Mag Failure

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

  1. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    Well, it is a perfect day for flying. So I took a vacation day and headed for the airport. Taxied out to the run up area. Left mag - check. Right mag - engine dies. Restart the engine and check the right mag again - engine immediately dies. Put her back in the hangar and scheduled maintenance. I am now a ground dweller. Wonder how much this will cost me.
     
  2. GMascelli

    GMascelli En-Route PoA Supporter

    Joined:
    Jul 27, 2005
    Messages:
    3,184
    Location:
    Ocean City, MD
    Display Name:

    Display name:
    GaryM
    Recently went through the same, except I wasn’t at the home base. Had to pay tie down fee, travel time for A&P and new mag.

    The repair bill break down as follows: $1,940.00
    • Troubleshoot and remove right mag
    • Install new Slick Mag MN4370.
    • Install Mag Gaskets
    • Time both magnetos
    • Run engine and perform ops check. Good
    • Labor 4.5 hours
    • Travel 2.4 hours
     
    Last edited: Sep 4, 2020
  3. EdFred

    EdFred Taxi to Parking

    Joined:
    Feb 25, 2005
    Messages:
    25,500
    Location:
    Michigan
    Display Name:

    Display name:
    Ed Frederick
    Same thing happened to me and mine was a 15 minute fix. The p lead broke inside the mag. Took cover off, resoldered the p lead to the backing plate, (a washer) reconnected, and all was well.
     
  4. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    I hope that’s all it is, but I doubt I could get that lucky.
     
    guzziguy likes this.
  5. Dana

    Dana Pattern Altitude

    Joined:
    Oct 19, 2016
    Messages:
    1,686
    Location:
    CT & NY
    Display Name:

    Display name:
    Dana
    A broken P lead would keep the mags hot so the engine would keep running, not quit... unless the broken end was contacting and shorting to the case.
     
  6. EdFred

    EdFred Taxi to Parking

    Joined:
    Feb 25, 2005
    Messages:
    25,500
    Location:
    Michigan
    Display Name:

    Display name:
    Ed Frederick
  7. bnt83

    bnt83 Final Approach PoA Supporter

    Joined:
    Dec 31, 2012
    Messages:
    9,259
    Location:
    Lincoln NE
    Display Name:

    Display name:
    Brian
    No broken P-leads but I've had a coil fail in a Slick mag before. The part alone was over $300.


    Most of my ignition troubles are fouled spark plugs, doesn't happen often thankfully.
     
  8. Tom-D

    Tom-D Taxi to Parking

    Joined:
    Feb 23, 2005
    Messages:
    34,133
    Display Name:

    Display name:
    Tom-D
    Do a complete Kit, with a TCM electronic mag set.
     
    Crashnburn and Huckster79 like this.
  9. Bathman

    Bathman Filing Flight Plan

    Joined:
    Jun 23, 2019
    Messages:
    24
    Display Name:

    Display name:
    Bathman
    Surefly
     
    Huckster79 and Morgan3820 like this.
  10. Tom-D

    Tom-D Taxi to Parking

    Joined:
    Feb 23, 2005
    Messages:
    34,133
    Display Name:

    Display name:
    Tom-D
    Why would you buy a half set of new mags.
     
  11. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    Worth considering, but I thought they replaced the left mag. The plane starts on the left mag. It is right mag that failed.
     
  12. FORANE

    FORANE Pattern Altitude

    Joined:
    Mar 7, 2013
    Messages:
    2,459
    Location:
    TN
    Display Name:

    Display name:
    FORANE
  13. Eldorado

    Eldorado Pre-Flight

    Joined:
    Feb 26, 2020
    Messages:
    95
    Display Name:

    Display name:
    Bill
    Check plugs first.
     
  14. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    I believe they are Slicks but not certain.
     
  15. Chip Sylverne

    Chip Sylverne Final Approach

    Joined:
    Jun 17, 2006
    Messages:
    5,098
    Display Name:

    Display name:
    Fear is the poison of our lives.
    Could be something as simple as a shorted condenser. Don't panic until you, or someone you TRUST, takes a look. Panicking in aicraft MX can cost you dearly for little return.
     
    guzziguy likes this.
  16. FORANE

    FORANE Pattern Altitude

    Joined:
    Mar 7, 2013
    Messages:
    2,459
    Location:
    TN
    Display Name:

    Display name:
    FORANE
    I have a backup set of Slick's in my garage just freshly overhauled. I learned it is cheaper to buy overhauled from QAA than buy parts and overhaul yourself.
     
    guzziguy likes this.
  17. flhrci

    flhrci Final Approach

    Joined:
    Jan 26, 2007
    Messages:
    5,759
    Location:
    Groveport, OH
    Display Name:

    Display name:
    David
    Time to buy a new plane. Yours has been abused too long and is tired.
     
