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Tim(at)MyRV10.com
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 Posted: Sat Jul 29, 2006 5:47 pm Post subject: Crossbow / Pinpoint News |
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OSH brought me a time to get more forward-looking news on the
AHRS problems of late 2005 and 2006, and I thought I'd pass on
a couple of quick things.
First, today I got some very disappointing news from a fellow
Chelton flyer. He left OSH and called me after his first leg.
He's flying a Crossbow 425EX that had previously been sent in
and "fixed" and returned to service. Previously I had heard that
there were 3 issues with the 425EX AHRS, two of which would
affect RV-10's and 1 of which would more affect composite planes.
They thought they had found the fixes and fixed those two issues,
but today's story indicates differently. The pilot reported
that the compass heading (at the top of the screen) rotated slowly
around 360 degrees every couple of minutes, even though the
plane was in straight and level flight. In talking with people
further, I learned that this is one of the known failure modes
of the instrument that would probably be noticed within about
a 45 minute leg. If that leg were continued for a longer
time, it would get worse, and eventually lead to a forward
rolling display, or possibly even flying backwards through the
HITS boxes. So, obviously it's not completely "fixed" and
owners are still encouraged not to fly IFR with the "fixed"
units.
News on the Pinpoint: My pinpoint testing has been going well.
I thought I hadn't noticed any issues at all, but on the
day I left for OSH I noticed a strange Airspeed readout
while at a standstill. I brought this up and found out the
good news that had already been caught, and taken care of for
the production units (I'm flying an engineering unit right now
as part of a test team) and that with the positive results of
the testing that the production units are now starting to come
out for distribution. I was going to jump on a production unit
but have decided to get my unit replaced with a unit that
not only has the production items in it, but some additional
enhancements as well that will need to now undergo some
additional testing. To date, in flight I have never noticed
any issues with the pinpoint, so other than some testing
when I get a new unit, I'm going to start flying in IMC as
required from here on out. Once everyone's back from OSH,
I should be receiving the new unit and I'll pass on info as
to how it works. I've heard that the first lot of production
units should help fill a lot of need by the flying and almost
flying builders.
--
Tim Olson - RV-10 N104CD - Flying
do not archive
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msmith(at)xbow.com
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| Posted: Sun Jul 30, 2006 11:20 am Post subject: Crossbow / Pinpoint News |
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Crossbow contacted the fellow flyer referred to in Tim Olson's email
after the reported problem on the same night. After speaking with the
pilot, we discovered that when the baggage compartment was emptied of
luggage and tools, the NAV425 performed correctly. The fellow flyer
also verified that the NAV425 is mounted close to the baggage
compartment. The cause of the heading error in this case can be
attributed to ferrous material in the baggage area located too close the
NAV425.
As noted in our user manual, Crossbow recommends a 24 inch minimum
distance between the NAV425 internal magnetometer and sources of
changing magnetic fields. Changing magnetic fields can come from moving
ferrous metal parts, changing DC electric currents, and ferrous metal
parts that have been moved, removed, or added to the aircraft since the
last magnetic alignment procedure. This general rule applies to all
types of magnetic heading sensors and all of them will incorrectly
indicate heading if an uncompensated magnetic disturbance is too close
to the magnetometer.
The 24 inch separation requirement is not unique to the NAV425 but
applies to our remote magnetometer products as well. The NAV425 uses a
high quality internal magnetometer to meet the original low cost goals
of the NAV425 program.
Crossbow is committed to building and servicing the best AHRS products
in General Aviation. The upgrade program is running and is fully
covered by Crossbow's warranty. Crossbow has updated over 40 units and
received positive feedback from its upgrade customers. Crossbow has
been supplying inertial systems for the aviation community for over 10
years. Our AHRS products are built and serviced in the U.S.A. at our
FAA certified facility in San Jose, CA. We are 100% committed to our
products and the satisfaction of our customers.
If you are having any problem with any version of the NAV425, Crossbow
wants to hear about it and have the opportunity to correct the problem
to your satisfaction. Please contact our Customer Service department at
408-965-3300 for assistance.
Mike Smith
Customer Service
Crossbow Technology, Inc.
