X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 05 Jan 2013 11:19:58 -0500 Message-ID: X-Original-Return-Path: Received: from [198.64.152.110] (HELO sdc.com) by logan.com (CommuniGate Pro SMTP 6.0.1) with ESMTP id 5996172 for lml@lancaironline.net; Sat, 05 Jan 2013 00:32:39 -0500 Received-SPF: pass receiver=logan.com; client-ip=198.64.152.110; envelope-from=ronald@sdc.com Received: from RONALD.local [12.164.46.51] by sdc.com with ESMTP (SMTPD-12.2.0.235) id 55640001caec61c7; Sat, 5 Jan 2013 00:28:51 -0500 X-Original-Message-ID: <50E7BAD7.3070506@sdc.com> X-Original-Date: Sat, 05 Jan 2013 00:32:07 -0500 From: Ronald Stevens User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 X-Original-To: Lancair Mailing List Subject: Re: [LML] Re: stalls References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------070102010605000708030908" This is a multi-part message in MIME format. --------------070102010605000708030908 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit I love your comments about the stalls in a IV-p, but with help of Matthew Collier's (Fibercraft) wing cuffs you would be surprised how different the IV-p flies. I was also very scared of even going close to a stall, but the cuffs definitely helps here. As a matter of fact my finals are usually around 90kts. And even at this speed the plane still feels very stable. My plane stalls at 70 but you can feel the buffet already coming 3kts earlier. The cufs (like on a cirrus/columbia) does wonderful things to increase the safety on the IV-p. And the speed difference, well I cruise 250kts, 18gph @17500ft, 1/2 tanks. (and my plane is heavy, I got the BRS parachute, full feather prop, AMSafe seatbelts, RDD De-ice etc etc) Now for sure there are guys out there that cruises faster on the same fuel flow, but I always wonder if those 10-15kts faster is worth leaving safety behind? I choose for fast and safer (I call my plane a cirrus on steroids lol) But coming back to how it flies, if someone wants to see how it performes, than see me in Spruce Creek (7FL6) and I take you up there and show you :) == Ronald, IVp (n45HL) >200hours , 1600hours total On 1/3/13 3:08 PM, Ralph Love wrote: > Great comments. Would you say the same thing about a Legacy? > Ralph Love > Pink Legacy > > On Jan 3, 2013, at 7:16 AM, Frederick Moreno > > wrote: > >> 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 >> stall. So why must Lancairs be stalled? >> 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 and a joy to fly (they are!)." >> Much wisdom there. >> I feel compelled to add a bit of technical content to the >> discussion. The 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. 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. >> 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. >> Most airplanes (SNJ's for sure, they are trainers), most aerobatic >> aircraft 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 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 benign and forgiving >> behavior each and every time. >> The Lancair IV most definitely was not. It was compromised in the >> direction 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 wing design that yields such low drag and high cruise >> speed coupled with other of the aircraft's characteristics and design >> features. >> 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 center, and then immediate recovery after >> the initial break. All this practice was 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. >> He emphasized that there are airplanes that you just don't stall - >> ever - because they bite. Many swept wing aircraft are in this >> category. On those the stall can progress from root to wing tip very >> rapidly and the airplane 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. >> 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 tenth. Without a spin chute and a personal >> parachute, exploring that territory is definitely test pilot stuff, >> so you better train and equip accordingly. >> 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. >> But deliberately putting the airplane into a deep stall is >> Russian Roulette. Many aircraft are like this. Why go there? >> Fred Moreno >> >> >> --------------070102010605000708030908 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit
I love your comments about the stalls in a IV-p, but with help of Matthew Collier's (Fibercraft) wing cuffs you would be surprised how different the IV-p flies.

I was also very scared of even going close to a stall, but the cuffs definitely helps here. As a matter of fact my finals are usually around 90kts. And even at this speed the plane still feels very stable.

My plane stalls at 70 but you can feel the buffet already coming 3kts earlier. The cufs (like on a cirrus/columbia) does wonderful things to increase the safety on the IV-p. And the speed difference, well I cruise 250kts, 18gph @17500ft, 1/2 tanks. (and my plane is heavy, I got  the BRS parachute, full feather prop, AMSafe seatbelts, RDD De-ice etc etc)

Now for sure there are guys out there that cruises faster on the same fuel flow, but I always wonder if those 10-15kts faster is worth leaving safety behind? I choose for fast and safer (I call my plane a cirrus on steroids lol)

But coming back to how it flies, if someone wants to see how it performes, than see me in Spruce Creek (7FL6) and I take you up there and show you :)

== Ronald, IVp (n45HL) >200hours , 1600hours total   

On 1/3/13 3:08 PM, Ralph Love wrote:
Great comments. Would you say the same thing about a Legacy?
Ralph Love
Pink Legacy

On Jan 3, 2013, at 7:16 AM, Frederick Moreno <frederickmoreno@bigpond.com> wrote:

 
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 stall.  So why must Lancairs be stalled?
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 and a joy to fly (they are!)." 
 
Much wisdom there.
 
I feel compelled to add a bit of technical content to the discussion.  The 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.  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. 
 
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.
 
Most airplanes (SNJ's for sure, they are trainers), most aerobatic aircraft 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 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 benign and forgiving behavior each and every time.
 
The Lancair IV most definitely was not. It was compromised in the direction 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 wing design that yields such low drag and high cruise speed coupled with other of the aircraft's characteristics and design features.
 
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 center, and then immediate recovery after the initial break.  All this practice was 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.
 
He emphasized that there are airplanes that you just don't stall - ever -  because they bite.  Many swept wing aircraft are in this category.  On those the stall can progress from root to wing tip very rapidly and the airplane 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.
 
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  tenth.  Without a spin chute and a personal parachute, exploring that territory is definitely test pilot stuff, so you  better train and equip accordingly.
 
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. 
 
But deliberately putting the airplane into a deep stall is Russian Roulette.  Many aircraft are like this.  Why go there?
 
Fred Moreno



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