X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 18 Aug 2014 08:16:37 -0400 Message-ID: X-Original-Return-Path: Received: from nm34.bullet.mail.ne1.yahoo.com ([98.138.229.27] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTPS id 7101068 for lml@lancaironline.net; Sun, 17 Aug 2014 20:37:02 -0400 Received-SPF: pass receiver=logan.com; client-ip=98.138.229.27; envelope-from=n103md@yahoo.com Received: from [127.0.0.1] by nm34.bullet.mail.ne1.yahoo.com with NNFMP; 18 Aug 2014 00:36:26 -0000 Received: from [98.138.100.117] by nm34.bullet.mail.ne1.yahoo.com with NNFMP; 18 Aug 2014 00:33:35 -0000 Received: from [66.196.81.171] by tm108.bullet.mail.ne1.yahoo.com with NNFMP; 18 Aug 2014 00:33:35 -0000 Received: from [98.139.212.197] by tm17.bullet.mail.bf1.yahoo.com with NNFMP; 18 Aug 2014 00:33:35 -0000 Received: from [127.0.0.1] by omp1006.mail.bf1.yahoo.com with NNFMP; 18 Aug 2014 00:33:35 -0000 X-Yahoo-Newman-Property: ymail-4 X-Yahoo-Newman-Id: 123737.69112.bm@omp1006.mail.bf1.yahoo.com Received: (qmail 49871 invoked by uid 60001); 18 Aug 2014 00:33:35 -0000 X-YMail-OSG: 89nvp44VM1nWaPlek43hWsOZcheFFxG_TQIe2EDQY40Av8Q kCWy9XrATzEZ0K7qRzlGBj64xXf0YsKcZStGdyuPbisEECSE_2M..jAQfQBE tireq_g7.TYDFdKbTPxSPIqi4XvhWEBj3e5vIvhD68QKUsd3tp18YQFzTE4j mkHW1A.y8FtyqcWV1NQht4oERoJJIAjQ6ihdndTLarrP5z69wd0ijHncvAUN c92TnKEs4eXRVdcLfyCIAm1gPNKWb72g0RfcYytQa7qJa2.sUUUFQKUEZ3bG qLScTOZzGUEFttJCuIYrMMA541F5p1DP5SIktYtBqLRzVLYzieg_aQShoQKw DqI_smSoknTwB3CPCxpKckJ01LadP3Gv8s87SANr71TOwsD0vz2xGSDuaMIF 43f0H.wq6B2LkdG67ULgt54OHns2P6sRlyMPvSpkOpOXk9IFkH.LN8Mn_EVm amKetcrzQghFviZy639fddFHmF4jcNqmurtyd7WTu6UNZFaPBfChOsQ1jSEj V2YxFKB6Q.pELvgUKkeYSIpQN8pdXp1QZuJSfWmfbdNx4NIMU8HpF.0fRA59 R Received: from [192.147.44.15] by web161001.mail.bf1.yahoo.com via HTTP; Sun, 17 Aug 2014 17:33:34 PDT X-Rocket-MIMEInfo: 002.001,PiAuLi5idXQgYSBmb3VyIGRpcmVjdGlvbiBzcGVlZCB0ZXN0IHNob3dzIHRoYXQgbXkgYWlyc3BlZWQgaXMgd2l0aGluIG9uZSBrbm90IG9mIHRoZSBncHMuCgpUaGlzIGlzIGEgY29tbW9uIG1pc2NvbmNlcHRpb24uIEFpcnNwZWVkIHRlc3RzIGRvIG5vdCBzaG93IHRoYXQgdGhlIHN0YXRpYyBwb3J0IGlzIGZyZWUgb2YgZXJyb3IuIEl0IG9ubHkgc2hvd3MgdGhhdCB0aGUgc3RhdGljIHBvcnQgYW5kIHBpdG90IHBvcnQgaGF2ZSB0aGUgc2FtZSBwcmVzc3VyZSBlcnJvcnMgYXQgdGhlIHRlc3RlZCBhaXJzcGUBMAEBAQE- X-Mailer: YahooMailWebService/0.8.201.700 X-Original-Message-ID: <1408322014.20697.YahooMailNeo@web161001.mail.bf1.yahoo.com> X-Original-Date: Sun, 17 Aug 2014 17:33:34 -0700 From: bob mackey Reply-To: bob mackey Subject: Re: [LML] L360 static ports X-Original-To: "lml@lancaironline.net" MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-1453216575-916407231-1408322014=:20697" ---1453216575-916407231-1408322014=:20697 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable > ...but a four direction speed test shows that my airspeed is within one k= not of the gps.=0A=0AThis is a common misconception. Airspeed tests do not = show that the static port is free of error. It only shows that the static p= ort and pitot port have the same pressure errors at the tested airspeed. = =0A=0A=0ATo test static port accuracy, you need to fly different airspeeds = at the same known altitude and check for any variation. =0A=0AI used the ho= rizontal roofline of the tower at my local airport as the altitude referenc= e and flew successive laps of the landing pattern at speeds ranging from 60= kias to 200 kias. The faster I flew, the higher the indicated altitude (+3= 00' at 200 kias initially). The errors were parabolic (depending on the squ= are of the speed) as expected. Based on that information, I was able to rep= osition the static port until the altitude error was reduced to about 30 fe= et over the usual speed range.=A0=0A=0AI am using a Piper style combined pi= tot-static blade on the bottom of the wing. The adjustment that I made was = to remachine the end of the blade to a different angle to make it more forw= ard-facing. =0A=0A=0AAfter the static port is calibrated, THEN check the pi= tot pressure by comparison of ASI with GPS speed. =0A=0A=A0=0A=0Abob mackey= =0A ---1453216575-916407231-1408322014=:20697 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
> ...but a four direction speed test shows that my= airspeed is within one knot of the gps.

This is a common misconception. Airspeed tests do not show that the s= tatic port is free of error. It only shows that the static port and pitot port have the = same pressure errors at the tested airspeed.

T= o test static port accuracy, you need to fly different airspeeds at the sam= e known altitude and check for any variation.
I used the horizontal roofline of the tower at my lo= cal airport as the altitude reference and flew successive laps of the landi= ng pattern at speeds ranging from 60 kias to 200 kias. The faster I flew, t= he higher the indicated altitude (+300' at 200 kias initially). The errors = were parabolic (depending on the square of the speed) as expected. Based on= that information, I was able to reposition the static port until the altitude e= rror was reduced to about 30 feet over the usual speed range. 

I am using a Piper style combined pitot-static bl= ade on the bottom of the wing. The adjustment that I made was to remachine = the end of the blade to a different angle to make it more forward-facing. <= br>

After the static port is calibrated, THEN check= the pitot pressure by comparison of ASI with GPS speed.
 
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bob mackey
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