Dan Checkoway's RV-7 Project

August 23, 2004

Today I flew up to Cable to see Larry Hackney, who just got his airworthiness certificate for his RV-7A on Sunday. Congratulations, Larry! He's getting ready for his first flight and wanted to get some "7" stick time to be fresh right before his big day. We went flying and Larry felt out the slow flight and stall characteristics, and I had him do all the flying except for the takeoff roll and very last couple of seconds before touchdown. He's not a taildragger guy, but Larry owned an RV-6A a few years back. He's modest about everything, including his flying skills...once you've got any real amount of time in an RV, it's never gonna feel unfamiliar again. Best of luck, Larry, and have a safe and enjoyable Phase I.

Back at the hangar tonight I did some surgery on 14D. Very minor stuff. Lately I've started experiencing some issues with the Dynon EFIS-D10. I may have mentioned it in recent site updates, but here's the deal...

The biggest issue is that the horizon wanders slightly at times. It's such a minor deviation, but it's more than enough cause for concern for me. Basically what originally was happening (about 2 weeks ago) was that the heading seemed to wander about 10 or more degrees in either direction, kind of a slow oscillation of sorts. This would happen randomly for spurts of about 5 minutes or so. When the heading wandered, the horizon would eventually start wagging slightly, only a couple of degrees, but definitely noticeable. I assumed that the magnetic heading is probably tied into the attitude calculation. I believe *everything* is tied into attitude calculation in some fashion. Anyway, as the heading wagged, the horizon started wagging, too. So I upgraded the firmware and re-did the magnetic calibration of the EDC (external digital compass). That definitely improved things, but I'm still seeing an intermittent symptom where the horizon will randomly dip to one side, maybe 2 degrees, 3 degrees tops. This is when flying straight and level in smooth air. Trust me, it's not the pilot. Needless to say, this is unacceptable and no doubt I've stopped flying IFR until this is resolved.
The clock setting seems to get lost sometimes. I haven't put my finger on this one yet. I set the clock...and then usually several days later I look at it and see that it's way off. I never seem to catch it when it resets (presumably to 00:00). At Dynon's request, I confirmed 12 volts between pins 2 and 3, which are the KA (keep alive) circuit and ground. Something's up with this clock thing.
The last symptom is a very minor one, but it indicates either an internal hardware or software issue to me. Normally when you shut the D10 off manually, by holding the left button down, a little "popup" comes up at the bottom of the screen and says "HOLD FOR 2 SECS." Sometimes, and it's only rarely, I'll hold the button down and it will only say "SECS." The popup is the same size, it's just missing the "HOLD FOR" above and "2". Weird.

Anyway, I communicated these issues to Doug at Dynon, and he figured it's an internal issue and that I should send the unit back for repair. He hadn't seen these issues on any other installation, though, so his recommendation was first to acquire some data from the unit before removing it. The D10 has some undocumented features, one of which (I came to find out) is capability for a second serial adapter. The primary PC/serial capability is used for upgrading the OS, transferring airspeed constants, checklists, doing magnetic calibration, etc. The second serial adapter is really just for debugging, since it dumps the raw sensor data. Doug asked that I hook this up, go fly, and record data. When the problem occurs, he said that I should just do a pitch-up or something to "mark" the data...and I'll also keep a written record of the times at which the problem occurred. Doug said that in exchange for doing this troubleshooting, he would not only replace the unit (you'd kind of expect that from any company), but that he'd upgrade me to an EFIS-D10A, the newer model (which is faster, has more features, and has built-in EMI protection). I had considered upgrading, but in the end I decided not to because it wasn't really worth the money in my case. But this will work out nicely.

So tonight I wired up the alternate serial adapter and confirmed that the data loader worked. It did.

It was actually really easy to install. I just had to add a few pins and wires to the D25 female connector. When I installed the original serial harness, I left it about 4 feet long...it's coiled up and tie-wrapped under the panel (not in this photo). What I did this time is way easier to deal with, and is what I'll do going forward. I see a lot of people putting RS-232 ports on their panels, which while convenient is pretty friggin' ugly! Why put that port out in the open? Anyway, my approach now is to run a short length of shielded wire to a MATE-N-LOK connector, which is tucked up and out of sight, but is still within easy reach when you're sitting in the seats. Here you can see the 8" long (or so) wire runs down from the Dynon and has a MATE-N-LOK connector at the end, secured to the parking brake handle tube. All I do is reach forward under the panel and the connector is there. I made a 3' long wire that has the MATE-N-LOK connector on one end and a D9 female (serial) connector on the other end. Way easier than having the whole wire permanently attached to the Dynon's wiring harness, and having to cut it down when I want to use it, and then safety it back up when done. The port on the panel is easiest (and ugliest), but this is cheap and easy and out of sight.

NOTE: DO NOT ASK ME FOR THE WIRING PINOUT INFORMATION FOR THE SECOND SERIAL HARNESS. This is information that Dynon hasn't given out for a reason. Contact Dynon directly if you think you need that information for some reason. I can just picture it now...I'm gonna be getting enough friggin' emails as it is to the tune of, "Dan, how's that Dynon issue?" Don't be surprised if I don't reply. So save us both the time and just watch for a future update on this site.

Tomorrow or the next day I'll go up and record some raw sensor data to send to Dynon...it's almost midnight now, so no flying for me. I did get half an hour of night flying in tonight, though, before doing all of this. Seven hours of night flying in 14D so far. I'm finally at a point where I have enough trust in the plane where IFR and night flight don't have me on the edge of my seat, waiting for something to act up. Obviously the Dynon issue prevents me from doing IFR until that's done, but night flying on a clear night like tonight -- the fun factor has kicked in.

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