ECU 'gotcha' in my DA62

Any DA62 related topics

Moderators: Rick, Lance Murray

User avatar
photoSteveZ
4 Diamonds Member
4 Diamonds Member
Posts: 321
Joined: Wed Dec 23, 2020 4:10 pm
First Name: Steve
Aircraft Type: DA62
Aircraft Registration: N62DZ
Airports: KEIK Erie CO
Has thanked: 387 times
Been thanked: 226 times

Re: ECU 'gotcha' in my DA62

Post by photoSteveZ »

Chris wrote: Mon Apr 19, 2021 12:01 am I was wondering/worrying about this behavior earlier this past week while planning for some trips to Colorado later this year. I don't have any plans to fly into KLXV, but I'm curious how landing at KEIK will feel when DAs are at 9000+ feet in the summertime.
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.
User avatar
photoSteveZ
4 Diamonds Member
4 Diamonds Member
Posts: 321
Joined: Wed Dec 23, 2020 4:10 pm
First Name: Steve
Aircraft Type: DA62
Aircraft Registration: N62DZ
Airports: KEIK Erie CO
Has thanked: 387 times
Been thanked: 226 times

Re: ECU 'gotcha' in my DA62

Post by photoSteveZ »

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.
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.
User avatar
photoSteveZ
4 Diamonds Member
4 Diamonds Member
Posts: 321
Joined: Wed Dec 23, 2020 4:10 pm
First Name: Steve
Aircraft Type: DA62
Aircraft Registration: N62DZ
Airports: KEIK Erie CO
Has thanked: 387 times
Been thanked: 226 times

Re: ECU 'gotcha' in my DA62

Post by photoSteveZ »

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
User avatar
photoSteveZ
4 Diamonds Member
4 Diamonds Member
Posts: 321
Joined: Wed Dec 23, 2020 4:10 pm
First Name: Steve
Aircraft Type: DA62
Aircraft Registration: N62DZ
Airports: KEIK Erie CO
Has thanked: 387 times
Been thanked: 226 times

Re: ECU 'gotcha' in my DA62

Post by photoSteveZ »

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
User avatar
Soareyes
4 Diamonds Member
4 Diamonds Member
Posts: 306
Joined: Fri Feb 28, 2020 12:47 pm
First Name: Dan
Aircraft Type: DA42-VI
Aircraft Registration: N518R
Airports: KINF
Has thanked: 231 times
Been thanked: 191 times

Re: ECU 'gotcha' in my DA62

Post by Soareyes »

CFIDave wrote: Mon Apr 19, 2021 1:06 am He described exactly the same experience Steve had, with the engines unable to throttle back to idle when landing due to the programming of the ECU's to prevent diesel "combustion extinction" at higher altitudes.

Is it OK if I call it an engine "Flameout" instead? :)
Current: DA42-V1

Previous: Hang gliders, Paraglider, DA40(x3), Cessna 150 Aerobat, SR22
User avatar
Rich
5 Diamonds Member
5 Diamonds Member
Posts: 4592
Joined: Mon Aug 30, 2010 12:40 pm
First Name: Rich
Aircraft Type: DA40
Aircraft Registration: N40XE
Airports: S39 Prineville OR
Has thanked: 145 times
Been thanked: 1180 times

Re: ECU 'gotcha' in my DA62

Post by Rich »

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.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
User avatar
photoSteveZ
4 Diamonds Member
4 Diamonds Member
Posts: 321
Joined: Wed Dec 23, 2020 4:10 pm
First Name: Steve
Aircraft Type: DA62
Aircraft Registration: N62DZ
Airports: KEIK Erie CO
Has thanked: 387 times
Been thanked: 226 times

Re: ECU 'gotcha' in my DA62

Post by photoSteveZ »

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.
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.

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.
User avatar
Boatguy
5 Diamonds Member
5 Diamonds Member
Posts: 1827
Joined: Mon Jan 22, 2018 4:48 am
First Name: Russ
Aircraft Type: DA62
Aircraft Registration: N962M
Airports: KSTS
Has thanked: 1327 times
Been thanked: 1163 times

Re: ECU 'gotcha' in my DA62

Post by Boatguy »

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. :D

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?
Attachments
Screen Shot 2021-04-19 at 8.48.47 PM.png
User avatar
Chris
5 Diamonds Member
5 Diamonds Member
Posts: 935
Joined: Sat Jun 19, 2010 3:34 am
First Name: Chris
Aircraft Type: DA42NG
Aircraft Registration: N449TS
Airports: KHIO
Has thanked: 1050 times
Been thanked: 480 times

Re: ECU 'gotcha' in my DA62

Post by Chris »

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.

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.
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.

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%.
Chris
N449TS / DA42-NG / 42.AC049
KHIO
User avatar
jast
3 Diamonds Member
3 Diamonds Member
Posts: 77
Joined: Sun Sep 01, 2019 11:10 am
First Name: Jan
Aircraft Type: DA62
Aircraft Registration: DIODE
Airports: EDMA
Has thanked: 2 times
Been thanked: 48 times

Re: ECU 'gotcha' in my DA62

Post by jast »

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.
Post Reply