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Bruce Crain
I changed my mind on applying the Vortex Generators for now in leu of trying the zig zag turbulator tape as Scott Swing offered. I like to approach things slowly and if I can get the zig zag to work it seems that there would be less drag on the sparrow strainers. Will be a few days before they are delivered so stay tuned for data.
Bruce
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Bruce Crain
Not sure they would work on tape very well. Shoulda coulda woulda. I already ordered the tape on line. Thanks Michael!
Bruce
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Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
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|
I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
Matthew Curcio
419-290-3773
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Show quoted text
On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote:
Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
|
|
|
Jay Scheevel
Hi Matthew,
When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
Cheer,
Jay N8WQ
toggle quoted message
Show quoted text
-----Original Message----- From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio Sent: Saturday, December 21, 2019 1:32 PM To: main@q-list.groups.io Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner. I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program. If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree. For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here. Matthew Curcio 419-290-3773 On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote:
Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
|
|
|
Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware. Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things. A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure) Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons.
If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude. Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm. Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes.
That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1” long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure.
If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other. Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes!
Matthew Curcio
419-290-3773
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Show quoted text
On Dec 22, 2019, at 08:55, Jay Scheevel <jay@...> wrote:
Hi Matthew,
When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
Cheer,
Jay N8WQ
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Saturday, December 21, 2019 1:32 PM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
Matthew Curcio
419-290-3773
On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote:
Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
|
|
|
Matthew,
Thank you for your significant contributions to this discussion, they are much appreciated!
David J. Gall
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-----Original Message----- From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio Sent: Saturday, December 21, 2019 12:32 PM To: main@q-list.groups.io Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner. I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program. If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree. For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here. Matthew Curcio 419-290-3773 On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote:
Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
|
|
|
Jay Scheevel
Thanks for the more complete explanation. I have a manual "stick" type of control on my aileron reflexor. It fits into my left hand and feels and manipulates like a second stick (absent roll control obviously). I will have to try to see if I can fly the airplane using that reflexor control for pitch and the actual stick for roll. The sparrow strainers hold the elevator pretty much in trail for most AOA's (in the event that elevator continuity was absent), so I think it may be possible to fly the airplane with reflexor and aileron input only. I will try this out at a safe altitude and let you know.
Cheers,
Jay
toggle quoted message
Show quoted text
-----Original Message----- From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio Sent: Sunday, December 22, 2019 10:46 AM To: main@q-list.groups.io Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware. Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things. A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure) Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons. If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude. Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm. Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes. That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1” long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure. If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other. Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes! Matthew Curcio 419-290-3773 On Dec 22, 2019, at 08:55, Jay Scheevel <jay@...> wrote:
Hi Matthew,
When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
Cheer,
Jay N8WQ
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Saturday, December 21, 2019 1:32 PM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
Matthew Curcio
419-290-3773
On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote:
Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
|
|
|
Jay, I think to evaluate this conservatively you’ll have to disconnect the pitch trim springs since those help to stabilize the system in some ways.
Matthew Curcio
419-290-3773
toggle quoted message
Show quoted text
On Dec 22, 2019, at 10:44, Jay Scheevel <jay@...> wrote:
Thanks for the more complete explanation. I have a manual "stick" type of control on my aileron reflexor. It fits into my left hand and feels and manipulates like a second stick (absent roll control obviously). I will have to try to see if I can fly the airplane using that reflexor control for pitch and the actual stick for roll. The sparrow strainers hold the elevator pretty much in trail for most AOA's (in the event that elevator continuity was absent), so I think it may be possible to fly the airplane with reflexor and aileron input only. I will try this out at a safe altitude and let you know.
Cheers,
Jay
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Sunday, December 22, 2019 10:46 AM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware. Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things. A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure) Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons.
If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude. Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm. Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes.
That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1” long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure.
If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other. Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes!
Matthew Curcio
419-290-3773
On Dec 22, 2019, at 08:55, Jay Scheevel <jay@...> wrote:
Hi Matthew,
When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
Cheer,
Jay N8WQ
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Saturday, December 21, 2019 1:32 PM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
Matthew Curcio
419-290-3773
On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote: Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
|
|
|
Jay Scheevel
I do not have the elevator trim system installed. I have been using my aileron reflexor for pitch trim since I first flew my plane a year ago. The elevator seems fully stabilized without the trim system. I think that the sparrow strainers have a significant damping effect.
