X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Sat, 26 Aug 2006 15:19:58 -0400 Message-ID: X-Original-Return-Path: Received: from sccrmhc11.comcast.net ([63.240.77.81] verified) by logan.com (CommuniGate Pro SMTP 5.1c.3) with ESMTP id 1350005 for lml@lancaironline.net; Sat, 26 Aug 2006 14:43:48 -0400 Received-SPF: none receiver=logan.com; client-ip=63.240.77.81; envelope-from=mjrav@comcast.net Received: from mark1 (c-65-96-139-16.hsd1.ma.comcast.net[65.96.139.16]) by comcast.net (sccrmhc11) with SMTP id <20060826184304011008871oe>; Sat, 26 Aug 2006 18:43:04 +0000 X-Original-Message-ID: <005701c6c940$e47f3670$108b6041@mark1> From: "Mark Ravinski" X-Original-To: "Lancair Mailing List" Subject: Fw: Small-Tail LNC2 Stability X-Original-Date: Sat, 26 Aug 2006 14:53:17 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0054_01C6C91F.5D45C320" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1807 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1807 This is a multi-part message in MIME format. ------=_NextPart_000_0054_01C6C91F.5D45C320 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: George kalman=20 To: lml@lancaironline.net=20 Sent: Monday, August 21, 2006 6:58 PM Subject: Small-Tail LNC2 Stability To Small-Tail Lancair Flyers, Stability issues relative to the small-tail LNC2 have been debated for = years. My small- tail LNC2 exhibits an unstable flying mode that I have = not seen discussed. The purpose for submitting this informtation to lml = is two fold (1) solicit input from other small-tail LNC2 flyers whether = similar instability has been experienced and (2) provide a heads-up to = small-tail LNC2 flyers that this potential for instability exists. Instability Description: In the right cross-wind landing configuration = (right wing down, left rudder), the nose begins to oscillate up and = down. The oscillations increase in magnitude with or without pilot = control input. In 3 or 4 cycles the oscillations become uncomfortable = during flight tests at altitude and the uncontrolable oscillations are a = serious hazard during an actual landing approach. The problem does not = exist in a left cross-wind configuration. The problem appears to be caused by a loss of horizontal stabilzer = effectiveness as the air flow corkscrews around the fuselage. When the = horizontal stabilizer becomes ineffective, the nose drops. When the = nose drops, the airflow to the horizontal stabilizer becomes more = effective and the nose rises. The oscillations stop when the right wing = down and opposite rudder control inputs are neutralized. In the right = cross-wind configuration, elevator control inputs have no effected on = the oscillations. =20 The pilot can work around this stablilty problem once he knows that it = exists by (1) avoiding the right cross wind, (2) using the crab landing = technique. If the pilot is not aware of this problem, the natural = response is to assume that the oscillations are pilot induced and = attempt to dampen them prior to touch down. This pilot response will = likely test the ultimate structural integrity of the landing gear. I am sure small-tail LNC2 flyers have attempted many right cross-wind = landings and I have not seen problems with oscillations discussed. = Perhaps the problem is the result of some quirk in my construction. = Although the oscillations are so predictable and so pronounced, it is = hard to imagine that my airplane is so different from everyone elses. = The following is a description of some characteristics of my small-tail = Lancair 360.: * Kit number 383 * 180 hp Lycoming ) 360 A!AD engine, converted to fuel injection * Electronic fuel injection on one set of spark plugs * Hartzel 68 inch, standard Lancair prop * Perfomance -- Cruise speed 207 kts -- Clean stall 68 kts -- full flap stall 62 kts =20 I only recently became aware of the lml web site and it appears like an = appropriate place to pass on this type problem. I have not addressed = this matter with Lancair. They always seem defensive rather than = proactive in dealing with flight problems and after I drove my right = landing gear through the right wing on my first right cross-wind landing = attempt five years ago, the FAA had me take remedial landing lessons = with a certified flight instructor. That did not seem to fix the = problem. So this is my way of getting the word out to folks who may = really care. =20 George Kalman 509 372-6213 (W) 509 628-2461 (H) -------------------------------------------------------------------------= ------- Get your email and more, right on the new Yahoo.com ------=_NextPart_000_0054_01C6C91F.5D45C320 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----=20
From: George=20 kalman
Sent: Monday, August 21, 2006 6:58 PM
Subject: Small-Tail LNC2 Stability

To Small-Tail Lancair Flyers,
Stability issues relative to the small-tail LNC2 have been debated = for=20 years.  My small- tail LNC2 exhibits an unstable flying mode that I = have=20 not seen discussed.  The purpose for submitting this informtation = to lml is=20 two fold (1) solicit input from other small-tail LNC2 flyers whether = similar=20 instability has been experienced and (2) provide a heads-up to = small-tail LNC2=20 flyers that this potential for instability exists.
 
Instability Description:  In the right cross-wind landing=20 configuration (right wing down, left rudder), the nose begins to = oscillate up=20 and down.  The oscillations increase in magnitude with or without = pilot=20 control input.  In 3 or 4 cycles the oscillations become =20 uncomfortable during flight tests at altitude and the uncontrolable = oscillations are a serious hazard during an actual landing = approach.  The=20 problem does not exist in a left cross-wind configuration.
 
The problem appears to be caused by a loss of horizontal stabilzer=20 effectiveness as the air flow corkscrews around the fuselage.  When = the=20 horizontal stabilizer becomes ineffective, the nose drops.  When = the nose=20 drops, the airflow to the horizontal stabilizer becomes more effective = and the=20 nose rises.  The oscillations stop when the right wing down and = opposite=20 rudder control inputs are neutralized.   In the right = cross-wind=20 configuration, elevator control inputs have no effected on the=20 oscillations.   
 
The pilot can work around this stablilty problem once he knows that = it=20 exists by (1) avoiding the right cross wind, (2) using the crab landing=20 technique. If the pilot is not aware of this problem, the natural = response is to=20 assume that the oscillations are pilot induced and attempt to dampen = them prior=20 to touch down.  This pilot response will likely test the ultimate=20 structural integrity of the landing gear.
 
I am sure small-tail LNC2 flyers have attempted many right = cross-wind=20 landings and I have not seen problems with oscillations discussed.  = Perhaps=20 the problem is the result of some quirk in my construction.  = Although the=20 oscillations are so predictable and so pronounced, it is hard to imagine = that my=20 airplane is so different from everyone elses.  The following = is a=20 description of some characteristics of my small-tail Lancair 360.:
*  Kit number 383
*  180 hp Lycoming ) 360 A!AD engine, converted to fuel=20 injection
*  Electronic fuel injection on one set of spark plugs
*  Hartzel 68 inch, standard Lancair prop
*  Perfomance
    -- Cruise speed 207 kts
    -- Clean stall 68 kts
    --  full flap stall 62 kts
    
I only recently became aware of the lml web site and it appears = like an=20 appropriate place to pass on this type problem.  I have = not=20 addressed this matter with Lancair.  They always seem=20 defensive rather than proactive  in dealing with = flight problems=20 and after I drove my right landing gear through the right wing on = my first=20 right cross-wind landing attempt five years ago, the FAA had me take = remedial=20 landing lessons with a certified flight instructor.  That did not = seem=20 to fix the problem. So this is my way of getting the word out = to folks=20 who may really care.   
 
George Kalman
509 372-6213 (W)
509 628-2461 (H)

Get your email and more, right on the new=20 Yahoo.com ------=_NextPart_000_0054_01C6C91F.5D45C320--