Mag Failure

Discussion in 'Hangar Talk' started by Stingray Don, Sep 4, 2020.

  1. charheep

    charheep Line Up and Wait

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    Just FYI-Tom Woods is doing a Bonanza service clinic next weekend. Hopefully you can get in this week or early next week before that. I am sure they are pretty booked the end of next week.
     
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  2. Bacho

    Bacho Pre-takeoff checklist

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    This topic is timely. Made me double check my own mags. They were way past 500hrs. Yanked them off for OH last night.
     
  3. Chip Sylverne

    Chip Sylverne Final Approach

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    Fear is the poison of our lives.
    There's a little rolled tube of dielectric paper inside the housing of that reed that's supposed to keep it from grounding against the case. Over time, the reed can wear a hole through the paper and ground itself against the housing and kill the mag. The fix is to unroll and reroll the paper so the holes in the tube don't line up. Had that happen once, drove me nuts for a while tracking that down.
     
  4. Stingray Don

    Stingray Don En-Route

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    The verdict is in. It looks like I got screwed.

    The mag failed, and I need a complete rebuild. When I bought the plane in 2014, the right mag had 1,200 hours on it without ever being serviced. As part of the purchase agreement, I wanted the mag replaced which the seller agreed to do. The shop supposedly did the replacement. Well, my A&P said that one of the internal parts he hasn't even seen in the past 15 years and it did not appear to ever have been serviced. I doubt I have any recourse after 6 years, but I will consider my options.

    The good news is that the plane should be done later today.
     
  5. RyanB

    RyanB Administrator Management Council Member PoA Supporter

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    What type of mag did you end up going with? Just replacing it I assume?
     
    Last edited: Sep 10, 2020
  6. Stingray Don

    Stingray Don En-Route

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    It is a Slick mag and they are going to rebuild it.
     
  7. RyanB

    RyanB Administrator Management Council Member PoA Supporter

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    Excellent!
     
  8. PPC1052

    PPC1052 En-Route

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    Don't know which law applies to your deal, but breach of written contract in Indiana has a 10 year statute of limitations. Also, the statute probably begins to run from the date of discovery. The real issue is whether its worth it to raise a stink. My guess is it's not.
     
  9. Stingray Don

    Stingray Don En-Route

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    Yeah, I probably will just eat the loss. Just very surprised that it appears the work was never done.
     
  10. idahoflier

    idahoflier Line Up and Wait PoA Supporter

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    That sucks! Are the serial numbers the same? Perhaps the magneto in question was replaced with an old magneto. I have heard that Slick's aren't worth overhauling, you may want to consider a new magneto.
     
  11. flhrci

    flhrci Final Approach

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    @Stingray Don , so it had 1200 hours when you bought the plane? How many more did you put on it?

    I have conflicting thoughts on this one from safety (could have had issues), that thing lasted a long time, just wow!, to that sure did save money by not rebuilding it so often and maybe they don't need rebuilding so soon. Lots of different possible thinking in this situation.
     
  12. Tom-D

    Tom-D Taxi to Parking

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    Many Mags simply get repaired, not overhauled. :)
     
  13. Stingray Don

    Stingray Don En-Route

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    I’ve put about 175 hours on the plane. I know, I need to fly more! So apparently the mag lasted nearly 1,400 hours. It is a Slick mag, and the shop rebuilt it for a little over $1,000.
     
  14. WannFly

    WannFly Final Approach

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    Last year when I spoke to aircraftmagnetoservice in Helena, they had a breakdown of IRAN vs OH of slick, OH costs more than a new mag. It’s always IRAN for slick. Back then I didn’t have enough pireps on the sure fly thing, else would have taken that route.
     
  15. Tom-D

    Tom-D Taxi to Parking

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    This is the case in most mags. the parts to repair is equal the a overhaul and the liability is a lot less.
     
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  16. Dan Thomas

    Dan Thomas Final Approach

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    Slick recommends an internal inspection every 500 hours, not an overhaul. Typically, the points will need replacing at the second 500-hour inspection. Unless something is terribly wrong in there, the distributor stuff should go a full 200 hours.

    In an overhaul they want just about everything replaced, including distributor and bearings. That stuff adds up quickly and takes longer, too. Cheaper to buy a new mag.
     
  17. Tom-D

    Tom-D Taxi to Parking

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    typical of Slick mag at 500 hours.
     

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  18. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    The spark jumped that gap somewhere in the neighborhood of 37,000,000 times. Just something to think about.

    [​IMG]
     
  19. bnt83

    bnt83 Final Approach PoA Supporter

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    Looks like normal wear and serviceable. There is no service limits to measure, it is whatever it looks like.

