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Flight characteristics questions

q2fun #26161 Hi All, I have some questions about the flight characteristics of the Q-2. Pitch sensitivity. With an after c/g my Q2 seams pitch sensitive. My Q2 has the LS1 canard, Revmaster 65hp, tail dragger. Is it normal to get more pitch sensitive the more aft the C/G gets? Rudder to control bank. My rudder does not do anything for bank. If the wing is down 5 degrees and you use the rudder to bring it up, all that happens is the plane will yaw and the bank may even get steeper. Is that a normal characteristic of the Q design? With an increase in airspeed above 150 mph indicated the airplane wants to pitch down and farther increase airspeed/pitch down harder. Is this normal? Sparrow strainers to small for this airspeed? I have the standard pitch trim system. I have been flying my Q since April and now have 62 hours in it. It is a joy to blast around the pattern and it is even a joy to put gas in it after a long cross county. It is just a little too slow in cruise 130 kts. Thank You All. Tim Bryant KUNV N86TB
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Sam Hoskins <shoskins@...> #26163 1. I think pitch sensitivity is normal, especially with aft CG and at high (8,000+ft) altitude. 2. My plane does the same. The rudder doesn't control bank, the ailerons do. 2. This sounds a little odd. Maybe the sparrow strainers are too big or have too steep of an angle. It could also be that your canard needs to be adjusted up a degree or so. Maybe try installing adjustable sparrow strainers first. That would be an easy experiment. Sam Hoskins Q-200 1,600+ hrs. Murphysboro, IL _____ From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of q2fun Sent: Monday, October 16, 2006 6:28 PM To: Q-LIST@... Subject: [Q-LIST] Flight characteristics questions Hi All, I have some questions about the flight characteristics of the Q-2. Pitch sensitivity. With an after c/g my Q2 seams pitch sensitive. My Q2 has the LS1 canard, Revmaster 65hp, tail dragger. Is it normal to get more pitch sensitive the more aft the C/G gets? Rudder to control bank. My rudder does not do anything for bank. If the wing is down 5 degrees and you use the rudder to bring it up, all that happens is the plane will yaw and the bank may even get steeper. Is that a normal characteristic of the Q design? With an increase in airspeed above 150 mph indicated the airplane wants to pitch down and farther increase airspeed/pitch down harder. Is this normal? Sparrow strainers to small for this airspeed? I have the standard pitch trim system. I have been flying my Q since April and now have 62 hours in it. It is a joy to blast around the pattern and it is even a joy to put gas in it after a long cross county. It is just a little too slow in cruise 130 kts. Thank You All. Tim Bryant KUNV N86TB
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Jim Patillo #26164 TIM, FIRST CONGRATULATIONS ON YOUR 62 HOURS FLIGHT TIME IN A Q. YOU'VE JOINED A UNIQUE CLUB. --- In Q-LIST@..., "q2fun" <q2fun@...> wrote: Hi All, I have some questions about the flight characteristics of the Q- 2. Pitch sensitivity. With an after c/g my Q2 seams pitch sensitive. My Q2 has the LS1 canard, Revmaster 65hp, tail dragger. Is it normal to get more pitch sensitive the more aft the C/G gets? ABSOLUTELY! FAR AFT CG IS NOT A GOOD PLACE TO BE IN THIS PLANE. Rudder to control bank. My rudder does not do anything for bank. If the wing is down 5 degrees and you use the rudder to bring it up, all that happens is the plane will yaw and the bank may even get steeper. Is that a normal characteristic of the Q design? MAYBE. IN LEVEL FLIGHT, PUSHING THE RUDDER WILL DEFINATELY YAW THE TAIL BUT I HAVEN'T NOTICE THE BANK INCREASING. IN SLIGHT BANKS MINE WILL RECOVER USING THE RUDDER ONLY. I THINK THE SMALL RUDDER ON THESE PLANES DOES A GOOD JOB BUT RECOVERING FROM A BANK SOLELY USING RUDDER .......NOT SO GOOD. I WILL CHECK IT OUT WHEN I FLY AGAIN. With an increase in airspeed above 150 mph indicated the airplane wants to pitch down and farther increase airspeed/pitch down harder. Is this normal? Sparrow strainers to small for this airspeed? I have the standard pitch trim system. I CRUISED MY Q200 (LS1)SATURDAY FROM 130 TO 185K AND DID NOT NOTICE ANY TUCKING OR PITCHING. I ALSO HAVE A STANDARD TRIM SYSTEM. MAYBE YOUR STRAINERS ARE INSTALLED INCORRECT. I have been flying my Q since April and now have 62 hours in it. It is a joy to blast around the pattern and it is even a joy to put gas in it after a long cross county. It is just a little too slow in cruise 130 kts. YOU CAN FIX THAT! TIM WE SEE 160-165K CRUISE STANDARD WITH PUMPED 0200'S (TAIL DRAGGER VERSION). JUST COSTS A LITTLE $$$$$$$. REGARDS, JIM PATILLO Thank You All. Tim Bryant KUNV N86TB
