Matronics Email Lists :: View topic - Magnetometer Location in RV-7

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Magnetometer Location in RV-7

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

tompkinsl(at)integra.net
Guest

Posted: Mon Apr 30, 2007 10:01 am Post subject: Magnetometer Location in RV-7

It appears that one item I wasn't smart enough to  consider when I selected the position/landing/strobe light system for the RV-7 I  am building was magnetometer location for an EFIS.

  

 Looking through the installation manuals for Brand  AFS and brand GRT, one recommends 24" clearance and the other 12" clearance to  strobe wires.

  

 I installed a CreativAir single power pack strobe  sytem in the wings, which means that I have power supply wires and strobe wires  running through the wings.  

  

 Even using the rib hole locations specified by  Van's, the maximum spacing between wire runs is only 6".  Does this mean I  will have to replace the CreativAir sytem with individual power supplies?   Or is there an alternative?  I am assuming that I need only concern myself  with the magnetometer itself and not the leads to the magnetometer, but I don't  want to get into trouble with that assumption either.

  

 Thanks,

  

 Larry Tompkins

   [quote][b]

dave(at)abrahamson.net
Guest

Posted: Tue May 01, 2007 2:36 am Post subject: Magnetometer Location in RV-7

Larry,

 From your description, it seems to me you can keep the magnetometer 

(GRT) and its wiring away from the strobe wiring -- all the way to 

behind the panel if you choose to.  If you'd like to email me 

off-line (dave(at)abrahamson.net), I can send you pictures of where I 

mounted the magnetometer and describe to you how I routed my 

wires.  I can suggest to you a routing of your wires if you determine 

that the strobe power wires and magnetometer bundle must be kept 

apart from beginning to end.

David, N98DA, RV-7, flying.

nuckollsr(at)cox.net
Guest

Posted: Tue May 01, 2007 5:48 am Post subject: Magnetometer Location in RV-7

At 06:34 AM 5/1/2007 -0400, you wrote:



 	  Quote: 	
		  

<dave(at)abrahamson.net>



Larry,

 From your description, it seems to me you can keep the magnetometer (GRT) 

 and its wiring away from the strobe wiring -- all the way to behind the 

 panel if you choose to.  If you'd like to email me off-line 

 (dave(at)abrahamson.net), I can send you pictures of where I mounted the 

 magnetometer and describe to you how I routed my wires.  I can suggest to 

 you a routing of your wires if you determine that the strobe power wires 

 and magnetometer bundle must be kept apart from beginning to end.

David, N98DA, RV-7, flying.


	


   There is no good reason in physics for keeping magnetometer

   and strobe wiring separate if the magnetometer is wired with

   multiple wires twisted together (and probably under a shield

   to boot). This what one does to make said wired impervious to

   local magnetic effects. If the strobe POWER wire passes within

   2 feet of the magnetometer itself, then consider taking strobe

   power and ground past the magnetometer as a twisted pair.



   DO-160 has a protocol for investigating and quantifying

   magnetic effects . . . we look at these issues all the time.

   Wire bundles installed with any understanding and foresight

   at all are never a problem. Black boxes themselves are almost

   never a problem.



   It's easy to test. When everything is all installed, position

   your aircraft on 8 headings at 45 degree intervals around the

   compass and turn suspect antagonists on and off while observing

   displayed heading. Anything under 2 degrees of shift is generally

   considered acceptable and it's very seldom that we see ANY observable

   shifts.



   If we tried to pay homage to every ol' mechanic's tale about

   the need for separation of wire bundles for any reason, we'd

   never be able to build an airplane with electro-whizzies in it.

   Wire bundles have to go where there is room and systems that

   use wires in those bundles are expected to be designed with

   and installed with common sense about magnetically coupled

   noises.



   Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

trigo(at)mail.telepac.pt
Guest

Posted: Tue May 01, 2007 7:18 am Post subject: Magnetometer Location in RV-7

Larry

  

 In my RV-9A, I also have  my (Whelen) strobe units in the wing tips, therefore I decided to  install the magnetometer right aft the baggage compartment, below the upper  fuselage skin, and it's not my original idea, since I'm aware of some other  builders having done it.

 I cannot report any results, because I am still not  flying.

  

 Carlos Trigo

  

 [quote]   ---

nuckollsr(at)cox.net
Guest

Posted: Tue May 01, 2007 3:09 pm Post subject: Magnetometer Location in RV-7

At 04:14 PM 5/1/2007 +0100, you wrote:



 	  Quote: 	
		  Larry



In my RV-9A, I also have my (Whelen) strobe units in the wing tips, 

therefore I decided to install the magnetometer right aft the baggage 

compartment, below the upper fuselage skin, and it's not my original idea, 

since I'm aware of some other builders having done it.

I cannot report any results, because I am still not flying.


	


   I hope you'll conduct an "observable effects" test

   at your earliest convenience and report back to us!



   Thanks.



   Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

dave(at)abrahamson.net
Guest

Posted: Wed May 02, 2007 3:10 am Post subject: Magnetometer Location in RV-7

I am lucky to be flying my RV7 in phase I and have performed the GRT 

magnetometer calibration, as well as the in-flight Trutrak Digiflight 

II VSGV magnetometer alignment.  The latter uses GPS data to do its 

automatic calibration dance, as the anxious pilot looks for traffic, 

while the GRT calibration is done on the ground with the aid of a 

magnetic compass.  I am happy to report that the two magnetometers 

are in full agreement.

