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GRT AHRS Mounting and CG

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toaster73(at)embarqmail.c
Guest

Posted: Sat Aug 01, 2009 7:17 am Post subject: GRT AHRS Mounting and CG

Anyone have a feeling about how far it is acceptable to mount the AHRS from the CG? When does the “lever affect” really kick-in?  

I would like to put it on a shelf like others have done  - one bay behind the battery bay, with the magnetometers there too. What do those in the know think?  

Thank You  

Chris Lucas  

#40072  

       [quote][b]

rngurley

Joined: 21 Jan 2008
Posts: 18
Location: Indianapolis, IN

Posted: Sat Aug 01, 2009 1:17 pm Post subject: GRT AHRS Mounting and CG

I talked with the GRT folks about this at Oshkosh this week.  They recommend putting the AHRS back by the battery (Vans makes a shelf) and the magnetometers out on the wingtips.  They indicated that having both on the same shelf might cause too much electrical noise for the magnetometers.  

   

Dick Gurley  

   

--

bcondrey

Joined: 03 Apr 2006
Posts: 580

Posted: Sat Aug 01, 2009 2:13 pm Post subject: GRT AHRS Mounting and CG

Won't be a problem.

Bob 

  From: owner-rv10-list-server(at)matronics.com <owner-rv10-list-server(at)matronics.com> 

To: rv10-list(at)matronics.com <rv10-list(at)matronics.com> 

Sent: Sat Aug 01 07:52:50 2009

Subject: RV10-List: GRT AHRS Mounting and CG 

Anyone have a feeling about how far it is acceptable to mount the AHRS from the CG? When does the “lever affect” really kick-in?  

I would like to put it on a shelf like others have done  - one bay behind the battery bay, with the magnetometers there too. What do those in the know think?  

Thank You  

Chris Lucas  

#40072  

       [quote][b]

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Sat Aug 01, 2009 2:25 pm Post subject: Re: GRT AHRS Mounting and CG

 	  rngurley wrote: 	
		  I talked with the GRT folks about this at Oshkosh this week.  They recommend putting the AHRS back by the battery (Vans makes a shelf) and the magnetometers out on the wingtips.  They indicated that having both on the same shelf might cause too much electrical noise for the magnetometers.  

   

Dick Gurley  

   

-- 	




Darn! When I asked them the same question at Sun 'n fun they didn't blink an eye when I said I would mount both on a tray behind the battery bay. If you look at their installation documentation for both, they have to be within 0.5 degrees of each other in all orientations. Talk about CYA. I'm calling on Monday!

John

_________________
#40572 Phase One complete in 2011

bcondrey

Joined: 03 Apr 2006
Posts: 580

Posted: Sat Aug 01, 2009 3:20 pm Post subject: GRT AHRS Mounting and CG

I mounted the magnetometers up high in the bay with the batteries and have no issue - been flying over a year. YMMV.



Bob



---

toaster73(at)embarqmail.c
Guest

Posted: Sat Aug 01, 2009 6:09 pm Post subject: GRT AHRS Mounting and CG

Dick,  

SO your saying they told you the AHRS itself could interfere with the magnetometer performance?  That seems odd.  I wouldn’t think much is going on electrically in the AHRS plus it had that thick Al housing.   Let us know what they say John Goodman if you get a call in to GRT on Monday. I’ll call Tuesday to see if we get a third answer!!  

I think I am going to press forward based on the input from folks already in operation (I kinda just finished the mounting this evening anyway).    

When it comes time, I’ll give it all a thorough check out and move things later if I have to. It is very convenient to have it all on the shelf instead of having to run more wires out the wing etc.  

Thanks for the inputs.  

-Chris  

#40072  

       

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Richard Gurley

 Sent: Saturday, August 01, 2009 4:55 PM

 To: rv10-list(at)matronics.com

 Subject: RE: GRT AHRS Mounting and CG  

  

  

   

I talked with the GRT folks about this at Oshkosh this week.  They recommend putting the AHRS back by the battery (Vans makes a shelf) and the magnetometers out on the wingtips.  They indicated that having both on the same shelf might cause too much electrical noise for the magnetometers.  