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David J. Gall #26170 Sam, I think you're thinking backwards here. The described behavior indicates sparrow strainers that are too small, not too large; or not angled enough (trailing edge up) instead of too steeply. Without sparrow strainers, when the airplane inadvertently goes faster than its trimmed airspeed, the slight undercamber of the LS(1) elevator causes aerodynamic force that pushes the trailing edge of the elevator up. This lets the airplane's nose come down and allows the airplane to accelerate to a yet-higher speed. NOT GOOD! The sole purpose of sparrow strainers is to REVERSE this pattern. When the nose inadvertently drops and the speed builds, the sparrow strainers should push the trailing edge of the elevator down so as to raise the nose of the airplane, thus slowing it back down. Conversely, when the airplane slows down (due to an inadvertent climb) the decreasing dynamic pressure on the sparrow strainers lets them allow the trailing edge of the elevators to come up (usually in response to a down-spring in the trim system), lowering the nose and restoring the airplane to it's original airspeed. This is speed stability. It is closely associated with pitch stability, but is not the same thing. Burt Rutan devoted several issues of his Canard Pusher newsletter to describing it, discussing it, and reporting on the requirements for it in his several homebuilders' designs. Another clue to incorrect speed stability is light or "sensitive" pitch control, as reported in Mr. Q2fun's item #1. True, pitch sensitivity is also a function of CG position, but given two otherwise identical airplanes with the same CG location, the one with greater speed stability will have less-sensitive pitch feel. That's because the greater aerodynamic forces of the larger or more effective (larger/correct deflection angle) sparrow strainers will cause the elevator stick force to be greater for any given deflection of the elevators away from their trim position. It's kind of like using a larger paddle on a canoe, you just have to pull harder to get it to move through the water. A more effective sparrow strainer will also need to be met with greater tension in the pitch down-spring of the spring-type pitch trim system at higher airspeeds. If the down spring of the trim system is only lightly loaded at cruise speed or if the up-spring is loaded and the down spring is slack at cruise speed (heaven forbid!) then there is a real problem and a potentially dangerous situation. What happens if the up-spring is loaded at cruise? If the nose drops, the aerodynamic forces get stronger while the spring force stays the same, so the aerodynamic forces "win." The up-spring was resisting the aero forces that want to make the airplane dive, but those forces now win and the airplane dives. Conversely, if the down-spring is loaded at cruise, then a nose drop again means larger aero forces, but those forces (from the sparrow strainers) act to RAISE the nose, not lower it further. Raising the nose restores the airplane to level flight. Rutan advised his builders that his airplane designs should be AERODYNAMICALLY trimmed to a low-cruise airspeed when flown hands-off and with the pitch trim system disconnected. His rationale is that if a crucial part or connection in the pitch control system should fail thereby leaving an elevator completely disconnected from the trim system and the control system, it does not automatically kill the pilot. I do NOT advise disconnecting the trim system in a Q2 or Q200 or even a Quickie because of the risks involved, but you can certainly look at your trim springs and simulate a disconnect by moving the trim control to make them as equally slack as possible. By this method one might be able to get a relative idea of what the sparrow strainers are doing and what the airplane's aerodynamic trim speed is. In summary, I think there is a dangerous situation being described by Mr. Q2fun and I hope he gets his sparrow strainers and trim system looked at by one of the "old heads" on this list to see if it is rigged right or if there's something amiss. I'll wager that the up-spring is doing a lot of work at cruise speeds and just loses the battle against aero forces at speeds above 150 mph. Not good -- not safe! Just my worry-wart two cents worth, David J. Gall BSAE Sacramento, CA toggle quoted message Show quoted text -----Original Message----- From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of Sam Hoskins Sent: Monday, October 16, 2006 5:02 PM To: Q-LIST@... Subject: RE: [Q-LIST] Flight characteristics questions 1. I think pitch sensitivity is normal, especially with aft CG and at high (8,000+ft) altitude. 2. My plane does the same. The rudder doesn't control bank, the ailerons do. 2. This sounds a little odd. Maybe the sparrow strainers are too big or have too steep of an angle. It could also be that your canard needs to be adjusted up a degree or so. Maybe try installing adjustable sparrow strainers first. That would be an easy experiment. Sam Hoskins Q-200 1,600+ hrs. Murphysboro, IL _____ From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of q2fun Sent: Monday, October 16, 2006 6:28 PM To: Q-LIST@... Subject: [Q-LIST] Flight characteristics questions Hi All, I have some questions about the flight characteristics of the Q-2. Pitch sensitivity. With an after c/g my Q2 seams pitch sensitive. My Q2 has the LS1 canard, Revmaster 65hp, tail dragger. Is it normal to get more pitch sensitive the more aft the C/G gets? Rudder to control bank. My rudder does not do anything for bank. If the wing is down 5 degrees and you use the rudder to bring it up, all that happens is the plane will yaw and the bank may even get steeper. Is that a normal characteristic of the Q design? With an increase in airspeed above 150 mph indicated the airplane wants to pitch down and farther increase airspeed/pitch down harder. Is this normal? Sparrow strainers to small for this airspeed? I have the standard pitch trim system. I have been flying my Q since April and now have 62 hours in it. It is a joy to blast around the pattern and it is even a joy to put gas in it after a long cross county. It is just a little too slow in cruise 130 kts. Thank You All. Tim Bryant KUNV N86TB Quickie Builders Association WEB site http://www.quickiebuilders.org Yahoo! Groups Links
