Today's Message Index:
----------------------
1. 05:18 AM - TAS Error with my new EFIS (Owen Baker)
2. 05:51 AM - Re: TAS Error with my new EFIS (Michael Orth)
3. 10:03 AM - Re: TAS Error with my new EFIS (Scott Stearns)
4. 12:15 PM - Re: TAS Error with my new EFIS (Galin Hernandez)
5. 01:47 PM - Re: TAS Error with my new EFIS (Owen Baker)
6. 02:50 PM - Re: TAS Error with my new EFIS (Galin Hernandez)
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Subject: | TAS Error with my new EFIS |
10/22/2013
Hello Galin, On this subject you wrote (see copied below): =93Pardon the
long write-up.=94 No apology needed ' your post was very detailed and
valuable. I thank you for both the testing and the reminder write up
that you provided.
I also posted on this subject back in April 15, 2010 in Matronics KIS
list message #21700 under the subject =93Re: Here=92s an odd
question=94. I=92ll copy that posting below, but I don=92t know how well
it will come through.
I also have some pictures of my KIS TR-1 static ports with and without
wedge someplace in my computer. If I can find the pictures I will post
them separately.
Thank you again for your work on our behalf.
OC
===============
Match: #27 Message: #21700 From: <bakerocb(at)cox.net> Subject: Re:
Here's an odd question Date: Apr 15, 2010
4/15/2010
Hello Mike, You wrote: "Not sure why this (altitude variation with
airspeed)
would be, or more importantly, how to fix it."
Hello Bernie, You wrote: "There didn't seem to be any theory behind it."
This is not a very rare or mysterious phenomena. Inaccurate airspeed
indications can be caused by inaccurate dynamic and static air pressure
forces. Inaccurate altitude indications can be caused by inaccurate
static
pressure forces.
AIRSPEED. Let's talk about inaccurate airspeed measurements first. An
airspeed indicator is a balancing mechanism. It balances the difference
between a force created by dynamic air pressure and a force created by
static air pressure. The force from the dynamic air pressure is the
result
of the forward movement of the airplane. The faster the airplane moves
the
greater the force exerted.
In order to get an accurate measure of that dynamic force one needs to
accurately sense the free stream dynamic air pressure and send it to the
airspeed indicator via leak and kink free tubing. That means sensing the
air
movement in the actual direction that the airplane is moving and having
that
air movement not affected by some local air flow direction change caused
by
the airframe itself. This is why you sometimes see flight test airplanes
with a long boom sticking out forward with a small vane mechanism on the
front of it. This boom and vane mechanism, along with connecting tubing,
is
a pitot tube system intended to accurately measure the force from the
free
stream dynamic air pressure without any inaccuracies introduced by local
airframe air flow. See Note One below.
So much for the dynamic force side of the airspeed indicator balancing
act,
what about the static force side? An accurate static force is provided
by a
static port ideally located somewhere on the airframe such that it is
measuring the true static air pressure. But finding that ideal location
and
making the perfect static port that does not introduce static air
pressure
errors is not always so quick and easy. And what do we do if we discover
that the static port that we have installed is not producing accurate
static
air pressure? See Note Two below.
ALTITUDE. An altimeter is also a balancing mechanism. It measures the
difference between the initial altitude setting of the altimeter
mechanism
as compared to the static air pressure encountered by that same
mechanism
while in flight and displays that difference in some lineal measurement
(usually in feet in our part of the world). If the static pressure
provided
to the altimeter via the static port and the connecting tubing is in
error
or changes with the airplane's airspeed, when the actual altitude is
constant, then the altimeter's altitude indication will be in error. And
what do we do if we discover that the static port that we have installed
is
not producing accurate static air pressure? See Note Two below.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
Note One: Why don't we use these long boom and vane type pitot tubes on
our
experimental amateur built aircraft? Because the boom and vane would
take a
terrific beating from people walking into them on the ground and because
the
dynamic force errors introduced by the type of pitot tubes that we
commonly
use are just not great enough to cause us concern. There is not very
much we
can do about adjusting the force coming from dynamic air pressure other
than
using a pitot tube located a sufficient distance from a disturbing piece
of
airframe (usually the bottom surface of a wing) and avoiding a leak or
kink
in the tubing going from the pitot tube to the airspeed indicator.
