How Mags Fail
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- čas přidán 17. 03. 2021
- Following up on his previous EAA webinar about aircraft magnetos, Mike Busch A&P/IA discusses the various ways that magnetos can fail, how pilots can safely deal with these failures (and why they usually don't), and how proper maintenance can prevent these failures from happening in the first place. Savvy Aviation offers Professional Maintenance Services to owners of General Aviation aircraft, such as: SavvyMx (Professional Maintenance Management), SavvyQA (Expert Consulting), SavvyPrebuy, SavvyAnalysis (Engine Data Analysis) and Breakdown Assistance. Savvy also publishes a monthly newsletter with lots of interesting information for the general aviation enthusiast; subscribe to it at www.savvyaviation.com/home/ge.... For more information, visit us at savvyaviation.com. This webinar was hosted by the Experimental Aircraft Association (EAA).
- Auta a dopravní prostředky
It always amazes me that airplane engines are still basically lawn mower engines designed in the 40’s and are still using large amounts of unhealthy, dangerous fouling lead as an octane booster. Modern engines could easily be built with lots of redundancy with extremely low failure rates, but unfortunately we are still stuck in the 1940’s and 50’s.
Mike, my engine did quit on my inflight test. It was the first flight after a big annual maintenance. I had an experienced CFI in the right seat and the mechanic in the back. I was doing a post maintenance flight test as you taught me to do. I cut the mixture and switched to the good mag and reintroduced mixture as you described here. The only consequence was the mechanic regretted letting me convince him to fly with us, but did acknowledge the mag needed to be sent back to the overhaul shop!
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Had a mag fail due to an improper capacitor terminal installed by a well-known (in my area) mag overhaul shop. Rpms would vary 50-75 on mag check, traced it down after a bit and found the terminal too large for the connector in the mag causing a poor connection.
regarding, engine ends in "D" as Greg Ellis noted, o-320-D1D also is not a dual mag engine. The first 3 significant digits after the displacement number do not count. A Dual mag engine will end with D in the 4th or 5th position, like o-320-H2AD, and o-360-A1F6D.
That switching from Slick mags to Bendix, or vise versa, not only means a new harness but also new drive gears. Since they differ. Those are expensive. So those two items end up causing most owners to forgo the swap.
Hello from Sydney, Australia.
Thank you for the very comprehensive look at magnetos and the function they play in creating energy/current to the spark plug. Moreover, topics such as:
* different magnetos: (Their size, space and installation requirements.)
* troubleshooting (fault detection and diagnostic considerations: (internal parts and harness wiring P leads)).
* Intervals 500hrs for IRAN v overhaul/replacement - Slick/Bendik.
And finally the advantage of A&P specialist service shop providing a higher level of goods and services.
💥🕳👨🍳
Great webinar
Excellent information! Especially turning off each mag during sudden engine roughness. Really enjoy being a SAAVY member for questions and monitoring. 👍
Thank you!
I've never flown but I'm a mechanic and a racer and interested to start flying I live in walking distance to a small airport. I've watched almost all of these videos thanks for all of the information!
I had a mag fail once over Washington, and I turned it off and landed. If I’d continued to my destination, I’d probably be dead because my other mag quit 2 hours later after getting the dead one fixed.
I just went through a left Mag failure. I had my annual in May 2022 on my Cessna 210B. Mags were over 500 hrs. A&P sent then in to a Mag shop and they deemed my perfectly working MAGS unairworthy. Spent 1600.00 rebuilt mags and thought everything was A-OK. Started noticing a degrade in Left Mag performance during run up. Thought I had fouled plugs so I cleaned plugs, did a compression check and borescope. Found #4 was down to 50/80 and it was attributed to a bad roto-coil. Valve was lapped and new roto-coil installed returned to service. Went out for a test flight and had a rough running engine at take off at 500agl, called tower and asked for short approach and got it back on the ground. Replaced all plugs, another borescope and compression check and came back all above 74/80.