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michel & hélène moreau #26178 David, Does this apply to GU as well as LS1? I don't see a "slight undercamber" on my GU elevator. Thanks for such a clear explanation of the phenomenon. MM toggle quoted message Show quoted text ----- Original Message ----- From: "David J. Gall" <David@...> To: <Q-LIST@...> Sent: Tuesday, October 17, 2006 5:42 AM Subject: RE: [Q-LIST] Flight characteristics questions Sam, I think you're thinking backwards here. The described behavior indicates sparrow strainers that are too small, not too large; or not angled enough (trailing edge up) instead of too steeply. Without sparrow strainers, when the airplane inadvertently goes faster than its trimmed airspeed, the slight undercamber of the LS(1) elevator causes aerodynamic force that pushes the trailing edge of the elevator up. This lets the airplane's nose come down and allows the airplane to accelerate to a yet-higher speed. NOT GOOD! The sole purpose of sparrow strainers is to REVERSE this pattern. When the nose inadvertently drops and the speed builds, the sparrow strainers should push the trailing edge of the elevator down so as to raise the nose of the airplane, thus slowing it back down. Conversely, when the airplane slows down (due to an inadvertent climb) the decreasing dynamic pressure on the sparrow strainers lets them allow the trailing edge of the elevators to come up (usually in response to a down-spring in the trim system), lowering the nose and restoring the airplane to it's original airspeed. This is speed stability. It is closely associated with pitch stability, but is not the same thing. Burt Rutan devoted several issues of his Canard Pusher newsletter to describing it, discussing it, and reporting on the requirements for it in his several homebuilders' designs. Another clue to incorrect speed stability is light or "sensitive" pitch control, as reported in Mr. Q2fun's item #1. True, pitch sensitivity is also a function of CG position, but given two otherwise identical airplanes with the same CG location, the one with greater speed stability will have less-sensitive pitch feel. That's because the greater aerodynamic forces of the larger or more effective (larger/correct deflection angle) sparrow strainers will cause the elevator stick force to be greater for any given deflection of the elevators away from their trim position. It's kind of like using a larger paddle on a canoe, you just have to pull harder to get it to move through the water. A more effective sparrow strainer will also need to be met with greater tension in the pitch down-spring of the spring-type pitch trim system at higher airspeeds. If the down spring of the trim system is only lightly loaded at cruise speed or if the up-spring is loaded and the down spring is slack at cruise speed (heaven forbid!) then there is a real problem and a potentially dangerous situation. What happens if the up-spring is loaded at cruise? If the nose drops, the aerodynamic forces get stronger while the spring force stays the same, so the aerodynamic forces "win." The up-spring was resisting the aero forces that want to make the airplane dive, but those forces now win and the airplane dives. Conversely, if the down-spring is loaded at cruise, then a nose drop again means larger aero forces, but those forces (from the sparrow strainers) act to RAISE the nose, not lower it further. Raising the nose restores the airplane to level flight. Rutan advised his builders that his airplane designs should be AERODYNAMICALLY trimmed to a low-cruise airspeed when flown hands-off and with the pitch trim system disconnected. His rationale is that if a crucial part or connection in the pitch control system should fail thereby leaving an elevator completely disconnected from the trim system and the control system, it does not automatically kill the pilot. I do NOT advise disconnecting the trim system in a Q2 or Q200 or even a Quickie because of the risks involved, but you can certainly look at your trim springs and simulate a disconnect by moving the trim control to make them as equally slack as possible. By this method one might be able to get a relative idea of what the sparrow strainers are doing and what the airplane's aerodynamic trim speed is. In summary, I think there is a dangerous situation being described by Mr. Q2fun and I hope he gets his sparrow strainers and trim system looked at by one of the "old heads" on this list to see if it is rigged right or if there's something amiss. I'll wager that the up-spring is doing a lot of work at cruise speeds and just loses the battle against aero forces at speeds above 150 mph. Not good -- not safe! Just my worry-wart two cents worth, David J. Gall BSAE Sacramento, CA -----Original Message----- From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of Sam Hoskins Sent: Monday, October 16, 2006 5:02 PM To: Q-LIST@... Subject: RE: [Q-LIST] Flight characteristics questions 1. I think pitch sensitivity is normal, especially with aft CG and at high (8,000+ft) altitude. 