Today's Message Index:
----------------------
1. 06:11 AM - Re: Dynon Skyview Airspeed Calibration... (Bubblehead)
2. 06:28 AM - Re: Re: Dynon Skyview Airspeed Calibration... (Linn Walters)
3. 07:39 AM - Re: Dynon Skyview Airspeed Calibration... (Jim Ayers)
4. 09:25 AM - Re: Re: Dynon Skyview Airspeed Calibration... (Kevin Horton)
5. 09:41 AM - Re: Dynon Skyview Airspeed Calibration... (Kevin Horton)
6. 12:42 PM - Re: Dynon Skyview Airspeed Calibration... (Bubblehead)
7. 03:14 PM - Re: Re: Dynon Skyview Airspeed Calibration... (Bob Mills)
8. 03:31 PM - Re: Re: Dynon Skyview Airspeed Calibration... (Kevin Horton)
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Subject: | Re: Dynon Skyview Airspeed Calibration... |
One big question:
Does changing the geometry of the static port change indicated altitude when flying?
It seems like if we change the static pressure by applying washers or lips we would
change indicated altitude along with IAS.
--------
John
Keller, TX
RV-8 N247TD
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=362222#362222
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Subject: | Re: Dynon Skyview Airspeed Calibration... |
On 1/2/2012 9:07 AM, Bubblehead wrote:
> --> RV-List message posted by: "Bubblehead"<jdalmansr@gmail.com>
>
> One big question:
>
> Does changing the geometry of the static port change indicated altitude when
flying?
Yes, it surely could. If the static system isn't truly 'neutral' .....
no pressure or suction on it .... it really messes things up.
> It seems like if we change the static pressure by applying washers or lips we
would change indicated altitude along with IAS.
The reason for the 'washer' or 'rivet head' (whatever you use) is to get
the port out of the laminar flow down the fuselage into undisturbed
(relatively) air.
That makes location pretty important. It also means that port
location/thickness/shape/ ....... is the ONLY thing you can change to
fix airspeed/altitude errors in flight AFAIK.
It also means you need two ports, one on each side to cancel induced
errors due to uncoordinated flight.
Linn.
>
> --------
> John
> Keller, TX
> RV-8 N247TD
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=362222#362222
>
>
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Subject: | Re: Dynon Skyview Airspeed Calibration... |
Do you have a test method that we can all use to calibrate the alimeter at
cruise speed?
The altimeter only has the static system for its input.
Calibrating the static vents in cruise conditions for the altimeter could p
rovide a correction for airspeed readout errors.
Correcting airspeed readouts errors by changing the static vent geometery l
eaves your altitude readings at cruise speeds as a total unknown.
Jim Ayers
-----Original Message-----
From: Kevin Horton <khorton01@rogers.com>
Sent: Tue, Dec 27, 2011 11:50 am
Subject: Re: RV-List: Dynon Skyview Airspeed Calibration...
Checking altimeter accuracy against tops of ridge lines only works if the
emperature is close to standard temperature.
If the temperature differs from standard, the error is about 4 ft per 1000
ft
er degree C of difference from standard temperature. E.g., if the top of t
he
idge line is 2000 ft above the airport where the altimeter setting came fro
m,
nd the temperature is 15 deg C warmer than standard temperature, the altime
ter
ill read about 4/1000 * 2000 * 15 = 120 ft lower than the actual altitude
.
See:
http://bathursted.ccnb.nb.ca/vatcan/fir/moncton/WeeklyTopics/Archives/20040
104/CurrentTopic.html
ttp://44rf.com/misc/USAF_AIS_Cold_WX_Altimeter.ppt
Kevin Horton
On 2011-12-27, at 12:44 , Jim Ayers wrote:
> An easy way to check the static side of the airspeed indicator is to use
your
ltimeter.
I flew along a ridge line at cruise speed that has a 2200 feet peak as sho
wn
n my sectional.
I may not have been exactly at the same level. Could have been 10 or 20 f
eet
ff in hieght. My altimeter read 2,210 feet.
So, at that time, my static system was pretty close.
Jim Ayers
Less Drag Special sn 1 (Modified HR2)
-----Original Message-----
From: David Maib <dmaib@mac.com>
To: rv-list <rv-list@matronics.com>
Sent: Mon, Dec 26, 2011 8:03 pm
Subject: Re: RV-List: Dynon Skyview Airspeed Calibration...
>
Maybe a static port error? Check out some of Kevin Horton's articles
in Kitplanes. Static port errors can, and do, cause "fast" errors.
IIRC, Kevin says that pitot alignment does not have to be very
precise to be pretty accurate.
David Maib
Rv-10 40559
Flying.
On Dec 26, 2011, at 10:39 PM, Matt Dralle wrote:
dralle@matronics.com
>
>
> 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
>
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>
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> Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...
>
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>
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Subject: | Re: Dynon Skyview Airspeed Calibration... |
On 2012-01-02, at 09:07 , Bubblehead wrote:
>
> One big question:
>
> Does changing the geometry of the static port change indicated altitude when
flying?
>
> It seems like if we change the static pressure by applying washers or lips we
would change indicated altitude along with IAS.