Email: msmith(at)xbow.com
Phone: 408-965-3388
--
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Tim(at)MyRV10.com
Guest
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| Posted: Sun Jul 30, 2006 2:32 pm Post subject: Crossbow / Pinpoint News |
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I wondered why the crossbow would fail in a continuous rotational
manner, since it would seem that ferrous materials would cause
it to shift in heading, but not rotate....and this has been
seen before in improper installations. But because it did not
make sense to me, I inquired and passed on the thread. Here is the
response I got (see below). Unfortunately, one of the things
that would have been cool to see is an in-flight powercycle, but
that didn't happen. In my past failures of the Crossbow, a
powercycle brought it back to life.
<response>
----
Fellow pilot stated:
"When I departed OSH on runway 18, straight out departure, climb to
1300', the magnetic heading began a slow CCW turn and never stabilized.
It continued through 360 degrees of revolution continuously for the next
30-40 minutes, whereupon I decided to land north of Chicago, as most of
Illinois and Indiana were IFR."
IF the problem was a hard or soft iron field distortion, the heading
would show an offset NOT a continuous slow heading change. If you put a
magnet near a compass you will see an offset. The compass needle will
not start slowly rotating. If the magnet is very strong it will cause
the needle to "freeze" at a single heading, again no rotation. The
simple answer is that the 425 had some sort of magnetometer failure that
was undetected by the AHRS processor.
The pilot has since tried to duplicate the problem by repacking the
baggage compartment with the same items. No Joy. This test indicates
that the power cycle fixed the problem, not removing the baggage. The
425 in question had just been reinstalled after receiving the latest
upgrades at the factory. So much for having killed all the bugs.
While it is good practice to keep ferrous objects away from your compass
system, placing a ferris object near the 425 should never cause it to
report the heading is spinning. If X-bow has a reasonable explanation as
to the cause of the random heading generator, we would like to hear it.
If they don't have an explanation, then they better figure one out.
Kirk Hammersmith
----
Tim Olson
do not archive
Mike Smith wrote:
[quote]
Crossbow contacted the fellow flyer referred to in Tim Olson's email
after the reported problem on the same night. After speaking with the
pilot, we discovered that when the baggage compartment was emptied of
luggage and tools, the NAV425 performed correctly. The fellow flyer
also verified that the NAV425 is mounted close to the baggage
compartment. The cause of the heading error in this case can be
attributed to ferrous material in the baggage area located too close the
NAV425.
As noted in our user manual, Crossbow recommends a 24 inch minimum
distance between the NAV425 internal magnetometer and sources of
changing magnetic fields. Changing magnetic fields can come from moving
ferrous metal parts, changing DC electric currents, and ferrous metal
parts that have been moved, removed, or added to the aircraft since the
last magnetic alignment procedure. This general rule applies to all
types of magnetic heading sensors and all of them will incorrectly
indicate heading if an uncompensated magnetic disturbance is too close
to the magnetometer.
The 24 inch separation requirement is not unique to the NAV425 but
applies to our remote magnetometer products as well. The NAV425 uses a
high quality internal magnetometer to meet the original low cost goals
of the NAV425 program.
Crossbow is committed to building and servicing the best AHRS products
in General Aviation. The upgrade program is running and is fully
covered by Crossbow's warranty. Crossbow has updated over 40 units and
received positive feedback from its upgrade customers. Crossbow has
been supplying inertial systems for the aviation community for over 10
years. Our AHRS products are built and serviced in the U.S.A. at our
FAA certified facility in San Jose, CA. We are 100% committed to our
products and the satisfaction of our customers.
If you are having any problem with any version of the NAV425, Crossbow
wants to hear about it and have the opportunity to correct the problem
to your satisfaction. Please contact our Customer Service department at
408-965-3300 for assistance.
Mike Smith
Customer Service
Crossbow Technology, Inc.
Email: msmith(at)xbow.com
Phone: 408-965-3388
--
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http://www.matronics.com/Navigator?RV10-List |
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Tim(at)MyRV10.com
Guest
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| Posted: Sun Jul 30, 2006 2:33 pm Post subject: Crossbow / Pinpoint News |
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Ooops, one more quick reply from the pilot himself (not me, just
passing it along as he does not follow this list, AFAIK)
---
For the record I also took all metal pieces that were in the baggage
compartment and placed them MUCH closer to the AHRS by holding them
right above its location on the outside of the aircraft above the
fiberglass top. I also tried to induce a failure with a strong magnet.