2. My plane does the same. The rudder doesn't control bank, the ailerons do. 2. This sounds a little odd. Maybe the sparrow strainers are too big or have too steep of an angle. It could also be that your canard needs to be adjusted up a degree or so. Maybe try installing adjustable sparrow strainers first. That would be an easy experiment. Sam Hoskins Q-200 1,600+ hrs. Murphysboro, IL _____ From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of q2fun Sent: Monday, October 16, 2006 6:28 PM To: Q-LIST@... Subject: [Q-LIST] Flight characteristics questions Hi All, I have some questions about the flight characteristics of the Q-2. Pitch sensitivity. With an after c/g my Q2 seams pitch sensitive. My Q2 has the LS1 canard, Revmaster 65hp, tail dragger. Is it normal to get more pitch sensitive the more aft the C/G gets? Rudder to control bank. My rudder does not do anything for bank. If the wing is down 5 degrees and you use the rudder to bring it up, all that happens is the plane will yaw and the bank may even get steeper. Is that a normal characteristic of the Q design? With an increase in airspeed above 150 mph indicated the airplane wants to pitch down and farther increase airspeed/pitch down harder. Is this normal? Sparrow strainers to small for this airspeed? I have the standard pitch trim system. I have been flying my Q since April and now have 62 hours in it. It is a joy to blast around the pattern and it is even a joy to put gas in it after a long cross county. It is just a little too slow in cruise 130 kts. Thank You All. Tim Bryant KUNV N86TB Quickie Builders Association WEB site http://www.quickiebuilders.org Yahoo! Groups Links Quickie Builders Association WEB site http://www.quickiebuilders.org Yahoo! Groups Links
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David J. Gall #26179 Michel, Yes. There is no undercamber on the GU elevator so the aero forces involved are not large. However, the system does rely on the up-spring to hold the trailing edge of the elevetor down in flight. Early on in the pages of QuickTalk there were a couple of reports of trim system failures ("modified hackwaw blade" failures) in the original Quickie. The ensuing requirement for holding continuous back pressure was reported, as well as the fatigue level of doing so for as little as ten minutes. (I'm not going to look up the exact issue number.) I'm not planning to re-engineer or suggest that anyone else re-engineer the system on the GU canard, but be aware that it is a potential problem. IF<< I were to reengineer the system, I think I'd merely "reflex" the trailing edge of the elevator ever so slightly, as John Roncz did for the Roncz 1145MS replacement canard airfoil for the Long-EZ. IF<< I thought it was a problem of sufficient magnitude and was trying to retrofit the existing GU elevator, I think I'd add sparrow strainers, though they would not need to be angled nearly so severely as on the LS(1) elevator. Of course, exact size and placement aft of the trailing edge would be a matter of trial and error, and balancing the elevators against flutter with the additional mass of the sparrow strainers aft of the hinge line is an additional concern. Like I said, I'm not planning to re-engineer or suggest that anyone else re-engineer the system on the GU canard, but be aware that it is a potential problem in the event of a control system and/or trim system mechanical failure. David J. Gall -----Original Message----- From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of Michel Moreau Sent: Tuesday, October 17, 2006 7:43 AM To: Q-LIST@... Subject: Re: [Q-LIST] Flight characteristics questions David, Does this apply to GU as well as LS1? I don't see a "slight undercamber" on my GU elevator. Thanks for such a clear explanation of the phenomenon. MM ----- Original Message ----- From: "David J. Gall" <David@...> To: <Q-LIST@...> Sent: Tuesday, October 17, 2006 5:42 AM Subject: RE: [Q-LIST] Flight characteristics questions Sam, I think you're thinking backwards here. The described behavior indicates sparrow strainers that are too small, not too large; or not angled enough (trailing edge up) instead of too steeply. Without sparrow strainers, when the airplane inadvertently goes faster than its trimmed airspeed, the slight undercamber of the LS(1) elevator causes aerodynamic force that pushes the trailing edge of the elevator up. This lets the airplane's nose come down and allows the airplane to accelerate to a yet-higher speed. NOT GOOD! The sole purpose of sparrow strainers is to REVERSE this pattern. When the nose inadvertently drops and the speed builds, the sparrow strainers should push the trailing edge of the elevator down so as to raise the nose of the airplane, thus slowing it back down. Conversely, when the airplane slows down (due to an inadvertent climb) the decreasing dynamic pressure on the sparrow strainers lets them allow the trailing edge of the elevators to come up (usually in response to a down-spring in the trim system), lowering the nose and restoring the airplane to it's original airspeed. This is speed stability. It is closely associated with pitch stability, but is not the same thing. Burt Rutan devoted several issues of his Canard Pusher newsletter to describing it, discussing it, and reporting on the requirements for it in his several homebuilders' designs. Another clue to incorrect speed stability is light or "sensitive" pitch control, as reported in Mr. Q2fun's item #1. True, pitch sensitivity is also a function of CG position, but given two otherwise identical airplanes with the same CG location, the one with greater speed stability will have less-sensitive pitch feel. That's because the greater aerodynamic forces of the larger or more effective (larger/correct