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Magnetometer & common fuse wiring harness

SabreFlyr

Well Known Member
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I'm studying the drawings for the common fuselage wiring harness trying to determine whether or not I will plan on using it or doing my harness "from scratch." I know that I will have an addition or two if I use it. If it gets much more than that, I may be better off doing my own. One thing I can't seem to determine is whether the common harness provides for a tail-mounted magnetometer. I can see provision for the ADAHRS in the left wing in a couple of possible locations but no mention anywhere that I can see about the magnetometer in any location. I do see more autopilot wires going down the right side of the tail cone than I would have expected but I don't know that they would be related to the remote compass. Pitch trim functions are what I presume them to be.

What am I missing?
 
Go to the source

Ray,

I would call Stein directly about the harness. Since they make it for Vans they can tell you exactly what's what. Not sure if they can modify one to accommodate specific requests but it can't hurt to ask.
 
Hadn't thought about the possibility of having Stein modify the bundle. Also forgot that they made it. I just figured on bundling my additional wires to the appropriate part of the bundle. I'll give them a call tomorrow. Thanks.
 
Okay, looking closer at the harness drawings, I can see that it's not just the ADAHRS they are installing in the left wing. Some had mentioned the magnetometer in the left wing and I was sure they were mistaken and it was just the ADAHRS they were referring to. Seems to me there are far better locations for the remote compass such as the wing tip or tail cone. Guess that's the question I'll be asking Stein.
 
Ray,

You may want to check out the Garmin Magnetometer just announced that is to be available in May. Looks to be a lot easier to mount and appears to connect to the CAN bus directly (speculation on my part, it may still wire in serially to another device). It is the GMU 11. I have the GMU 22 that connects to the the Garmin ADAHRS.

From what I have read about it, I would have gone with it instead of the GMU 22.

However, no wiring or installation details have been released yet so hard to judge.
 
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Beware there is a max CAN bus length limitation.... when you start putting CAN bus items a long way from the panel components data error rates may climb. Can be overcome but has to be considered.

I've got pitot heat running to the left wing, so I'm not excited about putting a magnetometer in that left wing shelf. I don't really want to put the AHARS there either because I want to have all three air lines (static, dynamic, AOA) run behind the panel anyway for other backups. That shelf might be a great place for a GPS antenna though? The aluminum around it won't affect the signal much and it isn't hot like under the cowling.
 
That shelf might be a great place for a GPS antenna though? The aluminum around it won't affect the signal much and it isn't hot like under the cowling.

You can't put a GPS antenna (or any other kind of antenna) inside the aluminum structure. GPS signals are particularly weak and for optimum performance you want the antenna mounted externally on the top of the fuselage with clear line of sight to satellites. Even plexiglass and fiberglass will attenuate the signal somewhat, although in practice a GPS antenna placed on the glareshield (under the canopy) or under the cowl will work pretty well (as long as you don't have metallic paint on the cowl).
 
Beware there is a max CAN bus length limitation.... when you start putting CAN bus items a long way from the panel components data error rates may climb.

Well, there are two length to consider with CAN, bus length and stub length. Since all the runs will be bus length, I'm pretty sure you can keep the bus length under 40 meters in a 14, and that's for the highest bit rate.

Typical G3x stub lengths are on the order of an inch or two, well under the .3 meter length. The stub connection to the bus is made right in the connector.

However, please note that it may not be a CAN device. I have just inferred it from the promotional material and a Webinar Garmin gave on the new devices. It might still be a serial device. I hope not.
 
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