Double Start Blues

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RMarkSampson
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Double Start Blues

Post by RMarkSampson »

OK, I just finished an extended 3-month maintenance period to return my DA-20 to airworthy status. The starter bendix failed. Replacing a starter is not hard - my starter was removed the next morning and the bendix was diagnosed as faulty. The bad news was the crankshaft cluster gear that is engaged by the starter flywheel had abnormal damage (yep, it was determined that she was "double started" by one of my student pilots). One gear tooth is halfway severed off, there are two other teeth that have non-normal wear. So there was now hardened metal somewhere within the engine so a FOD inspection was needed. During disassembly, the gear tooth was located in the oil sump where you would expect it to end up - a magnet also found a few additional shards of metal in the sump. The oil pump and oil filter were clean - and the cam lobes and lifters looked perfect. So I thought I had a reasonably good path to airworthy.

Continental Service Bulletin 14-2 covers the Inspection and Replacement of IO240 Starter and Crankshaft Cluster Gear. It discusses a redesigned starter and crankshaft cluster gear - and it calls for the replacement of the crankcase needle bearing with a rear crankcase plug. It then goes on to say "The new starter assembly P/N 658291 and the matching crankshaft cluster gear P/N 656072 may be ordered through any CMI distributor." This is when I found the first huge hurdle in 6CT's repair - those two new parts (starter and crankshaft cluster gear) were not readily available. One estimate suggested a 233 day backorder status. Speaking with Continental's Service Department I got the impression they had the parts but all their parts were designated to go into new engines - and, despite promises by their customer service reps to dig deeper, getting one released to me never happened. I guess I could have simply bought a new engine to overcome this hurdle - maybe that is customer service in their eyes...

So I was able to locate the original designed crankshaft cluster gear online that matched my damaged gear. Sheer luck I believe. I was also able to purchase the original starter from the manufacture of the starter that was originally installed on my aircraft (B & C starter P/N BC320-1). B&C was not tracking they were voted off the Continental IO-240 island... Anyway, I gave up on the SB 14-2 recommended solution and replaced parts per the original design.

So it took two months to run that gauntlet. The third month was a self-inflicted additional hurdle caused by not reconnecting the ground wire to the engine before the first start attempt - Oops... Without a ground wire, all those electrons going through the starter sought a different path back to the battery. That path was through my Shower of Sparks which subsequently failed to shower any sparks any more. So on a different post I will recount this hurdle and how that led to a SureFly Electronic Ignition system replacing my left (starting) magneto.

6CT is back in the air - she is performing better than before. I'm not sure if it can be attributed to the more energetic sparks coming from the SureFly or the increased useful load from shedding the weight of money from my wallet needed to get her airborne again. Calendar Year 2020 can't end soon enough...
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Derek
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Re: Double Start Blues

Post by Derek »

Thats way too much pain caused by an accidental double start. Imagine if a car did that. How hard would it be to engineer some sort of safety to prevent so much damage from happening.
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Re: Double Start Blues

Post by DiamondDavid »

Wait.....you replaced the cluster gear and needle bearing but not the new-spec starter?
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Spinner
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Re: Double Start Blues

Post by Spinner »

If you don't have a push to start ignition key I would suggest that you invest in one. Also as DD says I would also look at the new Skytec starters. I think it gains you around 7 lbs or so of useful load.
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RMarkSampson
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Re: Double Start Blues

Post by RMarkSampson »

Did not need to replace the needle bearing - not damaged. If I went with the new starter, then the needle bearing would be replaced by a plug as the new starter has a shaft that inserts into that plug and starting gear rides along that shaft. Sticking with the original design meant that I just needed to maintain a camphor-tooth crankshaft cluster gear and purchase the B&C starter which has the floating starter gear that uses the needle bearing and correctly meshes with the cluster gear.

I have not researched a "push to start" option too much. Even my daughter's 6 year old Ford Escape has that feature. Once again, aviation lags behind. Maybe in a decade or so someone will brilliantly think of a voice recognition starting system. "Alexa, start the plane..." Only seen "for experimental only" stuff at Aircraft Spruce. I also have not seen any SB from Diamond so I am guessing it would require another STC. For now, plenty of training and awareness for those who turn that key. I'm actually more worried about someone rushing a mag check and going to "start" than when starting the aircraft. Ultimately I have operated my aircraft as a club aircraft for about eight years - this was the first "gotcha" other than a couple of flat spots showing up on a main tire. Can't remove all risk - training, training and more training has been the best defense - plus cherry picking the best of the local pilot community to share the aircraft. My two "NEXT GEN" student pilots has certainly been the biggest risk - but I remain committed to fostering a next generation so I will maintain the opportunity for them to fly my DA-20.
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RMarkSampson
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Re: Double Start Blues

Post by RMarkSampson »

Need to correct something I previously said. Diamond does have a Push to Start Service Bulletin for the DA-20. Service Bulletin No.: DAC1-74-03 Rev 2. Guess I was not paying attention. Simple change-out of the starting switch to a new PN 10-357210-1. Looks like you need to turn the key then push to key inward to activate the starter. That would afford an additional level of protection, especially with someone rushing through a mag check.

To add salt to the wound, my last annual in June, my IA insisted I replace the starter switch citing an AD that was issued six years before my plane was built in 1999. If I would have been tracking this SB, then my Double Start blues would likely have been avoided because I would have wanted the switch replaced using this Service Bulletin. Sigh.....
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