Unable to reduce load

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greg
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Re: Unable to reduce load

Post by greg »

chili4way wrote: Thu Nov 05, 2020 5:56 pm Diamond Tech Support has an unpublished (i.e. not in the AFM) alternate/backup manual runup procedure they make available to specific owner/operators based out of very high altitude airports with recurring runup issues.
That seems a bit silly. So someone who only occasionally visits high altitude airports will have to have a few run up failures, doubtless meaning cancelled flights, finding a mechanic who doesn't understand the problem and worrying about their broken aeroplane before Diamond tells them there's "another way". If this other way works and is acceptable, they should publish it so everyone can use it!
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chili4way
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Re: Unable to reduce load

Post by chili4way »

My takeaway from checking into this is that the regular EECU runup check should be expected to work (as it did reliably in the summer at KASE and as reported by Scott O'Hare). If it doesn't, and the pilot has checked the list of mistakes that can cause the EECU warning, it would seem unwise to assume everything is "really OK". The alternate procedure is very simplified, less thorough, and assumes there is no problem with the EECU or its associated sensors. The two procedures are not equivalent. I can see why Diamond makes it available as a contingency to high-altitude fleet operators and not to the occasional visitor.

What prompted me to check was the post: "Not first hand experience yet, but I've heard that at high elevation airports it's not possible to perform an ECU test on runup due to the idle power correction preventing the engines from making idle power." [my emphasis]
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Boatguy
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Re: Unable to reduce load

Post by Boatguy »

Can somebody please publish this "alternate" manual run up procedure?

I agree with @greg that waiting until we're in that position is not a good system. The list of things than can cause an ECU failure is very long, basically every sensor in the engine, and there is no good way to know which sensor is triggering the failure without pulling the ECU logs which is not feasible at most airports.

As the OP of this thread, when I had to call Diamond AOG, I got a very ambiguous response about whether or not my engine was healthy to fly home. I hung up with no more confidence in my engine than when I made the call.

I understand the the alternate procedure is an "end run" on the primary procedure without any way to be confident that the original procedure was producing a false positive. This is fundamentally a flaw of the primary procedure. The system knows the indicated altitude, or could know it, and what Austro should do is adapt the primary procedure dynamically to the indicated altitude as they do with the minimum power to prevent combustion extinction.

In the absence of Austro fixing the firmware for the primary procedure, I'd rather have the backup procedure available, understand the situations in which it is applicable, and be able to use it rather than to be dialing for support and hoping to get a quality answer. This situation is analogous to the minimum power to prevent combustion extinction graph which is in the Austro manual, but not the AFM, which was the trigger for this thread. Why does Austro insist upon keeping pilots in the dark about the behavior of their engine(s) in various corner cases? To operate the aircraft safely we need all available information.
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