I mounted my GRT magnetometer in the same location as Carlos, and ran 

the wire down the middle of the plane, through the spar bulkhead 

where it joins a large bundle that includes the Whelen power supply 

and ground wires, on the way to the space behind the panel.  The 

magnetometer wire bundle consists of several loose 22AWG wires, 

neither twisted, nor shielded, whose routing GRT says is unimportant 

as long as the magnetometer standoff is as directed.  I mounted the 

unit on an aluminum shelf, and secured it with two brass screws.

David

nuckollsr(at)cox.net
Guest

Posted: Wed May 02, 2007 5:23 am Post subject: Magnetometer Location in RV-7

At 07:08 AM 5/2/2007 -0400, you wrote:



 	  Quote: 	
		  

<dave(at)abrahamson.net>



I am lucky to be flying my RV7 in phase I and have performed the GRT 

magnetometer calibration, as well as the in-flight Trutrak Digiflight II 

VSGV magnetometer alignment.  The latter uses GPS data to do its automatic 

calibration dance, as the anxious pilot looks for traffic, while the GRT 

calibration is done on the ground with the aid of a magnetic compass.  I 

am happy to report that the two magnetometers are in full agreement.

I mounted my GRT magnetometer in the same location as Carlos, and ran the 

wire down the middle of the plane, through the spar bulkhead where it 

joins a large bundle that includes the Whelen power supply and ground 

wires, on the way to the space behind the panel.  The magnetometer wire 

bundle consists of several loose 22AWG wires, neither twisted, nor 

shielded, whose routing GRT says is unimportant as long as the 

magnetometer standoff is as directed.  I mounted the unit on an aluminum 

shelf, and secured it with two brass screws.

David


	


   Good data sir. Thank you.



   Bob . . .

tompkinsl(at)integra.net
Guest

Posted: Wed May 02, 2007 10:35 am Post subject: Magnetometer Location in RV-7

Bob,

  

 Thank you for your reply. I have determined  that a tail installation (as suggested by another lister) is less  pratical because of accessability than a wing location.   I WILL  have to take the strobe power cable within two feet of the magnetometer.   The cable that was supplied for the high voltage power from the power pack to  the flasher is a 3 conductor shielded cable. The wires are supply ground and  trigger.

  

 The following information was ink-stamped on the  cable jacket:

  

 Manhattan/CDT P/N  M13227   E120910   3/C 22 AWG

 60C (UL) Typer CM    OR AWM  2093  LL 41103 CSA TYPE CMG

  

 It doesn't seem to me that a 3 conductor  cable can be a "twisted pair."  Is there something else I should be  using?  Is it possible to shield the strobe cable locally where it is  whithin 24" of the magnetometer?

  

 Thank you,

  

 Larry

   [quote][b]

nuckollsr(at)cox.net
Guest

Posted: Wed May 02, 2007 11:27 am Post subject: Magnetometer Location in RV-7

At 11:34 AM 5/2/2007 -0700, you wrote:



 	  Quote: 	
		  Bob,



Thank you for your reply. I have determined that a tail installation (as 

suggested by another lister) is less pratical because of accessability 

than a wing location.   I WILL have to take the strobe power cable within 

two feet of the magnetometer.  The cable that was supplied for the high 

voltage power from the power pack to the flasher is a 3 conductor shielded 

cable. The wires are supply ground and trigger.



The following information was ink-stamped on the cable jacket:



Manhattan/CDT P/N  M13227  E120910   3/C 22 AWG

60C (UL) Typer CM    OR AWM 2093  LL 41103 CSA TYPE CMG




	


    This is no doubt the grey, twisted trio with

    an aluminum foil shield and drain wire. This

    is the stuff shipped with strobe kits for about

    40 years.



 	  Quote: 	
		  It doesn't seem to me that a 3 conductor cable can be a "twisted 

pair."  Is there something else I should be using?  Is it possible to 

shield the strobe cable locally where it is whithin 24" of the magnetometer?


	


    "Twisted pair" is like calling all copy machines

    "Xerox". Twisting is a generic process that applies

    to ANY number of wires that are either potential victims

    for MAGNETICALLY coupled noise pickup or potential

    antagonists for noise radiation to other wires.

    Adding the "Beldfoil" shield over this grouping of

    wires breaks a tiny CAPACITIVELY coupled noise

    component from the trigger wire. You can run this

    cable right past the magnetometer with zero risk

    of interfering with the magnetometer.



    The MAGIC that happens when using this cable demands

    that no grounds be attached to airframe at the

    wing tip. Make connections only to the three wires

    at the strobe lamp fixture. Leave the shield ground

    open at the lamp.  Connect the three wires to the

    appropriate three pins at the power supply and connect

    the shield ground to the strobe supply case mounting

    screw.



    Bob . . .

        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

tompkinsl(at)integra.net
Guest

Posted: Thu May 03, 2007 8:32 am Post subject: Magnetometer Location in RV-7

Bob,

  

 Thank you for continuing to educate me once again  .  Based on your comments as well as David Abrahamson's installation and  positive experience with that location, I am satisfied that David's fuselage  location is an excellent one.

  

 In case you haven't been following this thread,  David fabricated a horizontal shelf high in his RV-7's empennage and just behind  the baggage compartment rear bulkhead.  His GRT magnetometer is attached to  that shelf.  While that location does not quite meet the GRT recommendation  of 18" away from the baggage compartment, he has positive test data to support  the use of that location.  Anything heavy or ferrous is probably going to  be close to the baggage compartment floor, which IS more than 18" from that  location.

  

 David also e-mailed me photos of the installation  that are very helpful.  He has a nice website documenting his RV-7's  construction as well.

  

 Larry Tompkins

   [quote][b]

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum