What's new
Van's Air Force

The definitive Van's Aircraft support community! Buying, building or flying an RV? Join our exclusive family of mentors and enthusiasts!

Magnetometer: Tailcone vs Wingtip?

K

kirkbauer

Well Known Member
I was going to put my GMU11 in my wingtip since my current RV-10 has its magnetometer in its wingtip. But I'm a bit worried about CAN bus length and I could cut off quite a few feet if I mount my magnetometer at the top of my tailcone. I do see quite a few builders on Youtube that have put their magnetometer in the tailcone, but mostly those are GMU22s.

Has anybody installed a GMU11 in the tailcone and have you had any issues?
 
By tailcone, do we mean mid tailcone using the ADAHRS bracket from Vans or similar? Or do we mean all the way back on the horizontal stabilizer deck? I have seen several RV7s, etc with the GMU11 mounted on the rear deck which seems like a clean install, but on an RV-10, I was worried about interference from the trim cables.

I went with GMU22 in the wingtip.
 
gkochers said:
By tailcone, do we mean mid tailcone using the ADAHRS bracket from Vans or similar? Or do we mean all the way back on the horizontal stabilizer deck? I have seen several RV7s, etc with the GMU11 mounted on the rear deck which seems like a clean install, but on an RV-10, I was worried about interference from the trim cables.

I went with GMU22 in the wingtip.
Click to expand...
Mine (GMU 44) is mounted mid tailcone at the top of the F-1008 frame in a bracket specifically made for the purpose I bought from Steinair back in the day.IMG_1935.jpeg
 
I guess I should clarify. I was considering using the vans ADAHRS shelf which I believe goes on the bulkhead just aft of the batteries. It seems that's where most people mount the magnetometers in the tail. I could go one more bulkhead aft but that would be harder to access now or later.

I do know that the manual mentions the Tailcone as a mounting location but it also mentions staying at least 10ft away from magnets or electrical current. On the forward bulkhead I'm probably only 3ft away from a bunch of that. On the aft bulkhead maybe about 6ft. Even on the wingtip probably not 10ft though.

Besides the batteries I will have a few contactors plus two autopilot servos back there.
 
I have GMU 22’s installed in the tail cone (on the aft deck) in two airplanes, and thought I’d put the GMU 11 there for the Rocket - but after some discussions with Garmin experts I decided to go ahead and do the wingtip install because the GMU 11 is a different animal than the 22 - it apparently a bit more sensitive, which makes it more sensitive to any moving ferrous material. I’d far rather have it in the fuselage from an “ease of installation” standpoint. Hadn’t thought about the vertical fin tip - but I wonder if that is stable enough? Flying surfaces move more than pilots want to think about…..
 
Ironflight said:
I have GMU 22’s installed in the tail cone (on the aft deck) in two airplanes, and thought I’d put the GMU 11 there for the Rocket - but after some discussions with Garmin experts I decided to go ahead and do the wingtip install because the GMU 11 is a different animal than the 22 - it apparently a bit more sensitive, which makes it more sensitive to any moving ferrous material. I’d far rather have it in the fuselage from an “ease of installation” standpoint. Hadn’t thought about the vertical fin tip - but I wonder if that is stable enough? Flying surfaces move more than pilots want to think about…..
Click to expand...
It's interesting that they would say that when their own manual specifically approves that location. My GMU 11 is on the rear deck of my RV7, along with all the usual stuff plus an ELT antenna and it passed the interference test easily. The highest interference I saw was 17% of max allowable.
 
Desert Rat said:
It's interesting that they would say that when their own manual specifically approves that location. My GMU 11 is on the rear deck of my RV7, along with all the usual stuff plus an ELT antenna and it passed the interference test easily. The highest interference I saw was 17% of max allowable.
Click to expand...
Different airframes have different magnetometer installation guidance. You are correct that the aft deck is recommended for the RV-7, but for the RV-8 the recommended location is different. Based on my experience, I would think the RV-8 guidance would be a good starting point for a Rocket, i.e. the magnetometer probably will work best either in the mid-tailcone area or in a wingtip.
 
I have a GMU 11 installed on my RV-10 tailcone just forward of F-1008 on the upper skin (composite); it passed the interference test without issue. It is also the termination point for my CAN bus with a total length of about 64 feet.
 
rongawer said:
I have a GMU 11 installed on my RV-10 tailcone just forward of F-1008 on the upper skin (composite); it passed the interference test without issue. It is also the termination point for my CAN bus with a total length of about 64 feet.
Click to expand...

What do you mean by that? The skin there is aluminum not composite -- and are you saying that you mounted it to the skin directly? Sorry if I'm being dense and missing something.
 
I put my GMU 11 in the right wing tip of my RV-10, which has functioned without any issues and passed the interference test. I didn't put it in the tail cone as I installed an AC system, and the blower motor is just behind the baggage bulkhead. Motors such as these generate strong EMF fields, so I felt it wouldn't be wise to mount the GMU there.

Regards
 
As an alternative, Van's sells a installation kit for the RV14 to place the GMU11 on a mount at the inboard most inspection panel on the wing. As we know the RV14 and RV10 wings are the same except for length so it is a 1 to 1 fit. It is setup for the left wing, but I inverted it and used it in the right wing instead. If you went left wing then it would be a very easy install (still fine on the right with some mount modification). The benefit is that you are in the CAN BUS between the GSA28 actuator in the wing and the wing root so no substantial extra length added. Also, it gives good seperation from the Stainless Steel counterweight in the aileron. Just how I did mine, your results may vary.
 

Attachments

  • Electrical 29.jpg
    Electrical 29.jpg
    379.3 KB · Views: 70
  • GMU 4.jpg
    GMU 4.jpg
    239.4 KB · Views: 71
  • GMU 5.jpg
    GMU 5.jpg
    293.7 KB · Views: 73
kirkbauer said:
What do you mean by that? The skin there is aluminum not composite -- and are you saying that you mounted it to the skin directly? Sorry if I'm being dense and missing something.
Click to expand...
I replaced my tailcone upper skin with a ShowPlanes composite one, and then made a shelf attached to that skin. If I were using the aluminum skin, I would have mounted the GMU on a shelf attached to the forward side of the F-1008 bulkhead. Either skin material is actually irrelevant to magnetometer interference, but did provide me the mounting option I chose.
 
The RV-12iS avionics kit mounts the GMU 11 at about the top center of the tailcone. It is quite close to the DUAL fuel pumps, GSU 25 adahrs, pitch servo, and ADS-B receiver. Despite the many RV-12iS's (SLSA and ELSA) flying, it's never been an issue to my knowledge.

I'd save yourself the CANBUS run and put it in the tailcone.
 
You must log in or register to reply here.
Back
Top