  18. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    If I win the lottery, there will be a new plane in my hangar in short order. Until then....
     
    RyanB likes this.
  19. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    6,704
    Display Name:

    Display name:
    Dan Thomas
    All four (or six) plugs fired by that mag would have to be shot. That is VERY unlikely.

    Bendix recommends mag removal and internal inspection every 400 hours. Slick advises it every 500. In the flight school fleet I did it every 500 and found the points still good, and replaced them at the next 500, or 1000 hours since new or the last points replacement. Most private airplanes don't get that level of care and so they are run until they quit, often at some really inconvenient airport far from home. The same philosophy is applied to alternators and vacuum pumps, often presenting some unpleasant surprises for the pilot. Failure is 99% inevitable when airplanes are maintained that way.
     
  20. GRG55

    GRG55 Final Approach

    Joined:
    Dec 29, 2015
    Messages:
    8,244
    Display Name:

    Display name:
    Aztec Flyer
    ^^^This.
    I am amazed at the lack of magneto maintenance and spark plug maintenance. I ask owners I know how many hours on the mags since the last servicing. Most of them can't even find a log entry.

    I think one of the reasons is we now have a "throw the part away and replace" mentality in our societies (that's how we maintain cars now) and there are fewer and fewer really experienced mechanics that know how to service and overhaul these accessories properly. Like Dan, they are all retiring... :(
     
    biplanebob and flhrci like this.
  21. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    Maintenance on my plane is done by the book. No shortcuts or deferred maintenance. The right magneto only has about 150 hours on it.
     
  22. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    6,704
    Display Name:

    Display name:
    Dan Thomas
    Sounds, then, like something failed in it. Will be interesting to see what is found.
     
  23. Shepherd

    Shepherd En-Route

    Joined:
    Nov 24, 2012
    Messages:
    4,422
    Location:
    Hopewell Jct, NY
    Display Name:

    Display name:
    Shepherd
    Anyone have SureFly electronic ignition installed?
    Just curious about your experience, vs magneto.
     
  24. cessna180patrick

    cessna180patrick Filing Flight Plan

    Joined:
    Sep 5, 2020
    Messages:
    2
    Display Name:

    Display name:
    cessna180patrick
    Everyone seems to have overlooked the possibility of ignition switch failure. Unhook the P-lead on the suspect mag which should make it hot. Start up and select the ignition switch to off. The engine should continue to run if the hot/disconnected mag is good. That would make me look at the lead or the switch. If the engine does not continue to run, you know the mag is not hot, even when disconnected and therefore it is the failed unit.
     
  25. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    6,704
    Display Name:

    Display name:
    Dan Thomas
    I had considered and rejected it as unlikely. The moving contacts in the switch would have to keep the mag shorted somehow. Bad switches tend to fail to short a mag.

    Now, there is a possibility that the wire terminals on the back of the mag switch have come loose or somehow been disturbed so that the relevant terminal is contacting the ground terminal. That stuff is in close quarters back there. Once in a while on annuals I have found those terminal screws loose.
     
  26. flhrci

    flhrci Final Approach

    Joined:
    Jan 26, 2007
    Messages:
    5,759
    Location:
    Groveport, OH
    Display Name:

    Display name:
    David
    Everyone has failed to recognize the failure of @Stingray Don to properly service the hamster's in the mags. :D
     
    Stingray Don likes this.
  27. PPC1052

    PPC1052 En-Route

    Joined:
    Feb 2, 2012
    Messages:
    4,809
    Display Name:

    Display name:
    PPC
    Yeah, Tom Wood Aviation has a very good maintenance shop.
     
  28. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    Agreed. They are very thorough. They are pretty busy right now so not sure how long it will take before they can get it in.
     
  29. Justin M

    Justin M Pre-takeoff checklist PoA Supporter

    Joined:
    Oct 23, 2016
    Messages:
    447
    Display Name:

    Display name:
    JM
    Yesterday, I decided to take a friend to the beach. Went out to the run-up area, test left mag fine, test right mag the plane shakes violently and drops 300 RPM. Taxi back to tie-down and left message with the chief pilot. I'll be curious what he does to fix it.
     
