Chris, I’ve noodled over the performance charts, since at summer density altitudes EIK’s 4700’ single runway is none too long for a fully loaded DA62. Landings are fine, but above 80° F. I will be leery of taking off heavy, particularly if the winds favor rwy 15, which is uphill with rising terrain to the south.
ECU 'gotcha' in my DA62
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Re: ECU 'gotcha' in my DA62
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Re: ECU 'gotcha' in my DA62
The chart makes it clear that I could have anticipated the increase in minimum power at LXV, but it’s flat out wrong in claiming that a 0% power lever position translates to 2150 rpm. I saw no increase in rpm when I retarded the levers to 0% in the flare.Boatguy wrote: ↑Mon Apr 19, 2021 12:12 am Screen Shot 2021-04-18 at 5.09.43 PM.png
This is from the AE300 Ops manual. At higher altitudes, the ECU's maintain a minimum power to ensure the diesels keep running. I encountered this the first time attempting to descend steeply from 13,000' and couldn't get the power below about 25%. This is for the E4, but your engine will be very close to this chart.
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Re: ECU 'gotcha' in my DA62
If anyone's interested in the way the DA62 lands with the power 'stuck' between 13% (taxiing) and 20% (landing), here's a video of the landing circuit, taxi and shutdown at KLXV yesterday.
https://www.dropbox.com/s/poi7pvmo6zm9e ... 7.mp4?dl=0
https://www.dropbox.com/s/poi7pvmo6zm9e ... 7.mp4?dl=0
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Re: ECU 'gotcha' in my DA62
If anyone's interested in the way the DA62 behaves with the power 'stuck' between 13% (taxiing) and 20% (landing), here's a video of the landing circuit, taxi and shutdown at KLXV yesterday.
https://www.dropbox.com/s/poi7pvmo6zm9e ... 7.mp4?dl=0
https://www.dropbox.com/s/poi7pvmo6zm9e ... 7.mp4?dl=0
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Re: ECU 'gotcha' in my DA62
Is it OK if I call it an engine "Flameout" instead?
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Re: ECU 'gotcha' in my DA62
It'd be interesting to explain a little more about the expected behavior that failed to materialize. For us with the more primitive/dumb Lycoming engines, pulling the throttle back to idle (actually, in my plane, something less than ~10" IIRC), means the prop will be at its flattest possible pitch and certainly at idle power the prop is basically driving the engine RPM. My plane won't even budge at idle power.
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Re: ECU 'gotcha' in my DA62
The ECUs controlling the Austro engines and props are programmed to hold 1800 rpm in flight at 6% power (determined by the position of the power lever) and 2150 rpm at 0% power. On the ground, 0% gives 710 +/-30 rpm. There is no prop control afforded the pilot.Rich wrote: ↑Mon Apr 19, 2021 11:30 pm It'd be interesting to explain a little more about the expected behavior that failed to materialize. For us with the more primitive/dumb Lycoming engines, pulling the throttle back to idle (actually, in my plane, something less than ~10" IIRC), means the prop will be at its flattest possible pitch and certainly at idle power the prop is basically driving the engine RPM. My plane won't even budge at idle power.
However, above a critical pressure altitude the ECUs increase the engine’s minimum load factor; I saw 13% @1500 rpm, with the power levers at idle, while stationary on the ground at 9934’ MSL and 0° C.
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Re: ECU 'gotcha' in my DA62
I can't speak to the DA42-VI and DA62.
But regarding the Austro engine and prop in the DA40NG, there are two different things going on. Maybe the 42/62 are similar, maybe not. Presumably @CFIDave will let us know.
Pitch is controlled by the power lever, which is a simple hall effect sensor. As far as I know there is no intelligence that ties pitch to the actual power being produced by the engine. For example, in the event of an engine failure we are advised to set the power lever to the position that would otherwise produce 20% power (marked with tape in my plane) because that will be as close to "feathering" as we can get. We DA40NG pilots are otherwise blissfully ignorant about pitch control.
The minimum power decision is made by the EECU and overrides the throttle lever per the previously posted graph. Ambient pressure which controls the minimum power, is DA expressed in millibars rather than translated to an ISA altitude.