    If its not burned or discolored in the spring tower area, keep running it.
     
  20. Tom-D

    Tom-D Taxi to Parking

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    [QUOTE="bnt83, post: 2977009, member: 13913"If its not burned or discolored in the spring tower area, keep running it.[/QUOTE]
    I don't tear down mags that are operating properly.
     
  21. Dan Thomas

    Dan Thomas Final Approach

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    I don't tear down mags that are operating properly.[/QUOTE]
    So you run them to failure? Isn't that what we're trying to avoid with a 500-hour inspection? Things can be going wrong in there and nobody notices until it just quits. Or the engine won't start. Or the rusting impulse spring breaks.
     
  22. Bell206

    Bell206 En-Route

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    FYI: for some the 500 hr inspection will no longer be optional as several new engine model variants are being certified under Part 33 vs CAR 13 which include airworthiness limitation sections and standalone maintenance manuals. On the Lycoming side the 3 inspections included in the required AL section are the 100hr fuel injector lines, 1000hr exhaust valve/guide inspection, and the 500hr mag inspection. As I mentioned in a different thread, going to Part 33 with AL sections has caught a few people off guard in making these inspections mandatory.
     
  23. Tom-D

    Tom-D Taxi to Parking

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    So you run them to failure? Isn't that what we're trying to avoid with a 500-hour inspection? Things can be going wrong in there and nobody notices until it just quits. Or the engine won't start. Or the rusting impulse spring breaks.[/QUOTE]
    Explain the difference between a high mag drop, and a complete failure.

    Or are you simply trying to say something I did not imply?

    look at what I said in the picture.
     
  24. Jamie Kirk

    Jamie Kirk Line Up and Wait

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    I do everything by the book. Currently in annual and I’m at 472 hours so I pulled both mags sent them off for 500 hour service.
     
  25. bnt83

    bnt83 Final Approach PoA Supporter

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    Are you following calendar times as well or just the hourly?

    Example, a lot of McCauley props have a 60 month TBO. Engines are typically 10 or 12 years.
     
  26. Jamie Kirk

    Jamie Kirk Line Up and Wait

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    Been flying 300+ hours a year so I’ve ran mostly into hours.
     
  27. Stingray Don

    Stingray Don En-Route

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    Just a quick side note. The mag was running fine before the failure. RPM drop on each mag was no more than 50 RPM. There was no sign impending failure. Ran fine the previous flight and was completely dead during the following run up. I assume the mag died at some point during my previous flight, but I didn’t notice anything amiss.
     
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  28. Dan Thomas

    Dan Thomas Final Approach

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    Explain the difference between a high mag drop, and a complete failure.

    Or are you simply trying to say something I did not imply?

    look at what I said in the picture.[/QUOTE]
    Look at where that spark has been jumping. Right at the edges of the electrodes. That tells me that the internal timing has been off for some time. Either the distributor gears are off one tooth, or the E-gap wasn't set right, or the points or the cam wore out far too soon and threw the E-gap off. Slick has had quality issues with both the points and the cams and there are service bulletins on them. There is also an SB on the carbon brush and coil finger; some factory worker wasn't getting the finger nice and level and it made the brush wear against the side of its bore in the distributor rotor, sometimes totally wearing it out and the shaft would then eat into the finger and cause a sudden mag failure. Another problem was the copper distributor finger coming off the rotor.

    We once took a pair of nicely-running mags off a 30-year-old Archer because it appeared that they had never been inspected. Found them completely corroded inside, ready to pack up suddenly. I once took a Bendix off an old O-300 because it had failed suddenly on the owner, and found the front bearing had corroded and the balls had escaped and messed things up. Could have torn the accessory gearing up too. Took both mags off a 1976 IO-360 and found them beyond economical repair. Evey one of these could still be running just fine if they'd had timely inspections. Instead, the owners had to buy new magnetos. A real bargain, that.

    Mag inspections matter even if they're running fine. So do vacuum pump inspections, because they run fine too until they suddenly don't. And alternators do the same thing. They can be generating well right up until those worn-out brushes pop out of their holder. The fact is that too many owners are cheap, or they just don't know, or the mechanics can't be bothered, or they're scared they'll lose the customer if they tell him some money needs to be spent.
     
  29. Tom-D

    Tom-D Taxi to Parking

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    [/QUOTE] at where that spark has been jumping. Right at the edges of the electrodes. That tells me that the internal timing has been off for some time.[/QUOTE]

    BS the mag picture were 500 from factory new.

