X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 29 Jun 2011 13:14:44 -0400 Message-ID: X-Original-Return-Path: Received: from [69.84.129.240] (HELO asp.reflexion.net) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTPS id 5037152 for lml@lancaironline.net; Wed, 29 Jun 2011 11:54:01 -0400 Received-SPF: none receiver=logan.com; client-ip=69.84.129.240; envelope-from=cberland@systems3.net Received: (qmail 4729 invoked from network); 29 Jun 2011 15:53:12 -0000 Received: from unknown (HELO mail-cs-03.app.dca.reflexion.local) (10.81.19.3) by 0 (rfx-qmail) with SMTP; 29 Jun 2011 15:53:12 -0000 Received: by mail-cs-03.app.dca.reflexion.local (Reflexion email security v6.50.3) with SMTP; Wed, 29 Jun 2011 11:53:12 -0400 (EDT) Received: (qmail 22433 invoked from network); 29 Jun 2011 15:53:12 -0000 Received: from unknown (HELO remote.systems3.net) (98.172.79.178) by 0 (rfx-qmail) with (AES128-SHA encrypted) SMTP; 29 Jun 2011 15:53:12 -0000 Received: from S3SBS08SERVER.Systems3.local ([fe80::6077:364b:fa39:c71b]) by S3SBS08SERVER.Systems3.local ([fe80::6077:364b:fa39:c71b%10]) with mapi; Wed, 29 Jun 2011 08:53:10 -0700 From: Craig Berland. X-Original-To: Lancair Mailing List X-Original-Date: Wed, 29 Jun 2011 08:53:07 -0700 Subject: [LML] Airplane needs to be "fixed," Stall Speeds, Wing Cuffs, Vortex ... Thread-Topic: [LML] Airplane needs to be "fixed," Stall Speeds, Wing Cuffs, Vortex ... Thread-Index: Acw2cOHN3Br3cnkoSySveY+pb4ckyAAAYM0Q X-Original-Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_D7A6B5700A0803448C27264F1F5387364E90C761D9S3SBS08SERVER_" MIME-Version: 1.0 --_000_D7A6B5700A0803448C27264F1F5387364E90C761D9S3SBS08SERVER_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Scott, Excellent post. Just a few months ago I experienced a 30 kt wind shear at = 600 AGl going into John Wayne in Santa Ana, CA. Due to the turbulence and = "on shore" wind I was quite fast on final and obviously didn't stall howeve= r the three passengers were quite shaken. In this situation, I'm not aware= of any instrumentation available to GA aircraft that would have helped. J= ohn Wayne ATIS was shortly thereafter modified to warn pilots of the wind s= hear near the end of the runway. Craig Berland Terrence, It doesn't always take the pilot to pull the wing beyond the critical AOA -= The air is not always smooth as in a stable fluid body - turbulence, wind = shear, slow flight over different heat radiating bodies in the summer (gree= n fields vs black dirt), crosswinds that tumble over trees on a strip carve= d out of the woods or over nearby hangars, etc. The margin above the stall= AOA may disappear in a slow highly banked turn or even on a straight in if= the air is not compliant regardless of the trim. I have been impressed with our 200-300 series reflexed laminar flow wing - = have you noticed a slow down (loss of laminar flow) in turbulence? Is that = just drag or is lift also affected? Does the critical AOA change if the la= minar flow is disturbed? Is this more important when the wing is already a= t a high AOA when slow and is no longer in reflex (flaps partially deployed= )? Note that if the speed changes, the trim is no longer correct. I believe that the 300 series Lancairs are unstable at low speed high AOA b= ecause the margin may be too narrow. It may not be the pilot unintentional= ly pulling past the critical AOA, but an abrupt change in the airflow that = causes the angle to be exceeded. Even though the AOA was calibrated in cle= an air, the calculated margin speed above stall by formula (1.15 x stall) m= ay not be enough for these high performance wings. Scott Krueger --_000_D7A6B5700A0803448C27264F1F5387364E90C761D9S3SBS08SERVER_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Scott,

 =

Excellent post.  Just a f= ew months ago I experienced a 30 kt wind shear at 600 AGl going into John W= ayne in Santa Ana, CA.  Due to the turbulence and “on shore̶= 1; wind I was quite fast on final and obviously didn’t stall however = the three passengers were quite shaken.  In this situation, I’m = not aware of any instrumentation available to GA aircraft that would have h= elped.  John Wayne ATIS was shortly thereafter modified to warn pilots= of the wind shear near the end of the runway.

 

Craig Berland

 = ;

Terrence,<= /p>

 

It doesn't always take the pilot to pull the wing= beyond the critical AOA - The air is not always smooth as in a stable= fluid body - turbulence, wind shear, slow flight over different heat radia= ting bodies in the summer (green fields vs black dirt), crosswinds tha= t tumble over trees on a strip carved out of the woods or ov= er nearby hangars, etc.  The margin above the stall AOA may disap= pear in a slow highly banked turn or even on a straight in if the air is no= t compliant regardless of the trim.  

=

 

I have been impressed with our 200-300 series reflexed lam= inar flow wing - have you noticed a slow down (loss of laminar flow) i= n turbulence? Is that just drag or is lift also affected?  Does t= he critical AOA change if the laminar flow is disturbed?  Is this more= important when the wing is already at a high AOA when slow and is no longe= r in reflex (flaps partially deployed)?  Note that if the speed change= s, the trim is no longer correct.

 

I believe that the 300 series Lancairs are unstable at low speed h= igh AOA because the margin may be too narrow.  It may not be the pilot= unintentionally pulling past the critical AOA, but an abrupt change in the= airflow that causes the angle to be exceeded.  Even though the AOA wa= s calibrated in clean air, the calculated margin speed above stall by formu= la (1.15 x stall) may not be enough for these high performance wi= ngs.

 

Scott Krueger

 

= --_000_D7A6B5700A0803448C27264F1F5387364E90C761D9S3SBS08SERVER_--