   

Dick Gurley  

   

--

Ron.McGann(at)thalesgroup
Guest

Posted: Sun Aug 02, 2009 2:40 pm Post subject: GRT AHRS Mounting and CG

I would support this.



My AHRS and magnetometer are located in the 'standard' position on a

tray above and aft of the battery.  I thought it was magnetically

benign, but about 10 mins into every flight my displays suffer the

'leans' by about 5degs.  Still trying to get to the bottom of the issue.

GRT seem to be fairly sure that there is some magnetic interference

there.  I will be moving the magnetometer to the wingtip shortly.



I reckon magnetometer installation is a chook raffle (crapshoot to you

guys up north).  AHRS on the tray and magnetomoeters in the wingtip

should be standard IMHO.



Cheers,

Ron

VH-XRM

Flying in oz 

--

bcondrey

Joined: 03 Apr 2006
Posts: 580

Posted: Mon Aug 03, 2009 8:24 am Post subject: Re: GRT AHRS Mounting and CG

The AHRS can be mounted on the standard tray next to the battery however the magnetometer must be at least 24" (IIRC) from the contactors and AP servo both of which are strong sources of magnetic energy.  I found that a shelf about 3" below the top of the tailcone, attached to the J channel stringers works great.  I did look into mounting a shelf across the longerons but my testing with a simple compass in that location showed large variations as things were switched on/off and the AP servo exercised.  Just a few inches higher made a huge difference.



Wingtips would also be an excellent location.



Bob

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Mon Aug 03, 2009 10:05 am Post subject: Re: GRT AHRS Mounting and CG

 	  Quote: 	
		  SO your saying they told you the AHRS itself could interfere with the magnetometer performance? That seems odd. I wouldnâ€™t think much is going on electrically in the AHRS plus it had that thick Al housing. Let us know what they say John Goodman if you get a call in to GRT on Monday. Iâ€™ll call Tuesday to see if we get a third answer!! 	




I called, but only a few are back from Oshkosh. Left a message for a call back.

John

_________________
#40572 Phase One complete in 2011

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Mon Aug 03, 2009 10:30 am Post subject: Re: GRT AHRS Mounting and CG

OK,

I got a call back from Jeff at GRT. It is true that the AHRS interferes with the magnometer. The stock answer is that the magnometer can be no closer than 18" to a magnetic source. He's not sure what the exact distance for the AHRS is, but it contains stuff that will interfere. They recommend a wing tip as first choice, otherwise a separate mount in the tail far away from everything. Back to the drawing board....

John

_________________
#40572 Phase One complete in 2011

MauleDriver(at)nc.rr.com
Guest

Posted: Mon Aug 03, 2009 11:08 am Post subject: GRT AHRS Mounting and CG

I'm exactly 18" from closest edge of AHRS to closest edge of 

Magnetometer.  I tried to maximize the distance from the pitch AP servo 

and the Strobe flash unit.



I recall some previous posts on be careful with the AHRS around the 

pitch trim unit in the rear of the tail cone.  It's further forward than 

you think and I recall it being  difficult to setup the 18" clearance.



Let's hear some more flying experiences with the GRTs.



Bill "Firewall Forward" Watson

johngoodman wrote:

 	  Quote: 	
		   



 OK,

 I got a call back from Jeff at GRT. It is true that the AHRS interferes with the magnometer. The stock answer is that the magnometer can be no closer than 18" to a magnetic source. He's not sure what the exact distance for the AHRS is, but it contains stuff that will interfere. They recommend a wing tip as first choice, otherwise a separate mount in the tail far away from everything. Back to the drawing board....

 John



 --------

 #40572 QB Fuselage, wings finished. Finish Kit progressing. Engine &amp; Panel delivery soon.

 N711JG reserved





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 55821#255821

toaster73(at)embarqmail.c
Guest

Posted: Mon Aug 03, 2009 6:38 pm Post subject: GRT AHRS Mounting and CG

Ok, I'll rethink too then.

Thanks

Chris

#40072



--

billderou(at)yahoo.com
Guest

Posted: Tue Aug 04, 2009 9:42 am Post subject: GRT AHRS Mounting and CG

Guys-

 I have not been following this thread so my comments may have already been covered.

