X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 26 Feb 2014 07:23:32 -0500 Message-ID: X-Original-Return-Path: Received: from ndjsnpf02.ndc.nasa.gov ([198.117.1.122] verified) by logan.com (CommuniGate Pro SMTP 6.0.8) with ESMTP id 6749415 for lml@lancaironline.net; Tue, 25 Feb 2014 16:30:26 -0500 Received-SPF: pass receiver=logan.com; client-ip=198.117.1.122; envelope-from=valin.b.thorn@nasa.gov Received: from ndmsppt103.ndc.nasa.gov (ndmsppt103.ndc.nasa.gov [198.117.0.68]) by ndjsnpf02.ndc.nasa.gov (Postfix) with ESMTP id E3B57A8079 for ; Tue, 25 Feb 2014 15:29:50 -0600 (CST) Received: from NDMSCHT115.ndc.nasa.gov (ndmscht115-pub.ndc.nasa.gov [198.117.0.215]) by ndmsppt103.ndc.nasa.gov (8.14.5/8.14.5) with ESMTP id s1PLTo25009519 for ; Tue, 25 Feb 2014 15:29:50 -0600 Received: from NDMSMBX402.ndc.nasa.gov ([169.254.2.103]) by NDMSCHT115.ndc.nasa.gov ([198.117.0.215]) with mapi id 14.03.0174.001; Tue, 25 Feb 2014 15:29:50 -0600 From: "Thorn, Valin B. (JSC-VA411)" X-Original-To: Lancair Mailing List X-Original-CC: "Thorn, Valin B. (JSC-VA411)" Subject: RE: [LML] Legacy Accident History Update Thread-Topic: [LML] Legacy Accident History Update Thread-Index: AQHPMkexreJZXrFp506uUeo/gAJaXJrGRDkw X-Original-Date: Tue, 25 Feb 2014 21:29:50 +0000 X-Original-Message-ID: <0705A91F9164914998F23A2F0BB661A90F44DC@NDMSMBX402.ndc.nasa.gov> References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [66.35.41.1] Content-Type: multipart/alternative; boundary="_000_0705A91F9164914998F23A2F0BB661A90F44DCNDMSMBX402ndcnasa_" MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.11.87,1.0.14,0.0.0000 definitions=2014-02-25_07:2014-02-25,2014-02-25,1970-01-01 signatures=0 --_000_0705A91F9164914998F23A2F0BB661A90F44DCNDMSMBX402ndcnasa_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable I think the trap that gets set is that the canopy can sit down in its close= d position without being latched. The friction of the canopy against the c= anopy seal keeps the canopy closed while rolling down the runway at low AOA= . Then once the airplane is rotated for liftoff and the flow field changes= with the higher AOA, the canopy is pulled open. So setting up high speed = taxi tests that would include rotating for takeoff would be risky. I expect when the canopy opens that it changes the horizontal stabilizer's = AOA in proportion to how much it is open. I think higher airplane AOAs and= higher beta/side slip angles increase how far the canopy opens. In the Ge= raldton, Australia accident, witnesses report the canopy being open as much= as 30 degrees while the plane was turning at low speed - probably from hig= h AOA and the side slip - ball wasn't in the middle. So the dynamics of th= e canopy changing how far it is open as the AOA and beta change and thus ch= anging the air flow over the tail effects the airplane's pitch attitude, ca= n create an ever changing stability and control challenge for any pilot. T= hat's what was reported by the surviving Longmont, Colorado pilot's open ca= nopy crash landing. I expect the temptation of a pilot reacting to the canopy being open in fli= ght is to slow down thinking that it might allow them to get the canopy dow= n and latched. The slower speed, though, just means a higher AOA and a wid= er open canopy with more pitch instability. I suspect that flying faster m= ight improve the pitch instability. From these bits of evidence and conjecture, I think anyone finding themselv= es in an open canopy situation should fly straight ahead and climb to sever= al thousand feet above the ground before experimenting with turns and confi= guration changes and figuring out what is most stable. Once a stable landi= ng configuration for flaps, airspeed, and power setting is determined, the = airplane approach and landing should be flown with minimal changes to that = configuration, small bank angle turns, minimum power changes, etc. Yes, I wouldn't recommend anyone deliberately flight test this. But, if so= meone finds themselves in this situation, if they can get to altitude and f= igure out how best to configure for best stability on approach and landing= with the canopy open, that would be very helpful... Valin From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Denn= is Johnson Sent: Tuesday, February 25, 2014 9:36 AM To: lml@lancaironline.net Subject: [LML] Legacy Accident History Update Regarding concerns about taking off with an open canopy in the Legacy, Mark= Summers, a new Legacy pilot, has asked me to post a message here advising = that there is a discussion about open canopy problems in the Vans RV-12 at = this link: https://groups.yahoo.com/neo/groups/Vans_RV-12/conversations/messages/7 Personally, I remain a little skeptical about this perceived problem. On o= ne hand, I can't imagine aerodynamic forces that would cause the canopy to = open more than a few inches and have second hand knowledge of a Legacy open= canopy on takeoff that exhibited no problems. On the other hand, there ha= ve been fatal accidents following an open canopy on takeoff, which cannot b= e ignored. It would be nice if someone could offer a plausible explanation of forces t= hat could open a Legacy canopy more than a few inches. Even better if som= eone did high speed taxi tests with the canopy unlatched, with a video came= ra on a chase car recording the results. But I'm not volunteering! Best, Dennis Legacy, 680 hours --_000_0705A91F9164914998F23A2F0BB661A90F44DCNDMSMBX402ndcnasa_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

