Ryan ORL Posted Thursday at 03:12 AM Report Posted Thursday at 03:12 AM tl;dr - I have had two impulse couplings destroy themselves in less than 200 flying hours, resulting in 1 and now more than likely 2 engine IRANs. Background: I had my Mooney M20J's IO-360-A3B6, equipped w/ Slick 4372 and 4370 magnetos sent for major overhaul in January 2024. It returned to service in March 2024 and had 110 trouble-free flying hours, with no adverse symptoms. In fact, we flew to Alaska and back, and everything performed perfectly. Engine ran like a top and barely used any oil and leaked not a drop for 110 hours. In July 2024, when starting up the engine at my home field self-serve pump, I heard a strange (very loud) whirring sound that I thought was an electric fuel pump sound at first (which should have been and was off, as in a normal start). The engine ran very poorly so I shut it down. After some simple investigation, we found pulling the prop through revealed the impulse coupling was very messed up. Rather than click-180-click, it was click-click-click. My home shop removed the left magneto and discovered that the impulse coupling had destructively let go, destroying the magneto drive gear, damaging the accessory drive gear(s), and rained metal debris into my accessory case, resulting in the engine being removed for IRAN and sent back to my engine shop for a warranty claim. The engine shop dutifully performed an IRAN under warranty... and apparently the magneto shop (QAA), paid for this labor, since they were the provider of the magnetos during the major overhaul. After some delays, I was back flying in October 2024 with a freshly IRAN engine and a replacement (still QAA) Slick 4372. Due to some electrical issues (unrelated to this), I have only been able fly around 80 hours since. Fast forward to this week. As I write this, I am in South Dakota and my Mooney is at KRAP. I started up the aircraft, and it ran fairly poorly. (Although without the loud whirring sound as before). A quick magneto check revealed that the left magneto was DEAD. Engine totally dies. Shut it down and inspected. On a hunch, pulled the prop around by hand. NO impulse clicks at all. Shop on field took a look and we quickly removed the magneto to find... utter carnage, again. Photos attached. It appears that the rivets failed in the impulse coupling and the pawls became stuck at high speed and the whole unit destroyed itself, breaking off large, thick metal chunks and again damaging the gears. I am at an utter loss. How could this happen again in so few flying hours. Is there anything on the engine side that could be causing this? Could a drive gear be misaligned or wrongly-sized or putting side load on the magneto drive gear or something? Looking at the accessory drive gears I see absolutely no way this should affect the impulse coupling but again I have no idea. This is getting into serious money now and nobody has any ideas what the hell might be going on here. 1
Ryan ORL Posted Thursday at 03:13 AM Author Report Posted Thursday at 03:13 AM More of the impulse internals
Ryan ORL Posted Thursday at 03:21 AM Author Report Posted Thursday at 03:21 AM Incidentally… anyone who can recommend an engine shop somewhat near South Dakota, would love to have some other options
Mooney in Oz Posted Thursday at 07:07 AM Report Posted Thursday at 07:07 AM I’m so sorry to read the predicament that you are in Ryan. I have the D3000 Bendix magnetos and only once in 24 years has the impulse coupling needed maintenance. I have no mechanical or electrical knowledge and I hope this doesn’t sound silly, but is there any chance the magnetos may be the cause? I ask this question as from what I’ve seen on this forum, Slick magnetos don’t exactly have a stellar reputation.
GeeBee Posted Thursday at 12:15 PM Report Posted Thursday at 12:15 PM You have two commonalities. Slick 4000 mag and QAA. I know of people who won't have anything to do with QAA. Not entirely their fault, they "try to overhaul Slicks" which is a reputation destroyer. They should stop. I would call Aircraft Magneto Service up in Montana. I know what he will say. First thing is he is going to tell you is what is on his web site "Slick 4000 series magneto were the "throw away mag" and were intended to be run for 800 hours then removed from service. No parts nor maintenance manuals were produced to support/ inspect/ repair this series of magneto. We recommend you replace these with a new Bendix kit or Slick kit. Contact us with your complete engine model number and size of spark plug being used and we can provide price and availability for each kit." So basically any overhaul facility is "flying blind" because there is no manufacturers manuals or parts. If I were you, I would convert to Bendix mags. The Lycomings have a tendency for kickback on start and shutdown and the Bendix units are more robust in that regard. Almost every SuperCub guy in Alaska converts to Bendix on their O-320 and O360s. A lot of people only start and shut down their Lycomings on one mag to minimize kick back. I don't think that is necessary here, but get rid of those Slicks. 2
N201MKTurbo Posted Thursday at 12:32 PM Report Posted Thursday at 12:32 PM You should contact Beegles and see if they can help you. https://www.beeglesaircraft.com
Ryan ORL Posted Thursday at 01:02 PM Author Report Posted Thursday at 01:02 PM 28 minutes ago, N201MKTurbo said: You should contact Beegles and see if they can help you. https://www.beeglesaircraft.com Maybe I am not seeing it on their site but do they do engine work? Otherwise I’m not sure what I might be able to get their help with, we are AOG in KRAP so couldn’t get the plane itself to them in any case.