  

 The best place to locate a magnometer (and/or the AHRS if they do not interfer with one another)  is on a shelf that spans the fuselage laterally between the three longeron bolts that secure the aft seat belt attachment. This location has four good advantages:

  

 I have measured the magnetic interference and this location is the farthest distance from the autopilot elevator servo and the elevator trim servo. Do not underestimate the interference from the little trim servo - it is more of a problem than the autopilot.

  

 A shelf in this orientation is automatically aligned with the pitch and roll axis.

  

 If the sensor contains accelerometers or rate gyros it will function more accurately along the centerline of the fuselage than a wing tip.

  

 This location is far from the baggage compartment and the unpredictable magnetic forces contained in the unpredictable baggage.

  

 Also - you will never get a sensor accurately aligned in a wing tip. I just had a good example of how the wing will move about between ground and air.

  

 Bill DeRouchey

 N939SB

  

  

  

 



--- On Mon, 8/3/09, Chris <toaster73(at)embarqmail.com> wrote:



 [quote]

From: Chris <toaster73(at)embarqmail.com>

Subject: RE: Re: GRT AHRS Mounting and CG

To: rv10-list(at)matronics.com

Date: Monday, August 3, 2009, 7:36 PM



 --> RV10-List message posted by: "Chris" <toaster73(at)embarqmail.com (toaster73(at)embarqmail.com)>



Ok, I'll rethink too then.

Thanks

Chris

#40072



--

toaster73(at)embarqmail.c
Guest

Posted: Tue Aug 04, 2009 6:43 pm Post subject: GRT AHRS Mounting and CG

Good points Bill. I decided to make the shelf for the magnetometers just ahead of the seat belt attach. I am putting another shelf forward of that slightly aft of the battery to hold the AHRS. Both units will be completely aligned though separated based on GRT’s inputs that the AHRS can cause some disturbance in the magnetometer.  

-Chris Lucas  

#40072  

     

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Bill DeRouchey

 Sent: Tuesday, August 04, 2009 1:40 PM

 To: rv10-list(at)matronics.com

 Subject: RE: Re: GRT AHRS Mounting and CG  

  

              

Guys-   

      

I have not been following this thread so my comments may   have already been covered.   

      

    

      

The best place to locate a magnometer   (and/or the AHRS if they do not interfer with one another)  is on a   shelf that spans the fuselage laterally between the three longeron bolts   that secure the aft seat belt attachment. This location has four good   advantages:   

      

    

      

I have measured the magnetic interference and this   location is the farthest distance from the autopilot elevator servo and the   elevator trim servo. Do not underestimate the interference from the little   trim servo - it is more of a problem than the autopilot.   

      

    

      

A shelf in this orientation is automatically aligned with   the pitch and roll axis.   

      

    

      

If the sensor contains accelerometers or rate gyros it   will function more accurately along the centerline of the fuselage than a   wing tip.   

      

    

      

This location is far from the baggage compartment and the   unpredictable magnetic forces contained in the unpredictable baggage.   

      

    

      

Also - you will never get a sensor accurately aligned in a   wing tip. I just had a good example of how the wing will move   about between ground and air.   

      

    

      

Bill DeRouchey   

      

N939SB   

      

    

      

    

      

    

      



   

   --- On Mon, 8/3/09, Chris <toaster73(at)embarqmail.com>   wrote:   

   [quote]   



   From: Chris <toaster73(at)embarqmail.com>

   Subject: RE: Re: GRT AHRS Mounting and CG

   To: rv10-list(at)matronics.com

   Date: Monday, August 3, 2009, 7:36 PM      

--> RV10-List message posted by: "Chris" <toaster73(at)embarqmail.com>

   

   Ok, I'll rethink too then.

   Thanks

   Chris

   #40072

   

   --

MauleDriver(at)nc.rr.com
Guest

Posted: Wed Aug 05, 2009 4:52 am Post subject: GRT AHRS Mounting and CG

I'm sticking with my already completed installation.



I built a shelf across the longerons just aft of the bay containing the 

AP servo. The magnetometers are mounted on the left side to maximize the 

distance from the servo and the strobe power unit mounted on the right wall.



