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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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 Posted: Mon Dec 26, 2011 7:43 pm Post subject: Dynon Skyview Airspeed Calibration... |
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Dear Listers,
I've been flying the new 10" Dynon Skyview in the RV-6 for a few weeks now and it seems like the airspeed is reading maybe 10mph fast. The GS always reads 10mph or more slower than the True airspeed, no matter which way I fly with respect to the current wind. Looking through the configuration options on the Skyview, I'm not seeing parameters to calibrate the airspeed. If the airspeed were *slow* compared to the GS, I could envision making adjustments to the Pitot tube to get it in better alignment with slipstream. But *fast* is a head scratcher. If there's no electronic configuration parameters to adjust, what do you do? Are there Pitot line "attenuators" like for RF in coax? 
Matt
-
Matt "Red Dawg" Dralle
RV-8 #82880 N998RV "Ruby Vixen"
http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log
http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...
RV-6 #20916 N360EM "The Flyer"
http://www.mattsrv6.com - Matt's RV-6 Revitalization Log
Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode
| | - The Matronics AeroElectric-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:
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Matt Dralle
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email(at)jaredyates.com
Guest
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| Posted: Mon Dec 26, 2011 8:43 pm Post subject: Dynon Skyview Airspeed Calibration... |
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Perhaps it is an issue with the way it is calculating tas. Do you have an ias indication? If so perhaps you could use a flight computer to verify. Have the Dynon folks had any input?
On Dec 26, 2011, at 22:39, Matt Dralle <dralle(at)matronics.com> wrote:
| Quote: |
Dear Listers,
I've been flying the new 10" Dynon Skyview in the RV-6 for a few weeks now and it seems like the airspeed is reading maybe 10mph fast. The GS always reads 10mph or more slower than the True airspeed, no matter which way I fly with respect to the current wind. Looking through the configuration options on the Skyview, I'm not seeing parameters to calibrate the airspeed. If the airspeed were *slow* compared to the GS, I could envision making adjustments to the Pitot tube to get it in better alignment with slipstream. But *fast* is a head scratcher. If there's no electronic configuration parameters to adjust, what do you do? Are there Pitot line "attenuators" like for RF in coax?
Matt
-
Matt "Red Dawg" Dralle
RV-8 #82880 N998RV "Ruby Vixen"
http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log
http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...
RV-6 #20916 N360EM "The Flyer"
http://www.mattsrv6.com - Matt's RV-6 Revitalization Log
Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode
|
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bbradburry(at)bellsouth.n
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| Posted: Mon Dec 26, 2011 9:06 pm Post subject: Dynon Skyview Airspeed Calibration... |
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The problem is with your static port. Check out this link.
http://www.kilohotel.com/rv8/rvlinks/ssec.html
Bill B
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Tue Dec 27, 2011 6:06 am Post subject: Dynon Skyview Airspeed Calibration... |
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12/27/2011
Hello Matt, You wrote:
1) "Are there Pitot line "attenuators" like for RF in coax?"
Not pitot tube line attenuators, but both attenuators and augmentors in the
form of wedges before or after the static port portion of the pitot - static
system that can be used to tweak airspeed (and altitude) indications.
2) "But *fast* is a head scratcher. If there's no electronic configuration
parameters to adjust, what do you do?"
See this posting to the aeroelectric list for a more complete explanation of
the use of wedges to adjust airspeed indications:
http://www.matronics.com/searching/getmsg_script.cgi?INDEX=88398860?KEYS=static_port?LISTNAME=AeroElectric?HITNUMBER=9?SERIAL=0431117943?SHOWBUTTONS=YES
A bit of search around in your Matronic's archive system on pitot static
systems and airspeed, particularly any posting on this arena by Kevin
Horton, will reveal a host of material for thought and action.
'OC' Baker Says: "The best investment we can make is the time and effort to
gather and understand knowledge."
========================================================
Time: 07:43:08 PM PST US
From: Matt Dralle <dralle(at)matronics.com>
Subject: Dynon Skyview Airspeed Calibration...
Dear Listers,
I've been flying the new 10" Dynon Skyview in the RV-6 for a few weeks now
and
it seems like the airspeed is reading maybe 10mph fast. The GS always reads
10mph
or more slower than the True airspeed, no matter which way I fly with
respect
to the current wind. Looking through the configuration options on the
Skyview,
I'm not seeing parameters to calibrate the airspeed. If the airspeed were
*slow* compared to the GS, I could envision making adjustments to the Pitot
tube to get it in better alignment with slipstream. But *fast* is a head
scratcher.