deflection angle) sparrow strainers will cause the elevator stick force to be greater for any given deflection of the elevators away from their trim position. It's kind of like using a larger paddle on a canoe, you just have to pull harder to get it to move through the water. A more effective sparrow strainer will also need to be met with greater tension in the pitch down-spring of the spring-type pitch trim system at higher airspeeds. If the down spring of the trim system is only lightly loaded at cruise speed or if the up-spring is loaded and the down spring is slack at cruise speed (heaven forbid!) then there is a real problem and a potentially dangerous situation. What happens if the up-spring is loaded at cruise? If the nose drops, the aerodynamic forces get stronger while the spring force stays the same, so the aerodynamic forces "win." The up-spring was resisting the aero forces that want to make the airplane dive, but those forces now win and the airplane dives. Conversely, if the down-spring is loaded at cruise, then a nose drop again means larger aero forces, but those forces (from the sparrow strainers) act to RAISE the nose, not lower it further. Raising the nose restores the airplane to level flight. Rutan advised his builders that his airplane designs should be AERODYNAMICALLY trimmed to a low-cruise airspeed when flown hands-off and with the pitch trim system disconnected. His rationale is that if a crucial part or connection in the pitch control system should fail thereby leaving an elevator completely disconnected from the trim system and the control system, it does not automatically kill the pilot. I do NOT advise disconnecting the trim system in a Q2 or Q200 or even a Quickie because of the risks involved, but you can certainly look at your trim springs and simulate a disconnect by moving the trim control to make them as equally slack as possible. By this method one might be able to get a relative idea of what the sparrow strainers are doing and what the airplane's aerodynamic trim speed is. In summary, I think there is a dangerous situation being described by Mr. Q2fun and I hope he gets his sparrow strainers and trim system looked at by one of the "old heads" on this list to see if it is rigged right or if there's something amiss. I'll wager that the up-spring is doing a lot of work at cruise speeds and just loses the battle against aero forces at speeds above 150 mph. Not good -- not safe! Just my worry-wart two cents worth, David J. Gall BSAE Sacramento, CA -----Original Message----- From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of Sam Hoskins Sent: Monday, October 16, 2006 5:02 PM To: Q-LIST@... Subject: RE: [Q-LIST] Flight characteristics questions 1. I think pitch sensitivity is normal, especially with aft CG and at high (8,000+ft) altitude. 2. My plane does the same. The rudder doesn't control bank, the ailerons do. 2. This sounds a little odd. Maybe the sparrow strainers are too big or have too steep of an angle. It could also be that your canard needs to be adjusted up a degree or so. Maybe try installing adjustable sparrow strainers first. That would be an easy experiment. Sam Hoskins Q-200 1,600+ hrs. Murphysboro, IL _____ From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of q2fun Sent: Monday, October 16, 2006 6:28 PM To: Q-LIST@... Subject: [Q-LIST] Flight characteristics questions Hi All, I have some questions about the flight characteristics of the Q-2. Pitch sensitivity. With an after c/g my Q2 seams pitch sensitive. My Q2 has the LS1 canard, Revmaster 65hp, tail dragger. Is it normal to get more pitch sensitive the more aft the C/G gets? Rudder to control bank. My rudder does not do anything for bank. If the wing is down 5 degrees and you use the rudder to bring it up, all that happens is the plane will yaw and the bank may even get steeper. Is that a normal characteristic of the Q design? With an increase in airspeed above 150 mph indicated the airplane wants to pitch down and farther increase airspeed/pitch down harder. Is this normal? Sparrow strainers to small for this airspeed? I have the standard pitch trim system. I have been flying my Q since April and now have 62 hours in it. It is a joy to blast around the pattern and it is even a joy to put gas in it after a long cross county. It is just a little too slow in cruise 130 kts. Thank You All. Tim Bryant KUNV N86TB
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Paul Buckley #26181 Dave As a matter of interest, an old method of achieving trim was to 'dope' a length of string along the airfoil trailing edge, varying the length to achieve the desired effect. Do you think that this method could be used underneath the GU elevators as an alternative to camber, if only as a temporary explorative measure? Paul Buckley Cheshire England toggle quoted message Show quoted text ----- Original Message ----- From: David J. Gall To: Q-LIST@... Sent: Tuesday, October 17, 2006 6:22 PM Subject: RE: [Q-LIST] Flight characteristics questions Michel, Yes. There is no undercamber on the GU elevator so the aero forces involved are not large. However, the system does rely on the up-spring to hold the trailing edge of the elevetor down in flight. Early on in the pages of QuickTalk there were a couple of reports of trim system failures ("modified hackwaw blade" failures) in the original Quickie. The ensuing requirement for holding continuous back pressure was reported, as well as the fatigue level of doing so for as little as