DA62 road landing in Dallas, Texas

The ramblings of our community of aviators.

Moderators: Rick, Lance Murray

User avatar
Chris
5 Diamonds Member
5 Diamonds Member
Posts: 962
Joined: Sat Jun 19, 2010 3:34 am
First Name: Chris
Aircraft Type: DA42NG
Aircraft Registration: N449TS
Airports: KHIO
Has thanked: 1209 times
Been thanked: 506 times

Re: DA62 road landing in Dallas, Texas

Post by Chris »

I agree and am really curious about what the rest of the story is. Were both battery packs wired up incorrectly? What other things, if any, lined up to result in complete electrical system failure? If the mis-wired batteries were indeed the sole cause, then it quite ironic given that they exist solely as an emergency backup power source.
Chris
N449TS / DA42-NG / 42.AC049
KHIO
User avatar
ememic99
5 Diamonds Member
5 Diamonds Member
Posts: 1149
Joined: Wed Apr 09, 2014 10:31 am
First Name: Emir
Aircraft Type: DA42
Aircraft Registration: SEMAD
Airports: LDZA LDVA
Has thanked: 212 times
Been thanked: 426 times

Re: DA62 road landing in Dallas, Texas

Post by ememic99 »

Davestation wrote: Thu Nov 17, 2022 8:19 pm P.S. the 42NG and the 42-TDI batteries are identical to the 62.
Why didn't DAI issue same SIL for DA42NG and DA42TDI?
User avatar
tjmoody
3 Diamonds Member
3 Diamonds Member
Posts: 101
Joined: Tue Oct 27, 2020 8:52 pm
First Name: Trevor
Aircraft Type: DA42-VI
Aircraft Registration: N62DL
Airports: KRNT
Has thanked: 142 times
Been thanked: 76 times

Re: DA62 road landing in Dallas, Texas

Post by tjmoody »

The NSTB final just got published. Thanks to my friend Ian for pointing this out to me.

Unfortunately its still a head scratcher. There are two issues here:
1. Something happened with the electrical system to require the ECU backup batteries to support the ECUs. While there is some speculation in the report, they weren't able to get to a root cause
2. The ECU backup batteries (which would normally provide 30 min when all else fails) were installed incorrectly. Apparently in parallel instead of in series so only 12v was available instead of 24v .. so no backup

If the backup batteries had been correctly installed, this should have been a non-event and the pilot could have easily gotten to the airport. After we learned about this, I've asked my shop to take a photo of the battery wiring after installation to double check all is correct. Apparently there are tests in the TDI manual to confirm correct installation but not in the NG manual.

As far as the primary issue that lead to this, its frustrating that there's no answer. They reference that the battery had slightly low "capacitance" but the alternators should have been providing power as well. My understanding was that both the alternators and the main battery need to die (incredibly unlikely) before we need the backup batteries to come into play? There is reference to "Additionally, the alternator relays were wired such that the alternator would not disconnect the alternator power from the main electrical system." I'm not sure if this means there was a problem in the wiring for this particular plane or a design issue?
Attachments
Report_CEN23LA014_106135_11_28_2024 10_26_42 PM (003).pdf
(738.68 KiB) Downloaded 35 times
User avatar
rdrobson
3 Diamonds Member
3 Diamonds Member
Posts: 92
Joined: Thu Jan 25, 2018 2:16 pm
First Name: Ron
Aircraft Type: DA62
Aircraft Registration: N84LT
Airports: KFAR
Has thanked: 31 times
Been thanked: 35 times

Re: DA62 road landing in Dallas, Texas

Post by rdrobson »

tjmoody wrote: Fri Nov 29, 2024 7:42 pm My understanding was that both the alternators and the main battery need to die (incredibly unlikely) before we need the backup batteries to come into play? There is reference to "Additionally, the alternator relays were wired such that the alternator would not disconnect the alternator power from the main electrical system." I'm not sure if this means there was a problem in the wiring for this particular plane or a design issue?
From my reading of the report, it seems that the alternator relays were wired incorrectly at some point. Either during build or some later event. I think if the design were that way, they would say something different on page 2 instead of 'wired incorrectly'.

This is a bit scary as this used to be my airplane. Glad it never dropped me into Lake Michigan as I crossed that body of water a number of times during my ownership.
User avatar
jast
3 Diamonds Member
3 Diamonds Member
Posts: 103
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: 64 times

Re: DA62 road landing in Dallas, Texas

Post by jast »

If I remember correctly there is a diode from the main 24V system to the ECU bus which is supposed to be 24V as well and keep the ECU batteries charged. If it’s 12V it overcharges the batteries which draws too much power, blows fuses and causes other issues. Every signal line between the now 12V system and than 24V system creates leakage currents because it was not designed to be 12V. It’s likely a real bad mistake causing an avalanche of issues.