Note Two: So we have built our airplane, installed our static port(s),
and
discovered that we are getting inaccurate airspeed and / or altitude
indications and decide to do something about it. We could just go on
installing new static ports in different locations, but that is a lot of
work and we are not assured of better results. So we should do just what
the
big boy aerodynamic types do, we fudge or bandaid as needed to get the
air
to give us the results that we want.
Let's say that the airspeed indicator is reading too high -- it says the
airplane is going faster than it really is. (See Note Three). The
dynamic
air pressure side of the airspeed indicator is providing too much force
in
the desired balancing act. How can we counteract that excess dynamic
force?
We increase the static force being fed to the airspeed instrument by the
static port by installing a small wedge just aft of the opening on the
static port (thin edge of the wedge facing forward towards the hole).
This
small wedge causes air to pile up and increase the static air pressure
going
to the airspeed indicator (and also to the altimeter unless you have
provided separate static ports for the two instruments) and give us the
accurate force balance measurement that we want.
Let's say that the altimeter reading goes down 200 feet when you speed
up 60
miles per hour (Mike, you did not say which direction your altitude was
changing with the changes in airspeed). This means that the static port
is
feeding greater than static pressure as your airplane flies faster. How
can
we reduce that undesired increase in static air pressure? We install a
small
wedge in front of the hole in the static port (thin edge of the wedge
facing
aft towards the hole) to shield it a bit from dynamic air pressure
coming
from the front in order to get a more stable and accurate altitude
reading.
How do we get the right size wedge facing the correct direction to get
the
airspeed and altitude results that we want? The same way the big boys
do:
TRIAL AND ERROR and MORE TRIAL AND ERROR. Because our airplanes are
experimental, amateur built we are permitted to do just that --
experiment.
Note Three: So now we know how to tweak our static port(s) to give us
accurate airspeed and altitude information, but how do we know that the
airspeed and altitude information is inaccurate in the first place and
during our trial and error efforts how do we know when we have achieved
the
accuracy that we are seeking? The answer to those two questions is not
as
simple as one might first expect. I won't attempt to answer them here
because the answers are too big and complex to answer in this forum.
What I
will suggest is that the reader google "accurate airspeed" and "accurate
altitude" and delve into those subjects to the level desired. Here is
just
one source you will find:
http://gpsinformation.net/main/altitude.htm
Note Four: This is a personal view point. There are several methods
available for determining accurate true airspeed. Some rather elaborate
--
some use GPS. Just google "accurate airspeed using GPS".
One thing that I've never quite understood regarding these methods is
the
focus on precisely determining airspeed accuracy indication in the
cruising
airspeed range. If I determine that my airspeed indicator shows 150
knots
indicated airspeed and I determine through some elaborate scheme that I
am
actually only going 145 knots through the air what do I do with that
information? Being 5 nautical miles short of my destination after a one
hour
flight is a trivial navigation error contribution compared to all the
other
error sources (such as heading, wind, and climb airspeed) that I have to
contend with and should overcome anyway by some means of real time
enroute
navigation.
I think that if I were going to invest a lot of time and effort in
determining my exact airspeed error I would be inclined to do that
determination in the approach airspeed arena, not the cruising airspeed
arena. And even then I would not be obsessed with absolute airspeed
accuracy, I'd just want to know what number on the indicator gives me
the
right kind of safe approach and landing time after time.
======================
----- Original Message -----
From:
Cc: "mike mccann" ; "Pulsar builders"
Sent: Thursday, April 15, 2010 9:18 AM
Subject: Re: Here's an odd question
>I noticed that the back half of the round washer where the static exits
on
> the SR22 had the back half of it filed down so there was in effect a
> little shield protecting the static exit hole. ((Sorry about this
> description.)
>
> I asked the people at their booth why they did that. I think I
attended
> four air shows before I found someone who was involved with the
> engineering of the system. The answer - - - - "That is what we had to
do
> to make the system work right". There didn't seem to be any theory
behind
> it. They indicated that they had to fiddle around to get it to behave
the
> way they wanted. Maybe they were just trying to get rid of me.
>
> In any event, I did the same with mine and it works fine.
>
> Bernie Wilder
===================
>>
>> ----- Original Message -----
>> From: mike mccann
>> To: Pulsar builders
>> Sent: Thursday, April 15, 2010 5:06 AM
>> Subject: Here's an odd question
>>
>>
>> All,
>>
>> Utilizing a GPS, I've found that my altimeter in my Pulsar varies
with
>> changes in airspeed (altitude will change 100-200 feet with speed
>> changes of 60 mph).