ten minutes. (I'm not going to look up the exact issue number.) I'm not planning to re-engineer or suggest that anyone else re-engineer the system on the GU canard, but be aware that it is a potential problem. >>IF<< I were to reengineer the system, I think I'd merely "reflex" the trailing edge of the elevator ever so slightly, as John Roncz did for the Roncz 1145MS replacement canard airfoil for the Long-EZ. >>IF<< I thought it was a problem of sufficient magnitude and was trying to retrofit the existing GU elevator, I think I'd add sparrow strainers, though they would not need to be angled nearly so severely as on the LS(1) elevator. Of course, exact size and placement aft of the trailing edge would be a matter of trial and error, and balancing the elevators against flutter with the additional mass of the sparrow strainers aft of the hinge line is an additional concern. Like I said, I'm not planning to re-engineer or suggest that anyone else re-engineer the system on the GU canard, but be aware that it is a potential problem in the event of a control system and/or trim system mechanical failure. David J. Gall > -----Original Message----- > From: Q-LIST@... [mailto:Q-LIST@...] > On Behalf Of Michel Moreau > Sent: Tuesday, October 17, 2006 7:43 AM > To: Q-LIST@... > Subject: Re: [Q-LIST] Flight characteristics questions > > David, > > Does this apply to GU as well as LS1? I don't see a "slight > undercamber" on my GU elevator. > Thanks for such a clear explanation of the phenomenon. > > MM > > ----- Original Message ----- > From: "David J. Gall" <David@...> > To: <Q-LIST@...> > Sent: Tuesday, October 17, 2006 5:42 AM > Subject: RE: [Q-LIST] Flight characteristics questions > > > > Sam, > > > > I think you're thinking backwards here. The described > behavior indicates > > sparrow strainers that are too small, not too large; or not > angled enough > > (trailing edge up) instead of too steeply. > > > > Without sparrow strainers, when the airplane inadvertently > goes faster > > than > > its trimmed airspeed, the slight undercamber of the LS(1) > elevator causes > > aerodynamic force that pushes the trailing edge of the > elevator up. This > > lets the airplane's nose come down and allows the airplane > to accelerate > > to > > a yet-higher speed. NOT GOOD! > > > > The sole purpose of sparrow strainers is to REVERSE this > pattern. When the > > nose inadvertently drops and the speed builds, the sparrow > strainers > > should > > push the trailing edge of the elevator down so as to raise > the nose of the > > airplane, thus slowing it back down. Conversely, when the > airplane slows > > down (due to an inadvertent climb) the decreasing dynamic > pressure on the > > sparrow strainers lets them allow the trailing edge of the > elevators to > > come > > up (usually in response to a down-spring in the trim > system), lowering the > > nose and restoring the airplane to it's original airspeed. > > > > This is speed stability. It is closely associated with > pitch stability, > > but > > is not the same thing. Burt Rutan devoted several issues of > his Canard > > Pusher newsletter to describing it, discussing it, and > reporting on the > > requirements for it in his several homebuilders' designs. > > > > Another clue to incorrect speed stability is light or > "sensitive" pitch > > control, as reported in Mr. Q2fun's item #1. True, pitch > sensitivity is > > also > > a function of CG position, but given two otherwise > identical airplanes > > with > > the same CG location, the one with greater speed stability will have > > less-sensitive pitch feel. That's because the greater > aerodynamic forces > > of > > the larger or more effective (larger/correct deflection > angle) sparrow > > strainers will cause the elevator stick force to be greater > for any given > > deflection of the elevators away from their trim position. > It's kind of > > like > > using a larger paddle on a canoe, you just have to pull > harder to get it > > to > > move through the water. > > > > A more effective sparrow strainer will also need to be met > with greater > > tension in the pitch down-spring of the spring-type pitch > trim system at > > higher airspeeds. If the down spring of the trim system is > only lightly > > loaded at cruise speed or if the up-spring is loaded and > the down spring > > is > > slack at cruise speed (heaven forbid!) then there is a real > problem and a > > potentially dangerous situation. > > > > What happens if the up-spring is loaded at cruise? If the > nose drops, the > > aerodynamic forces get stronger while the spring force > stays the same, so > > the aerodynamic forces "win." The up-spring was resisting > the aero forces > > that want to make the airplane dive, but those forces now > win and the > > airplane dives. Conversely, if the down-spring is loaded at > cruise, then a > > nose drop again means larger aero forces, but those forces > (from the > > sparrow > > strainers) act to RAISE the nose, not lower it further. > Raising the nose > > restores the airplane to level flight. > > > > Rutan advised his builders that his airplane designs should be > > AERODYNAMICALLY trimmed to a low-cruise airspeed when flown > hands-off and > > with the pitch trim system disconnected. His rationale is that if a > > crucial > > part or connection in the pitch control system should fail > thereby leaving > > an elevator completely disconnected from the trim system > and the control > > system, it does not automatically kill the pilot. I do