After many run ups I was able to reproduce the MAG issue 100% after getting getting IO-470 up to temp. I would watch #2, #4, # 6 cylinder EGTs fall off the grid on the left MAG. You would think that all cylinders would stop firing but I had only the left bank failing. Sent the MAG back to shop and they confirmed the "contacts" (points) were bad. It is odd to me that only 3 cylinders would fail. MAG should be returned to service in a Day or 2. Will report my findings here after I get plane signed off tomorrow. I also, failed to switch to Right Mag and leave it there as Mike Busch clearly notes. This has been a good learning experience and would not have known about the bad sealing valve and roto-coil.
You can see my Run up test here:
czcams.com/video/ngOLwUO18Tw/video.html
10/22/22 Update: I spoke with the MAG shop this morning and it tuns out it was a "manufacturing defect" in the rivets the connect the cam Follower to the points.
48:03 During ground-runup, couldn't you follow the full-rich mag check with an aggressively-leaned mag check? Regardless of mixture, there should be no risk of detonation at such a modest power setting. This would add only a few seconds to run up, but would allow for a fairly demanding ignition test before takeoff. Of course, your checklist would need to include a "reset mixture to full rich" before takeoff.
I also like Brian's suggestion of performing another mag check before shutdown. This gives you the opportunity to fix problems before planning the next flight.
I wanted to share my story. I had a mag spontaneously shed distributor teeth at 50ft AGL on takeoff at a rural airport surrounded by trees. No time for diagnosis of why the engine sounds like it's going to explode and no power to climb to clear trees. Got it down and stopped
I had a mag failure when doing power off 180's oddly enough. Once I touched down I put the power in and the plane started shaking violently. I pulled power then mixture since I was on the ground. I pulled the plane off the runway (untowered thankfully and no one was around). I wonder if the mags failed between when I pulled power at pattern altitude and landing or upon touchdown. If the former, I'm glad my 180 training was at least up to par. I kicked myself later for not diagnosing it on the runway, but only upon next start up. I agree, training is lacking. I was trained for pretty much every other failure. Hopefully I learned in case it ever happens in the air.
15:24 It's almost like there's a reason ignition switches were designed to shut off one magneto.
This was a great video… thank you for making it …..and possibly saving my neck at some point…
I’ve never had a Mag fail, but I have had I switch that would not come ungrounded and had to remove the ground making a hot prop to fly home.
Electroair received an STC for the D3000 a couple of weeks ago, using the same case.
Lead fouled plugs,hmmm. I remember the bad old days of leaded gas in automobiles and motorcycles. Haven't seen combustion chamber deposits quite like back then since it's elimination.
When the engine is running and turn the key to the off position which ignition is firing left, right or both?
Mike stated that if your engine ends in a -D then it has the dual mag. Well, I fly behind a Lycoming O-360-A1D and it does not have the dual mag nor did it ever have the dual mag. It has and always has had two separate mags.
The problem with redundant systems is people can get into the mindset that there is always a back up. That can defeat the object of the redundant system. I wouldn't want to run to fail on a redundant system anymore than on a non redundant system. E.g. I don't imagine 737s will run to fail on engines because there is another one, instead I would expect the engines to be maintained like a single engined aircraft.
The Bendix mags have the red tooth, I guess if you’re really good at keeping it centered in the hole, you don’t need to have a tool but there is a locking tool for those mags. Same principle of not moving the prop or the body of the magneto when the tool is in place
Seems to me after listening to your webinar, that owners should replace the magneto with a rebuilt one probably as often as they replace spark plugs or every 50-100 hours of usage. A brief online search reveals an overhauled magneto is around $500, swap them out periodically the first mag one year the other the next, and so on.. Why wouldn't you?
I used to fly a PA28 that had separate mag switches, an Archer III that my flying club owned. Now I know why
Far better system. We had a bad starting C152 until one day i saw student just slightly back off key when starting and engine fired up. So i told maintenance switch was faulty. They spent time messing about with everything but the mag switch. Finally they replaced it and cured the problem.