If there's no electronic configuration parameters to adjust, what do
you do? Are there Pitot line "attenuators" like for RF in coax?
Matt
-
Matt "Red Dawg" Dralle
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racerjerry
Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY
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| Posted: Tue Dec 27, 2011 7:12 am Post subject: Re: Dynon Skyview Airspeed Calibration... |
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If the airspeed is reading too HIGH, a quick & dirty solution is to install a controlled leak in the pitot system. Install a “T” in the pitot line and use the third port as a drilled jet to vent to cabin air. Begin with a #80 drill bit and open up. For calibration, extend the new line (plastic tubing) into the cockpit so your co-pilot can make adjustments in flight.
You may want to verify that your altimeter is reading the correct altitude. An altitude error reading would point to problems with the static port/system. If a static system problem exists, fix this first before trying to calibrate airspeed.
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Jerry King
Last edited by racerjerry on Tue Dec 27, 2011 7:39 am; edited 4 times in total |
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pwmac(at)sisna.com
Guest
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| Posted: Tue Dec 27, 2011 7:19 am Post subject: Dynon Skyview Airspeed Calibration... |
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Pitot is not an issue since it is pretty insensitive to angle of
attack. A quick check in just about any gas dynamics text will tell
you error vs angle of attack. My memory is bad, but its pretty hard
to get much of an error due to angle. Static location can be an
issue. The text book pitot static probe had many static ports and one
dynamic port.
Paul
============
At 08:39 PM 12/26/2011, you wrote:
| Quote: |
Dear Listers,
I've been flying the new 10" Dynon Skyview in the RV-6 for a few
weeks now and it seems like the airspeed is reading maybe 10mph
fast. The GS always reads 10mph or more slower than the True
airspeed, no matter which way I fly with respect to the current
wind. Looking through the configuration options on the Skyview, I'm
not seeing parameters to calibrate the airspeed. If the airspeed
were *slow* compared to the GS, I could envision making adjustments
to the Pitot tube to get it in better alignment with
slipstream. But *fast* is a head scratcher. If there's no
electronic configuration parameters to adjust, what do you do? Are
there Pitot line "attenuators" like for RF in coax?
Matt
-
Matt "Red Dawg" Dralle
RV-8 #82880 N998RV "Ruby Vixen"
http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log
http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...
RV-6 #20916 N360EM "The Flyer"
http://www.mattsrv6.com - Matt's RV-6 Revitalization Log
Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode
|
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n801bh(at)NetZero.com
Guest
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| Posted: Tue Dec 27, 2011 7:33 am Post subject: Dynon Skyview Airspeed Calibration... |
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That is a viable fix.... Another easy and adjustable way is to go to a pet supply store and buy a small needle valve they sell for aquariums and plumb it in the line. That way you can dial in the exact bleed off.
do not archive
electric-list(at)matronics.com
Subject: Re: Dynon Skyview Airspeed Calibration...
Date: Tue, 27 Dec 2011 07:12:09 -0800
--> AeroElectric-List message posted by: "racerjerry" <gki(at)suffolk.lib.ny.us>
If the airspeed is reading too HIGH, a quick & dirty solution is to install a controlled leak in the pitot system. Install a “T” in the pitot line and use the third port as a drilled jet to vent to cabin air. Begin with a #80 drill bit and open up. For calibration, extend the new line (plastic tubing) into the cockpit so your co-pilot can make adjustments in flight.
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=361733#361733
____________________________________________________________
53 Year Old Mom Looks 33
The Stunning Results of Her Wrinkle Trick Has Botox Doctors Worried
consumerproducts.com [quote][b]
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kuffel(at)cyberport.net
Guest
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| Posted: Tue Dec 27, 2011 8:34 am Post subject: Dynon Skyview Airspeed Calibration... |
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Matt,
Agree with others the symptoms indicate a static problem, specifically the
location is producing a vacuum when moving.
While introducing a "controlled leak" in the pitot side might fix the
airspeed error, probably at only one airspeed, it wouldn't fix the altitude
error also produced by static error.
Two very simple things you can do to confirm the problem and start toward a
solution.
First on takeoff set the altimeter to an exact division. Note as you speed
up and rotate if the altitude changes, even a little. Higher altitude
implies dynamic vacuum at the static port(s) which will produce the effect
you describe, lower altitude means dynamic pressure.
As a test, tape a wedge, or even a block such as a short piece or two of
tongue depressor, behind the port(s). If your error decreases you are on
the right track and set for a little cut and try with wedge size and
placement. Before starting be sure to have accurate error measurements.
Use the spreadsheet mentioned by others to get wind independent actual true
airspeeds. Or you are welcome to the spreadsheet I developed from the same
formula with 4 leg input. The 4th leg provides redundant information to
indicate the quality of the input data.
Tom Kuffel, CFI
EAA Flight Advisor
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khorton01(at)rogers.com
Guest
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| Posted: Tue Dec 27, 2011 8:51 am Post subject: Dynon Skyview Airspeed Calibration... |
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On 2011-12-27, at 11:12 , racerjerry wrote:
| Quote: |
If the airspeed is reading too HIGH, a quick & dirty solution is to install a controlled leak in the pitot system. Install a T in the pitot line and use the third port as a drilled jet to vent to cabin air. Begin with a #80 drill bit and open up. For calibration, extend the new line (plastic tubing) into the cockpit so your co-pilot can make adjustments in flight.
|
If the airspeed is reading too, it is quite likely a problem with the static system. This could be a static system leak, or a poorly designed or located static port. Errors in the static system will affect both airspeed and altitude, so it is much better to find and fix the static source problem than it is to create a pitot leak too.
If you were to fiddle with the pitot system to fix the ASI indication (or provide ASI adjustments, as some EFIS systems allow), you would still have errors in the altimeter, and these can be safety of flight issues. The TCAS systems on larger aircraft provide guidance to avoid collision with you based on whatever altitude is reported by your transponder. If you have static system errors, the TCAS system may be giving commands that increase the risk of collision.
Static system leaks on RVs often produce ASIs that read about 10 kt too high, so the first thing to do is a static system leak check. Another common problem is flush mounted static ports on RVs, but this typically leads to ASIs reading too low.
--
Kevin Horton
RV-8
Ottawa, Canada
http://www.kilohotel.com/rv8
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gerry.vandyk(at)shaw.ca
Guest
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| Posted: Tue Dec 27, 2011 9:22 am Post subject: Dynon Skyview Airspeed Calibration... |
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Matt, I've got a couple of thoughts: The pitot / static system depends on
the static port being true ambient pressure, which is actually pretty
difficult to achieve in airflow. If you've got the port(s) in a spot that
generates a slight positive pressure on the static side you will
de-calibrate the airspeed to the low side, if there's negative pressure at
the port airspeed will read high. On the C172SP I rent there's a 1/8" high
lip on the fitting right beside the static hole. As the lip is at an angle
to airflow, I presume they dial in the static system by rotating the fitting
so the angle gives the correct pressure at the port for a specific speed
range. I've read somewhere (perhaps the Bingelis books) about making
adjustments to the static port by laying strips of tape in front of or
behind the port. As an example, the area in front of the windshield on a
stock car is a high pressure area where they take the induction to the
engine, I would suggest laying down a few thicknesses of tape behind the
port to start. Then again if your port is in an area of laminar flow,
tripping the flow in front of the port may have the same effect.
I believe once you have a modification that works you can make a permanent
'fix' that would be more efficient than a bleed port in the line.
Hope this helps.
Gerry
--
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bbradburry(at)bellsouth.n
Guest
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| Posted: Tue Dec 27, 2011 1:39 pm Post subject: Dynon Skyview Airspeed Calibration... |
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If you build in a leak in the system, I doubt that you will ever pass your
biannual transponder check. Just something to consider...
Bill B
--
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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| Posted: Tue Dec 27, 2011 9:16 pm Post subject: Dynon Skyview Airspeed Calibration... |
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At 07:39 PM 12/26/2011 Monday, Matt Dralle wrote:
| Quote: | Dear Listers,
I've been flying the new 10" Dynon Skyview in the RV-6 for a few weeks now and it seems like the airspeed is reading maybe 10mph fast. The GS always reads 10mph or more slower than the True airspeed, no matter which way I fly with respect to the current wind. Looking through the configuration options on the Skyview, I'm not seeing parameters to calibrate the airspeed. If the airspeed were *slow* compared to the GS, I could envision making adjustments to the Pitot tube to get it in better alignment with slipstream. But *fast* is a head scratcher. If there's no electronic configuration parameters to adjust, what do you do? Are there Pitot line "attenuators" like for RF in coax?
