X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 09 May 2014 07:57:13 -0400 Message-ID: X-Original-Return-Path: Received: from argon.lunarpages.com ([216.97.227.30] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTPS id 6863344 for lml@lancaironline.net; Thu, 08 May 2014 00:30:19 -0400 Received-SPF: pass receiver=logan.com; client-ip=216.97.227.30; envelope-from=thorn@starflight.aero Received: from 71-218-221-246.hlrn.qwest.net ([71.218.221.246]:50261 helo=VAlien2) by argon.lunarpages.com with esmtpa (Exim 4.82) (envelope-from ) id 1WiFxl-0005LV-Uh for lml@lancaironline.net; Wed, 07 May 2014 21:29:42 -0700 From: "Valin & Allyson Thorn" X-Original-To: X-Original-Cc: "Valin & Allyson Thorn" Subject: Re: Legacy White Paper X-Original-Date: Wed, 7 May 2014 22:29:35 -0600 X-Original-Message-ID: <012201cf6a76$1ecb5140$5c61f3c0$@starflight.aero> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0123_01CF6A43.D433EE80" X-Mailer: Microsoft Outlook 15.0 Thread-Index: Ac9qc8cNP+sgRE66Qdubc9Ygtc4RVg== Content-Language: en-us X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - argon.lunarpages.com X-AntiAbuse: Original Domain - lancaironline.net X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - starflight.aero X-Get-Message-Sender-Via: argon.lunarpages.com: authenticated_id: thorn@starflight.aero This is a multipart message in MIME format. ------=_NextPart_000_0123_01CF6A43.D433EE80 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit I know there's some fatigue with this discussion topic... I'd like to make some final comments, though, regarding the criticisms of the Legacy Canopy Safety Issue Paper. My concern with leaving the dissenting opinions unchallenged, or it not being clear why the issue paper handles it the way it does, is that some Legacy builders and pilots will see the debate as cause to disregard the information in the issue paper and risk becoming our next unwilling test pilot of a Legacy with the canopy unlatched -- and possibly another easily preventable fatal accident. I appreciate all the feedback on the paper. The paper as released is much improved from the first and second drafts given the excellent feedback, contributions received from various writers, and additional time to ponder the issue. I sincerely believe that diversity of opinion is very healthy in debating any issue and looking for the best path forward. In this paper, various views including dissenting opinions received in response to the drafts are included in the "Commentary & Advice from the Community" section. I was surprised after two drafts being sent to the entire LML for review, and updates incorporated, that some with interest in the subject waited until the papers release to read it and comment. The key concerns raised are that (1) some see the paper as declaring the Legacy's design is flawed and (2) there has not been a comprehensive engineering study to clearly establish the root cause of the severe attitude control issues most pilots experienced when flying with their Legacy's canopy unlatched. First on the question of a Legacy design flaw... We're all sensitive to the reputation of our airplane model. It reflects on our own judgment in deciding to build, purchase, and fly that airplane, the view of the public towards the airplane, the market value of the airplane, the reputation of the designers, the willingness of family and friends to fly with us, and our own emotional relationship with the airplane. Nowhere in this paper is it stated that any potential flying misbehavior of the Legacy with the canopy unlatched is a design flaw. Most airplanes are not designed to fly with their doors and/or canopies open -- though, many light aircraft can. Those that cannot have "Operating Limitations" established to that effect. I do not consider it a design flaw if, without the canopy latched, the Legacy's stability and control can be seriously affected. It is another Operating Limitation of which every airplane has many. Now onto the root cause... I don't think there is anyone who wouldn't like to achieve clarity on this question. The problem is we're operating under cost, schedule, and risk constraints. Cost. The work on the canopy issue paper was funded by the volunteer time of all the contributors. I'm currently working with one of our NASA commercial partners on a lifting body spacecraft (Dream Chaser) where we're in the middle of Computational Fluid Dynamics (CFD) analyses and extensive wind tunnel (WT) testing across the entire Mach regime in at least five different wind tunnels. Now the Legacy is far simpler and operates in a much smaller Mach regime than the Dream Chaser - but, I can assure you from my unique insight into these costs that CFD and WT testing on this problem will run well into the millions. So without some very generous benefactor, that's just not going to happen. I considered doing some CFD work on it myself. Though I'm no CFD specialist, six months ago I did some 2D CFD work on a flap modification on our Legacy and it was fairly involved even as simple as it was. And this is a 3D problem requiring more complex and very accurate full airplane definition and modeling of a free-flying unlatched canopy -- a challenging CFD analysis problem. Then, when it's all said and done, CFD isn't good for modeling separated, chaotic air flow. That's one reason why we're still keeping so many wind tunnels busy. On the wind tunnel testing side, building wind tunnel models with all the necessary instrumentation and wind tunnel facility time is not cheap. Jack Addison has identified the lowest cost approach along these lines, in an LML post that just came in, where we'd recruit a Masters or PhD student to adopt this as their research project and find an abandoned Legacy kit to rig up and test in the full scale WT at Ames. This is an excellent idea though it will still incur considerable expense and