X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 20 Aug 2012 18:44:42 -0400 Message-ID: X-Original-Return-Path: Received: from imr-ma05.mx.aol.com ([64.12.100.31] verified) by logan.com (CommuniGate Pro SMTP 6.0c1) with ESMTP id 5720606 for lml@lancaironline.net; Mon, 20 Aug 2012 16:38:02 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.100.31; envelope-from=Sky2high@aol.com Received: from mtaomg-ma01.r1000.mx.aol.com (mtaomg-ma01.r1000.mx.aol.com [172.29.41.8]) by imr-ma05.mx.aol.com (8.14.1/8.14.1) with ESMTP id q7KKbHaD020659 for ; Mon, 20 Aug 2012 16:37:17 -0400 Received: from core-mtd003a.r1000.mail.aol.com (core-mtd003.r1000.mail.aol.com [172.29.235.201]) by mtaomg-ma01.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id DB049E000088 for ; Mon, 20 Aug 2012 16:37:16 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <2412e.294c7284.3d63f9fc@aol.com> X-Original-Date: Mon, 20 Aug 2012 16:37:16 -0400 (EDT) Subject: Re: [LML] Re: Question about TAS Error (and Winds Calculation) based on OAT (... X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_2412e.294c7284.3d63f9fc_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [67.175.156.123] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:461058368:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d290850329ffc1edf --part1_2412e.294c7284.3d63f9fc_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Tim, Arrrggghhh! I forgot to mention another static issue for non-pressurized aircraft.............. If a good altimeter can be found, take it on a flight with it just sitting on the seat with the same baro setting and note the altitude differences at cruise speed and slow flight. In my wee Lancair, at 185 KIAS cruise, my cabin is 300 feet higher than the panel indicated altitude and that goes to only about 50-100 feet at around 100 KIAS. The cabin altitude is reduced slightly when air vents are opened. Go ahead, give it a try - just another reason to go flying and learn more.... Grayhawk In a message dated 8/20/2012 1:03:49 P.M. Central Daylight Time, Tim@myrv10.com writes: Exactly...and so would be wind display and things that rely on getting an accurate TAS. That's why I actually change ports to get the error low. I don't know that without a lot of work a person can guarantee static port accuracy down to the 0-1kt range, especially when it changes with cruise speed, but I think it's very worthwhile to try to minimize the error. As Grayhawk says, if it is static error, it could mean altitude is off by a long ways too. There are ways to do things like build up little dams in front of or behind the static port, to test what effects you can have and make it read accurately. The first step though would be a good leak test. Once you know the system is tight, and you make sure your OAT probe is accurate and all the puzzle pieces have been inspected, it isn't too big of a problem to just troubleshoot port location error. It does take a few test flights, but this is what I see as our responsibility as homebuilt pilots...to make sure we can match quality and standards to certified levels. What I find is that if you do the diligence on your systems, it will pay in rewards of everything working well and being accurate. Tim On 8/20/2012 7:07 AM, Sky2high@aol.com wrote: > If your static port is off, so is your indicated altitude - by a > lot................. > Grayhawk > In a message dated 8/19/2012 1:19:03 P.M. Central Daylight Time, > Tim@myrv10.com writes: > > Could it be static error...maybe port location, or other? Mine was > off by 8 kts (reading low). A rework of the port to a domed one and > my error is now 2kts low. But, depending on your particular port > issue if any, yours could be reading high. > Tim -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html --part1_2412e.294c7284.3d63f9fc_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Tim,
 
Arrrggghhh!  I forgot to mention another static issue for=20 non-pressurized aircraft..............
 
If a good altimeter can be found, take it on a flight with it jus= t=20 sitting on the seat with the same baro setting and note the altitude= =20 differences at cruise speed and slow flight.  In my wee Lancair, = at=20 185 KIAS cruise, my cabin is 300 feet higher than the panel indicated= =20 altitude and that goes to only about 50-100 feet at around 100 KIAS.&n= bsp;=20 The cabin altitude is reduced slightly when air vents are opened.
 
Go ahead, give it a try - just another reason to go flying and learn= =20 more....
 
Grayhawk
 
In a message dated 8/20/2012 1:03:49 P.M. Central Daylight Time,=20 Tim@myrv10.com writes:
= Exactly...and so would be wind display and things that rely<= BR>on=20 getting an accurate TAS.  That's why I actually change ports
to g= et=20 the error low.  I don't know that without a lot of work
a person = can=20 guarantee static port accuracy down to the 0-1kt
range, especially whe= n it=20 changes with cruise speed, but I
think it's very worthwhile to try to= =20 minimize the error.  As
Grayhawk says, if it is static error, it = could=20 mean altitude
is off by a long ways too.

There are ways to do t= hings=20 like build up little dams in front
of or behind the static port, to te= st=20 what effects you can
have and make it read accurately.  The first= step=20 though
would be a good leak test.  Once you know the system is=20 tight,
and you make sure your OAT probe is accurate and all the=20 puzzle
pieces have been inspected, it isn't too big of a problem tojust=20 troubleshoot port location error. It does take a few test
flights, but= this=20 is what I see as our responsibility as homebuilt
pilots...to make sure= we=20 can match quality and standards to
certified levels.  What I find= is=20 that if you do the
diligence on your systems, it will pay in rewards o= f=20 everything
working well and being accurate.

Tim


On= =20 8/20/2012 7:07 AM, Sky2high@aol.com wrote:
> If your static port is= off,=20 so is your indicated altitude - by a
> lot.................
>= =20 Grayhawk
> In a message dated 8/19/2012 1:19:03 P.M. Central Daylig= ht=20 Time,
> Tim@myrv10.com writes:
>
>     C= ould=20 it be static error...maybe port location, or other?  Mine=20 was
>     off by 8 kts (reading low). A rework of th= e=20 port to a domed one and
>     my error is now 2kts= =20 low.  But, depending on your particular port
>   &nb= sp;=20 issue if any, yours could be reading high.
>    =20 Tim

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For archives and unsub=20 http://mail.lancaironline.net:81/lists/lml/List.html
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