Matt
|
Listers,
Thank you for all the great suggestions on resolving this airspeed issue! I took a look at the static ports on the RV-6 today and found that they are done using a flush head screw with a hole drilled in the center on either side of the fuselage. They do *not* protrude from the side of the plane at all. They are totally flush (see attached picture). Just for fun, I whipped up a couple of quick test deals using a 3/16" washer and some electrical tape. I poked a 1/16" hole in the center of the tape and then put the washer centered over the static ports on both sides of the fuselage (see attached pictures). Then, I went flying on this beautiful December 27 day in California!
I didn't have time to do any real scientific multi-leg testing, but I was amazed that the True Airspeed is now falling in a much more believable range compared to the GPS-derived ground speed. On one cross-country leg, I had an exactly 90 degree crosswind component and the True Airspeed and GPS Ground Speed were tracking exactly the same. Yahoo!
Obviously I need to do some additional, more scientific measurements and probably come up with a slightly more "permanent" washer arrangement, but the early returns are very promising! 
Thanks again for all the great feedback!
Matt
-
Matt "Red Dawg" Dralle
RV-8 #82880 N998RV "Ruby Vixen"
http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log
http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...
RV-6 #20916 N360EM "The Flyer"
http://www.mattsrv6.com - Matt's RV-6 Revitalization Log
Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode
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peter(at)sportingaero.com
Guest
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| Posted: Wed Dec 28, 2011 3:00 am Post subject: Dynon Skyview Airspeed Calibration... |
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You could just cut the head off the pop rivet that Van's recommends and
stick that on with epoxy (or double sided tape to start with)?
Peter
On 28/12/2011 05:12, Matt Dralle wrote:
| Quote: | At 07:39 PM 12/26/2011 Monday, Matt Dralle wrote:
> Dear Listers,
>
> I've been flying the new 10" Dynon Skyview in the RV-6 for a few weeks now and it seems like the airspeed is reading maybe 10mph fast. The GS always reads 10mph or more slower than the True airspeed, no matter which way I fly with respect to the current wind. Looking through the configuration options on the Skyview, I'm not seeing parameters to calibrate the airspeed. If the airspeed were *slow* compared to the GS, I could envision making adjustments to the Pitot tube to get it in better alignment with slipstream. But *fast* is a head scratcher. If there's no electronic configuration parameters to adjust, what do you do? Are there Pitot line "attenuators" like for RF in coax?
>
> Matt
Listers,
Thank you for all the great suggestions on resolving this airspeed issue! I took a look at the static ports on the RV-6 today and found that they are done using a flush head screw with a hole drilled in the center on either side of the fuselage. They do *not* protrude from the side of the plane at all. They are totally flush (see attached picture). Just for fun, I whipped up a couple of quick test deals using a 3/16" washer and some electrical tape. I poked a 1/16" hole in the center of the tape and then put the washer centered over the static ports on both sides of the fuselage (see attached pictures). Then, I went flying on this beautiful December 27 day in California!
I didn't have time to do any real scientific multi-leg testing, but I was amazed that the True Airspeed is now falling in a much more believable range compared to the GPS-derived ground speed. On one cross-country leg, I had an exactly 90 degree crosswind component and the True Airspeed and GPS Ground Speed were tracking exactly the same. Yahoo!
Obviously I need to do some additional, more scientific measurements and probably come up with a slightly more "permanent" washer arrangement, but the early returns are very promising!
Thanks again for all the great feedback!
Matt
-
Matt "Red Dawg" Dralle
RV-8 #82880 N998RV "Ruby Vixen"
http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log
http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...
RV-6 #20916 N360EM "The Flyer"
http://www.mattsrv6.com - Matt's RV-6 Revitalization Log
Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode
|
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Wed Dec 28, 2011 5:15 am Post subject: Dynon Skyview Airspeed Calibration... |
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12/28/2011
Hello Matt, I think that you are on the right track. The correct approach is
to use a semi circular wedge either before or aft of the static port in
order to achieve the results required. Here is the sequence that I went
through with my two static ports (one on each side of the fuselage) in order
to lower my airspeed indicator airspeed indication before I was satisfied
with the results:
1) Taped over one side static port and test flew.
2) Removed the first tape, taped over the other side static port and test
flew.
3) Put wedges aft of both side static ports using double sided sticky tape
and test flew.
4) Removed wedge from one side static port and test flew.
5) Switched the single wedge from one side static port to the other side
static port and test flew.
6) Declared victory and installed the single wedge more permanently.
