X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 03 Jan 2013 10:16:28 -0500 Message-ID: X-Original-Return-Path: Received: from blu0-omc3-s18.blu0.hotmail.com ([65.55.116.93] verified) by logan.com (CommuniGate Pro SMTP 6.0.1) with ESMTP id 5993086 for lml@lancaironline.net; Thu, 03 Jan 2013 09:41:19 -0500 Received-SPF: neutral receiver=logan.com; client-ip=65.55.116.93; envelope-from=frederickmoreno@bigpond.com Received: from BLU0-SMTP26 ([65.55.116.72]) by blu0-omc3-s18.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675); Thu, 3 Jan 2013 06:40:44 -0800 X-EIP: [9T9nLJLeiKWkZAKAQ5yRVqm497pDPNVU6GuSWzZ+FQ8=] X-Originating-Email: [frederickmoreno@bigpond.com] X-Original-Message-ID: X-Original-Return-Path: frederickmoreno@bigpond.com Received: from Razzle ([121.217.176.199]) by BLU0-SMTP26.blu0.hotmail.com over TLS secured channel with Microsoft SMTPSVC(6.0.3790.4675); Thu, 3 Jan 2013 06:40:42 -0800 MIME-Version: 1.0 X-Original-Date: Thu, 3 Jan 2013 22:40:20 +0800 Content-Type: multipart/alternative; charset="iso-8859-1"; boundary="------------Boundary-00=_8R02MZNCCJD000000000" X-Mailer: IncrediMail (6395248) From: Frederick Moreno References: X-FID: FLAVOR00-NONE-0000-0000-000000000000 X-Priority: 3 X-Original-To: "Lancair Mail (lml@lancaironline.net)" Subject: Re: [LML] Re: stalls X-OriginalArrivalTime: 03 Jan 2013 14:40:43.0522 (UTC) FILETIME=[4F310E20:01CDE9C0] --------------Boundary-00=_8R02MZNCCJD000000000 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable =0D Bob wrote:=0D =0D "Interesting: In all the twins I have flown not once was a stall an appro= ved procedure. Approach to stall sure, but never a full stall. So why must Lancairs be stalled?=0D Seems that the Lancairs are in the twin situation. So learn the feel at = the approach to a stall (I have), us an AoA (I do), and the planes are safe a= nd a joy to fly (they are!)." =0D =0D Much wisdom there.=0D =0D I feel compelled to add a bit of technical content to the discussion. Th= e Lancair IV wing was tailored to maintain laminar flow as far as possible over the top and bottom of the wing. The resulting wing profile has exceptionally low frictional drag, but an unpredictable stall performance= , a common characteristic of wing profiles with long reaches of laminar flow.= =20 Laminar boundary layers are just not very energetic and can separate from the wing in a flash. The flow may separate at the root and stay there (conventional stall), or the separated air flow zone may suddenly spread = all the way to the wing tip in which case a snap roll into a spin will be the result. And the spin may be unrecoverable. =0D =0D The LIV is not certified, and its stall capability along with many other characteristics mean it never could be. It is Experimental. Don't treat= it like a certified or aerobatic airplane. It isn't.=0D =0D Most airplanes (SNJ's for sure, they are trainers), most aerobatic aircra= ft like the Zlin (which have big fat leading edges which are highly stall resistant and relatively forgiving) and certified aircraft are relatively benign in stall. Aerobatic aircraft and many others are guaranteed to be spin recoverable. Virtually all modern certified aircraft) must have win= g designs that are compromised to provide buffet in advance of stall, they quit flying gently (and only slightly) with a straightforward relatively benign stall, and provide normal straightforward recovery. I flew a fri= end s Cirrus and it was even more benign than my old C182. These airplanes w= ere designed and comprehensively tested to assure this benign and forgiving behavior each and every time. =0D =0D The Lancair IV most definitely was not. It was compromised in the directi= on of speed at any cost. And part of that cost is occasionally unpredictabl= e and potentially deadly stall behavior if not carefully and cautiously handled. It is the nature of the laminar flow wing design that yields s= uch low drag and high cruise speed coupled with other of the aircraft's characteristics and design features.=0D =0D I was instructed by a 20,000+ hour Qantas captain who also flew a Lancair= IV and was the Australian national aerobatic champion. This guy really understands unusual flight attitudes and aerodynamics. His instructions = for the LIV practice were approach to stall at 10,000 feet in the landing configuration, an IRONCLAD rule that the ball be kept EXACTLY in the cent= er, and then immediate recovery after the initial break. All this practice w= as done in the landing configuration except for a couple of very cautious approach to stall tests with airplane clean which we did to establish a calibration point for my angle of attack indicator. He was adamant: once that data point is collected, there is no reason to go back there again. = =0D =0D He emphasized that there are airplanes that you just don't stall - ever -= =20 because they bite. Many swept wing aircraft are in this category. On th= ose the stall can progress from root to wing tip very rapidly and the airplan= e then immediately rolls on its back and drops into a spin. On the Lancair= , a deep stall with ball out of center can on occasion enter an unrecoverable spin. Let the ball get far enough out of center and it will almost certainly drop into a spin. =0D =0D In short, he said, there is absolutely NO REASON to put a Lancair IV into= a deep stall. Slow flight practice, fine. Nibble at stall (approach to stall) also fine subject to ball in the middle and 10,000 feet. Get ball out of center and/or hold the stall a bit too long and the outcome maybe fine 9 out of 10 times, but you may get an unrecoverable spin on the ten= th. Without a spin chute and a personal parachute, exploring that territory = is definitely test pilot stuff, so you better train and equip accordingly. = =0D =0D Stay away from everything except the approach to stall with ball centered= , use an angle of attack indicator (should be mandatory in these aircraft), practice some slow flight maneuvers at 10,000 feet, and practice forced landings. =0D =0D But deliberately putting the airplane into a deep stall is Russian Roulet= te. Many aircraft are like this. Why go there?=0D =0D Fred Moreno --------------Boundary-00=_8R02MZNCCJD000000000 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
Bob wrote:
 
