GMU11 mount

[Aerodon]

Here is my first attempt at making a GMU11 mount for a Mooney. I struggled to do the bends on a standard brake, but I now know what tooling to get to be able to do this nicely.

It's designed to go on a rib, and is tilted at 6 degrees. I could do -6 degrees and then you could mount on the inboard side of a rib? GMU11 can be mounted facing forward or rearward, and there is enough space to install a cable tie down.  

Aerodon

[N201MKTurbo]

I just drilled 4 holes in the bottom wing skin and screwed it down. No bracket, meets all the criteria. It works great. 

[Aerodon]

7 hours ago, N201MKTurbo said:

I just drilled 4 holes in the bottom wing skin and screwed it down. No bracket, meets all the criteria. It works great. 

I saw a Mooney like that and told the installer I would be really unhappy if they did it like in my plane.  I have spoken with several installers who agree with me that it would not be acceptable to drill  into the wing skin.  For a start, Garmin specify a minimum thickness of 0.032 directly connect to the airframe structure.  Antennas require a doubler, so I would think that if you attached to a wing skin you would need a doubler attached to a rib?  The wing skin is likely at 6 degrees, the GMU11 must be within 3 degrees of horizontal. But it's your plane, do whatever you like.

Aerodon

 

 

 

[N201MKTurbo]

1 hour ago, Aerodon said:

I saw a Mooney like that and told the installer I would be really unhappy if they did it like in my plane.  I have spoken with several installers who agree with me that it would not be acceptable to drill  into the wing skin.  For a start, Garmin specify a minimum thickness of 0.032 directly connect to the airframe structure.  Antennas require a doubler, so I would think that if you attached to a wing skin you would need a doubler attached to a rib?  The wing skin is likely at 6 degrees, the GMU11 must be within 3 degrees of horizontal. But it's your plane, do whatever you like.

Aerodon

 

 

 

The wing skin curves around, put it at the bottom of the curve.

If you want to do something more complex, knock your lights out. I’m sure it will be awesome.

[Aerodon]

The wing skin outboard of the ailerons is 0.025, so attaching there does not meet all the criteria.  Yes, levelling fore and aft can be done by locating in the right place.  Levelling laterally could be done with washers.  

(and I don't know how thick a wing rib is, but I will go measure)

 

Aerodon

 

[JimB]

On 12/4/2020 at 12:09 PM, Aerodon said:

Here is my first attempt at making a GMU11 mount for a Mooney. I struggled to do the bends on a standard brake, but I now know what tooling to get to be able to do this nicely.

It's designed to go on a rib, and is tilted at 6 degrees. I could do -6 degrees and then you could mount on the inboard side of a rib? GMU11 can be mounted facing forward or rearward, and there is enough space to install a cable tie down.  

Aerodon

 

 

Very nice!

[OR75]

On 12/4/2020 at 10:27 AM, N201MKTurbo said:

I just drilled 4 holes in the bottom wing skin and screwed it down. No bracket, meets all the criteria. It works great. 

I believe I read in the G5 install manual that you actually cannot do that 

[N201MKTurbo]

53 minutes ago, OR75 said:

I believe I read in the G5 install manual that you actually cannot do that 

What page?

[ArtVandelay]

Mine is in the tail on a bracket. Seems like it would be better to be on centerline of the plane.

[OR75]

39 minutes ago, N201MKTurbo said:

What page?

Page 66/67 of the latest manual ... 

the GMU cannot be installed on an inspection panel 

the GMU has to be +-3 degrees of the roll axis ... 

i believe the Mooney has a “nice” dihedral angle ... so if you put it on the skin , you may have to put a few a few washers to level it up . Probably not a big deal anyways. 

when it ain’t broken , don’t fix it 

[N201MKTurbo]

5 hours ago, OR75 said:

Page 66/67 of the latest manual ... 

the GMU cannot be installed on an inspection panel 

the GMU has to be +-3 degrees of the roll axis ... 

i believe the Mooney has a “nice” dihedral angle ... so if you put it on the skin , you may have to put a few a few washers to level it up . Probably not a big deal anyways. 

when it ain’t broken , don’t fix it 

I didn’t install it anywhere near an inspection panel. The reason they don’t want it in an inspection panel is because the screws and nut plates are steel.