However I’m wondering if there is a possibility to check the ECU batteries and their voltage in a pre flight check. Especially after a ship visit and before over water or over high terrain flights you want to be sure…
User avatar
tjmoody
3 Diamonds Member
3 Diamonds Member
Posts: 101
Joined: Tue Oct 27, 2020 8:52 pm
First Name: Trevor
Aircraft Type: DA42-VI
Aircraft Registration: N62DL
Airports: KRNT
Has thanked: 142 times
Been thanked: 76 times

Re: DA62 road landing in Dallas, Texas

Post by tjmoody »

jast wrote: Sat Nov 30, 2024 7:50 am If I remember correctly there is a diode from the main 24V system to the ECU bus which is supposed to be 24V as well and keep the ECU batteries charged. If it’s 12V it overcharges the batteries which draws too much power, blows fuses and causes other issues. Every signal line between the now 12V system and than 24V system creates leakage currents because it was not designed to be 12V. It’s likely a real bad mistake causing an avalanche of issues.

However I’m wondering if there is a possibility to check the ECU batteries and their voltage in a pre flight check. Especially after a ship visit and before over water or over high terrain flights you want to be sure…
Yes that's correct but there is also a 32A fuse which I assume blew and could have been the "pop" the pilot heard when the 24v system was connected to the 12v ecu batteries. The engines went quiet at this point but at least the fuse protected against an electrical fire etc.

For those with an electrical interest, its worth reading the attached Systems Report which was in the NTSB docket. It gives more detail on the mis-wiring of the alternator relays. Basically they were bypassed. I may be missing something but I don't see how this would have contributed to the engine failures. By accidentally bypassing the alternator relays, I think this would have just prevented the alternators from being disconnected from the LH/RH Main Buses. There is no mention of the alternator switches being moved. So if I am interpreting this correctly, the mis-wiring of the alternator relays (while clearly a bad thing) didn't contribute to the engine failures.

Regarding a preflight check of the ECU backup batteries, that would be great but there doesn't appear to be anyway to do this.
Attachments
CEN23LA014 Systems Factual Report final-Rel.pdf
(2.99 MiB) Downloaded 31 times
User avatar
jast
3 Diamonds Member
3 Diamonds Member
Posts: 103
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: 64 times

Re: DA62 road landing in Dallas, Texas

Post by jast »

Thank you! That's very interesting!

What bugs me is that there is no check as pilot of the ECU batteries are working or not according to a checklist. Based on the electrical wiring diagram I thought of a simple idea how to proof that the ECU batteries are working without pulling fuses or just switching off Master in ground. If you get into the aircraft and activate the either engine switch and just listen for the fuel pump sound (which is clearly audible), I think you can be sure that this engine would run on the ECU battery if the main battery would fail. Obviously you would have to do it one engine after another and every time you do this you would create an additional pre-heating cycle (which likely is good for the engine anyway if it's cold). I asked this question also to our Diamond support if there are any negative side effects if you do this tests e.g. before a flight over water or at night. Answer is pending, but I'm curious to hear thoughts from experts here?!
User avatar
tjmoody
3 Diamonds Member
3 Diamonds Member
Posts: 101
Joined: Tue Oct 27, 2020 8:52 pm
First Name: Trevor
Aircraft Type: DA42-VI
Aircraft Registration: N62DL
Airports: KRNT
Has thanked: 142 times
Been thanked: 76 times

Re: DA62 road landing in Dallas, Texas

Post by tjmoody »

That's interesting and simple. I'd be interested to hear what response you you get. One question I would have is would you still hear the pumps activate if there was only 12v available ... as in this scenario with the DA62 in Dallas? I don't know the answer. If the pumps require the ECU to be running then it might be a valid test.
User avatar
mfdutra
4 Diamonds Member
4 Diamonds Member
Posts: 315
Joined: Mon Apr 26, 2021 10:49 pm
First Name: Marlon
Aircraft Type: DA62
Aircraft Registration: N272DD
Airports: KHWD
Has thanked: 266 times
Been thanked: 219 times

Re: DA62 road landing in Dallas, Texas

Post by mfdutra »

jast wrote: Mon Dec 02, 2024 10:44 pm What bugs me is that there is no check as pilot of the ECU batteries are working or not according to a checklist.
The NTSB doc above explains perfectly how they tested it. Pages 22 and 23.

It's quite simple actually.
User avatar
jast
3 Diamonds Member
3 Diamonds Member
Posts: 103
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: 64 times

Re: DA62 road landing in Dallas, Texas

Post by jast »

Yeah, but they do it with the engine running and this could a) potentially create hiccups/ecu faults and b) needs more time after a startup clearance because of the master SW off/on and c) doesn’t bring you to a clean state of a checklist start so it’s more a modification rather than a pre-check. But maybe it is the right way…
Post Reply