Descending into the desert from 13,000 I pulled the power all the way back and still got 25% power. Descending at 900fpm and 25% power did not slow my speed or steepen my angle of descent as I had intended. I immediately began thinking about how I was going to land with 25% power and at what point on final I would switch off the engine master and glide in. Thoughts I did not share with my wife. As I descended, the power slowly dropped. By the time I got to 6,000' the engine was responding normally.
Probably the most disturbing thing about my experience was that when I called Diamond's 24/7 support line, they told me nothing about the minimum power programmed into the EECU. When I asked if the plane was airworthy to fly home, they said that since it was normal when I landed, I was probably OK. My regular mechanic was similarly ignorant. Obviously neither of those instilled any confidence and it was a nervous 2 1/2 hour flight home. It wasn't until I got home, posted on DAN, and got an informative reply from @CFIDave, that I looked in the Austro Ops manual and gained an understanding of what I had experienced, and realized it was not a problem, but the intended behavior.
Anyone else think this should be in the AFM?
But regarding the Austro engine and prop in the DA40NG, there are two different things going on. Maybe the 42/62 are similar, maybe not. Presumably @CFIDave will let us know.
Pitch is controlled by the power lever, which is a simple hall effect sensor. As far as I know there is no intelligence that ties pitch to the actual power being produced by the engine. For example, in the event of an engine failure we are advised to set the power lever to the position that would otherwise produce 20% power (marked with tape in my plane) because that will be as close to "feathering" as we can get. We DA40NG pilots are otherwise blissfully ignorant about pitch control.
The minimum power decision is made by the EECU and overrides the throttle lever per the previously posted graph. Ambient pressure which controls the minimum power, is DA expressed in millibars rather than translated to an ISA altitude.
Descending into the desert from 13,000 I pulled the power all the way back and still got 25% power. Descending at 900fpm and 25% power did not slow my speed or steepen my angle of descent as I had intended. I immediately began thinking about how I was going to land with 25% power and at what point on final I would switch off the engine master and glide in. Thoughts I did not share with my wife. As I descended, the power slowly dropped. By the time I got to 6,000' the engine was responding normally.
Probably the most disturbing thing about my experience was that when I called Diamond's 24/7 support line, they told me nothing about the minimum power programmed into the EECU. When I asked if the plane was airworthy to fly home, they said that since it was normal when I landed, I was probably OK. My regular mechanic was similarly ignorant. Obviously neither of those instilled any confidence and it was a nervous 2 1/2 hour flight home. It wasn't until I got home, posted on DAN, and got an informative reply from @CFIDave, that I looked in the Austro Ops manual and gained an understanding of what I had experienced, and realized it was not a problem, but the intended behavior.
Anyone else think this should be in the AFM?
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Re: ECU 'gotcha' in my DA62
I agree that the charts should be in the AFM and it should be called out explicitly somewhere in the performance section. In fact, I would seriously question whether the performance chart entries for landing distance at 10000' PA have anything to do with reality.
My DA42 taxis rather briskly at 5% power on flat tarmac, so I can only imagine how much I'd need to be riding the brakes if it were stuck at 13%.
I think it's as simple as imagining you can't pull your throttle all the way back to idle and don't have any way to adjust the propeller pitch since you've given up that privilege to the FADEC.Rich wrote: ↑Mon Apr 19, 2021 11:30 pmIt'd be interesting to explain a little more about the expected behavior that failed to materialize. For us with the more primitive/dumb Lycoming engines, pulling the throttle back to idle (actually, in my plane, something less than ~10" IIRC), means the prop will be at its flattest possible pitch and certainly at idle power the prop is basically driving the engine RPM. My plane won't even budge at idle power.
My DA42 taxis rather briskly at 5% power on flat tarmac, so I can only imagine how much I'd need to be riding the brakes if it were stuck at 13%.
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Re: ECU 'gotcha' in my DA62
Good discussion and important to know! I learned about this effect at my DA62 factory training in Austria. They made it sound as it is important to know, but practically speaking not a big issue.
I‘d assume that the official performance charts are real values flown with this effect. Also keep in mind that the air is significantly thinner, so 13% in power does not result in the same thrust generated as at MSL.
I‘d assume that the official performance charts are real values flown with this effect. Also keep in mind that the air is significantly thinner, so 13% in power does not result in the same thrust generated as at MSL.