a path. Those wankels also used leading and trailing plugs. I’m not sure if it had anything at all to do with fear of falling from the sky as they frequently fouled up as I understand promoting people to install fuel shut offs so they could run the engine and intake dry avoiding plug fouling. Just though you should know that since you presented it as fact but this is just 1 example of many variations of automotive spark plugs. Funny I don’t know why they were called lawn mower plugs as none of the mowers I’ve had have any strange plugs. They were all the old standby that everyone sees in their head when they hear spark plug.

[@nickydoes]

Thanks for that clarification. Design evolution at work. Reminds me of a book you might enjoy "The Evolution of Useful Things" by Henry Petroski.

[@motodude23]

I have never had a spark plug go bad my whole life, they lose some performance after 180k miles but thats long after the service life, heard of 1 losing the tip and destroying something. Seems like aviation is stuck in the past because "if it aint broke don't fix it" mentality. Not that safety isn't the number 1 priority but come on.

[@ShortArmOfGod]

Fascinating anecdote.

[@markb1764]

I am guessing with what a set of plugs is worth that the cost of new gaskets would go unnoticed Don't be pennywise and pound foolish with an aircraft

[@rkan2]

6:30 - every piston engine aviation fuel*

[@nickydoes]

Some airplanes are certificated to run on 'mogas' auto fuel. A new unleaded fuel 'G100UL' from GAMI in Ada, Oklahoma, was recently approved by the FAA with STC for all aircraft as a replacement for 100LL (the current 'blue' leaded avgas). That'll make a good video topic!

[@davidkuehne476]

twice the ground straps are twice the chance for one to fall off and lunch the whole engine, like that one that looks to be separating...

[@nickydoes]

The electrodes do separate. It's reasonably rare, though. When it does happen, it's not often catastrophic. It usually takes out a single cylinder - gets stuck in a valve.