The Murphy Builders Site

Do not take for granted that by using the GPS you can calibrate the ASI (instrument, pitot and static) , the GPS is very accurate in providing Ground speed values but it can not give wind speed and direction . What keeps us in the air is not the ground speed but the Air Speed and you always have few knots of wind that give you a different reading between the GPS and the ASI . The best is to choose a calm day to make the comparison with the GPS .

Francesco Simioni
Rebel 562






Legeorgen@aol.com
Sent by: <murphy-rebel@dcsol.com>
12/10/2002 03.39
Please respond to murphy-rebel

To: murphy-rebel@dcsol.com
cc:
Fax to:
Subject: Re: Static Port Location


Hi Terry,

Yea, I played around with the washer thing too but never got it to read right. An alternate source for static is a good idea, even if it's just being able reach under the dash and disconnect it and go with the "cabin" static air. Flying an unfamiliar plane, for the first time, without an accurate or even working speed indicator is not fun!

I will check my port tomorrow and see if it's open as well, but I'm guessing it is and just is not doing its job. Right now, with cabin static air, my indicated speed is 6-8 MPH high according to my GPS. I'll keep you informed.

Bruce 357R

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You're right, Francesco - but, since there's almost always some
wind, the best way is to fly along a highway (or just take a
heading), and fly it for a few minutes, then turn 180 degrees,
and fly back. If you average the GPS readings, you should be
pretty close ....

.....bobp

-------------------------------orig.--------------------------------------
At 10:38 PM 10/12/02 +0200, you wrote:

Do not take for granted that by using the GPS you can calibrate the ASI
(instrument, pitot and static) , the GPS is very accurate in providing
Ground speed values but it can not give wind speed and direction . What
keeps us in the air is not the ground speed but the Air Speed and you
always have few knots of wind that give you a different reading between
the GPS and the ASI . The best is to choose a calm day to make the
comparison with the GPS .

Francesco Simioni
Rebel 562








Legeorgen@aol.com
Sent by: <murphy-rebel@dcsol.com>
12/10/2002 03.39
Please respond to murphy-rebel


To: murphy-rebel@dcsol.com
cc:
Fax to:
Subject: Re: Static Port Location


Hi Terry,

Yea, I played around with the washer thing too but never got it to read
right. An alternate source for static is a good idea, even if it's just
being able reach under the dash and disconnect it and go with the "cabin"
static air. Flying an unfamiliar plane, for the first time, without an
accurate or even working speed indicator is not fun!

I will check my port tomorrow and see if it's open as well, but I'm
guessing it is and just is not doing its job. Right now, with cabin static
air, my indicated speed is 6-8 MPH high according to my GPS. I'll keep you
informed.

Bruce 357R


<br><font size=2 face="sans-serif">Do not take for granted that by using

the GPS you can calibrate the ASI (instrument, &nbsp;pitot and static) ,
&nbsp;the GPS is very accurate in providing Ground speed values but it can
not give wind speed and direction . What keeps us in the air is not the
ground speed but the Air Speed and you always have few knots of wind that
give you a different reading between the GPS and the ASI . The best is to
choose a &nbsp;calm day to make the comparison with the GPS .</font>

<br>
<br><font size=2 face="sans-serif">Francesco Simioni</font>
<br><font size=2 face="sans-serif">Rebel 562 <br>
<br>
<br>
<br>
</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td>
<td><font size=1 face="sans-serif"><b>Legeorgen@aol.com</b></font>
<br><font size=1 face="sans-serif">Sent by:

<murphy-rebel@dcsol.com></font>

<p><font size=1 face="sans-serif">12/10/2002 03.39</font>
<br><font size=1 face="sans-serif">Please respond to murphy-rebel</font>
<br>
<td><font size=1 face="Arial">&nbsp; &nbsp; &nbsp; &nbsp; </font>
<br><font size=1 face="sans-serif">&nbsp; &nbsp; &nbsp; &nbsp; To: &nbsp;

&nbsp; &nbsp; &nbsp;murphy-rebel@dcsol.com</font>

<br><font size=1 face="sans-serif">&nbsp; &nbsp; &nbsp; &nbsp; cc: &nbsp;

&nbsp; &nbsp; &nbsp;</font>

<br><font size=1 face="sans-serif">&nbsp; &nbsp; &nbsp; &nbsp; Fax to:

&nbsp; &nbsp; &nbsp; &nbsp;</font>

<br><font size=1 face="sans-serif">&nbsp; &nbsp; &nbsp; &nbsp; Subject:

&nbsp; &nbsp; &nbsp; &nbsp;Re: Static Port Location</font></table>

<br>
<br>
<br><font size=2>Hi Terry,</font>
<br>
<br><font size=2>Yea, I played around with the washer thing too but never

got it to read right. An alternate source for static is a good idea, even if
it's just being able reach under the dash and disconnect it and go with the
"cabin" static air. Flying an unfamiliar plane, for the first
time, without an accurate or even working speed indicator is not fun! </font>

<br>
<br><font size=2>I will check my port tomorrow and see if it's open as

well, but I'm guessing it is and just is not doing its job. Right now, with
cabin static air, my indicated speed is 6-8 MPH high according to my GPS.
I'll keep you informed.</font>

<br>
<br><font size=2>Bruce 357R</font>
<br>
<br>

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Hi Francesco,

You are correct about wind affecting your GPS indicated ground speeds. You can with a little effort, even on a windy day, determine your actual ground speed with your GPS by flying a 360 degree pattern of two or more equal legs and averaging the GPS speeds to negate any wind variables. I just left out all those details. But I do appreciate your input. We should not take anything for granted and I know you where only interested in my well being. I just wanted you to know I was on top of it.

Bruce 357R

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