Cheers,
Jay
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Show quoted text
-----Original Message----- From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio Sent: Sunday, December 22, 2019 11:57 AM To: main@q-list.groups.io Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers Jay, I think to evaluate this conservatively you’ll have to disconnect the pitch trim springs since those help to stabilize the system in some ways. Matthew Curcio 419-290-3773 On Dec 22, 2019, at 10:44, Jay Scheevel <jay@...> wrote:
Thanks for the more complete explanation. I have a manual "stick" type of control on my aileron reflexor. It fits into my left hand and feels and manipulates like a second stick (absent roll control obviously). I will have to try to see if I can fly the airplane using that reflexor control for pitch and the actual stick for roll. The sparrow strainers hold the elevator pretty much in trail for most AOA's (in the event that elevator continuity was absent), so I think it may be possible to fly the airplane with reflexor and aileron input only. I will try this out at a safe altitude and let you know.
Cheers,
Jay
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Sunday, December 22, 2019 10:46 AM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware. Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things. A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure) Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons.
If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude. Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm. Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes.
That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1” long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure.
If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other. Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes!
Matthew Curcio
419-290-3773
On Dec 22, 2019, at 08:55, Jay Scheevel <jay@...> wrote:
Hi Matthew,
When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
Cheer,
Jay N8WQ
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Saturday, December 21, 2019 1:32 PM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
Matthew Curcio
419-290-3773
On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote: Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
|
|
|
Richard Thomson
Yay Jay, I think we already discussed, I have been beating my 2 brain cells together over the situation that I only have the elevator helper spring fitted (that was in when I bought FN) and trying to work out if I needed the full elevator trim fitted. So your stick rests around neutral in cruise without the trim ?
Thanks for the tips you sent earlier on testing set up for the reflex, I have copied those off to add to my notes.
Best present yet this year, merry Christmas. :-)
Rich.
toggle quoted message
Show quoted text
On 22/12/2019 19:12, Jay Scheevel wrote: I do not have the elevator trim system installed. I have been using my aileron reflexor for pitch trim since I first flew my plane a year ago. The elevator seems fully stabilized without the trim system. I think that the sparrow strainers have a significant damping effect.
Cheers,
Jay
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Sunday, December 22, 2019 11:57 AM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
Jay, I think to evaluate this conservatively you’ll have to disconnect the pitch trim springs since those help to stabilize the system in some ways.
Matthew Curcio
419-290-3773
On Dec 22, 2019, at 10:44, Jay Scheevel <jay@...> wrote:
Thanks for the more complete explanation. I have a manual "stick" type of control on my aileron reflexor. It fits into my left hand and feels and manipulates like a second stick (absent roll control obviously). I will have to try to see if I can fly the airplane using that reflexor control for pitch and the actual stick for roll. The sparrow strainers hold the elevator pretty much in trail for most AOA's (in the event that elevator continuity was absent), so I think it may be possible to fly the airplane with reflexor and aileron input only. I will try this out at a safe altitude and let you know.
Cheers,
Jay
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Sunday, December 22, 2019 10:46 AM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware. Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things. A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure) Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons.
If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude. Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm. Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes.
That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1” long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure.
If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other. Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes!
Matthew Curcio
419-290-3773
On Dec 22, 2019, at 08:55, Jay Scheevel <jay@...> wrote:
Hi Matthew,
When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
Cheer,
Jay N8WQ
-----Original Message-----
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
Sent: Saturday, December 21, 2019 1:32 PM
To: main@q-list.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
Matthew Curcio
419-290-3773
On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote: Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
Intention was for this to be the trim system.
Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
CharlieN
|
|
|
Jay Scheevel
Hi Richard,
My reflexor has been totally adequate for all loading so far. By adjusing power and reflexor, I can stabilize anywhere from 140 mph IAS level cruise to 85 mph standard final descent (3 degrees), all with neutral stick force (hands off).
I have found that I can increase max level cruise by about 5 mph by reducing forward forward reflexor and pushing a little forward stick instead (reflexing elevator slightly). This means that there is room for cruise speed optimization if I were to install elevator trim. That will be a future project after I have built my wheel pants.
Cheers, Jay
Cheers, Jay
Sent from my Verizon Wireless 4G LTE DROID Richard Thomson <richard@...> wrote: Yay Jay, I think we already discussed, I have been beating my 2 brain cells together over the situation that I only have the elevator helper spring fitted (that was in when I bought FN) and trying to work out if I needed the full elevator trim fitted. So your stick rests around neutral in cruise without the trim ? Thanks for the tips you sent earlier on testing set up for the reflex, I have copied those off to add to my notes. Best present yet this year, merry Christmas. :-) Rich.
On 22/12/2019 19:12, Jay Scheevel wrote:
> I do not have the elevator trim system installed. I have been using my aileron reflexor for pitch trim since I first flew my plane a year ago. The elevator seems fully stabilized without the trim system. I think that the sparrow strainers have a significant damping effect.
>
> Cheers,
> Jay
>
> -----Original Message-----
> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
> Sent: Sunday, December 22, 2019 11:57 AM
> To: main@q-list.groups.io
> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>
> Jay, I think to evaluate this conservatively you’ll have to disconnect the pitch trim springs since those help to stabilize the system in some ways.
>
> Matthew Curcio
> 419-290-3773
>> On Dec 22, 2019, at 10:44, Jay Scheevel <jay@...> wrote:
>>
>> Thanks for the more complete explanation. I have a manual "stick" type of control on my aileron reflexor. It fits into my left hand and feels and manipulates like a second stick (absent roll control obviously). I will have to try to see if I can fly the airplane using that reflexor control for pitch and the actual stick for roll. The sparrow strainers hold the elevator pretty much in trail for most AOA's (in the event that elevator continuity was absent), so I think it may be possible to fly the airplane with reflexor and aileron input only. I will try this out at a safe altitude and let you know.
>>
>> Cheers,
>> Jay
>>
>> -----Original Message-----
>> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
>> Sent: Sunday, December 22, 2019 10:46 AM
>> To: main@q-list.groups.io
>> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>>
>> Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware. Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things. A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure) Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons.
>>
>> If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude. Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm. Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes.
>>
>> That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1” long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure.
>>
>> If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other. Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes!
>>
>> Matthew Curcio
>> 419-290-3773
>>> On Dec 22, 2019, at 08:55, Jay Scheevel <jay@...> wrote:
>>>
>>> Hi Matthew,
>>>
>>> When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
>>>
>>> Cheer,
>>> Jay N8WQ
>>>
>>> -----Original Message-----
>>> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
>>> Sent: Saturday, December 21, 2019 1:32 PM
>>> To: main@q-list.groups.io
>>> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>>>
>>> I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
>>>
>>> I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
>>>
>>> If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
>>>
>>> For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
>>>
>>> Matthew Curcio
>>> 419-290-3773
>>>>> On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote:
>>>> Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
>>>> Intention was for this to be the trim system.
>>>> Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
>>>> CharlieN
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>>
>
>
>
>
>
>
>
|
|
|
Jay, I understand that you “…do not have the elevator trim system installed.” However, please clarify: Do you or do you not have any springs “attached” to your elevator control system? Thank you, David J. Gall
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jay Scheevel
Sent: Sunday, December 22, 2019 6:50 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers My reflexor has been totally adequate for all loading so far. By adjusing power and reflexor, I can stabilize anywhere from 140 mph IAS level cruise to 85 mph standard final descent (3 degrees), all with neutral stick force (hands off). I have found that I can increase max level cruise by about 5 mph by reducing forward forward reflexor and pushing a little forward stick instead (reflexing elevator slightly). This means that there is room for cruise speed optimization if I were to install elevator trim. That will be a future project after I have built my wheel pants. Sent from my Verizon Wireless 4G LTE DROID
Richard Thomson <richard@...> wrote:
Yay Jay, I think we already discussed, I have been beating my 2 brain
cells together over the situation that I only have the elevator helper
spring fitted (that was in when I bought FN) and trying to work out if I
needed the full elevator trim fitted. So your stick rests around neutral
in cruise without the trim ?
Thanks for the tips you sent earlier on testing set up for the reflex, I
have copied those off to add to my notes.
Best present yet this year, merry Christmas. :-)
Rich.
On 22/12/2019 19:12, Jay Scheevel wrote:
> I do not have the elevator trim system installed. I have been using my aileron reflexor for pitch trim since I first flew my plane a year ago. The elevator seems fully stabilized without the trim system. I think that the sparrow strainers have a significant damping effect.
>
> Cheers,
> Jay
>
> -----Original Message-----
> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
> Sent: Sunday, December 22, 2019 11:57 AM
> To: main@q-list.groups.io
> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>
> Jay, I think to evaluate this conservatively you’ll have to disconnect the pitch trim springs since those help to stabilize the system in some ways.
>
> Matthew Curcio
> 419-290-3773
>> On Dec 22, 2019, at 10:44, Jay Scheevel <jay@...> wrote:
>>
>> Thanks for the more complete explanation. I have a manual "stick" type of control on my aileron reflexor. It fits into my left hand and feels and manipulates like a second stick (absent roll control obviously). I will have to try to see if I can fly the airplane using that reflexor control for pitch and the actual stick for roll. The sparrow strainers hold the elevator pretty much in trail for most AOA's (in the event that elevator continuity was absent), so I think it may be possible to fly the airplane with reflexor and aileron input only. I will try this out at a safe altitude and let you know.
>>
>> Cheers,
>> Jay
>>
>> -----Original Message-----
>> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
>> Sent: Sunday, December 22, 2019 10:46 AM
>> To: main@q-list.groups.io
>> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>>
>> Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware. Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things. A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure) Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons.
>>
>> If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude. Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm. Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes.
>>
>> That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1” long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure.
>>
>> If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other. Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes!
>>
>> Matthew Curcio
>> 419-290-3773
>>> On Dec 22, 2019, at 08:55, Jay Scheevel <jay@...> wrote:
>>>
>>> Hi Matthew,
>>>
>>> When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
>>>
>>> Cheer,
>>> Jay N8WQ
>>>
>>> -----Original Message-----
>>> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
>>> Sent: Saturday, December 21, 2019 1:32 PM
>>> To: main@q-list.groups.io
>>> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>>>
>>> I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
>>>
>>> I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
>>>
>>> If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
>>>
>>> For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
>>>
>>> Matthew Curcio
>>> 419-290-3773
>>>>> On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote:
>>>> Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
>>>> Intention was for this to be the trim system.
>>>> Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
>>>> CharlieN
>>>>
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Jay Scheevel
Hi David,
I do not have springs of any kind attached to my elevator control system. Linkage consists of two pushrods attached to a common bolt on the stick. The other ends are attached to the right or left elevator horns. I do have a mass balance arm for each elevator attached just inside the fuselage walls on the left and right sides. That is the entire setup.
Cheers, Jay
Sent from my Verizon Wireless 4G LTE DROID "David J. Gall" <David@...> wrote: Jay, I understand that you “…do not have the elevator trim system installed.” However, please clarify: Do you or do you not have any springs “attached” to your elevator control system? Thank you, David J. Gall
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jay Scheevel
Sent: Sunday, December 22, 2019 6:50 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers My reflexor has been totally adequate for all loading so far. By adjusing power and reflexor, I can stabilize anywhere from 140 mph IAS level cruise to 85 mph standard final descent (3 degrees), all with neutral stick force (hands off). I have found that I can increase max level cruise by about 5 mph by reducing forward forward reflexor and pushing a little forward stick instead (reflexing elevator slightly). This means that there is room for cruise speed optimization if I were to install elevator trim. That will be a future project after I have built my wheel pants. Sent from my Verizon Wireless 4G LTE DROID
Richard Thomson <richard@...> wrote:
Yay Jay, I think we already discussed, I have been beating my 2 brain
cells together over the situation that I only have the elevator helper
spring fitted (that was in when I bought FN) and trying to work out if I
needed the full elevator trim fitted. So your stick rests around neutral
in cruise without the trim ?
Thanks for the tips you sent earlier on testing set up for the reflex, I
have copied those off to add to my notes.
Best present yet this year, merry Christmas. :-)
Rich.
On 22/12/2019 19:12, Jay Scheevel wrote:
> I do not have the elevator trim system installed. I have been using my aileron reflexor for pitch trim since I first flew my plane a year ago. The elevator seems fully stabilized without the trim system. I think that the sparrow strainers have a significant damping effect.
>
> Cheers,
> Jay
>
> -----Original Message-----
> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
> Sent: Sunday, December 22, 2019 11:57 AM
> To: main@q-list.groups.io
> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>
> Jay, I think to evaluate this conservatively you’ll have to disconnect the pitch trim springs since those help to stabilize the system in some ways.
>
> Matthew Curcio
> 419-290-3773
>> On Dec 22, 2019, at 10:44, Jay Scheevel <jay@...> wrote:
>>
>> Thanks for the more complete explanation. I have a manual "stick" type of control on my aileron reflexor. It fits into my left hand and feels and manipulates like a second stick (absent roll control obviously). I will have to try to see if I can fly the airplane using that reflexor control for pitch and the actual stick for roll. The sparrow strainers hold the elevator pretty much in trail for most AOA's (in the event that elevator continuity was absent), so I think it may be possible to fly the airplane with reflexor and aileron input only. I will try this out at a safe altitude and let you know.