Ryan ORL Posted Thursday at 01:04 PM Author Report Posted Thursday at 01:04 PM 46 minutes ago, GeeBee said: You have two commonalities. Slick 4000 mag and QAA. I know of people who won't have anything to do with QAA. Not entirely their fault, they "try to overhaul Slicks" which is a reputation destroyer. They should stop. I would call Aircraft Magneto Service up in Montana. I know what he will say. First thing is he is going to tell you is what is on his web site "Slick 4000 series magneto were the "throw away mag" and were intended to be run for 800 hours then removed from service. No parts nor maintenance manuals were produced to support/ inspect/ repair this series of magneto. We recommend you replace these with a new Bendix kit or Slick kit. Contact us with your complete engine model number and size of spark plug being used and we can provide price and availability for each kit." So basically any overhaul facility is "flying blind" because there is no manufacturers manuals or parts. If I were you, I would convert to Bendix mags. The Lycomings have a tendency for kickback on start and shutdown and the Bendix units are more robust in that regard. Almost every SuperCub guy in Alaska converts to Bendix on their O-320 and O360s. A lot of people only start and shut down their Lycomings on one mag to minimize kick back. I don't think that is necessary here, but get rid of those Slicks. I think when all is said and done here, there is no way I install another Slick impulse couples magneto… I will almost certainly go to a SureFly. That being said that only covers one mag… what’s involved with going to Bendix on this engine? Aren’t they larger?
Slick Nick Posted Thursday at 01:08 PM Report Posted Thursday at 01:08 PM 5 hours ago, Mooney in Oz said: I’m so sorry to read the predicament that you are in Ryan. I have the D3000 Bendix magnetos and only once in 24 years has the impulse coupling needed maintenance. I have no mechanical or electrical knowledge and I hope this doesn’t sound silly, but is there any chance the magnetos may be the cause? I ask this question as from what I’ve seen on this forum, Slick magnetos don’t exactly have a stellar reputation. Same here. Still on a dual mag, and haven't had any issues. I know that doesn't necessarily help the OP, but another pro for the dual mag nonetheless. At overhaul time, I'm not looking forward to the conversion.
Fly Boomer Posted Thursday at 01:16 PM Report Posted Thursday at 01:16 PM 10 hours ago, Ryan ORL said: The engine shop dutifully performed an IRAN under warranty... and apparently the magneto shop (QAA), paid for this labor, since they were the provider of the magnetos during the major overhaul. Discussion has concentrated on Slick vs Bendix but, as @GeeBee pointed out, I would find a way to factor QAA out of the equation as well. 1
N201MKTurbo Posted Thursday at 01:28 PM Report Posted Thursday at 01:28 PM 20 minutes ago, Ryan ORL said: Maybe I am not seeing it on their site but do they do engine work? Otherwise I’m not sure what I might be able to get their help with, we are AOG in KRAP so couldn’t get the plane itself to them in any case. They are the closest major shop to you. I had them do two repairs on my plane back in the 80s. They were very helpful and talented back in the day. If nothing else, they can give you recommendations. BTW, their side gig is BAS air parts. 2
Ryan ORL Posted Thursday at 01:34 PM Author Report Posted Thursday at 01:34 PM 16 minutes ago, Fly Boomer said: Discussion has concentrated on Slick vs Bendix but, as @GeeBee pointed out, I would find a way to factor QAA out of the equation as well. I had already replaced the right magneto w/ a brand new Champion Slick for unrelated reasons (chasing mag noise, didn't solve it) I think for the impulsed mag (left) I will definitely be going SureFly to get rid of the couplings altogether. 2
GeeBee Posted Thursday at 01:35 PM Report Posted Thursday at 01:35 PM 30 minutes ago, Ryan ORL said: I think when all is said and done here, there is no way I install another Slick impulse couples magneto… I will almost certainly go to a SureFly. That being said that only covers one mag… what’s involved with going to Bendix on this engine? Aren’t they larger? Again I would contact Aircraft Magneto Service. I only fly two kinds of mags, new Bendix or a Bendix serviced by AMS. Everything else is crap IMHO. They can advise you on fitment.
jetdriven Posted Thursday at 01:46 PM Report Posted Thursday at 01:46 PM We have a few clients with a Surefly/Bendix combo, including me. Slick magnetos on these planes are more expensive and not as good. QAA doesn't have the best reputation and neither does the 4000 series slick mag. But over hauling them, Kelly, for example, wrote into their manual, they don't have to replace anything and they can call it overhauled.
