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mstrickel(at)verizon.net
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 Posted: Wed Oct 23, 2013 3:16 pm Post subject: KIS-List Digest: 1 Msgs - 10/21/13 |
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From: KIS-List Digest Server <kis-list(at)matronics.com>
To: KIS-List Digest List <kis-list-digest(at)matronics.com>
Sent: Tuesday, October 22, 2013 3:00 AM
Subject: KIS-List Digest: 1 Msgs - 10/21/13
*
Online Versions of Today's List Digest Archive
=========================
Today's complete KIS-List Digest can also be found in either of the
two Web Links listed below. The .html file includes the Digest formatted
in HTML for viewing with a web browser and features Hyperlinked Indexes
and Message Navigation. The .txt file includes the plain ASCII version
of the KIS-List Digest and can be viewed with a generic text editor
such as Notepad or with a web browser.
HTML Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=html&Chapter=2013-10-21&Archive=KIS
Text Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=txt&Chapter=2013-10-21&Archive=KIS
=======================
EMail Version of Today's List Digest Archive
================================================
----------------------------------------------------------
KIS-List Digest Archive
---
Total Messages Posted Mon 10/21/13: 1
----------------------------------------------------------
Today's Message Index:
----------------------
1. 11:04 PM - TAS Error with my new EFIS (Galin Hernandez)
________________________________ Message 1 _____________________________________
Time: 11:04:20 PM PST US
From: Galin Hernandez <galinhdz(at)gmail.com (galinhdz(at)gmail.com)>
Subject: TAS Error with my new EFIS
Pardon the long write-up.
After buying my airplane several years ago I did a series of maneuvers at
different power settings and, by using GPS groundspeeds, I made a fairly
accurate calibrated airspeed chart. For the next few years I used the CAS
chart often and found that, at normal power settings, I consistently
cruised at 143KTAS.
Fast forward to this year when I installed a complete DYNON Skyview EFIS
system which automatically calculates TAS. But, at normal cruise power
settings, the Skyview consistently showed me cruising at 156KTAS. The
Skyview also showed that no matter which direction I was flying, I always
had a headwind. Knowing that the Skyview did not change the aerodynamics of
the airplane and the system had just passed an IFR check, something was not
right.
On subsequent flights I calculated my TAS using my old CAS chart and came
back to 143KTAS not the 156KTAS the Skyview was displaying. The plots on my
CAS chart shows that as my airspeed increases, IAS and CAS spread apart
with IAS being almost 20KT faster at full power. Since the Skyview does not
have a method of factoring in a CAS, it uses IAS for the calculations. With
the significantly higher IAS used by the Skyview it would display a higher
TAS than actual matching what I was seeing.
Talking with the engineers at DYNON, they told me that in a =93well designe
d=94
system the difference between IAS and CAS should not be more than a few
knots. If my IAS and CAS was that far apart, there is a problem with either
the pitot or static source position. Having IAS significantly higher than
CAS meant that either the pitot tube is in an area of =93higher=94 pressure
or
the static source is in an area of =93lower=94 pressure. If the pitot is in
an
area of =93higher=94 pressure the error would only be in airspeed. But if t
he
static source is in an area of =93lower=94 pressure, altitude indications w
ill
show me flying at a higher altitude than I really am. This is a potentially
deadly situation when flying real IMC, which I do.
To isolate if the error was in the pitot or static, I flew to different
airports with ILS approaches over the next few months. I found that when at
the FAF on the glideslope of each airport, the Skyview displayed a
consistent 100-110=92 higher than what the approach plate showed. In order
to
confirm what I found, I did several high speed passes, over different
airports, trying to stay about 10=92 above the runway. At each airport the
Skyview displayed a consistent 100-110=92 higher than what the runway reall
y
was . This matched what I found with the FAF experiment. Since my CAS chart
showed the IAS and CAS getting further apart the faster I flew, the data
obtained from the test flights was consistent with the static source being
in an area where pressure drops as airspeed increases. So I needed to
correct the static source placement.