>
> --------
> John
===================
If the original IAS error was due to a poorly located or shaped static port (i.e.
static system position error), then the original errors would have affected
both IAS and altitude indications. In this case the correct fix is whatever
it takes to get the static port to sense a pressure that is as close as possible
to true ambient pressure. This will correct both the IAS and altitude indications.
If the source of the error is static source position error, then any "fix" that
only addressed the IAS (such as the adjustments that some EFIS provide) will
only correct the IAS. The indicated altitude will still be wrong, and this error
could easily be much more than 100 ft.
--
Kevin Horton
RV-8
Ottawa, Canada
http://www.kilohotel.com/rv8
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Subject: | Re: Dynon Skyview Airspeed Calibration... |
The classical test method that directly compares actual vs indicated altitude is
the "tower fly-by". Typically a camera is placed on top of a tower about 100
ft high, with the tower abeam the middle of a long runway. The camera is very
accurately aimed, and the geometry of the tower, camera lens, etc is very
well known so that the height of the aircraft above the runway can be determined
from the images, assuming the aircraft accurately tracks down the runway centreline.
The aircraft instrumentation system records the altitude, with a very
accurate time stamp. Ground instrumentation records the altitude and OAT at
ground level, and the camera images have an accurate time stamp. Post flight
analysis is used to determine the actual vs indicated altitude as the aircraft
passes by the tower at a range of airspeeds. This is used by some major test
centres, but it is not practical for us as it requires too much specialized
equipment to achieve reasonable accuracy.
The method that is most practical for us is the speed course method (sometimes
called ground course method). It assumes that the pitot pressure is accurate,
which is a reasonable assumption, and there are no static or pitot leaks, which
can be confirmed by ground test. The ASI instrument error must be measured.
The TAS is measured using one of several possible methods (GPS data from a
four course box pattern is the current best method), and the CAS is back calculated
from the TAS, indicated altitude and OAT. The difference between CAS and
IAS (corrected for instrument error) must be due to static source position error.
More info:
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2023-8B/$FILE/Final-Part8.pdf
http://www.kilohotel.com/rv8/rvlinks/ssec.html
Kevin Horton
On 2012-01-02, at 10:35 , Jim Ayers wrote:
> Do you have a test method that we can all use to calibrate the alimeter at cruise
speed?
>
> The altimeter only has the static system for its input.
>
> Calibrating the static vents in cruise conditions for the altimeter could provide
a correction for airspeed readout errors.
>
> Correcting airspeed readouts errors by changing the static vent geometery leaves
your altitude readings at cruise speeds as a total unknown.
>
> Jim Ayers
> -----Original Message-----
> From: Kevin Horton <khorton01@rogers.com>
> To: rv-list <rv-list@matronics.com>
> Sent: Tue, Dec 27, 2011 11:50 am
> Subject: Re: RV-List: Dynon Skyview Airspeed Calibration...
>
> >
>
> Checking altimeter accuracy against tops of ridge lines only works if the
> temperature is close to standard temperature.
>
> If the temperature differs from standard, the error is about 4 ft per 1000 ft
> per degree C of difference from standard temperature. E.g., if the top of the
> ridge line is 2000 ft above the airport where the altimeter setting came from,
> and the temperature is 15 deg C warmer than standard temperature, the altimeter
> will read about 4/1000 * 2000 * 15 = 120 ft lower than the actual altitude.
>
> See:
>
>
> http://bathursted.ccnb.nb.ca/vatcan/fir/moncton/WeeklyTopics/Archives/20040104/CurrentTopic.html
> http://44rf.com/misc/USAF_AIS_Cold_WX_Altimeter.ppt
>
>
> Kevin Horton
>
> On 2011-12-27, at 12:44 , Jim Ayers wrote:
>
> > An easy way to check the static side of the airspeed indicator is to use your
> altimeter.
> >
> > I flew along a ridge line at cruise speed that has a 2200 feet peak as shown
> on my sectional.
> >
> > I may not have been exactly at the same level. Could have been 10 or 20 feet
> off in hieght. My altimeter read 2,210 feet.
> > So, at that time, my static system was pretty close.
> >
> > Jim Ayers
> > Less Drag Special sn 1 (Modified HR2)
> >
> > -----Original Message-----
> > From: David Maib <
> dmaib@mac.com
> >
> > To: rv-list <
> rv-list@matronics.com
> >
> > Sent: Mon, Dec 26, 2011 8:03 pm
> > Subject: Re: RV-List: Dynon Skyview Airspeed Calibration...
> >
> dmaib@mac.com
>
> > >
> >
> > Maybe a static port error? Check out some of Kevin Horton's articles
> > in Kitplanes. Static port errors can, and do, cause "fast" errors.
> > IIRC, Kevin says that pitot alignment does not have to be very
> > precise to be pretty accurate.
> >
> > David Maib
> > Rv-10 40559
> > Flying.
