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I will be doing a multi-engine course in a 2006 Diamond DA-42 soon and I'm curious if this is true for the aircraft and under what circumstances the propeller would auto feather. For example, if the engine is starved of fuel or fails for whatever reason, would it auto feather? How about if the governor fails, and if so, under what types of failure with respect to that system would it auto feather? Or maybe the ECU has a fault and the system doesn't automatically switch to ECU B for that engine without pilot input. The POH doesn't specify if this aircraft will do this or not for any sort of scenario.

I am aware that turning the engine master off will cause the governor valve to open and the oil to flow out, resulting in the pitch becoming coarser/higher and feathering, during which time the accumulator will close to maintain pressure to unfeather when it's needed (engine master turning back on). I am also aware that if the RPM is below 1300, then feathering isn't possible due to the coarse pitch stops.

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  • $\begingroup$ The DA-42 does not have Autofeather. Autofeather means that the prop will automatically feather when a a loss of thrust is sensed. There may be some mechanical abnormalities that would cause the prop to feather, but that is still not Autofeather. $\endgroup$ Commented Jun 9, 2023 at 0:10
  • $\begingroup$ By auto feather, I didn't mean "autofeather" / a system on board that tells the propeller to feather under certain circumstances. I meant, what failures would cause the propeller to result in a feathered position. I should've written that better. $\endgroup$
    – Austin A.
    Commented Jun 10, 2023 at 1:09

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There is no autofeather function per se on a DA-42 - and by that I mean analogous to an autofeather system that you would find in a larger or turboprop powered airplane. Automatic feathering of the propellers will occur if an engine is shut down or fails, for whatever reason, at an engine speed in excess of 1300 RPM. A prop governor failure, however, will not cause the propeller to feather, nor will it cause it automatically shut down. See the emergency procedures section of the AFM. As to the ECUs, the system should automatically detect a failure of the active ECU and switch over to other ECU. If this does not occur, then the pilot may manually select the other ECU using the voter switches on the left side of the instrument panel.

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  • $\begingroup$ Automatic feathering does not occur if the engine fails. Feathering is accomplished by shutting down the engine with the appropriate engine master switch. $\endgroup$ Commented Jun 9, 2023 at 3:57
  • $\begingroup$ If the propeller governor fails, isn't that what is keeping the pressure in the prop hub and keeping the blades from feathering while flying? $\endgroup$
    – Austin A.
    Commented Jun 10, 2023 at 1:10
  • $\begingroup$ No, if the governor fails, the propeller will not feather. The service manual says a loss of propeller oil pressure will feather the propeller, but it isn’t clear if they mean an abnormal loss of pressure, or a reduction in pressure due to the normal operation of turning off the Engine Master Switch. I have no experience with the DA42 but when I read the Flight Manual and the Service Manual, it seems ambiguous. I guess that is why you are also asking about it. $\endgroup$ Commented Jun 10, 2023 at 4:39

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