X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 05 Jun 2007 09:13:33 -0400 Message-ID: X-Original-Return-Path: Received: from imo-d04.mx.aol.com ([205.188.157.36] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with ESMTP id 2084633 for lml@lancaironline.net; Tue, 05 Jun 2007 03:38:20 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.157.36; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-d04.mx.aol.com (mail_out_v38_r9.2.) id q.bde.148e5fc9 (32915) for ; Tue, 5 Jun 2007 03:37:33 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Tue, 5 Jun 2007 03:37:33 EDT Subject: Re: [LML] Re: trailing static / pitot bomb ? X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1181029053" X-Mailer: 9.0 Security Edition for Windows sub 5365 X-Spam-Flag: NO -------------------------------1181029053 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 6/5/2007 12:25:09 A.M. Central Daylight Time, n103md@yahoo.com writes: My aircraft is fitted with a heated Piper blade pitot+static probe under the left wing. The pressure at the port decreases with airspeed, causing an altitude error that varies with speed. As others have noted, this is worth fixing. Most of us have had no problem with the standard static port locations below and behind the aft window, but then I don't know anyone who has actually tested their system to see if it is accurate. Even the CAFE tests did not calibrate the static system, but rather the pitot-static difference. Bob, I didn't like my answer when I saw my reply in the LML echo in that it didn't respond your actual question. This reply won't answer it well either, but I do have experience with trying to make a heated Piper blade work. It doesn't. I then tried using an enormous L-shaped heated pitot/static (it had static ports on the top and bottom of the foot long pitot. It didn't work either. I currently utilize a standard sized L-shaped heated pitot and have located the static ports on both fuselage sides at the Lancair recommended position. The pitot tubes have always been mounted on the aileron bell crank access door to avoid any possible influence from the prop. My indicated true airspeed is within one knot of GPS derived airspeeds over a broad speed range and the altitude reasonably matches certificated aircraft flown on my wing at different altitudes. It is good to know that I am flying with the same altitude indications as the spam can fleet that fills the skies around my airport. Another way to test altimeter readings might be to fly horizontally parallel to the tops of known tall towers close to barometric pressure reporting stations to see if speed has any effect on static pressures (even if the speed is inaccurately reported because of static problems). One more method could be to fly an ILS glide slope and note the altitude crossing the FA fix (as accurately reported by a GPS) with the needle centered to see if it matches the published altitude. Of course, one must remember that even certified instrumentation has quite an error allowance and use of the static/transponder test data, recorded in the aircraft log, can provide useful correction data. Scott Krueger AKA Grayhawk Lancair N92EX IO320 SB 89/96 Aurora, IL (KARR) Darwinian culling phrase: Watch This! ************************************** See what's free at http://www.aol.com. -------------------------------1181029053 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 6/5/2007 12:25:09 A.M. Central Daylight Time,=20 n103md@yahoo.com writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>My=20 aircraft is fitted with a heated Piper blade pitot+static probe
under t= he=20 left wing. The pressure at the port decreases with airspeed,
causing an= =20 altitude error that varies with speed. As others have
noted, this is wo= rth=20 fixing. Most of us have had no problem with the
standard static port=20 locations below and behind the aft window, but then
I don't know anyone= who=20 has actually tested their system to see if it
is accurate. Even the CAF= E=20 tests did not calibrate the static system,
but rather the pitot-static=20 difference.
Bob,
 
I didn't like my answer when I saw my reply in the LML echo i= n=20 that it didn't respond your actual question.  This reply won't ans= wer=20 it well either, but I do have experience with trying to make a heated P= iper=20 blade work.  It doesn't.  I then tried using an enormous L-shaped=20 heated pitot/static  (it had static ports on the top and bottom of the=20= foot=20 long pitot.  It didn't work either.  I currently utilize a standar= d=20 sized L-shaped heated pitot and have located the static ports on both=20 fuselage sides at the Lancair recommended position.  The pitot tub= es=20 have always been mounted on the aileron bell crank access door to avoid any=20 possible influence from the prop.
 
My indicated true airspeed is within one knot of GPS derived airsp= eeds=20 over a broad speed range and the altitude reasonably matches certificat= ed=20 aircraft flown on my wing at different altitudes.  It is good to know t= hat=20 I am flying with the same altitude indications as the spam can fleet th= at=20 fills the skies around my airport.
 
Another way to test altimeter readings might be to fly horizontall= y=20 parallel to the tops of known tall towers close to barometric=20 pressure reporting stations to see if speed has any effect on static=20 pressures (even if the speed is inaccurately reported because of static=20 problems).  One more method could be to fly an ILS glide slope and note= the=20 altitude crossing the FA fix (as accurately reported by a GPS) wit= h=20 the needle centered to see if it matches the published altitude.
 
Of course, one must remember that even certified instrumentation has qu= ite=20 an error allowance and use of the static/transponder test data, recorded in=20= the=20 aircraft log, can provide useful correction data.
 
Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL=20 (KARR)

Darwinian culling phrase: Watch=20 This!



See what's fr= ee at AOL.com.=
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