X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 20 Jan 2006 23:40:22 -0500 Message-ID: X-Original-Return-Path: Received: from web61320.mail.yahoo.com ([209.73.179.74] verified) by logan.com (CommuniGate Pro SMTP 5.0.6) with SMTP id 934265 for lml@lancaironline.net; Fri, 20 Jan 2006 10:42:37 -0500 Received-SPF: none receiver=logan.com; client-ip=209.73.179.74; envelope-from=charliekohler@yahoo.com Received: (qmail 92973 invoked by uid 60001); 20 Jan 2006 15:37:17 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:Date:From:Reply-To:Subject:To:MIME-Version:Content-Type; b=3JTDqEcY+hVYG7N+Iz9IFj8jr3yt1buUqUAsbTAjIUyaoxU/7qFXHUAzpXXWLTaLGyoxoUQSpeOq7JyTv4ul8UPq3zy8ldUckEYSc8itbrUw45h9qch0BqBDaj4c/VzxsXraUTpvm7nGsx4hlgXaHS9MPDlwd+82+jaJiESFqaM= ; X-Original-Message-ID: <20060120153717.92971.qmail@web61320.mail.yahoo.com> X-Original-Date: Fri, 20 Jan 2006 07:37:17 -0800 (PST) From: Charlie Kohler Reply-To: Charlie Kohler Subject: Winglets versus Wingtips X-Original-To: LancairList MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-541244539-1137771437=:91450" --0-541244539-1137771437=:91450 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable The results of the winglet versus wingtip tests are in. The tests were con= ducted with an airplane that has winglets installed and we made the IAS ver= sus altitude tests with the same manifold pressure-rpm and exactly the same= TIT. And then we landed and replaced the winglets with standard wingtips = and did the same tests. In a nutshell, we all knew the winglets have more drag than the wingtips.= If you were still laboring under the idea that they somehow added to the = speed at any altitude, you are misguided. A designer at Gulfstream once to= ld me that if we were cruising at .55 Mach or greater, they could be an ass= et with detailed engineering and wind tunnel tests. Otherwise they are a p= retty, but unnecessary, drag producing device. The genesis of the winglets = is around the venting (overboard spilling) of fuel because of a bad fuel se= lector valve while parked on a sloping ramp. The winglets objective was to = get the vent higher than the wing fuel level. They succeeded in doing that= . The fuel valve has since been fixed and we hardly ever hear of a overboar= d venting of fuel --except in fast turns onto the runway with full fuel tan= ks. And they are incorporating check valves in the vents to prevent that. Here are the results of my test. All numbers indicate a slower indicated = airspeed for the winglet airplane at constant and equal power settings, at = the various altitudes and repeated using the standard wingtips. Sea level =3D12 kn =20 5000 feet =3D11 kn=20 10,000 feet =3D9 kn=20 15,000 feet =3D7 1/2 kn 20,000 feet =3D5 kn 22,000 feet =3D4 kn. The surprise in these tests (to me) was that the highly touted benefit that= the winglets cause a reduction in deck angle at altitude, and therefore re= duced drag, was false. I found that at the lower altitudes the deck angle = was higher (averaging 1=C2=B0) with the winglets. At 22,000 feet they were= roughly the same. Therefore the added area just helped to offset the reduc= ed angle-of-attack. After thinking about it I attributed it to the washout= of the wing and that on the wingtip the angle-of-attack is a low-er theref= ore an increased angle-of-attack is needed to provide the lift. Am I think= ing correctly? Any and all comments to add light on the subject are appreciated. =20 Charlie K. --0-541244539-1137771437=:91450 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable

The results of the winglet versus wingtip tests are in. = ; The tests were conducted with an airplane that has winglets installed and= we made the IAS versus altitude tests with the same manifold pressure-rpm = and exactly the same TIT. And then we landed and replaced the winglet= s with standard wingtips and did the same tests.

In a nutshel= l, we all knew the winglets have more drag than the wingtips. If you = were still laboring under the idea that they somehow added to the speed at = any altitude, you are misguided. A designer at Gulfstream once told m= e that if we were cruising at .55 Mach or greater, they could be an asset w= ith detailed engineering and wind tunnel tests. Otherwise they are a = pretty, but unnecessary, drag producing device. The genesis of the winglets= is around the venting (overboard spilling) of fuel because of a bad fuel s= elector valve while parked on a sloping ramp. The winglets objective was to= get the vent higher than the wing fuel level. They succeeded in doin= g that. The fuel valve has since been fixed and we hardly ever hear of a ov= erboard venting of fuel --except in fast turns onto the runway with full fu= el tanks. And they are incorporating check valves in the vents to prevent t= hat.

Here are the results of my test. All numbers indicate a = slower indicated airspeed for the winglet airplane at constant and equal po= wer settings, at the various altitudes and repeated using the standard wing= tips.
Sea level =3D12 kn =
5000 feet =3D11 kn
10,000 feet =3D9 kn
15,000 feet =3D7 1/2 kn=
20,000 feet =3D5 kn
22,000 feet =3D4 kn.

The surprise in thes= e tests (to me) was that the highly touted benefit that the winglets cause = a reduction in deck angle at altitude, and therefore reduced drag, was fals= e. I found that at the lower altitudes the deck angle was higher (ave= raging 1=C2=B0) with the winglets. At 22,000 feet they were roughly t= he same. Therefore the added area just helped to offset the reduced angle-o= f-attack. After thinking about it I attributed it to the washout of t= he wing and that on the wingtip the angle-of-attack is a low-er therefore a= n increased angle-of-attack is needed to provide the lift. Am I think= ing correctly?

Any and all comments to add light on the subject are = appreciated.

Charlie K.

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