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How to mount GRT Magnetometer in RV-9?

KazooRV-9A

Well Known Member
Patron
I am looking at mounting the GRT EFIS Magnetometer in an RV-9 (The GRT EFIS apparently has an internal AHARS, there's no separate unit). There's a lot of wire cable on the magnetometer lead so I was assuming that it probably want's to be moved away from the firewall and gauge panel. The GRT instructions guide you to checking potential locations with a whiskey compass while operating flight controls and any electrical equipment, which is not possible at the stage of construction I'm at.

I bought the OP-47 AHARS Bracket, is this a good mount location for the Magnetometer? I do plan to install an altitude hold servo at the elevator belcrank, which is somewhat close to the location of the OP-47 bracket. The GRT manual mentions possible wing installation of the magnetometer also, which would seem difficult as the wings are now closed up.

What is a good location for mounting the GRT Magnetometer? Is the Van's AHARS bracket an acceptable location?

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my installation

I installed the GRT magnetometer in the left wingtip of the RV7a 12 years ago and it has worked well there. When I bought an RV10 and upgraded the panel to GRT 8 years ago, I installed the magnetometer behind the baggage wall as high up as possible. It works ok there until you put a steel lawn chair on top of a full baggage compartment and then as expected it doesn't work so well. Based on that experience, I would suggest keeping the mount location a couple feet away from any steel.

Good luck.
 
Mine is mounted on a fabricated gussette on the second bulkhead back from the rear baggage bulkhead. If you have a slider anything closer forward and the steel in the slider frame will interfere.
 
I had installed mine in the RV7A/tip-up, at the top of the bulkhead right behind the baggage area with no issues. But if you are a slider, this might not be as good of a place.

Also, mine was a separate mag/AHAR unit, so I am not sure how a combine unit will work. I will assume you will need to pay as much attention to the functionality of the AHAR which has a specific requirements.
 
Mine is mounted on a fabricated gussette on the second bulkhead back from the rear baggage bulkhead. If you have a slider anything closer forward and the steel in the slider frame will interfere.

I did the same and it has worked out well.

Chris
 
Dual Dynon ADAHARS units mounted behind baggage compartment piggyback on centerline, mounted to longerons No slider interference however I did need to have shoulder harness cables changed to Stainless.
 
X2 on Painless' recommendation. I've had one mounted there and it calibrated nicely. GRT recommends wingtip mounting for RV's, and describes that in their installation manuals. I have one there now in my RV-7, and likewise it calibrated well.
 
Thank you.

The panel was wired by Aerotronics, and I'll see how much cable they included with the Magnetometer. Not sure at the moment, how far it would reach.

I gather from these answers, that the floor mount Van's AHARS bracket between the two bulkheads rear of the luggage area, may not be the best location because of metal things that may be carried in that area? Or other concerns for that location?

But why would Van's Engineer this location for an AHARS, if it wouldn't prove acceptable to function? It's not clear to me, what the difference between AHARS and Magnetometer sensor functions are. I was assuming that the AHARS sensor was built into the panel mounted GRT EFIS unit itself, but can't seem to find a direct reference to this in their manual, unless I've missed it.
 
Like Tom Lewis mine is mounted in the left wing tip. It was originally mounted on a shelf beneath the vertical stabilizer but had too much electromagnetic interference because there was significant heading difference between dual GRTs and my backup Dynon EFIS. Moving both to the left wing tip cleared up the problem.

If your wire isn’t long enough get some four wire shielded cable and run a new wire. It isn’t hard to do and it’s fairly easy to rewire the sub pin connection. It’s also a good idea to run ithe wires inside some plastic conduit since those rib holes are sharp.
 
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For a wingtip mount, was the Magnetometer simply attached to the fiberglass tip, or was a plate or bracket fabricated?
 
Thank you.

The panel was wired by Aerotronics, and I'll see how much cable they included with the Magnetometer. Not sure at the moment, how far it would reach.