[OR75]

2 hours ago, N201MKTurbo said:

I didn’t install it anywhere near an inspection panel. The reason they don’t want it in an inspection panel is because the screws and nut plates are steel.

understood.  but if on the skin, you would need a few washers on the fuselage  side of the GMU to level it 

[Yetti]

Drilling wing ribs seems like something to avoid unless a DER is involved.    So I used long brass screws and nuts and washers and mounted to an inspection port.   When I said nuts I used nuts along with brass washers as spacers.  The Dynon magnotometer is supposed to be mostly level.   Leveling it moves it away from the inspection panel nuts and screws.  Which screws are stainless.  so it's just the nut plates.

In the Dynon there is a test page to see if you got the mount right.   It tested good.

[Yetti]

Oh nice metal work

[N201MKTurbo]

1 hour ago, OR75 said:

understood.  but if on the skin, you would need a few washers on the fuselage  side of the GMU to level it 

You are correct the dihedral exceeds the limit, maybe I'll fix that one of these days. It still works perfect. 

[McMooney]

11 hours ago, ArtVandelay said:

Mine is in the tail on a bracket. Seems like it would be better to be on centerline of the plane.

Mind taking a pic?  I want to put mine in the tail where the current brittain magnetic sensor is mounted.

[ArtVandelay]

Mind taking a pic?  I want to put mine in the tail where the current brittain magnetic sensor is mounted.

Here u go

[EricJ]

Mine's in the tail, too, but up on the left side of the airplane.

 

[JimB]

I reused the Brittain mount for mine. 

 

[Aerodon]

15 hours ago, Yetti said:

Drilling wing ribs seems like something to avoid unless a DER is involved.   

OK, so then use stainless click bonds with a composite base epoxied into place:

I agree, one should be really careful when drilling into any aircraft component.  Often the maintenance and repair manual gives guidance on repairs, and I'd drill into a wing rib before a wing spar, and never into a wing skin.  But I guess a wing skin is no different to a fuselage skin, and if you followed the same guidance for an antenna installation with doublers, that would be the basis for a wing skin mounted GMU 11.

I've had a HID light ballast installed on a Super Cub wing spar.  It had a metal plate mounted directly onto the flange of the spar.  

 

Aerodon

 

[JimB]

I dug up an old photo. Here is the original Brittain mounted sensor. 

[ArtVandelay]

I dug up an old photo. Here is the original Brittain mounted sensor. 

The problem with this and similar locations is modern servos are installed in the tail, and there needs to be a minimum clearance, which is why mine is further back. I believe you need something like 2-3 ft of distance from any motors.

[JimB]

14 minutes ago, ArtVandelay said:

The problem with this and similar locations is modern servos are installed in the tail, and there needs to be a minimum clearance, which is why mine is further back. I believe you need something like 2-3 ft of distance from any motors.

You are correct. That is why I mounted mine where I did. With it mounted that high up, I have at least 2 feet and a little more from where the servos will be mounted when I install the GFC 500. I'd be very surprised if there is an interference issue but I will be checking it again when the servos get installed. Further back actually puts it directly over top of the pitch/yaw servos. 

 M20J/K installation

 

 

[DCarlton]

On 12/7/2020 at 2:43 PM, JimB said:

I reused the Brittain mount for mine. 

 

Dumb question.  I'm not an aircraft mechanic.  Any tips on how to get your (older) body up in there to reach and effectively work on the Brittain sensor mounting location?  I've installed electronics on the tray right inside the access panel, but the last time I looked, the Brittain sensor location seemed like a reach too far.  

[ArtVandelay]

You are correct. That is why I mounted mine where I did. With it mounted that high up, I have at least 2 feet and a little more from where the servos will be mounted when I install the GFC 500. I'd be very surprised if there is an interference issue but I will be checking it again when the servos get installed. Further back actually puts it directly over top of the pitch/yaw servos. 
 M20J/K installation

 
 

I dont think that drawing is to scale, you can see the magnetometer shelf high and aft of the shelf the pitch servo is on, yaw servo would also be there if installed.