Note that my focus was on good airspeed indication at landing approach
airspeeds, not at cruise airspeeds. On a calm / no wind day a check between
my airspeed indicator airspeed and my GPS ground speed on landing approach
are very nearly identical. I see no significant altimeter change indication
with airspeed change.
The next time I am out at the airport (if I remember) I will take a photo or
two of the single aluminum wedge on one of my static ports and email it to
you.
Good luck.
'OC' Baker Says: "The best investment we can make is the time and effort to
gather and understand knowledge."
======================================================
Listers,
Thank you for all the great suggestions on resolving this airspeed issue! I
took
a look at the static ports on the RV-6 today and found that they are done
using
a flush head screw with a hole drilled in the center on either side of the
fuselage. They do *not* protrude from the side of the plane at all. They
are
totally flush (see attached picture). Just for fun, I whipped up a couple
of quick test deals using a 3/16" washer and some electrical tape. I poked
a
1/16" hole in the center of the tape and then put the washer centered over
the
static ports on both sides of the fuselage (see attached pictures). Then, I
went flying on this beautiful December 27 day in California!
I didn't have time to do any real scientific multi-leg testing, but I was
amazed
that the True Airspeed is now falling in a much more believable range
compared
to the GPS-derived ground speed. On one cross-country leg, I had an exactly
90 degree crosswind component and the True Airspeed and GPS Ground Speed
were
tracking exactly the same. Yahoo!
Obviously I need to do some additional, more scientific measurements and
probably
come up with a slightly more "permanent" washer arrangement, but the early
returns are very promising!
Thanks again for all the great feedback!
Matt
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Sat Dec 31, 2011 5:04 am Post subject: Dynon Skyview Airspeed Calibration... |
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12/31/2011
Hello Matt, Attached are pictures of the two static ports on the foward
fuselage sides of my KIS TR-1:
0599 is the plain static port on the right side of the fuselage.
0602 is the same basic static port on the left side of the fuselage, but
with a self made aluminum wedge installed on it.
Since the wedge is installed aft of the opening in the static port it has
the effect of slightly increasing the static pressure that this port is
sensing and sending to the rest of the static portion of the pitot static
system. This slight increase in static pressure, in the airspeed indicator,
balances out or reduces the effective force being applied to the indicator
by the air pressure coming in from the pitot tube. The result is that the
airspeed indicator indicates a slightly lower airspeed than it would without
the wedge.
A wedge applied before the static port opening would have the opposite
effect.
Plan on doing a lot of test flying to get your wedge(s) fine tuned to
accomplish what you want in the way of airspeed reading without
significantly adversely affecting your altimeter readings.
My thinking is that it is more important to have the airspeed reading what
it should be in the approach speed arena rather than the cruise speed arena.
'OC' Baker Says: "The best investment we can make is the time and effort to
gather and understand knowledge."
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tim2542(at)sbcglobal.net
Guest
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| Posted: Sat Dec 31, 2011 6:48 am Post subject: Dynon Skyview Airspeed Calibration... |
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I just did all this on my plane, the GRT equipment has a calibration utility built in that makes it a snap. Just fly the heading displayed and push a button for a given airspeed. Very simple &easy.
I would imagine the Dynon has something similar.
Tim
Sent from my iPad
On Dec 31, 2011, at 5:00 AM, <bakerocb(at)cox.net> wrote:
| Quote: | 12/31/2011
Hello Matt, Attached are pictures of the two static ports on the foward fuselage sides of my KIS TR-1:
0599 is the plain static port on the right side of the fuselage.
0602 is the same basic static port on the left side of the fuselage, but with a self made aluminum wedge installed on it.
Since the wedge is installed aft of the opening in the static port it has the effect of slightly increasing the static pressure that this port is sensing and sending to the rest of the static portion of the pitot static system. This slight increase in static pressure, in the airspeed indicator, balances out or reduces the effective force being applied to the indicator by the air pressure coming in from the pitot tube. The result is that the airspeed indicator indicates a slightly lower airspeed than it would without the wedge.
A wedge applied before the static port opening would have the opposite effect.
Plan on doing a lot of test flying to get your wedge(s) fine tuned to accomplish what you want in the way of airspeed reading without significantly adversely affecting your altimeter readings.
My thinking is that it is more important to have the airspeed reading what it should be in the approach speed arena rather than the cruise speed arena.
'OC' Baker Says: "The best investment we can make is the time and effort to gather and understand knowledge."
<100_0599.jpg>
<100_0602.jpg>
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