The dual static source I have was installed by Rich Trickel back in 2008
and I really didn=92t want to change where they were located. So in order t
o
correct for a possible changing static pressure situation I experimented by
placing a piece of Gorilla tape just behind each static port hole and doing
the flight checks again. With one piece of tape, the FAF and high speed
runway checks altitude error dropped to about 40=92. My displayed TAS error
,
based on my CAS chart, had also dropped to about 10kts.
I figured I was on the right track so I added a second piece of tape
effectively doubling the thickness behind the static port hole. The next
series of flights showed my FAF and high speed runway checks had dropped to
within a few feet. My TAS error had also dropped to within 2Kts at normal
cruise. A third piece of tape caused the FAF and high speed runway checks
to show the altitude difference was about 40=92 but in the opposite
direction. Now the TAS error was back to about 10Kts, also in the opposite
direction than before. Armed with this information, I went back to using
two pieces of Gorilla tape just behind the static source hole.
During the next flights the FAF and high speed runway checks showed the
altitude error was within 10 feet of what I was expecting. Additionally I
did a series of maneuvers at different power settings and, by using GPS
groundspeeds, calculated that my TAS was within a few knots of what the
Skyview was displaying. During my final test flight (October 21, 2013) I
found that normal approach speed (90Kts) and normal cruise (143Kts) speeds
were within 2Kts of calculated. I also found that as I approached to land,
the wind aloft display matched very closely to what the tower was
reporting. Now I know what I have to do to correct my static source
position error. I can complete the work by making a piece of aluminum the
thickness of two pieces of Gorilla tape and permanently attach it just
behind to the static source hole.
So, if your EFIS show an airspeed higher than what the =93book=94 shows you
r
airplane should be doing, check it out. You may have a pitot/static source
error that can be corrected. Overall I think I corrected a possibly serious
situation and now completely trust my Skyview is displcs.com/Navigator?KIS-List" "http://forums.matronics.com/" target="_blank">http://forums.matronics.cosp; -nics.com/contribution" target="_blank">http://www.matronics.com/contribut===============
[quote][b]
| | - The Matronics KIS-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?KIS-List |
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mstrickel(at)verizon.net
Guest
|
| Posted: Wed Oct 23, 2013 3:16 pm Post subject: KIS-List Digest: 1 Msgs - 10/21/13 |
|
|
From: KIS-List Digest Server <kis-list(at)matronics.com>
To: KIS-List Digest List <kis-list-digest(at)matronics.com>
Sent: Tuesday, October 22, 2013 3:00 AM
Subject: KIS-List Digest: 1 Msgs - 10/21/13
*
Online Versions of Today's List Digest Archive
=========================
Today's complete KIS-List Digest can also be found in either of the
two Web Links listed below. The .html file includes the Digest formatted
in HTML for viewing with a web browser and features Hyperlinked Indexes
and Message Navigation. The .txt file includes the plain ASCII version
of the KIS-List Digest and can be viewed with a generic text editor
such as Notepad or with a web browser.
HTML Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=html&Chapter=2013-10-21&Archive=KIS
Text Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=txt&Chapter=2013-10-21&Archive=KIS
=======================
EMail Version of Today's List Digest Archive
================================================
----------------------------------------------------------
KIS-List Digest Archive
---
Total Messages Posted Mon 10/21/13: 1
----------------------------------------------------------
Today's Message Index:
----------------------
1. 11:04 PM - TAS Error with my new EFIS (Galin Hernandez)
________________________________ Message 1 _____________________________________
Time: 11:04:20 PM PST US
From: Galin Hernandez <galinhdz(at)gmail.com (galinhdz(at)gmail.com)>
Subject: TAS Error with my new EFIS
Pardon the long write-up.
After buying my airplane several years ago I did a series of maneuvers at
different power settings and, by using GPS groundspeeds, I made a fairly
accurate calibrated airspeed chart. For the next few years I used the CAS
chart often and found that, at normal power settings, I consistently
cruised at 143KTAS.
Fast forward to this year when I installed a complete DYNON Skyview EFIS
system which automatically calculates TAS. But, at normal cruise power
settings, the Skyview consistently showed me cruising at 156KTAS. The
Skyview also showed that no matter which direction I was flying, I always
had a headwind. Knowing that the Skyview did not change the aerodynamics of
the airplane and the system had just passed an IFR check, something was not
right.
