REFLECTOR: SkyView folks ... More ADAHRS placement problems

[Alex Balic]

Many hydraulic and pneumatic cylinders have magnetic inserts on the pistons
that allow the use of proximity switches for location confirmation- possibly
the main gear cylinder has this even though it is not used- not sure, but
that is a pretty strong field to interact that strongly from that distance.
Maybe it is from the gear linkage itself?  I have my AHRS mounted about 20
inches away from the cylinder on  a small shelf in the foreword gear
bulkhead- so far, so good, but I might need to see if retracting the gear
changes anything..

 

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From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Darrell & Nora Kufalk
Sent: Sunday, August 14, 2011 10:47 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: SkyView folks ... More ADAHRS placement problems

 

I have been flying with my new SkyView for 7 weeks now.  My biggest concern
with the SkyView system was the fact that the magnetometer was inside the
ADAHRS and its placement could be a problem in a Velocity.  I found out
today my concern was justified.  After a few flights, I noticed the magnetic
heading was a little off compared to the GPS ground track when heading in
certain directions.  I double checked it on the ground and all seemed fine.
Then I made a test flight in a big square box.  Heading north I recorded the
difference between magnetic heading and GPS ground track and did the same
thing for east, south and west.  I was shocked it was off by 30 degrees
going north and south.  I landed and checked it on the ground and it all
seemed correct again.  It worked on the ground but not in flight !?!?

 

I had a hunch what the problem was, so today I put it up on jacks and ran
the gear up and down.  Sure enough, the main gear cylinder causes the
heading to move 31 degrees while facing south.  I have my ADAHRS mounted
under the rear seat.  I measured the distance to the main gear cylinder and
it is only about 9 inches away.  That thing must have a huge amount of
residual magnetism left in it.  Needless to say I'm looking for a new
location for that thing.

 

Word of caution to other builders.  Under the rear seat does NOT work in RG
models.

 

Darrell

 

 

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Peter Braswell
Sent: Friday, August 12, 2011 2:13 PM
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: SkyView folks ...

 

I just did a blog entry on the importance of proper calibration of you
SkyView system.  I know there was some discussion regarding where to put the
ADAHRS unit, this explains one of the reasons why it's important ...

 

http://blog.sky-gadgets.com/2011/08/dynon-skyview-why-its-important-to-get-y
our-compass-calibrated/

 

Peter


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