>>
>> Cheers,
>> Jay
>>
>> -----Original Message-----
>> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
>> Sent: Sunday, December 22, 2019 10:46 AM
>> To: main@q-list.groups.io
>> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>>
>> Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware. Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things. A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure) Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons.
>>
>> If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude. Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm. Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes.
>>
>> That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1” long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure.
>>
>> If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other. Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes!
>>
>> Matthew Curcio
>> 419-290-3773
>>> On Dec 22, 2019, at 08:55, Jay Scheevel <jay@...> wrote:
>>>
>>> Hi Matthew,
>>>
>>> When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick?
>>>
>>> Cheer,
>>> Jay N8WQ
>>>
>>> -----Original Message-----
>>> From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio
>>> Sent: Saturday, December 21, 2019 1:32 PM
>>> To: main@q-list.groups.io
>>> Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers
>>>
>>> I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner.
>>>
>>> I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program.
>>>
>>> If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree.
>>>
>>> For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here.
>>>
>>> Matthew Curcio
>>> 419-290-3773
>>>>> On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote:
>>>> Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos.
>>>> Intention was for this to be the trim system.
>>>> Being we have not flown this plane yet I have no clue how well this would work. Seems right thought.
>>>> CharlieN
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
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Jim Patillo
Hey David, nice to see you posting again. You too have made significant contributions to the safer handling of our our planes with your posts regarding wheel alignment. Thanks again.
Are you working “NorCal” SAC Area by any chance?
Jim
N46JP Q-200
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Hi Jim, Thanks for the compliment. I retired from that job three years ago. I’ve been chasing my boyhood dream of being an airline pilot by flying for SkyWest Airlines ever since, and I’m still pursuing propeller design and other aeronautical oddities. The twins are five now so life is a bit overwhelming…. Merry Christmas to you and to everyone on the Q-List! David J. Gall
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Jim Patillo
Sent: Monday, December 23, 2019 8:46 PM
To: main@Q-List.groups.io
Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers Hey David, nice to see you posting again. You too have made significant contributions to the safer handling of our our planes with your posts regarding wheel alignment. Thanks again.
Are you working “NorCal” SAC Area by any chance?
Jim
N46JP Q-200
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Jim Patillo
Morning, David,
I’m glad you are enjoying your new career. It was my childhood dream as well. I enjoyed and met so many wonderful people during my years at United Airlines. Memories I will never forget. Where do you live now. I moved to Auburn.
Jim
N46JP - Q200
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I’m in Marin County but my hangar is in Petaluma. In the fog. 😝
On Dec 24, 2019, at 8:41 AM, Jim Patillo <logistics_engineering@...> wrote:
Morning, David,
I’m glad you are enjoying your new career. It was my childhood dream as well. I enjoyed and met so many wonderful people during my years at United Airlines. Memories I will never forget. Where do you live now. I moved to Auburn.
Jim
N46JP - Q200
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Hello Matthew,
A belated thanks for your excellent explanation. I learned a lot, like the problems of certifying a tandem wing and canard aircraft. It makes me wonder how (for example) the Gyroflug Speed Canard was certified in Germany.
Rob
toggle quoted message
Show quoted text
At 18:45 22 12 2019, you wrote: Yes but a lot more than that. This may be common knowledge for you but I’ll explain in some detail since I think most people aren’t fully aware.
Taking a step back, part 23 and part 25 both say that you cannot have any single points of failure in flight control systems that are catastrophic (airplane is a total loss and more than one fatality). Look at a 172. If a pushrod or cables breaks going to the elevator (one or both panels), you can still fly with the trim tab, if you lose aileron authority (both panels) you can take advantage of adverse yaw to maintain roll authority - the quickie can’t do either of those things.
A lot of pilots are aware of this but see it as a neat trick - they don’t realize it’s actually a requirement. The FARs also state stick load limits, with time functions for failure cases (This is why most twins end up with rudder trim and roll trim to deal with control loads after an engine failure)
Additionally, if a 172 loses signal to one of its elevators the pilot would have ~50% elevator authority and the associated rolling moment would easily be reacted by the ailerons. If a quickie loses signal to one elevator (hand wavey assessment here) you’re not going to have enough roll authority to react the rolling moments for continued safe flight and landing, assuming one elevator is faired and the other is being used to control pitch attitude.