"Interesting: In all the twins I have flown not once was a stall an = approved procedure.  Approach to stall sure, but never a full s= tall.  So why must Lancairs be stalled?
Seems that the Lancairs are in the twin situation.  So lea= rn the feel at the approach to a stall (I have), us an AoA (I do), and th= e planes are safe and a joy to fly (they are!)." 
 
Much wisdom there.
 
I feel compelled to add a bit of technical content to the discussion= =2E  The Lancair IV wing was tailored to maintain laminar flow as fa= r as possible over the top and bottom of the wing.  The resulting wi= ng profile has exceptionally low frictional drag, but an unpredictable st= all performance, a common characteristic of wing profiles with long reach= es of laminar flow.  Laminar boundary layers are just not very energ= etic and can separate from the wing in a flash.  The flow may s= eparate at the root and stay there (conventional stall), or the separated= air flow zone may suddenly spread all the way to the wing tip in which c= ase a snap roll into a spin will be the result.  And the spin may be= unrecoverable. 
 
The LIV is not certified, and its stall capability along with many o= ther characteristics mean it never could be.  It is Experimental.&nb= sp; Don't treat it like a certified or aerobatic airplane.  It isn't= =2E
 
Most airplanes (SNJ's for sure, they are trainers), most aeroba= tic aircraft like the Zlin (which have big fat leading edges wh= ich are highly stall resistant and relatively forgiving) and certifi= ed aircraft are relatively benign in stall.  Aerobatic aircraft= and many others are guaranteed to be spin recoverable.  V= irtually all modern certified aircraft) must have wing designs that  = ;are compromised to provide buffet in advance of stall, they quit flying = gently (and only slightly) with a straightforward relatively benign = stall, and provide normal straightforward recovery.   I flew a = friend's Cirrus and it was even more benign than my old C182.  These= airplanes were designed and comprehensively tested to assure this b= enign and forgiving behavior each and every time.
 
The Lancair IV most definitely was not. It was compromised in the di= rection of speed at any cost.  And part of that cost is occasionally= unpredictable and potentially deadly stall behavior if not carefully and= cautiously handled.   It is the nature of the laminar flow win= g design that yields such low drag and high cruise speed coupled with oth= er of the aircraft's characteristics and design features.
 
I was instructed by a 20,000+ hour Qantas captain who also flew a La= ncair IV and was the Australian national aerobatic champion.  This g= uy really understands unusual flight attitudes and aerodynamics.  Hi= s instructions for the LIV practice were approach to stall at 10,000 feet= in the landing configuration, an IRONCLAD rule that the ball be kept&nbs= p;EXACTLY in the center, and then immediate recovery after the initial br= eak.  All this practice was done in the landing configuration except= for a couple of very cautious approach to stall tests with airplane clea= n which we did to establish a calibration point for my angle of attack in= dicator.  He was adamant: once that data point is collected, there i= s no reason to go back there again.
 
He emphasized that there are airplanes that you just don't stal= l - ever -  because they bite.  Many swept wing aircraft are in= this category.  On those the stall can progress from root to wing t= ip very rapidly and the airplane then immediately rol= ls on its back and drops into a spin.  On the Lancair, a d= eep stall with ball out of center can on occasion enter an unre= coverable spin.  Let the ball get far enough out of center and it wi= ll almost certainly drop into a spin.
 
In short, he said, there is absolutely NO REASON to put a Lancair IV= into a deep stall.  Slow flight practice, fine.  Nibble at sta= ll (approach to stall) also fine subject to ball in the middle and 10,000= feet.  Get ball out of center and/or hold the stall a bit too long&= nbsp;and the outcome maybe fine 9 out of 10 times, but you may get a= n unrecoverable spin on the  tenth.  Without a spin chute and a= personal parachute, exploring that territory is definitely test pilot st= uff, so you  better train and equip accordingly.
 
Stay away from everything except the approach to stall wit= h ball centered, use an angle of attack indicator (should be mandatory in= these aircraft), practice some slow flight maneuvers at 10,000 feet, and= practice forced landings. 
 
But deliberately putting the airplane into a deep stall is Russian&n= bsp;Roulette.  Many aircraft are like this.  Why go there?
 
Fred Moreno
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