I gather from these answers, that the floor mount Van's AHARS bracket between the two bulkheads rear of the luggage area, may not be the best location because of metal things that may be carried in that area? Or other concerns for that location?

But why would Van's Engineer this location for an AHARS, if it wouldn't prove acceptable to function? It's not clear to me, what the difference between AHARS and Magnetometer sensor functions are. I was assuming that the AHARS sensor was built into the panel mounted GRT EFIS unit itself, but can't seem to find a direct reference to this in their manual, unless I've missed it.

What GRT EFIS do you have? The HS, HX, HXr models have externally mounted AHARS boxes, as well as an external magnetometer. The other models (Sport, etc) have internal AHARS gizmos, but still an external magnetometer. The vans location for the AHARS is okay, as that box is not sensitive to stray magnetic fields. As magnetic fields are not shielded by aluminum, the magnetometer can be inside the wing. Just not close to current carrying wires, which do generate magnetic fields.
 
I have the GRT sport SX and a GRT multifunction display. The panel was built by Aerotronics and they do supply you with a fair amount of cable. The magnetometer is in the right wing tip on a bracket attached to the end rib. And my left wing has a wing leveler servo in the left wing. The location works very well and has been in place since 2009. Good luck with your placement. Lots of good suggestions. Steve
 
Thank you.

The panel was wired by Aerotronics, and I'll see how much cable they included with the Magnetometer. Not sure at the moment, how far it would reach.

I gather from these answers, that the floor mount Van's AHARS bracket between the two bulkheads rear of the luggage area, may not be the best location because of metal things that may be carried in that area? Or other concerns for that location?

But why would Van's Engineer this location for an AHARS, if it wouldn't prove acceptable to function? It's not clear to me, what the difference between AHARS and Magnetometer sensor functions are. I was assuming that the AHARS sensor was built into the panel mounted GRT EFIS unit itself, but can't seem to find a direct reference to this in their manual, unless I've missed it.

That's a popular AHARS mounting spot for Dynon SkyView systems, in which the (external) AHARS also includes a magnetometer. It would probably work fine for the GRT magnetometer, but it's more work (have to install the bracket) for no real benefit. Unlike the Dynon product the current GRT offering doesn't care about being precisely aligned with the direction of flight. Same goes for their "adaptive AHRS" which can be mounted on a panel rib. Since you have an internal AHRS (means you have a Sport or a Mini) you don't have to care about the latter.

I'm guessing that Aerotronics is just passing along the GRT-supplied magnetometer wiring harness, which is about 20 feet long if memory serves. Enough to get from the wingtip to behind the panel, barely, on a side by side RV.
 
GRT Magnetometer

I mounted mine on one of the inspection panels in the wing, and had no problems. I am now building an RV 8 and will mount it the same area, however in this case may position it further aft by reaching through the access panel and positioning it alongside the rib. I have found mounting with commercial grade Velcro has been very satisfactory.
The best position can be checked by merely moving the magnetometer around the aircraft to find the best ?quiet? position, or by downloading a magnet meter APP on to an IPhone and using that.

Good luck, Brent
 
For a wingtip mount, was the Magnetometer simply attached to the fiberglass tip, or was a plate or bracket fabricated?

In my 7A, have a GRT Magnetometer mounted in each wing tip. I fabricated mounts that I attached to the end (outside) ribs. Been working fine for 400+ hours. I might be able to find a photo if you'd like.
 
Or if you are lazy like me, GRT says they can be mounted on a vertical surface, so I did. 2 holes through the end rib of the wing, another for a zip tie to retain wires. Done. Which is not to disparage brackets, which look nice. Only to point out that mounting options are pretty flexible with these things, compared to the legacy magnetometers that required careful alignment.
 
Looks like I have JUST enough cable to get out to the wing tip. This unit is supposed to lie flat and of course in alignment with the EFIS.

Wing tip it is. Probably make a bracket off the end rib.
 
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