Austro flywheel/TVD failure rate

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CFIDave
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Re: Austro flywheel/TVD failure rate

Post by CFIDave »

ultraturtle wrote: Sat Mar 14, 2020 12:34 pm Be sure to update EECU software to version 23 (Nov 2019). My guy tells me that it helps with governor issues.
I believe this is because V23 provides a more gentle shut-down, i.e., the prop doesn't stop so abruptly (due to the high compression diesel engine) when you turn off the Engine Master switch.
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Re: Austro flywheel/TVD failure rate

Post by Colin »

On Twin Bonanzas with the geared engines you do not descend without power to the engines. Otherwise you bite the backs off the teeth on the gears. I imagine we are going to see the same sort of best practices recommendation.
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Re: Austro flywheel/TVD failure rate

Post by pietromarx »

In college I used to borrow a 1982 Nissan Sentra that had this issue. The starter would tear teeth off the flywheel every now and then.

Please don't take this comment to be snarky to anyone on this board; there is a lesson here. It has been said elsewhere that aviation sometimes gets the dregs from other modes of transportation. Given that the Austro comes from a relatively small and widely distributed automotive engine, one would think that they would be more considered on how a 30 KG propellor and governor mates to the engine ...
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Re: Austro flywheel/TVD failure rate

Post by neema »

Colin wrote: Sun Mar 15, 2020 7:32 pm On Twin Bonanzas with the geared engines you do not descend without power to the engines. Otherwise you bite the backs off the teeth on the gears. I imagine we are going to see the same sort of best practices recommendation.
T Bones go so far to keep power up on ground ops for positive power going though the gearbox. An otherwise lumpy idle bounces back and forth between the gears' lash and beats them up.

Frankly, I can hear something to the same effect in the 42, but not sure if I'm hearing the flywheels clunking around or the gearbox.

Anyway mods of the board can make this a poll? Curious to see number of flywheels that have passed vs fail inspections.
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Re: Austro flywheel/TVD failure rate

Post by Henrik »

ultraturtle wrote: Fri Mar 13, 2020 8:34 pm Excessive wear of inner rivet heads
I checked my maintenance records & both flywheels had failed on this inspection item...

"Both dual-mass flywheels failed the rivet wear check. "

My mechanics had already ordered replacement flywheels months in advance. (anticipating failing the inspection) Good thing we did - delivery time from Austro ended up taking > 3 months. Parts delays continues being the major issue with Diamonds.
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Re: Austro flywheel/TVD failure rate

Post by chili4way »

CFIDave wrote: Sun Mar 15, 2020 4:23 pm
ultraturtle wrote: Sat Mar 14, 2020 12:34 pm Be sure to update EECU software to version 23 (Nov 2019). My guy tells me that it helps with governor issues.
I believe this is because V23 provides a more gentle shut-down, i.e., the prop doesn't stop so abruptly (due to the high compression diesel engine) when you turn off the Engine Master switch.
I also got confirmation from Austro that version 23 EECU software changes pertain to the prop governor operation.

What would the EECU do differently during shutdown once the Engine Master switch is turned off to provide a more gentle shutdown?

I assumed this "governor" aspect of the EECU software update pertained to Diamond SI40NG-069 (Governor MIN/MAX RPM Stop Setting) which includes the following text: "The governor jam warning is caused by a wrong signal, due to certain combinations of governor and software." [my italics]
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Re: Austro flywheel/TVD failure rate

Post by CFIDave »

chili4way wrote: Mon Mar 16, 2020 3:03 pmI also got confirmation from Austro that version 23 EECU software changes pertain to the prop governor operation.

What would the EECU do differently during shutdown once the Engine Master switch is turned off to provide a more gentle shutdown?
Only speculation, but it might be possible for the ECU to ramp down fuel or airflow before shutting down the engine. It all depends on whether Engine Master OFF simply removes power from the ECU, or (more likely) sends a signal to begin orderly shutdown including writing of engine parameters to non-volatile memory, e.g., while we're waiting for the red/yellow Xs on MFD.
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Re: Austro flywheel/TVD failure rate

Post by Henrik »

Another piece of input - flyvwheels on the DA42NG/-VI apparently experience more wear & tear than DA40NG flywheels, to the extent that used DA42NG/-VI flywheels can never be refitted on a DA40NG...

https://austroengine.at/uploads/pdf/SIE4009r0.pdf

I don't actually know whether you can run a DA40NG prop in "speed brake" mode (0% power) similar to the DA42NG/-VI, or whether it's purely the frequent in-air engine restarts during ME training that exerts the additional wear & tear on the DA42NG/-VI flywheels.
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Re: Austro flywheel/TVD failure rate

Post by Davestation »

My scientific wild-ass guess is that I've had around a 50% inspection failure rate. At the very least, the fail rate was high enough that Diamond stopped selling inspected units and would only sell them brand new - Neema I'm guessing that's why you saw your mx cost jump significantly. Now I believe the number is a little higher still because they're serializing the hubs to the flywheels on their newest version so when the flywheel fails you have to buy a new hub as well (the new hubs look much beefier than the old ones although I've never heard of one of those failing, which would be catastrophic).
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Re: Austro flywheel/TVD failure rate

Post by Davestation »

CFIDave wrote: Sun Mar 15, 2020 4:20 pm One shop (SouthTec Aviation at KRUQ) addresses this issue by keeping a spare set of flywheels in stock. When you take your Diamond twin to them for flywheel inspection, they'll send your units in to Diamond for inspection, but immediately install the spare set of flywheels on your plane. Then when your original flywheels come back from Canada, they're available to be installed on the next aircraft that comes into the shop.
IMO that seems like quite the hassle for a shop that works on these so often, why don't they just buy the jig? You're paying higher inspection cost as well as round trip shipping. And if yours fail inspection wouldn't you have to pay for brand new ones to replace their stock even though the ones you got were actually used??
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