No joy. I'm convinced now that this was some kind of initialization
failure. In trying to understand every aspect of what might have been
different than any other startup, I did notice that the airplane was
probably 10 degrees off of level when I started the engine at OSH, due
to the grassy area right outside the flight line parking. Every other
time I have started in a level attitude. And yes, at OSH, I did wait
until both displays came up with the attitude display before moving the
aircraft.
---
Tim Olson - RV-10 N104CD - Flying
do not archive
Mike Smith wrote:
[quote]
Crossbow contacted the fellow flyer referred to in Tim Olson's email
after the reported problem on the same night. After speaking with the
pilot, we discovered that when the baggage compartment was emptied of
luggage and tools, the NAV425 performed correctly. The fellow flyer
also verified that the NAV425 is mounted close to the baggage
compartment. The cause of the heading error in this case can be
attributed to ferrous material in the baggage area located too close the
NAV425.
As noted in our user manual, Crossbow recommends a 24 inch minimum
distance between the NAV425 internal magnetometer and sources of
changing magnetic fields. Changing magnetic fields can come from moving
ferrous metal parts, changing DC electric currents, and ferrous metal
parts that have been moved, removed, or added to the aircraft since the
last magnetic alignment procedure. This general rule applies to all
types of magnetic heading sensors and all of them will incorrectly
indicate heading if an uncompensated magnetic disturbance is too close
to the magnetometer.
The 24 inch separation requirement is not unique to the NAV425 but
applies to our remote magnetometer products as well. The NAV425 uses a
high quality internal magnetometer to meet the original low cost goals
of the NAV425 program.
Crossbow is committed to building and servicing the best AHRS products
in General Aviation. The upgrade program is running and is fully
covered by Crossbow's warranty. Crossbow has updated over 40 units and
received positive feedback from its upgrade customers. Crossbow has
been supplying inertial systems for the aviation community for over 10
years. Our AHRS products are built and serviced in the U.S.A. at our
FAA certified facility in San Jose, CA. We are 100% committed to our
products and the satisfaction of our customers.
If you are having any problem with any version of the NAV425, Crossbow
wants to hear about it and have the opportunity to correct the problem
to your satisfaction. Please contact our Customer Service department at
408-965-3300 for assistance.
Mike Smith
Customer Service
Crossbow Technology, Inc.
Email: msmith(at)xbow.com
Phone: 408-965-3388
--
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
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msmith(at)xbow.com
Guest
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| Posted: Tue Aug 01, 2006 8:11 am Post subject: Crossbow / Pinpoint News |
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After my conversation with the pilot on Sunday, we were informed that
the unit had been powercycled during flight with the same behavior. It
was also our understanding that upon landing the baggage was removed and
the unit was powercycled a third time. Upon powercycling the third time
with the baggage area emptied the unit maintained the proper heading.
Magnetic field disturbances or large ferrous materials can lead to a
shift in heading or continuous heading errors if the disturbance is
severe enough. Earth's magnetic field is relatively weak, and a very
large disturbance (from a magnet for example) could easily skew the
magnetometer readings. In extreme cases this can also appear in roll
and pitch values as well. It is also important to note placing a magnet
near the NAV425 is not recommended and can result in severe damage to
the unit as we have noted in the user manual.
Crossbow has contacted the customer again to ensure that he is getting
the maximum performance out of his unit. We have a large number of
these upgraded units in the field and have not had any problems with the
upgrades that were made in the last three months. Crossbow will also
offer the customer the option of returning the unit to Crossbow for
examination at no charge if he so desires.
If any of our customers are having problems with the NAV425, please
contact us directly. We would be more than happy to help you
troubleshoot any problems that you may be having.
Sincerely,
Michael Smith
Application Engineer Inertial Systems
Crossbow Technology
Email: msmith(at)xbow.com
Phone: 408-965-3388
--
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
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