  30. smv

    smv Pattern Altitude

    Joined:
    Dec 30, 2019
    Messages:
    1,663
    Display Name:

    Display name:
    smv
    99.99% chance they will fix it by running it up to 2000 RPM and leaning it out until it stumbles then waiting for it to clear. In nearly 20 years of runups, the only time this has not worked was when the plug wire was loose.
     
    guzziguy, Huckster79 and EdFred like this.
  31. Tom-D

    Tom-D Taxi to Parking

    Joined:
    Feb 23, 2005
    Messages:
    34,133
    Display Name:

    Display name:
    Tom-D
    Wouldn't you rather have the problem fixed, so it will stay fixed
     
  32. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    Well aware of how to clear fouled plugs. That’s not the issue.
     
  33. Huckster79

    Huckster79 Cleared for Takeoff PoA Supporter

    Joined:
    Nov 22, 2018
    Messages:
    1,319
    Display Name:

    Display name:
    Huckster79
    I got wierd looks when I mentioned I was getting my plugs gapped n cleaned and rotated (will get the tools myself for next time)

    “isn’t that just done at annual?” I was asked...

    nope, not when ya fly em... but I wonder how many folks do it just at annual regardless of flying time..
     
  34. GMascelli

    GMascelli En-Route PoA Supporter

    Joined:
    Jul 27, 2005
    Messages:
    3,184
    Location:
    Ocean City, MD
    Display Name:

    Display name:
    GaryM
    Was the mag the issue, and are you back flying yet?
     
  35. Ted

    Ted The pilot formerly known as Twin Engine Ted Management Council Member

    Joined:
    Oct 9, 2007
    Messages:
    27,153
    Display Name:

    Display name:
    iFlyNothing
    I haven't followed any of these products in a while, but I had thought at least some of the electronic ignition solutions replaced the right mag. Then the engine ends up starting on 2 mags, and that's part of how they get the improved starting.

    I could be completely wrong, though, since it's been close to 3 years since I've even had to think about mags and it was back in the 310 days (so 4-5 years ago) that it was something I was actively looking at wanting to do. Of course in those days there were fewer options out there.
     
    Stingray Don and GMascelli like this.
  36. Stingray Don

    Stingray Don En-Route

    Joined:
    Dec 21, 2014
    Messages:
    2,910
    Location:
    Indianapolis, Indiana
    Display Name:

    Display name:
    Stingray Don
    The shop was pretty busy and told me they couldn't take a look right away. Still waiting for an open spot. I will update once they provide a diagnosis.
     
    GMascelli likes this.
  37. CJones

    CJones Final Approach

    Joined:
    Mar 14, 2005
    Messages:
    5,220
    Location:
    Jawjuh
    Display Name:

    Display name:
    uHaveNoIdea
    We put SureFly on the left mag on the -7A (IO-360) a month or so ago. Fires right up. Seems to run a little more smoothly on left mag when running mag checks. Other than that, haven't really put enough time on it to tell a difference.
     
    Shepherd and GMascelli like this.
  38. CJones

    CJones Final Approach

    Joined:
    Mar 14, 2005
    Messages:
    5,220
    Location:
    Jawjuh
    Display Name:

    Display name:
    uHaveNoIdea
    To the OP: Could it be possible that the mag slipped time and is firing, but at wrong timing? Other than that, I would say likely a grounded wire somewhere up to and including internal to the ignition switch.
     
  39. flhrci

    flhrci Final Approach

    Joined:
    Jan 26, 2007
    Messages:
    5,759
    Location:
    Groveport, OH
    Display Name:

    Display name:
    David
    Safe for another day...:D
     
    Stingray Don likes this.
  40. Dan Thomas

    Dan Thomas Final Approach

    Joined:
    Jun 16, 2008
    Messages:
    6,704
    Display Name:

    Display name:
    Dan Thomas
    Firing at the wrong time causes massive power losses. Even if it fired on the exhaust stroke it would show up as a lot of afterfiring when the other mag was shut off during the runup.

    Many Bendix mags had a P-lead connection similar to a sparkplug lead. A nut held an insulator with a contact on its tip in a fitting on the mag. It contacted a springy reed in the mag that grounded itself when the P-lead was disconnected or if the nut came off. They're not prone to doing that but you never know...