Prop Governor fail

wolfvoador · Post by **wolfvoador** » Thu Jul 11, 2013 3:19 am

DA42NG (a recent conversion) owner for 3 months. Love my new toy. But had all sorts of issues, first ECU FAIL in the middle of Amazon 2 months ago, was a software issue (after flying in Diamond guy from Sao Paulo). 4 weeks ago, here in Bahamas, tested engine-out left side, flew 1:30 minutes only rh engine, but then lh engine wouldn't unfeather, stayed feathered. Interrupted flight, landed nearest AP with rh only humming (not an issue, DA42 performs superbly on 1 motor). No quick fix, mechanic from Florida (I have quite some bills flying Diamond mechanics around..) diagnosed some metal in governor, coming from gearbox. RH gearbox received a newer version of Austro gearbox (with filter), lh has no filter, just a magnet to hold metal scrapings. Governor using same oil seems more prone to failure than gearbox itself. Anybody same issue with those old "non-filtered" gearboxes?

Colin · Post by **Colin** » Thu Jul 11, 2013 3:26 am

Wait, if it was a conversion to NG then why would the left and right sides be different?

wolfvoador · Post by **wolfvoador** » Thu Jul 11, 2013 3:46 am

Good point.conversion was done 2 years and 200 hours ago. RH had similar issues on pre-buy inspection, and Austro agreed to change to new "filtered" gearbox at that point. LH remained old, "unfiltered"

carym · Post by **carym** » Thu Jul 11, 2013 1:53 pm

I know that with at least one of the earlier NG conversions there was a problem with the metallurgy or manufacture of the gearbox such that it was shedding too much metal and Diamond replaced that gear box. I wonder if you have the same problem. I don't know the exact details, but I believe Great Lakes Aviation knows more about that situation. the airplane was based out of Columbus OH.

GLDAS · Post by **GLDAS** » Fri Jul 12, 2013 2:16 am

carym wrote:I know that with at least one of the earlier NG conversions there was a problem with the metallurgy or manufacture of the gearbox such that it was shedding too much metal and Diamond replaced that gear box. I wonder if you have the same problem. I don't know the exact details, but I believe Great Lakes Aviation knows more about that situation. the airplane was based out of Columbus OH.

The Austro uses gearbox oil for the prop control because diesel engine oil is so dirty, I believe. Yes, one of the flight training organizations in our region had this on an early NG. The symptoms were exactly the same: prop wouldn't unfeather, though on the ground, you could force it manually IIRC. DAI did an excellent job getting this plane back in the air quickly, and there have been, as you pointed out, improvements in the design.

We haven't seen any similar failures for some time now. It's inconvenient, for sure, and I'm glad your A&Ps were able to get you squared away.

DE
Dan@greatlakesdiamond.com

wolfvoador · Post by **wolfvoador** » Fri Jul 12, 2013 1:35 pm

Thanks Dan. Yes, seems governor has smaller parts/valves which may get clogged more easily, engine oil would not work at all, but even the small particles from the gearbox may create an issue in governor (while, fortunately, not affecting the functionality of the gearbox itself). Austro seems to have addressed this with the filter in newer gearbox versions. This filter can not be retrofitted, it needs a new box.

Also, wonder how someone could manually unfeather the prop on the ground. As long as you have no pressure in governor, I believe even if you could twist the blades by hand (I tried that, but couldn't move them at all), they would fall back into feathered position. Since we had no spare governor on that island, we swapped the good and bad governor between engines, and then unfeathered the left prop. That made the engine start again, to fly it to Florida for maintenance.

carym · Post by **carym** » Fri Jul 12, 2013 1:59 pm

There is a technique to unfeather a prop on the ground. It requires 2 boards, one on either side of a prop blade, to get the needed leverage. With this technique you can twist the blades to unfeather the prop. I had to do this many times on my C310 when I had engine failures. My only word of caution here is that I can't guarantee this will work on the DA42, but I don't see any reason why not.

wolfvoador · Post by **wolfvoador** » Fri Jul 12, 2013 2:17 pm

Thanks, Cary ... well this technique is obviously not in the book, but I will ask my mechanics if I can use that next time I get stranded with feathered prop on a far away island.... Mechanically also not clear, how you would create pressure in the governor to hold the prop in place, just by twisting the blades... suppose that action sucks oil into the governor, and then you have to pray that a valve closes. Interesting ...

wolfvoador · Post by **wolfvoador** » Fri Aug 02, 2013 9:47 pm

Progress report from governor failure: governor was sent to MT in Straubing, disassembled, and one can see that the block (pic) was severely damaged, by the metal scraps coming from the (old) gearbox. MT assembled the governor with a new block within 24 hours, retuned the part to MT USA (well done, MT!), and my mechanic is waiting for the new gearbox to arrive from Austro, given under the already expired warranty (thanks for understanding, Austro, but still want to see to believe), and the governor/accumulator/prop set from MT. In a week I am hopefully airborne again!

Hawker · Post by **Hawker** » Mon Mar 10, 2014 7:38 am

Good Morning

We faced same problem on a 200 hrs. DA42-V1 during x-mas. DAI gave us a new governor and changed the a filter. Yesterday, same problem on same engine! Any ideas?

Keep you updated!

Michael

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