    Like always, Bloviatio, Yack Yack. never did answer the question.
     
    Last edited: Sep 11, 2020
  30. Dan Thomas

    Dan Thomas Final Approach

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    You're trying to tell us that Slick never screws up on new mags. then. So why all the service bulletins on new mags?
     
  31. Tom-D

    Tom-D Taxi to Parking

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    Things do get updated. many SBs are methods to do maintenance.

    still no answer?

    "Explain the difference between a high mag drop, and a complete failure."
     
  32. Dan Thomas

    Dan Thomas Final Approach

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    Surely you don't think most pilots and mechanics can't tell the difference? Or are you challenging me to list the ways a mag can fail suddenly and completely?

    Let's see:
    I had a mag fail in flight when the wire between the coil and points failed due to vibration. Totally dead. EdFred back in post #3 had the lead come off and the mag quit.

    As I mentioned earlier, I took a mag off an engine that had shed its ball bearings. Total failure, since it messed up the operation of the points.

    I opened a mag for its first 500-hour inspection and found that the rotor gear hadn't been pushed all the way onto the rotor shaft and the lower flange of the gear had been chewing away at the distributor gear. Both are nylon gears. There was so much plastic dust in the mag it was amazing that it hadn't gotten between the points and failed the mag.

    Condensers have been known to fail. Without an operating condenser there is no spark. I know, lots of people have been taught that the condenser is only there to control points erosion, but that isn't the whole story. It stops the arcing as the points open, helping to arrest the primary flow rather than letting arcing continue that flow. Condensers tend to fail suddenly, by shorting or opening. Dead mag. http://pceonline.com/wp-content/uploads/2017/04/SB651DualMagCapacitor.pdf

    If the screws holding the points assembly come loose, the gap closes and the mag fails suddenly. If they're overtightened and cracked they'll eventually let go. That's why Slick specifies 18 inch-pounds for the screws.

    If the coil tang isn't level the distributor carbon brush wears out and the shaft eats into the tang. The carbon dust causes arcing inside themag and burns the distributor stuff. Once the tang is burned away the mag doesn't work. https://www.aeronca.org/Slick-SB3-08.pdf

    If the points lose their silver contacts they erode extremely fast and fail the mag. https://7ad7ffc8-b66c-4d33-9a3f-fad...d/0b3466_a3b53cb6ad9f4296b12bd8540473f666.pdf

    If the impulse coupling falls apart some read bad things happen. https://www.championaerospace.com/assets/technical/SB2-19A.pdf
    and https://7ad7ffc8-b66c-4d33-9a3f-fad...d/0b3466_a47136480c8148b0add2ed509e0aec23.pdf

    If that distributor finger comes off the mag fails instantly. https://www.championaerospace.com/assets/technical/SB1-15A_20181112.pdf

    The stuff above can cause partial (big mag drop) OR total and instant failure. There are others that can cause big mag drops:

    The cam wears, and some cams had to be recalled. https://www.aeronca.org/Slick-SB3-08.pdf

    As that cam wears it throws the internal and external timing off. Points wear does it, too. Many mechanics will simply retime the mag to the engine to correct the external timing without wondering why it was so far off, and soon the mag's performance is getting seriously bad. Slick has stuff to say about that: https://www.championaerospace.com/assets/technical/SL_Magneto4300_6300_001.pdf

    Distributor block bushings have had wear problems: https://7ad7ffc8-b66c-4d33-9a3f-fad...d/0b3466_5e9b6d6863c84c7786bf92659b68bc19.pdf

    Timely mag inspections can catch all of this stuff before it causes a failure. For bad parts like the points or cams that might not even get to the 500-hour mark, a mechanic should be paying attention to the SBs for whatever mags he's looking after, and in any case when he retimes a mag he should be thinking a bit about why it's off.

    How many of those SBs were related to maintenance practices?
     
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  33. Tom-D

    Tom-D Taxi to Parking

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    So you believe a high mag drop is a complete failure.
     
  34. FORANE

    FORANE Pattern Altitude

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  35. Ron Stowell

    Ron Stowell Pre-Flight

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    In the immortal words of Walt Marple......everything works fine.......right up to the point of failure.
     
  36. Ron Stowell

    Ron Stowell Pre-Flight

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    We pull and send off mags weekly for 500 hr inspections. We also routinely pull the mags at annual, check points, coils, and we find mags with less that 175 hrs since new the impulse coupling is corroded, and the pins are completely loose with is cause for rejection. We bench run our mags prior to installation.

    We also are an installer for the Sure Fly electronic mags. We are in the same hanger complex with them.