NOT advise > > disconnecting the trim system in a Q2 or Q200 or even a > Quickie because of > > the risks involved, but you can certainly look at your trim > springs and > > simulate a disconnect by moving the trim control to make > them as equally > > slack as possible. By this method one might be able to get > a relative idea > > of what the sparrow strainers are doing and what the airplane's > > aerodynamic > > trim speed is. > > > > In summary, I think there is a dangerous situation being > described by Mr. > > Q2fun and I hope he gets his sparrow strainers and trim > system looked at > > by > > one of the "old heads" on this list to see if it is rigged > right or if > > there's something amiss. I'll wager that the up-spring is > doing a lot of > > work at cruise speeds and just loses the battle against > aero forces at > > speeds above 150 mph. Not good -- not safe! > > > > Just my worry-wart two cents worth, > > > > > > David J. Gall > > BSAE > > Sacramento, CA > > > >> -----Original Message----- > >> From: Q-LIST@... [mailto:Q-LIST@...] > >> On Behalf Of Sam Hoskins > >> Sent: Monday, October 16, 2006 5:02 PM > >> To: Q-LIST@... > >> Subject: RE: [Q-LIST] Flight characteristics questions > >> > >> 1. I think pitch sensitivity is normal, especially with aft > >> CG and at high > >> (8,000+ft) altitude. > >> > >> 2. My plane does the same. The rudder doesn't control bank, > >> the ailerons do. > >> > >> 2. This sounds a little odd. Maybe the sparrow strainers > >> are too big or have too steep of an angle. It could also be > >> that your canard needs to be adjusted up a degree or so. > >> Maybe try installing adjustable sparrow strainers first. > >> That would be an easy experiment. > >> > >> Sam Hoskins Q-200 1,600+ hrs. > >> > >> Murphysboro, IL > >> > >> > >> > >> _____ > >> > >> From: Q-LIST@... [mailto:Q-LIST@...] > >> On Behalf Of q2fun > >> Sent: Monday, October 16, 2006 6:28 PM > >> To: Q-LIST@... > >> Subject: [Q-LIST] Flight characteristics questions > >> > >> > >> > >> Hi All, > >> > >> I have some questions about the flight characteristics of the Q-2. > >> Pitch sensitivity. With an after c/g my Q2 seams pitch sensitive. > >> My Q2 has the LS1 canard, Revmaster 65hp, tail dragger. Is it > >> normal to get more pitch sensitive the more aft the C/G gets? > >> > >> Rudder to control bank. My rudder does not do anything for bank. > >> If the wing is down 5 degrees and you use the rudder to bring > >> it up, all that happens is the plane will yaw and the bank > >> may even get steeper. Is that a normal characteristic of the > >> Q design? > >> > >> With an increase in airspeed above 150 mph indicated the > >> airplane wants to pitch down and farther increase > >> airspeed/pitch down harder. Is this normal? Sparrow strainers > >> to small for this airspeed? I have the standard pitch trim system. > >> > >> I have been flying my Q since April and now have 62 hours in > >> it. It is a joy to blast around the pattern and it is even a > >> joy to put gas in it after a long cross county. It is just a > >> little too slow in cruise 130 kts. > >> > >> Thank You All. > >> Tim Bryant > >> KUNV > >> N86TB ------------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.408 / Virus Database: 268.13.4/477 - Release Date: 16/10/2006
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Peter Harris <peterjfharris@...> #26182 David for what it's worth the subject of pitch spring effect came up a couple of years ago. I had complained that when the engine quit there is a scramble to adjust the trim to hold the nose up. The trim spring made the nose seem VERY heavy at a time when we do not need that kind of a distraction and my plans adjuster was stiff and hard to reach with the left hand. I was not going to let go of the stick! . I was surprised to find that most of the guys let the trim freewheel unlocked. It is not designed that way due to the mechanical advantage but if the bearing is made loose in construction it would freewheel like a buzz saw. Anyhow I redesigned my trim so it is now operated by a throttle cable control near my left hand and very easy to disengage. It is a real pleasure to use close to the throttle, I lock it only when stabilized in cruise, and also I lock it fully elevator up for final approach and flare. (My throttle is done with a mixture adjuster cable and that is also nice to use, just set and forget) At the present time I am dealing with a related problem: Although trimmed max elev up I need forward pressure to hold the nose down and TE up (3/16" at 170KTS). Aeleron reflex is 3/8"up. Unless I made a mistake the CG is same as for the Norton but the Norton line of thrust was 17mm higher. Do you think that the thrust couple would explain the issue? I am planning to flush the aelerons again. Peter _____ From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of David J. Gall Sent: Tuesday, 17 October 2006 7:43 PM To: Q-LIST@... Subject: RE: [Q-LIST] Flight characteristics questions Sam, I think you're thinking backwards here. The described behavior indicates sparrow strainers that are too small, not too large; or not angled enough (trailing edge up) instead of too steeply. Without sparrow strainers, when the airplane inadvertently goes faster than its trimmed airspeed, the slight undercamber of the LS(1) elevator causes aerodynamic force that pushes the trailing edge of the elevator up. This lets the airplane's nose come down and allows the airplane to accelerate to a yet-higher speed. NOT GOOD! The