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Dprestonsr

Member
HELP !!! WOULD APPRECIATE ANY FEEDBACK REGARDING CHELTON AHRS OR AFS MAGNATOMETER. ANYONE HAVE FLYING RV WITH THESE UNITS MOUNTED IN THE WING, WING ROOT, AFT FUSELAGE OR ???? WHERE IS THE BEST LOCATION? MINE IS IN THE WING ROOT OF RV10 & NOT FUNCTIONING PROPERLY. I AM NOT THE BUILDER.
THANKS IN ADVANCE.
DOUG PRESTON
#40372
[email protected]
 
Doug,
Have you contacted AFS? Rob is great getting back to you if you miss him by phone. Rob is currently building a 10 and has pictures of his installation on their forum where he has placed his twin Magnatometers in the tail section.
Where did they place the Mag in the wing root? I can see it in the tip which was my first consideration but I am now planning on placing mine in the tail.
I am currently finishing Section 29 he** so can't help you with the flying part.
 
Well, I have GRT units, but I suspect that physics will overrule brand names in this instance, so here is what I have------discussed with, and approved by, the folks at GRT.

A flat tray arrangement is suspended from the tail cone top, right above the battery area. It is about a foot square, holds both AHRS, and Magnetometers.

It is mounted by riveting pieces to the "J" stiffeners, one at each corner of the tray. The front mount is just held with "C" clamps at this time, final drilling will be after final assembly of the plane, so as to be able to get the tray level.

Pretty simple, really. I can post a photo if you need.
 
Chelton MSU

I assume you have the new Chelton GADAHARS and not the Crossbow. That being the case, most people are putting their magnetometers (MSU) in the wing tip or tail area. If your MSU is in the wing root, that could be a problem. The Crossbow has a magnetometer built into the AHARS which of course needs to be on the center line.

You need to sign on to WWW.CheltonEFISPilots.com where you will find some very helpful RV-10/Chelton owners. Post your question there and I am sure you will get the information you seek.
 
Doug,

I have mine mounted on the top of a fuselage bulkhead behind the baggage compartment.

Did you ever try your magnetometer pointed in the right direction? The connector MUST be pointed to the front of the plane and away from magnetic material.

Any problems we've had have been due to the magnetometer being pointed in the wrong direction or too close to steel.

Call me any time for help.

Sincerely,

Rob Hickman
Advanced Flight Systems
(503) 263-0037
 
AHARS

Probably a little far-fetched, but we had issues with the (high $$ Collins) AHARS in airliners if the airplane was parked over something with a lot of iron in it like a pipeline. Took a while to figure out that the failures were always in the same spot on the ramp.

John Clark
RV8 N18U "Sunshine"
KSBA
 
GRT MAGNETOMETER LOCATION

Dear Mike:

In regards to your post of:

QUTOE: "Well, I have GRT units, but I suspect that physics will overrule brand names in this instance, so here is what I have------discussed with, and approved by, the folks at GRT.

A flat tray arrangement is suspended from the tail cone top, right above the battery area. It is about a foot square, holds both AHRS, and Magnetometers."

I have 185 hours on my RV-10 and also built a shelf above the battery area and mounted it to the J stiffeners and mounted my duel AHRS and duel Magnetometers on the shelf.

I consistently had problems getting my heading to read correctly on both sets of GRT systems (Duel Horizons & Sport HZ). At Osh2008 I got some of the GRT people to come out to my RV-10 to help me determine why my headings were never accurate. They determined that I was getting electrical interference because the location was above the battery.

I ran a new line for the Magnetometer mounted on the far right side (passenger) of the shelf from the right wing tip and tied it into the right side Magnetometer's wiring and moved the Right Side Magnetometer to a shelf bracket I built on the right wing outside rib.

I then retested the effect of moving the Right Side Magnetometer and found that I still had some electrical interference problems but not as much as before. I then moved the Left Side Magnetometer over to the far right hand side of the shelf where the other Magnetometer had been and again tested. Everything worked fine and after about 30 hours flying since then I have had no problems.

My opinion is that because the battery is wired into the left side of the airplane that there was enough electrical interference on the left side of the shelf above the battery to cause the problem. If you are running a single Magnetometer and you mount it to the far side away from the battery electrical connections you should be OK. Out of an abundance of caution I would strongly recommend that you run an extra set of wiring out to the wingtip during the build so that if you have any problems it is easy to change out.
 
Russ, thanks for the info.

As it turns out, I slightly mis-stated the location of my tray in my earlier post, it is actually above, and behind the battery--------should have made that clearer, it is back behind the next bulkhead aft.

The idea of extra conduit in the wing is a good one.

Thanks.
 
I assume you have the new Chelton GADAHARS and not the Crossbow. That being the case, most people are putting their magnetometers (MSU) in the wing tip or tail area. If your MSU is in the wing root, that could be a problem. The Crossbow has a magnetometer built into the AHARS which of course needs to be on the center line.
Click to expand...

Not exactly. We always recommend that you mount the AHRS as close to the center line of the aircraft as possible, however in such small aircraft the "lever affect" really doesn't come into play unless you put it in the wing.

In our user manual, we use a general 24" rule away from moving ferrous material or changing magnetic fields. Large pieces of stationary ferrous material can also be an issue, but are less common.

We've had several good installs in the back of an RV-10 just aft of the baggage wall with the AHRS. If you have a remote mag, you should take advantage of that and place it in the wing if possible. Just keep an eye out for strobe light ballasts and wiring.

Michael Smith
Applications Engineer Inertial Systems
Crossbow Technology
 
Mike, thanks for jumping in here.

It is always good to hear from a manufacturer, the info tends to be a lot more accurate.

It is even better to hear that the way my stuff is mounted should be O.K., at least the AHRS.

My magnetometers are on the same tray, above/behind the battery area.

The strobe power unit is on the floor, a foot or so ahead of the tray, with about two foot of vertical separation.

Do you see any problems with this setup??

Thanks in advance for your input.
 
That's sounds like the same location I was referring to. You should check with the AHRS manufacturer as well in case they have any final thoughts (it doesn't sound like its ours and I don't want to step on anyone's toes and give bad info).

I used to worry about the battery, but its actually the cables that run to the battery that tend to cause the problem. After startup there's a large amount of current that runs back through those cables to recharge the battery and it can drive you mad to try and find out why the heading accuracy comes and goes after startup.

Sincerely,
Michael Smith
Application Engineer Inertial Systems
Crossbow Technology
 
It is a GRT system, I am not the one who did the install, purchased the partially completed plane.

I did call GRT, mainly to discuss the routing of the wiring for the AHRS/Magnetometer, which the prior owner had set up to parallel to the strobe high voltage lines, only an inch or so apart for over four feet of run.

I re ran the strobe wires, far side of the cockpit, and they now dont come any closer to the AHRSetc wires than a foot, and at a right angle, not parallel.

The above was at the recommendation of the GRT folks.
 
silly ahrs bracket question

For some reason i bought the vans ahrs mount tray/bracket. I have no idea what i will go with for the panel (dynon, mgl, etc....just not sure if since i have it, i should install it. vans builds the bracket to go just aft of the baggage wall on the floor of the 9. Due to being QB, i will have to drill our a few rivets and do some dimpling that will be difficult on the floor skins. Since i have no clue if i will use it....any idea if its worth the trouble to install, or usefull as a mount for other stuff down the road. I already have vans elt and strobe brackets installed.???
 
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