I purchased Van's AHRS shelf which mounts on the floor next to the AP 

servo. The GRT AHRS holes are pre-drilled and the shelf appears to be 

properly aligned.



This puts the Magnetometers and AHRS exactly 18" apart. The 

Magnetometers are 23" from the AP servo and 24+ from the stobe power unit.



I hope it all works well.



Chris wrote:

 	  Quote: 	
		  

 Good points Bill. I decided to make the shelf for the magnetometers 

 just ahead of the seat belt attach. I am putting another shelf forward 

 of that slightly aft of the battery to hold the AHRS. Both units will 

 be completely aligned though separated based on GRT’s inputs that the 

 AHRS can cause some disturbance in the magnetometer.



 -Chris Lucas



 #40072



 *From:* owner-rv10-list-server(at)matronics.com 

 [mailto:owner-rv10-list-server(at)matronics.com] *On Behalf Of *Bill 

 DeRouchey

 *Sent:* Tuesday, August 04, 2009 1:40 PM

 *To:* rv10-list(at)matronics.com

 *Subject:* RE: Re: GRT AHRS Mounting and CG



 Guys-



 I have not been following this thread so my comments may have already 

 been covered.



 The best place to locate a magnometer (and/or the AHRS if they do not 

 interfer with one another) is on a shelf that spans the fuselage 

 laterally between the three longeron bolts that secure the aft seat 

 belt attachment. This location has four good advantages:



 I have measured the magnetic interference and this location is the 

 farthest distance from the autopilot elevator servo and the elevator 

 trim servo. Do not underestimate the interference from the little trim 

 servo - it is more of a problem than the autopilot.



 A shelf in this orientation is automatically aligned with the pitch 

 and roll axis.



 If the sensor contains accelerometers or rate gyros it will function 

 more accurately along the centerline of the fuselage than a wing tip.



 This location is far from the baggage compartment and the 

 unpredictable magnetic forces contained in the unpredictable baggage.



 Also - you will never get a sensor accurately aligned in a wing tip. I 

 just had a good example of how the wing will move about between ground 

 and air.



 Bill DeRouchey



 N939SB

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Wed Aug 05, 2009 5:13 am Post subject: Re: GRT AHRS Mounting and CG

 	  Quote: 	
		  I'm sticking with my already completed installation. 



I built a shelf across the longerons just aft of the bay containing the 

AP servo. The magnetometers are mounted on the left side to maximize the 

distance from the servo and the strobe power unit mounted on the right wall. 



I purchased Van's AHRS shelf which mounts on the floor next to the AP 

servo. The GRT AHRS holes are pre-drilled and the shelf appears to be 

properly aligned. 



This puts the Magnetometers and AHRS exactly 18" apart. The 

Magnetometers are 23" from the AP servo and 24+ from the stobe power unit. 



I hope it all works well. 	




The Van's AHRS shelf sounds like a possibility. Van's drawing shows it on the left side, can it be mounted on the right? I've already got the A/P servo on that side.

John

_________________
#40572 Phase One complete in 2011

MauleDriver(at)nc.rr.com
Guest

Posted: Wed Aug 05, 2009 11:11 am Post subject: GRT AHRS Mounting and CG

johngoodman wrote:

 	  Quote: 	
		   

   

> I'm sticking with my already completed installation. 

>

> I built a shelf across the longerons just aft of the bay containing the 

> AP servo. The magnetometers are mounted on the left side to maximize the 

> distance from the servo and the strobe power unit mounted on the right wall. 

>

> I purchased Van's AHRS shelf which mounts on the floor next to the AP 

> servo. The GRT AHRS holes are pre-drilled and the shelf appears to be 

> properly aligned. 

>

> This puts the Magnetometers and AHRS exactly 18" apart. The 

> Magnetometers are 23" from the AP servo and 24+ from the stobe power unit. 

>

> I hope it all works well. 

>     

 The Van's AHRS shelf sounds like a possibility. Van's drawing shows it on the left side, can it be mounted on the right? I've already got the A/P servo on that side.

 John

   


	


I think it is left side only unless they made a right side.  Did you 

install something other than TruTrak? My TruTrak servo is on the right.

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