> > On Dec 26, 2011, at 10:39 PM, Matt Dralle wrote:
> >
> >
> dralle@matronics.com
>
> > >
> > >
> > > 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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Subject: | Re: Dynon Skyview Airspeed Calibration... |
Kevin,
I've been on your site a lot today reading about this. Next weekend if weather
permits I will collect a lot of Numbers to plug into your speadsheet to see about
IAS and TAS. I suspect the TAS on my Skyview is significantly off because
I am getting wind vectors that disagree significantly with forecast winds aloft
and what I observe for a correction angle (crab angle) while flying.
In your experience if I correct my IAS and TAS by modifying the static port will
I cause large changes and induce possible error on "indicated" altitude?
As info i have the SafeAir1 system on my 8 including static ports and the static
leak test was passed with flying colors just a month ago.
I appreciate all the info you've share on this and other topics.
John
--------
John
Keller, TX
RV-8 N247TD
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=362269#362269
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Subject: | Re: Dynon Skyview Airspeed Calibration... |
John,
As you prepare to make your airspeed calibration runs, I'd also recommend
you ensure your compass is well calibrated also. I have a legacy Dynon
panel, but have also found that I saw very odd wind readouts before I ran a
compass cal (or re-ran the cal after maintenance). Heading and speed errors
will both wreak havoc with the GPS wind readouts, so eliminating both is
important. Recommend running the compass cal with engine running, avionics
on, and canopy closed...as close as you can get to normal in-flight
conditions.
I've used the NTPS spreadsheet from Kevin's site a lot (thanks Kevin), and
it's a great tool! My TAS readout is consistently 2-4 knots faster than GPS
readouts...lower when the standard deviation block on the spreadsheet is
lower (meaning the data is better). My static ports are the standard rivet,
so I think the shape is good. I actually think I have a bit of an issue with
OAT (actually a touch of Ram Rise), since I always test at top speed (for
speed mods), and I can see a change in OAT just by slowing or accelerating.
Before I add thickness to the static port, I'm going to run some tests at
slower speeds to see if the TAS-GPS speed delta decreases, then try moving
the OAT probe from under the H-stab to inside the fuselage back there. We'll
see.
Just mentioned all this, as there are a few inputs to consider, and nulling
out the others before making static port changes may be a good idea. I'd
also like to hear Kevin's (and others') thoughts on the speed error versus
altitude error question, but I would think that with all inputs calibrated,
making a physical change to the static ports to reduce IAS/TAS errors would
also reduce other static system output errors (like altitude).
Good discussion!
Cheers,
Bob
RV-6 N600SS
Reno, NV
-----Original Message-----
From: owner-rv-list-server@matronics.com
[mailto:owner-rv-list-server@matronics.com] On Behalf Of Bubblehead
Sent: Monday, January 02, 2012 12:37 PM
Subject: RV-List: Re: Dynon Skyview Airspeed Calibration...
Kevin,
I've been on your site a lot today reading about this. Next weekend if
weather permits I will collect a lot of Numbers to plug into your speadsheet
to see about IAS and TAS. I suspect the TAS on my Skyview is significantly
off because I am getting wind vectors that disagree significantly with
forecast winds aloft and what I observe for a correction angle (crab angle)
while flying.
In your experience if I correct my IAS and TAS by modifying the static port
will I cause large changes and induce possible error on "indicated"
altitude?
As info i have the SafeAir1 system on my 8 including static ports and the
static leak test was passed with flying colors just a month ago.
I appreciate all the info you've share on this and other topics.
John
--------
John
Keller, TX
RV-8 N247TD
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=362269#362269
Message 8
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Subject: | Re: Dynon Skyview Airspeed Calibration... |
John,
Modifying the static ports to reduce the error in IAS will also reduce the error
in the indicated altitude, IF the static port is the source of your problem.
If the static port is not the source of your problem you could be introducing
new errors in your altitude by modifying the static ports. Be very sure that
you have ruled out other possible errors before attacking the static ports.
1. Be very sure that you don't have leaks in the static or pitot systems - do your
own checks, rather than assuming the result from a month ago is still valid
- you could easily have a new leak.
2. Measure the ASI instrument error in your EFIS - don't simply assume it is zero
- my Dynon EFIS has some ASI instrument error.
3. And be sure your OAT is reasonably accurate.
If after doing the three items above without finding a problem, then you must have
issues with the static ports, which will affect both airspeed and altitude.
Static port changes that reduce the ASI error will also reduce the altimeter
error.
Kevin
On 2012-01-02, at 15:36 , Bubblehead wrote:
>
> Kevin,
>
> I've been on your site a lot today reading about this. Next weekend if weather
permits I will collect a lot of Numbers to plug into your speadsheet to see
about IAS and TAS. I suspect the TAS on my Skyview is significantly off because
I am getting wind vectors that disagree significantly with forecast winds aloft
and what I observe for a correction angle (crab angle) while flying.
>
> In your experience if I correct my IAS and TAS by modifying the static port will
I cause large changes and induce possible error on "indicated" altitude?
>
> As info i have the SafeAir1 system on my 8 including static ports and the static
leak test was passed with flying colors just a month ago.
>
> I appreciate all the info you've share on this and other topics.
>
> John
>
> --------
> John
> Keller, TX
> RV-8 N247TD
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=362269#362269
>
>
>
>
>
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