>>
>> Has anyone ever heard of this. Not sure why this would be, or more
>> importantly, how to fix it.
>>
>> Many thanks,
>>
>> Mike
>>
>> Pulsar 1
>> N116Km
End Msg: #27
===
From: Galin Hernandez
Sent: Tuesday, October 22, 2013 2:03 AM
Subject: KIS-List: 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
designed=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 the static source
is in an area of =93lower=94 pressure, altitude indications will 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 really 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 to 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
your 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
displaying correct information.
Message 2
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Subject: | Re: TAS Error with my new EFIS |
Galin,
Great information.
Good write-up.
Thanks,
Michael
-------------------------------------------------------------------------
-------
-------------------------------------------------------------------------
-------
From: Galin Hernandez
Sent: Monday, October 21, 2013 11:03 PM
Subject: KIS-List: 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
designed=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 the static source
is in an area of =93lower=94 pressure, altitude indications will 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 really 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 to 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
your 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
displaying correct information.
No virus found in this message.
Checked by AVG - www.avg.com
10/20/13
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Subject: | Re: TAS Error with my new EFIS |
Where are your pitot and static ports?
Scott
On Oct 22, 2013, at 5:51 AM, "Michael Orth" <mosurf@xplornet.com> wrote:
> Galin,
> Great information.
> Good write-up.
> Thanks,
> Michael
> From: Galin Hernandez
> Sent: Monday, October 21, 2013 11:03 PM
> To: kis-list@matronics.com
> Subject: KIS-List: 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 d
ifferent power settings and, by using GPS groundspeeds, I made a fairly accu
rate calibrated airspeed chart. For the next few years I used the CAS chart o
ften and found that, at normal power settings, I consistently cruised at 143
KTAS.
>
> Fast forward to this year when I installed a complete DYNON Skyview EFIS s
ystem which automatically calculates TAS. But, at normal cruise power settin
gs, 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 a
nd 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 b
ack to 143KTAS not the 156KTAS the Skyview was displaying. The plots on my C
AS chart shows that as my airspeed increases, IAS and CAS spread apart with I
AS 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 si
gnificantly higher IAS used by the Skyview it would display a higher TAS tha
n actual matching what I was seeing.
>
> Talking with the engineers at DYNON, they told me that in a =9Cwell d
esigned=9D system the difference between IAS and CAS should not be mor
e 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 h
igher than CAS meant that either the pitot tube is in an area of =9Chi
gher=9D pressure or the static source is in an area of =9Clower
=9D pressure. If the pitot is in an area of =9Chigher=9D pres
sure the error would only be in airspeed. But if the static source is in an a
rea of =9Clower=9D pressure, altitude indications will show me f
lying at a higher altitude than I really am. This is a potentially deadly si
tuation when flying real IMC, which I do.
>
> To isolate if the error was in the pitot or static, I flew to different ai
rports with ILS approaches over the next few months. I found that when at th
e FAF on the glideslope of each airport, the Skyview displayed a consistent 1
00-110=99 higher than what the approach plate showed. In order to conf
irm what I found, I did several high speed passes, over different airports, t
rying to stay about 10=99 above the runway. At each airport the Skyvie
w displayed a consistent 100-110=99 higher than what the runway really
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 ob
tained from the test flights was consistent with the static source being in a
n area where pressure drops as airspeed increases. So I needed to correct th
e static source placement.
>
> The dual static source I have was installed by Rich Trickel back in 2008 a
nd I really didn=99t want to change where they were located. So in ord
er to correct for a possible changing static pressure situation I experiment
ed by placing a piece of Gorilla tape just behind each static port hole and d
oing the flight checks again. With one piece of tape, the FAF and high speed
runway checks altitude error dropped to about 40=99. 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 effec
tively doubling the thickness behind the static port hole. The next series o
f 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 t
hird piece of tape caused the FAF and high speed runway checks to show the a
ltitude difference was about 40=99 but in the opposite direction. Now t
he TAS error was back to about 10Kts, also in the opposite direction than be
fore. Armed with this information, I went back to using two pieces of Gorill
a tape just behind the static source hole.
>
> During the next flights the FAF and high speed runway checks showed the al
titude 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 groundspe
eds, calculated that my TAS was within a few knots of what the Skyview was d
isplaying. During my final test flight (October 21, 2013) I found that norma
l approach speed (90Kts) and normal cruise (143Kts) speeds were within 2Kts o
f calculated. I also found that as I approached to land, the wind aloft disp
lay matched very closely to what the tower was reporting. Now I know what I h
ave to do to correct my static source position error. I can complete the wor
k by making a piece of aluminum the thickness of two pieces of Gorilla tape a
nd permanently attach it just behind to the static source hole.