 <= /span>

I think the trap t= hat gets set is that the canopy can sit down in its closed position without= being latched.  The friction of the canopy against the canopy seal keeps the canopy closed while rolling down the runway at low A= OA.  Then once the airplane is rotated for liftoff and the flow field = changes with the higher AOA, the canopy is pulled open.  So setting up= high speed taxi tests that would include rotating for takeoff would be risky.

 <= /span>

I expect when the = canopy opens that it changes the horizontal stabilizer’s AOA in propo= rtion to how much it is open.  I think higher airplane AOAs and higher beta/side slip angles increase how far the canopy opens.  In t= he Geraldton, Australia accident, witnesses report the canopy being open as= much as 30 degrees while the plane was turning at low speed – probab= ly from high AOA and the side slip – ball wasn’t in the middle.  So the dynamics of the canopy changing how far it is = open as the AOA and beta change and thus changing the air flow over the tai= l effects the airplane’s pitch attitude, can create an ever changing = stability and control challenge for any pilot.  That’s what was reported by the surviving Longmont, Colorado pilot&#= 8217;s open canopy crash landing. 

 <= /span>

I expect the tempt= ation of a pilot reacting to the canopy being open in flight is to slow dow= n thinking that it might allow them to get the canopy down and latched.  The slower speed, though, just means a higher AOA and a= wider open canopy with more pitch instability.  I suspect that flying= faster might improve the pitch instability. 

 <= /span>

From these bits of= evidence and conjecture, I think anyone finding themselves in an open cano= py situation should fly straight ahead and climb to several thousand feet above the ground before experimenting with turns and configu= ration changes and figuring out what is most stable.  Once a stable la= nding configuration for flaps, airspeed, and power setting is determined, t= he airplane approach and landing should be flown with minimal changes to that configuration, small bank angle turn= s, minimum power changes, etc. 

 <= /span>

Yes, I wouldn̵= 7;t recommend anyone deliberately flight test this.  But, if someone f= inds themselves in this situation, if they can get to altitude and figure out  how best to configure for best stability on approach and = landing with the canopy open, that would be very helpful…<= /span>

 <= /span>

Valin

 <= /span>

 <= /p>

 <= /span>

From: Lancair = Mailing List [mailto:lml@lancaironline.net] On Behalf Of Dennis Johnson
Sent: Tuesday, February 25, 2014 9:36 AM
To: lml@lancaironline.net
Subject: [LML] Legacy Accident History Update

 

Regarding concerns about taking off with an open can= opy in the Legacy, Mark Summers, a new Legacy pilot, has asked me to post a= message here advising that there is a discussion about open canopy problem= s in the Vans RV-12 at this link:

 

 

Personally, I remain a little skeptical about this p= erceived problem.  On one hand, I can't imagine aerodynamic forces tha= t would cause the canopy to open more than a few inches and have second han= d knowledge of a Legacy open canopy on takeoff that exhibited no problems.  On the other hand, there have be= en fatal accidents following an open canopy on takeoff, which cannot be ign= ored. 

 

It would be nice if someone could offer a plausible = explanation of forces that could open a Legacy canopy more than a few inche= s.   Even better if someone did high speed taxi tests with the ca= nopy unlatched, with a video camera on a chase car recording the results.  But I'm not volunteering!

 

Best,

Dennis

Legacy, 680 hours 

 

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