take a couple of years to implement at best. Schedule. The flight history has shown, no matter what the root cause is, that this issue presents risks not present in flying most light aircraft. Is anyone surprised? Look at the difference between a door popping open on a Cessna 172 vs. the large canopy spanning the entire overhead of the cockpit of a Legacy. Every day of delay communicating to the community the options available to mitigate these risks increases the probability of another unlatched canopy accident. Risks. The lowest cost, fastest, and highest confidence results would be achieved by conducting flight tests of the Legacy with the canopy unlatched. This is, however, the highest risk approach. Since according to accident and surviving pilot reports, the control difficulty appears to present itself at high angles of attack -- exploring the weight and c.g. envelope in this regime with the canopy unlatched would incur significant risks of stall and spin. The test Legacy would require a specially rigged canopy or mechanism that allowed it to free fly about its hinge and be retracted in flight before landing. To help manage these flight test risks the airplane should also be rigged with a spin chute. Of course, let's not forget the DAS (Data Acquisition System). Since some critics are very skeptical of pilot reports, we'd need to instrument the airplane with sensors, resolvers and pressure transducers to measure flight conditions, control surface positions, etc. (back to cost challenges) for rigorous engineering assessment of "hard data" and not unreliable subjective human feedback (okay, I'm being sarcastic here...). In the human spaceflight business we are usually fretting because we have little or no flight history and pile on tons of analysis and ground testing to work our flight risks down. It's somewhat ironic for me that in this situation we have real flight history with little analysis and test data. I'm perplexed, though, that the surviving pilot feedback and accident investigation reports are given such little credibility by some. Yes, they are not professional test pilots, but... Let's say we had a professional test pilot fly the Legacy and he/she said with the canopy unlatched, at 100 kts, and no flaps, they considered the handling qualities to be a 9 on the Cooper-Harper scale. In contrast, an example of our accident pilot reporting is: "Without event, I climbed to pattern altitude, 1000 AGL, and reduced power to prepare for landing. At that time, the canopy assumed a much more open position and started to oscillate up and down (6" to 12" motion) also causing the aircraft to be very difficult control in pitch (at least 6" stick movements where normal is 1" to 2"). I tried to resume the full power climb attitude again as I thought the change of attitude may have caused this, but this only exaggerated the situation. My concerns were the large oscillations of the canopy, my restricted forward visibility, and the violent pitch changes. I continued with the approach and tried to look out the side opening of the canopy to get myself in a position to land on Runway 29 and avoid any other property damage. I kept the airspeed at around 110 knots with significant power to maintain as much control as possible over the oscillations, but only remember trying to minimize them on final when I impacted the ground." Regular pilots may not know what the Cooper- Harper Handling Qualities Scale is. Yes, professional test pilots are more likely to have an engineer's view of the behavior. But why should valuable accident pilot reporting be disregarded...? Useful data does not just come in the form of plots and strip charts or require professional test pilots to interpret for us. So now to summarize. Yes, there is some question as to the root cause. It will be very expensive and risky to pin it down and there is no funding to support it. At the core of most dissenting opinions is the view that the pilots of the accident airplanes, shocked and distracted by the open canopy, noise, and wind, over controlled their airplanes and induced PIOs (Pilot Induced Oscillations). I think the most compelling evidence opposing this view is the flight history of the Lancair 320/360 aircraft. The Legacy's predecessor 320/360s are abundant and have a flight history that extends beyond the Legacy's. Yet, there has not been one single report, not one single report, of any pilot having any difficulty with an unlatched 320/360 canopy in flight. So with that as a benchmark, how likely is it that for some reason, pilots who fly Legacys are so different from 360 pilots, that if taking off with their canopy unlatched they are likely to cause PIOs and crash their airplanes...? This is compelling evidence that the root cause is not a pilot flight technique issue. Even if we did all the expensive analysis and risky flight testing and found that PIOs are the root cause, what do we do with that? Are we going to change the Legacy's design? Are we going to implement a special pilot training program with pilots practicing takeoffs with their canopy unlatched? Maybe only if we had no better options. I'm accustomed to having heated debates on aerospace system design changes to improve safety/reduce risks when the options are complex, expensive, and entail schedule impacts to projects. So I'm surprised to see passionate debate over the Legacy canopy safety issue when the risk mitigation measures are so simple and inexpensive and they control/prevent all the potential root cause(s) of the issues. If we can make sure pilots don't take a Legacy to flight without the canopy latched, then it really becomes only an academic question as to what's causing the control issues when the canopy is unlatched. Valin Thorn Legacy Project Boulder, Colorado USA ------=_NextPart_000_0123_01CF6A43.D433EE80 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

 

I know = there's some fatigue with this discussion topic...  I'd like to make some final = comments, though, regarding the criticisms of the Legacy Canopy Safety = Issue Paper.  My concern = with leaving the dissenting opinions unchallenged, or it not being clear = why the issue paper handles it the way it does, is that some Legacy = builders and pilots will see the debate as cause to disregard the = information in the issue paper and risk becoming our next unwilling test = pilot of a Legacy with the canopy unlatched -- and possibly another = easily preventable fatal accident.

 

I appreciate = all the feedback on the paper.  = The paper as released is much improved from the first and second = drafts given the excellent feedback, contributions received from various = writers, and additional time to ponder the issue.  I sincerely believe that = diversity of opinion is very healthy in debating any issue and looking = for the best path forward.  = In this paper, various views including dissenting opinions = received in response to the drafts are included in the "Commentary = & Advice from the Community" section.  I was surprised after two = drafts being sent to the entire LML for review, and updates = incorporated, that some with interest in the subject waited until the = papers release to read it and comment.

 

The key = concerns raised are that (1) some see the paper as declaring the = Legacy's design is flawed and (2) there has not been a comprehensive = engineering study to clearly establish the root cause of the severe = attitude control issues most pilots experienced when flying with their = Legacy's canopy unlatched.

 

First on the = question of a Legacy design flaw...  We're all sensitive to the = reputation of our airplane model.  = It reflects on our own judgment in deciding to build, purchase, = and fly that airplane, the view of the public towards the airplane, the = market value of the airplane, the reputation of the designers, the = willingness of family and friends to fly with us, and our own emotional = relationship with the airplane.  = Nowhere in this paper is it stated that any potential flying = misbehavior of the Legacy with the canopy unlatched is a design = flaw.  Most airplanes are = not designed to fly with their doors and/or canopies open -- though, = many light aircraft can.  = Those that cannot have "Operating Limitations" = established to that effect.  = I do not consider it a design flaw if, without the canopy = latched, the Legacy's stability and control can be seriously = affected.  It is another = Operating Limitation of which every airplane has = many.

 

Now onto the = root cause...  I don't = think there is anyone who wouldn't like to achieve clarity on this = question.  The problem is = we're operating under cost, schedule, and risk = constraints.

 

Cost.  The work on the canopy issue = paper was funded by the volunteer time of all the contributors.  I'm currently working with one = of our NASA commercial partners on a lifting body spacecraft (Dream = Chaser) where we're in the middle of Computational Fluid Dynamics (CFD) = analyses and extensive wind tunnel (WT) testing across the entire Mach = regime in at least five different wind tunnels.  Now the Legacy is far simpler = and operates in a much smaller Mach regime than the Dream Chaser - but, = I can assure you from my unique insight into these costs that CFD and WT = testing on this problem will run well into the millions.  So without some very generous = benefactor, that's just not going to happen.  I considered doing some CFD = work on it myself.  Though = I'm no CFD specialist, six months ago I did some 2D CFD work on a flap = modification on our Legacy and it was fairly involved even as simple as = it was.  And this is a 3D = problem requiring more complex and very accurate full airplane = definition and modeling of a free-flying unlatched canopy -- a = challenging CFD analysis problem.  = Then, when it's all said and done, CFD isn't good for modeling = separated, chaotic air flow.  = That's one reason why we're still keeping so many wind tunnels = busy.  On the wind tunnel = testing side, building wind tunnel models with all the necessary = instrumentation and wind tunnel facility time is not cheap.  Jack Addison has identified the = lowest cost approach along these lines, in an LML post that just came = in, where we'd recruit a Masters or PhD student to adopt this as their = research project and find an abandoned Legacy kit to rig up and test in = the full scale WT at Ames.  = This is an excellent idea though it will still incur considerable = expense and take a couple of years to implement at = best.

 

Schedule.  The flight history has shown, = no matter what the root cause is, that this issue presents risks not = present in flying most light aircraft.  Is anyone surprised?  Look at the difference between = a door popping open on a Cessna 172 vs. the large canopy spanning the = entire overhead of the cockpit of a Legacy.  Every day of delay = communicating to the community the options available to mitigate these = risks increases the probability of another unlatched canopy = accident.