Ryan ORL Posted Thursday at 03:17 PM Author Report Posted Thursday at 03:17 PM Here is an opinion from Aircraft Magneto Service, who were kind enough to offer an opinion: Impulse cams failures happen, but I would call it exceptionally rare. QAA are now exclusively using Hartzell components, they have issued at least one service bulletin (SB 225) in which they had an issue with the snap rings coming loose. I have not seen many Hartzell mags 2024 or newer, its not out of the question that they have a manufacturing defect on newer impulse cams. Engine vibrations do reek havoc on impulse cams, If you haven't I would ensure the prop is balanced and no unusual vibrations are occurring. When installing the drive gear on the magneto, the drive gear should have some "slop" to it, end play up and down. I have experienced issues on Hartzell cams before where the gear was too tight and have to polish the black oxide off the portion that fits up through the gear. Also its prudent to apply grease inside the gear to prevent binding. Snap the magneto over in your hand after the gear has been installed and ensure its "smooth", no binding. Steve Cotton AMS 1
KSMooniac Posted Thursday at 04:25 PM Report Posted Thursday at 04:25 PM QAA and Hartzell are a match made in hell, sorry. And both of them working on a Slick mag, no thanks. Sorry you're going through this! I concur with converting to Bendix and optionally a Surefly or ElectroAir. I never had any such issues with my Bendix dual mag and now with two ElectroAir systems.
GeeBee Posted Thursday at 04:43 PM Report Posted Thursday at 04:43 PM 17 minutes ago, KSMooniac said: QAA and Hartzell are a match made in hell, sorry. And both of them working on a Slick mag, no thanks. This!^^^^^^^^^^^^^^^
philiplane Posted Thursday at 05:00 PM Report Posted Thursday at 05:00 PM (edited) 4 hours ago, GeeBee said: "Slick 4000 series magneto were the "throw away mag" and were intended to be run for 800 hours then removed from service. No parts nor maintenance manuals were produced to support/ inspect/ repair this series of magneto. We recommend you replace these with a new Bendix kit or Slick kit. So basically any overhaul facility is "flying blind" because there is no manufacturers manuals or parts. I'm also not a fan of Slick mags, but they certainly do have parts and maintenance manuals, and they have had them since their introduction more than 60 years ago. https://www.championaerospace.com/pdfs/techdocs/F1100/L-1363J_corrected 20210420.pdf Edited Thursday at 05:03 PM by philiplane 1
GeeBee Posted Thursday at 05:03 PM Report Posted Thursday at 05:03 PM 2 minutes ago, philiplane said: https://www.championaerospace.com/pdfs/techdocs/F1100/L-1363J_corrected 20210420.pdf I would suggest you forward it to AMS. They might have a viewpoint.
MikeOH Posted Thursday at 06:21 PM Report Posted Thursday at 06:21 PM 1 hour ago, GeeBee said: I would suggest you forward it to AMS. They might have a viewpoint. Sounds like it's QAA that might need the manual forwarded to them!
Paul Thomas Posted Thursday at 07:15 PM Report Posted Thursday at 07:15 PM Sorry Ryan. What does the drive gear look like? The angle of the most damage tooth looks off in some of the photos... is that an optical illusion?
Fritz1 Posted Thursday at 07:48 PM Report Posted Thursday at 07:48 PM I feel for you, getting stuck in RAP sucks, heard good things about AMS, sending mag including all destroyed parts to them for analysis probably good idea, pics of all teeth of the gear that drives the mag gear may also help, not sure if that gear can be removed without removing accessory case, seeing part no on the gear that drives mag gear would help to rule out that wrong gear is installed, may have to use mirror or borescope to see part no. I keep fingers crossed
Ryan ORL Posted Thursday at 09:19 PM Author Report Posted Thursday at 09:19 PM 2 hours ago, Paul Thomas said: Sorry Ryan. What does the drive gear look like? The angle of the most damage tooth looks off in some of the photos... is that an optical illusion? Pretty good view of the damage here, definitely needs replacement. Nothing much was visible on the engine side gear, just some small chipping. The biggest issue is the missing ear of the impulse coupling, which is a big chunk!
EricJ Posted Thursday at 10:27 PM Report Posted Thursday at 10:27 PM Which shop at KRAP is working on it? KRAP is hometown for me and was home base way back in the day. I know a little about some of the current operators and have had some experience from various trips home over the years, although nothing too recent. I wouldn't assume an IRAN is necessary, fwiw. And +1 to get a better ignition on there. I *think* there are Bendix mags approved for that installation, which I think would be a good choice. That said, also getting a non-QAA better Slick model on there would be good, too. I'm assuming the right mag has no impulse coupler? One thing to double check is that the right mag is cold (grounded p-lead) during start. Kickback due to a hot mag at high advance can do all kinds of damage, including fubaring the impulse coupler on the other mag. Have you witnessed any kickback during start?
Ryan ORL Posted Thursday at 10:57 PM Author Report Posted Thursday at 10:57 PM 3 hours ago, Fritz1 said: I feel for you, getting stuck in RAP sucks, heard good things about AMS, sending mag including all destroyed parts to them for analysis probably good idea, pics of all teeth of the gear that drives the mag gear may also help, not sure if that gear can be removed without removing accessory case, seeing part no on the gear that drives mag gear would help to rule out that wrong gear is installed, may have to use mirror or borescope to see part no. I keep fingers crossed Unfortunately a rather large part of the impulse coupling itself is lost into the accessory case (and is presumably in the sump)
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