Its an issue of moment arms, the elevator’s arm about the longitudinal axis is so close to the CG that they require huge authority to drive a pitching moment, hence the full span and associated high stick loads that drive the requirement for sparrow strainer (it’s a band aid) - but their arm from the cg in the lateral axis is bigger than the ailerons arm.
Hence, I argue that while the q2 has mostly separate load paths going to each elevator if either one fails it’s still not likely going to be survivable. I’d be thrilled if someone can prove me wrong or point to a case where that happened and it wasn’t catastrophic. There is nothing you can do to fix it, it’s just a flaw inherent with the design. Elevators should hav a big arm from the cg in the longitudinal axis and short about the lateral axis if you want to have a stable airplane, with benign failure modes.
That said, clearly if the bearing that supports the stick falls off your in a bad spot (BTW It should have a >1� long taped gusset in the x-y plane to react the loads in x that react the pilots pitch inputs, fiberglass tapes are terrible in reacting out of plane moment), if the bolt that connects the stick to elevator pushrods fails that’s single point and based on my assessment above, all the other linkage going to each surface is single point catastrophic failure.
If this were a part 25 airplane that bolt connecting the pushrods to the stick would be hollow with a second bolt running through it, the pushrods would have a second pushrod inside, as well as the torque tubes and horns a would all have parallel, independent load paths. Part 23 airplanes don’t usually end up requiring this level of complexity and the quickie just can’t be certified due to this reason and other.
Im stating all of this as fact but it’s mostly hand wavey assessment (based on my experience from a couple years of designing and evaluating flight controls to part 25 requirements) so feel free to poke holes!
Matthew Curcio 419-290-3773
On Dec 22, 2019, at 08:55, Jay Scheevel <mailto:jay@...> wrote: > > Hi Matthew, > > When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick? > > Cheer, > Jay N8WQ >>jay@...> wrote: > > Hi Matthew, > > When you state the that the elevator control linkage has single points of failure, are you referring to the fact that there are independent (left-right) control arms with separate push rods returning to a single point on the stick? > > Cheer, > Jay N8WQ >
-----Original Message----- > From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Matthew Curcio > Sent: Saturday, December 21, 2019 1:32 PM > To: main@q-list.groups.io > Subject: Re: [Q-List] Bruce's tuft study on sparrow strainers > > I would be extraordinarily careful with that setup and my professional recommendation would be don’t fly that. The problem is that unless you have fully evaluated the trim loads incurred during the trim runaway throughout the entire flight envelope, that failure will likely degrade handling qualities such that it would be a catastrophic single point of failure. It’d be nice to have but I wouldnt accept the risk, if not for me for a future owner. > > I was just talking about this with another engineer at work (the pitch control on the quickies is pretty terrifying). Where we ended up was that the elevator control linkage on the quickie has single points of failure that are catastrophic (obviously). They would carry a PF of 1e-6 (generic probability of failure / flight hour for any mechanical system) which is kind of stomachable but would never be allowed in a part 23 aircraft. If it’s mechanically controlled, a trimable sparrow strainer introduces another 1e-6 catastrophic single point of failure and in that regard it degrades safety. It doesn’t get rid of a single point of failure it just adds one. If you put an electric sparrow strainer on the PF is going to be appreciably worse unless you had an extremely slow actuator that could reduce the time of occurence. If there is anything more than a simple toggle switch (software) you would need an involved ver-Val test program. > > If a reputable aerospace company were to do this we would consider it a land as soon as practical EP, We’d determine the stick loads allowed for continued safe flight and landing, do extensive sims to test the pilots time of response to the failure in the worst phase of flight, add some margin to that time and then ensure that the trim Is slow enough to prevent those loads from developing before the pilot responds. This is not ever the preferred approach of mitigating a catastrophic failure and there’s a few hundred families who buried loved ones last year, due to a very similar scenario, that would likely agree. > > For reference Proteus has a trim-able sparrow strainer, everybody that touches the airplane is petrified of it (for good reason) and it’s the subject of a lot of conversation. Just bringing that up to say it’s a fairly well understood dilemma around here. > > Matthew Curcio > 419-290-3773 >> On Dec 21, 2019, at 11:46, charlie <ffmd@...> wrote: >> >> Way back in the mid '80s when I was building my Q1 with the first customer LS1 airfoil. I built the sparrow Strainers on hinges and drove then with model servos. >> Intention was for this to be the trim system. >> Being we have not flown this plane yet I have no clue how well this would work. Seems right thought. >> CharlieN >> >> >> >> > > > > > > >
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