How to get access to Dynon ADAHRS

It looks as though my Dynon ADAHRS has failed. I've twice lost altitude and airspeed data, in flight. I've sent a Diagnostic Data zip file to Dynon Support (on May 3) and am waiting to hear back about what it says my problem is. In the meantime, I'm trying to figure out how to get access to my ADAHRS, if in fact mine needs to be replaced or repaired. I have a Van's RV-12, and my ADAHRS is in the tail, behind the storage area bulkhead. There are no access panels in the tail. I've seen posts on the Dynon Forum by owners who said they replaced their ADAHRS, but they didn't say how they did it; and they may not have had RV-12s. I didn't build my plane; I purchased it from the builder. But the tail-cone location of my ADAHRS is the location called for in the builder's plans. I hope I don't have to replace the ADAHRS. But if it turns out I do, I also hope someone can tell me how to get access to it without disassembling my plane.

Hi Lon,

I'm still building and was just looking at that section of the plans and my plane. The ADAHRS is installed in the tailcone not far aft of the baggage bulkhead, which is removable. It's about as far back as the static ports so you should be able to reach it easily enough.

Regards,
Harry

Thanks Harry.

Is the baggage bulkhead riveted in place, or is it fastened with easily-removed screws? My bulkhead is covered with fabric, so I can't see what holds it in place.

Hopefully, you have the easily removable rear panel in the baggage compartment identifiable by separate panel that ramains fixed right behind the fuel tank. Early RV-12's had a one-piece rear bulkhead that required removal of the fuel tank to access panel fasteners. Needless to say, that was a PITA. Van's redesigned and added the stationary panel behind the fuel tank and most everyone has made the conversion. Hopefully, you're in that group. That said, you remove the rear bulkhead and your ADAHRS should be accessible.

Hi Jim,

My plane is a 2018 model, so I have reason to hope that my bulkhead is the easily removable one. The builder's plans show the bulkhead to be at least three separate panels: left, right and top.

Thanks, Lon

Lon,

With yours being so new, I feel sure it will be a two piece bulkhead. If their is a cloth or leather cover over it, once you remove it, there will be screws to remove and take it out. The ADAHRS is easily reachable once you remove the bulkhead.

You will have to pull off the fabric upholstery from the baggage bulkhead. It is held on by strips of Velcro. There may also be a couple of screws at the bottom edge. You have to bend the stiff upholstery panel and work at it carefully to get it off. Then there will be a number of phillips head screws holding on the panel. Be careful removing those and don't drop any behind the fuel tank. There are stainless and non-magnetic and you can't reach in there with a mechanic's magnet to retrieve them. I spent more time once trying to get back a dropped screw than taking everything apart to get access to the tail-cone!
The ADAHARS is up on the top of the tail-cone and pretty easy to get to. You do have to squeeze through the opening if the fuel tank is in place, and you will have to lie on your back to work. There are control cables running back to the tail. You could probably arrange 2 or 3 moving blankets to pad yourself and keep pressure off the cables. I made a little floor panel out of scrap because I have been back there a few times now and wanted a little more comfort. It rests on the first bulkhead back and it has slots to keep my weight off the cables.


The ADAHRS will have one electric D-sub and 3 tubing connections. Mark the tubing so as not to mix them up. The ADAHRS is held on to its mounting bracket by four small non-magnetic screws, nuts, washers. Be careful not to drop these small parts as they will be hard to find.

Try to figure out what tools you will need before going in. It's a real pain to get back there and need something. If I remember correctly you need a short #2 phillips and a small metric combination wrench, forgot the size, take a couple of your smallest. Have a helper on the outside.

I have put a padded sawhorse under the tail tie-down ring so if the plane wants to tip back from my being in tail-cone it won't go all the way to the hangar floor. I weigh about 190, it has never dropped back.

I hope you don't have to remove your ADAHRS but this may help if you do.

And make sure the tools you use to remove the ADAHRS are non magnetized and keep it away from magnetic fields after removal.

John and Tony,

Thank you! And Tony, thanks especially for the photos and the alerts about the screws being non-magnetic. I'm waiting, more or less patiently, to hear from Dynon. And I'm hoping my problem is more easily fixed than removing the ADAHRS would be. I've lost altitude and airspeed data twice, but I've also enjoyed flights where everything worked perfectly. And when the data disappeared, I did not get an "ADAHRS Failed" message or a red X through the display. All that happened was the airspeed dropped to 0 and the altitude shot up to 50,500!

The majority of electrical problems are caused by bad connections rather than
equipment failure. The fact that the problem is intermittent also points to a bad
connection. I suggest taking the connectors apart and checking for broken
wires or bad crimps or pins not seated properly.

Mich48041 said:

The majority of electrical problems are caused by bad connections rather than
equipment failure. The fact that the problem is intermittent also points to a bad
connection. I suggest taking the connectors apart and checking for broken
wires or bad crimps or pins not seated properly.

Click to expand...

Joe, Your advice gives me hope. I?m going to follow it. Thank you.

Tony's concern about dropped screw behind the fuel tank is noteworthy. There is very little room between bottom of fuel tank and baggage floor. Any foreign object that lodges under the fuel tank may cause abrasion and poke a hole in the thin bottom of the tank. I have placed a sheet of cork under my tank for this very reason. Not just wayward screw, but anything loose in the baggage compartment can cause problem.

Good idea Jim! I did something similar in the battery box placing a 1/8? thick piece of nylon sheet under the battery.