 

Risks.  The lowest cost, fastest, and = highest confidence results would be achieved by conducting flight tests = of the Legacy with the canopy unlatched.  This is, however, the highest = risk approach.  Since = according to accident and surviving pilot reports, the control = difficulty appears to present itself at high angles of attack -- = exploring the weight and c.g. envelope in this regime with the canopy = unlatched would incur significant risks of stall and spin.  The test Legacy would require a = specially rigged canopy or mechanism that allowed it to free fly about = its hinge and be retracted in flight before landing.  To help manage these flight = test risks the airplane should also be rigged with a  spin chute.  Of course, let's not forget the = DAS (Data Acquisition System).  = Since some critics are very skeptical of pilot reports, we'd need = to instrument the airplane with sensors, resolvers and pressure = transducers to measure flight conditions, control surface positions, = etc. (back to cost challenges) for rigorous engineering assessment of = "hard data" and not unreliable subjective human feedback = (okay, I'm being sarcastic here...).

 

In the human = spaceflight business we are usually fretting because we have little or = no flight history and pile on tons of analysis and ground testing to = work our flight risks down. It's somewhat ironic for me that in this = situation we have real flight history with little analysis and test = data.  I'm perplexed, = though, that the surviving pilot feedback and accident investigation = reports are given such little credibility by some.  Yes, they are not professional = test pilots, but...  Let's = say we had a professional test pilot fly the Legacy and he/she said with = the canopy unlatched, at 100 kts, and no flaps, they considered the = handling qualities to be a 9 on the Cooper-Harper scale.  In contrast, an example of our = accident pilot reporting is:

 

"Without event, = I climbed to pattern altitude, 1000 AGL, and reduced power to prepare = for landing.  At that time, = the canopy assumed a much more open position and started to oscillate up = and down (6" to 12" motion) also causing the aircraft to be = very difficult control in pitch (at least 6" stick movements where = normal is 1" to 2").  = I tried to resume the full power climb attitude again as I = thought the change of attitude may have caused this, but this only = exaggerated the situation.  = My concerns were the large oscillations of the canopy, my = restricted forward visibility, and the violent pitch changes.  I continued with the approach = and tried to look out the side opening of the canopy to get myself in a = position to land on Runway 29 and avoid any other property damage.  I kept the airspeed at around = 110 knots with significant power to maintain as much control as possible = over the oscillations, but only remember trying to minimize them on = final when I impacted the ground."

 

Regular = pilots may not know what the Cooper- Harper Handling Qualities Scale = is.  Yes, professional test = pilots are more likely to have an engineer’s view of the = behavior.  But why should = valuable accident pilot reporting be disregarded...?  Useful data does not just come = in the form of plots and strip charts or require professional test = pilots to interpret for us.

 

So now to = summarize…  Yes, = there is some question as to the root cause.  It will be very expensive and = risky to pin it down and there is no funding to support = it.

 

At the core = of most dissenting opinions is the view that the pilots of the accident = airplanes, shocked and distracted by the open canopy, noise, and wind, = over controlled their airplanes and induced PIOs (Pilot Induced = Oscillations).  I think the = most compelling evidence opposing this view is the flight history of the = Lancair 320/360 aircraft.  = The Legacy's predecessor 320/360s are abundant and have a flight = history that extends beyond the Legacy's.  Yet, there has not been one = single report, not one single report, of any pilot having any difficulty = with an unlatched 320/360 canopy in flight.  So with that as a benchmark, = how likely is it that for some reason, pilots who fly Legacys are so = different from 360 pilots, that if taking off with their canopy = unlatched they are likely to cause PIOs and crash their = airplanes...?  This is = compelling evidence that the root cause is not a pilot flight technique = issue.

 

Even if we = did all the expensive analysis and risky flight testing and found that = PIOs are the root cause, what do we do with that?  Are we going to change the = Legacy's design?  Are we = going to implement a special pilot training program with pilots = practicing takeoffs with their canopy unlatched?  Maybe only if we had no better = options.

 

I'm = accustomed to having heated debates on aerospace system design changes = to improve safety/reduce risks when the options are complex, expensive, = and entail schedule impacts to projects.  So I'm surprised to see = passionate debate over the Legacy canopy safety issue when the risk = mitigation measures are so simple and inexpensive and they = control/prevent all the potential root cause(s) of the issues.  If we can make sure pilots = don't take a Legacy to flight without the canopy latched, then it really = becomes only an academic question as to what's causing the control = issues when the canopy is unlatched.

 

Valin = Thorn

Legacy = Project

Boulder, = Colorado USA

 

 

 

 

 

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