On subsequent flights I calculated my TAS using my old CAS chart and came
back to 143KTAS not the 156KTAS the Skyview was displaying. The plots on my
CAS chart shows that as my airspeed increases, IAS and CAS spread apart
with IAS being almost 20KT faster at full power. Since the Skyview does not
have a method of factoring in a CAS, it uses IAS for the calculations. With
the significantly higher IAS used by the Skyview it would display a higher
TAS than actual matching what I was seeing.
Talking with the engineers at DYNON, they told me that in a =93well designe
d=94
system the difference between IAS and CAS should not be more than a few
knots. If my IAS and CAS was that far apart, there is a problem with either
the pitot or static source position. Having IAS significantly higher than
CAS meant that either the pitot tube is in an area of =93higher=94 pressure
or
the static source is in an area of =93lower=94 pressure. If the pitot is in
an
area of =93higher=94 pressure the error would only be in airspeed. But if t
he
static source is in an area of =93lower=94 pressure, altitude indications w
ill
show me flying at a higher altitude than I really am. This is a potentially
deadly situation when flying real IMC, which I do.
To isolate if the error was in the pitot or static, I flew to different
airports with ILS approaches over the next few months. I found that when at
the FAF on the glideslope of each airport, the Skyview displayed a
consistent 100-110=92 higher than what the approach plate showed. In order
to
confirm what I found, I did several high speed passes, over different
airports, trying to stay about 10=92 above the runway. At each airport the
Skyview displayed a consistent 100-110=92 higher than what the runway reall
y
was . This matched what I found with the FAF experiment. Since my CAS chart
showed the IAS and CAS getting further apart the faster I flew, the data
obtained from the test flights was consistent with the static source being
in an area where pressure drops as airspeed increases. So I needed to
correct the static source placement.
The dual static source I have was installed by Rich Trickel back in 2008
and I really didn=92t want to change where they were located. So in order t
o
correct for a possible changing static pressure situation I experimented by
placing a piece of Gorilla tape just behind each static port hole and doing
the flight checks again. With one piece of tape, the FAF and high speed
runway checks altitude error dropped to about 40=92. My displayed TAS error
,
based on my CAS chart, had also dropped to about 10kts.
I figured I was on the right track so I added a second piece of tape
effectively doubling the thickness behind the static port hole. The next
series of flights showed my FAF and high speed runway checks had dropped to
within a few feet. My TAS error had also dropped to within 2Kts at normal
cruise. A third piece of tape caused the FAF and high speed runway checks
to show the altitude difference was about 40=92 but in the opposite
direction. Now the TAS error was back to about 10Kts, also in the opposite
direction than before. Armed with this information, I went back to using
two pieces of Gorilla tape just behind the static source hole.
During the next flights the FAF and high speed runway checks showed the
altitude error was within 10 feet of what I was expecting. Additionally I
did a series of maneuvers at different power settings and, by using GPS
groundspeeds, calculated that my TAS was within a few knots of what the
Skyview was displaying. During my final test flight (October 21, 2013) I
found that normal approach speed (90Kts) and normal cruise (143Kts) speeds
were within 2Kts of calculated. I also found that as I approached to land,
the wind aloft display matched very closely to what the tower was
reporting. Now I know what I have to do to correct my static source
position error. I can complete the work by making a piece of aluminum the
thickness of two pieces of Gorilla tape and permanently attach it just
behind to the static source hole.
So, if your EFIS show an airspeed higher than what the =93book=94 shows you
r
airplane should be doing, check it out. You may have a pitot/static source
error that can be corrected. Overall I think I corrected a possibly serious
situation and now completely trust my Skyview is displcs.com/Navigator?KIS-List" "http://forums.matronics.com/" target="_blank">http://forums.matronics.cosp; -nics.com/contribution" target="_blank">http://www.matronics.com/contribut===============
[quote][b]
| | - The Matronics KIS-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?KIS-List |
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