Lost a friend to the dual mag issue. See NTSB for N50BJ accident report.
My question has always been.... on the switch, why is R on the left and L on the right?
Lol I wonder this too
Show me data showing dual mag failures
And that Slick mags are less reliable.
Plastic gears. Really? Brass is non-magnetic and so is aluminum. Back in the day, when there were no plastics, what were the gears made of? No criticism to you, Mike. What are these manufacturers and the FAA thinking?
Thanks for the great explanation!
If you lose a mag, DON"T continue to your destination, unless it's the closest suitable airport where you can get service. You have a single, critical system after one fails.
Right, it's better to land with an engine running on one mag, versus trying to land with no mags working :)
Magnetos gone wild!
Why aren't the distributor gears made out of something more durable. Brass or steel is out of the question since those conduct electricity. I'd imagine that ceramics might be a good alternative.
They make one gear out of plastic so if there's an internal jamming of the distributor arm, it doesn't explode or shear off teeth in the engine. Always a good idea to have a weak link somewhere. There's many other machines out there like ice machine flaker drives or washing machine transmissions that have one gear that is plastic. The idea being it's better to have a mag fail, and have that failure contained within that mag versus a potential uncontained failure where the mag comes apart completely that could result in a massive oil leak, or other really bad things. Ceramics are too brittle and could shatter unexpectedly. Brittle failure modes aren't good, those happen suddenly and can be quite catastrophic.
Engineers prefer to couple non-primary-output things to engines with belts or weaker components designed to shear.
Otherwise a seized bearing turns into a full on shrapnel event as the bearing and/or guts of the connected item get spewed into the engine. Or the torque shears a very expensive machined shaft which might cause internal components to bend and/or shed metal confetti inside the engine.
In all such cases without the ability to "shed the seized load" you risk severely damaging the engine or even causing it to also seize.
Engineers prefer to couple non-primary-output things to engines with belts or weaker components designed to shear.
Otherwise a seized bearing turns into a full on shrapnel event as the bearing and/or guts of the connected item get spewed into the engine. Or the torque shears a very expensive machined shaft which might cause internal components to bend and/or shed metal confetti inside the engine.
In all such cases without the ability to "shed the seized load" you risk severely damaging the engine or even causing it to also seize.
you say that none of the pilots continued to the destination. you left out all the pilots that did. I had a mag fail last year and is exactly what I did. Pax didn't even know there was an issue. This is kind of like an engine failure on a twin. A lot of engine failures aren't known. The pilot lands, its fixed, and everyone moves on. Not going to one mag when one fails is sorta like not feathering the prop when a twin motor fails.
Would you take off with one compromised magneto? Read comment from pilot "Dustin" above. In his case second mag failed within two hours of first mag. Wow, that is some incredible engineering.
12:18 are you F ing kidding me. One of the most BASIC things I learned as a Pvt pilot and taught as a CFI later (now ATP 28 yrs ago) was to TEST THE MAGS by trying L and R.... I wondered WHY turn one mag off if your engine is already running rough? So I researched it. Yep if a Mag is still firing but so off time it could made the engine rough turning it off will solve the issue. MAKES SENSE.... WHAT THE F.... As well turn boost pump on if applicable, primer locked, may be switch tanks if applicable, carb heat if applicable, adjust mixture.... Basic basic basic.... I looked at check list and YEP many from BIG Companies that sell check list say MAGS BOTH ON..... GIVE ME A BREAK.....
I always tell student try L or R, might just run better. I often see on check outs pilots say "starter" and go through motion turning key. I tell them why if the prop is already turning.
@@flybobbie1449 Ouch, engaging the starter with engine already turning can break expensive things. Not good :) Better to just unfeather the prop and let it windmill. Yes it's a little more drag, but so what.
Glorified Volkswagen engine lol