Air Conditioner and ADAHRS

So I've tentatively decided I want to install an Airflow systems air conditioner in my 10. I've also tentatively decided I want a Dynon/AFS panel. So I'm wondering about the mounting of the ADAHRS units in the tail, and any electronic interference from the A/C components. Does anyone have this combination and had any issues? How far back did you have to place the ADAHRS and is it still reasonably accessible? Pictures would be great!

Thanks in advance.
Lynn

I have exactly what you describe. I have Airflow Systems A/C and dual Dynon ADAHRs.

I have the ADAHRS mounted under the fiberglass cross shelf on the opposite side of the A/C blower. I have never seen an interference issue between the two. Turning the A/C on or off results in no change in the heading reference. The only time I ever saw the heading swing from interference was when the cable of the rear seat shoulder strap sagged down to within an inch or so of the ADAHRS which is why I mounted then to the bottom of the shelf (right side up of course) instead of on top. I was trying to maximize distance between the blower motor, the battery, and the ADAHRS pucks while still staying in the prescribed zone for the magnetometer. The external magnetometer option wasn't available at the time of my build and I probably would have used it at the time but haven't seen the need now.

I thought at one time to replace the cables with stainless steel from a sailboat rigger, but haven't had any issues in the current configuration. I always make sure that the shoulder straps are secured taut and not sagging down close to the shelf.

Airborne compass calibration went fine. No compass issues at al in over 200 hours. I have likely over 100 hours with A/C running as we use it much more than we thought we would.

I have listed in my ops specs and limitations that the A/C is to be off in IMC, but that was more to please the DAR. I don't think it is necessary. In today's GPS nav world, compass accuracy just isn't as vital as it was in the dead reckoning days of yore. When it comes right down to it, the biggest asset today from a perfect compass reading is accurate wind display on the EFIS. Otherwise, you're still going to navigate by the GPS track regardless.

Just because it was getting crowded back there and also because the magnetometer that will be sitting in the right wingtip gets cabled to the Garmin AHRS, I put mine under the right rear seat pan. This link is to the Kitlog entry describing the mount. When I put the seat pan in, I fabricated a simple hinged cover, shown here. Unfortunately, too simple. It was fine with pressure spread (a person sitting on it) but I was kneeling on the pan working in the baggage area and all that weight concentrated at my knee wrinkled the cover. A slight redesign as shown here and all is well.

Pictures

Myron,

Do you have any pictures of your set-up, I'm not as good with visualization. I hadn't looked into the option of a remote compass since everything I read was with Dynon anyways it is built into the AHAHRS boxes.


Patrick,

I like your set-up and build log, I'm going to have to go through your log in more detail.

Thanks,
Lynn

I have the airflow system installed on the shelf provided by airflow. My Chelton gadahars is mounted below the evaporator shelf next to the battery. Since my magnetometer is located on my wingtip, I do not have any issues with interference.

Vans Bracket For Dynon Magnetometer

Not knowing woxofswa's experience, I used a handheld compass to check locations for my ADAHRS in the tailcone with the AirFlow AC. Activating the AC's fan affected the compass up to 24" away, leaving me searching for a more distant spot. Then Dynon came out with its remote magnetometer.

The RV-14 kit has a bracket to mount a Dynon ADAHRS in the left wing. The bracket aligns the ADAHRS to the airplane's three axes automatically. As the -14 and -10 have the same wing firm, the bracket will fit in a -10.

I placed my dual Dynon ADAHRS behind the panel and the remote magnetometer in the left wing bracket. The magnetometer uses the same case shape as the AHAHRS. However, placing the bracket into a completed wing would be a challenge.

Remote Compass

I had originally planned on just putting a remote compass in the right wingtip, but then read about positioning of the ADAHRS on the Dynon forum as: "We can handle about 6' side to side or 15' fore/aft." So this made me think the remote compass needed to not be further out than 6' from the fuselage, or is it ok to be out that far as long as the ADAHRS unit isn't out there?

The Boy Scout compass test mentioned is very useful. The wingtip is a time saver, now... rather than later. To fix a problem will be painful.
AC units can swing a compass much farther than engineers will admit in many cases.

Lynnb, many magnetometers are located in wing tips per manufacturers' manuals. Dynon's six foot lateral limitation is for the ADAHRS position senors.