>
> So, if your EFIS show an airspeed higher than what the =9Cbook
=9D shows your 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 pos
sibly serious situation and now completely trust my Skyview is displaying co
rrect information.
>
>
> href="http://www.matronics.com/Navigator?KIS-List">http://www.matronics.
com/Navigator?KIS-List
> href="http://forums.matronics.com">http://forums.matronics.com
> href="http://www.matronics.com/contribution">http://www.matronics.com/c
> No virus found in this message.
> Checked by AVG - www.avg.com
>
>
>
==========================
=========
==========================
=========
==========================
=========
==========================
=========
>
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Subject: | Re: TAS Error with my new EFIS |
My pitot tube is on the outer side of the left wing, 12" below the wing.
The two static ports are on each side of the fuselage, just behind the rear
passenger seats 12" above the wing.
On Tuesday, October 22, 2013, Scott Stearns wrote:
> Where are your pitot and static ports?
>
> Scott
>
>
> On Oct 22, 2013, at 5:51 AM, "Michael Orth" <mosurf@xplornet.com<javascri
pt:_e({}, 'cvml', 'mosurf@xplornet.com');>>
> wrote:
>
> Galin,
> Great information.
> Good write-up.
> Thanks,
> Michael
> ------------------------------
> ------------------------------
> *From:* Galin Hernandez
> *Sent:* Monday, October 21, 2013 11:03 PM
> *To:* kis-list@matronics.com
> *Subject:* KIS-List: 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 n
ot
> 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 n
ot
> have a method of factoring in a CAS, it uses IAS for the calculations. Wi
th
> the significantly higher IAS used by the Skyview it would display a highe
r
> TAS than actual matching what I was seeing.
>
>
> Talking with the engineers at DYNON, they told me that in a =93well
> designed=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 wit
h
> either the pitot or static source position. Having IAS significantly high
er
> 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 t
he
> pitot is in an area of =93higher=94 pressure the error would only be in
> airspeed. But if the static source is in an area of =93lower=94 pressure,
> altitude indications will show me flying at a higher altitude than I r
>
> *
>
> ========================
> //www.matronics.com/Navigator?KIS-List
> ========================
===========cs.com
> ========================
===========matronics.com/contribution
> ========================
> *
>
> *
>
===========
===========
===========
===========
> *
>
>
Message 5
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Subject: | Re: TAS Error with my new EFIS |
10/22/2013
Hello KIS Listers, As mentioned earlier attached are copies of pictures
of the two static ports on the forward fuselage sides of my KIS TR-1.
One port has a home made wedge to create an increased static pressure at
the static port, 100_602. The other one, 100_599 does not.
The wedge has the effect of the airspeed indicator seeing a slightly
increased static air stream pressure which results in a slower airspeed
indication on the airspeed indicator needle as balanced against the
dynamic air stream pressure coming from the pitot tube into the airspeed
indicator.
This slight change in static airstream pressure causes me to speed up a
bit to see a specific airspeed indication number on the instrument.
This wedge ' no wedge combination on the two static ports gives me the
airspeed and altitude information that I want to see in the cockpit.
OC
Message 6
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Subject: | Re: TAS Error with my new EFIS |
OC, you have the exact same port I do and your "wedge" looks very similar
to what the tape looks like right down to the approximate height.
:)
On Tuesday, October 22, 2013, Owen Baker wrote:
> *10/22/2013*
> **
> *Hello KIS Listers, As mentioned earlier attached are copies of pictures
> of the two static ports on the forward fuselage sides of my KIS TR-1.*
> **
> *One port has a home made wedge to create an increased static pressure
> at the static port, 100_602. The other one, 100_599 does not.*
> **
> *The wedge has the effect of the airspeed indicator seeing a slightly
> increased static air stream pressure which results in a slower airspeed
> indication on the airspeed indicator needle as balanced against the dynam
ic
> air stream pressure coming from the pitot tube into the airspeed indicato
r.
> *
> **
> *This slight change in static airstream pressure causes me to speed up a
> bit to see a specific airspeed indication number on the instrument.*
> **
> *This wedge ' no wedge combination on the two static ports gives me th
e
> airspeed and altitude information that I want to see in the cockpit.*
> **
> *OC*
>
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