sole purpose of sparrow strainers is to REVERSE this pattern. When the nose inadvertently drops and the speed builds, the sparrow strainers should push the trailing edge of the elevator down so as to raise the nose of the airplane, thus slowing it back down. Conversely, when the airplane slows down (due to an inadvertent climb) the decreasing dynamic pressure on the sparrow strainers lets them allow the trailing edge of the elevators to come up (usually in response to a down-spring in the trim system), lowering the nose and restoring the airplane to it's original airspeed. This is speed stability. It is closely associated with pitch stability, but is not the same thing. Burt Rutan devoted several issues of his Canard Pusher newsletter to describing it, discussing it, and reporting on the requirements for it in his several homebuilders' designs. Another clue to incorrect speed stability is light or "sensitive" pitch control, as reported in Mr. Q2fun's item #1. True, pitch sensitivity is also a function of CG position, but given two otherwise identical airplanes with the same CG location, the one with greater speed stability will have less-sensitive pitch feel. That's because the greater aerodynamic forces of the larger or more effective (larger/correct deflection angle) sparrow strainers will cause the elevator stick force to be greater for any given deflection of the elevators away from their trim position. It's kind of like using a larger paddle on a canoe, you just have to pull harder to get it to move through the water. A more effective sparrow strainer will also need to be met with greater tension in the pitch down-spring of the spring-type pitch trim system at higher airspeeds. If the down spring of the trim system is only lightly loaded at cruise speed or if the up-spring is loaded and the down spring is slack at cruise speed (heaven forbid!) then there is a real problem and a potentially dangerous situation. What happens if the up-spring is loaded at cruise? If the nose drops, the aerodynamic forces get stronger while the spring force stays the same, so the aerodynamic forces "win." The up-spring was resisting the aero forces that want to make the airplane dive, but those forces now win and the airplane dives. Conversely, if the down-spring is loaded at cruise, then a nose drop again means larger aero forces, but those forces (from the sparrow strainers) act to RAISE the nose, not lower it further. Raising the nose restores the airplane to level flight. Rutan advised his builders that his airplane designs should be AERODYNAMICALLY trimmed to a low-cruise airspeed when flown hands-off and with the pitch trim system disconnected. His rationale is that if a crucial part or connection in the pitch control system should fail thereby leaving an elevator completely disconnected from the trim system and the control system, it does not automatically kill the pilot. I do NOT advise disconnecting the trim system in a Q2 or Q200 or even a Quickie because of the risks involved, but you can certainly look at your trim springs and simulate a disconnect by moving the trim control to make them as equally slack as possible. By this method one might be able to get a relative idea of what the sparrow strainers are doing and what the airplane's aerodynamic trim speed is. In summary, I think there is a dangerous situation being described by Mr. Q2fun and I hope he gets his sparrow strainers and trim system looked at by one of the "old heads" on this list to see if it is rigged right or if there's something amiss. I'll wager that the up-spring is doing a lot of work at cruise speeds and just loses the battle against aero forces at speeds above 150 mph. Not good -- not safe! Just my worry-wart two cents worth, David J. Gall BSAE Sacramento, CA toggle quoted message Show quoted text -----Original Message----- From: Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com [mailto:Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com] On Behalf Of Sam Hoskins Sent: Monday, October 16, 2006 5:02 PM To: Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com Subject: RE: [Q-LIST] Flight characteristics questions 1. I think pitch sensitivity is normal, especially with aft CG and at high (8,000+ft) altitude. 2. My plane does the same. The rudder doesn't control bank, the ailerons do. 2. This sounds a little odd. Maybe the sparrow strainers are too big or have too steep of an angle. It could also be that your canard needs to be adjusted up a degree or so. Maybe try installing adjustable sparrow strainers first. That would be an easy experiment. Sam Hoskins Q-200 1,600+ hrs. Murphysboro, IL _____ From: Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com [mailto:Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com] On Behalf Of q2fun Sent: Monday, October 16, 2006 6:28 PM To: Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com Subject: [Q-LIST] Flight characteristics questions Hi All, I have some questions about the flight characteristics of the Q-2. Pitch sensitivity. With an after c/g my Q2 seams pitch sensitive. My Q2 has the LS1 canard, Revmaster 65hp, tail dragger. Is it normal to get more pitch sensitive the more aft the C/G gets? Rudder to control bank. My rudder does not do anything for bank. If the wing is down 5 degrees and you use the rudder to bring it up, all that happens is the plane will yaw and the bank may even get steeper. Is that a normal characteristic of the Q design? With an increase in airspeed above 150 mph indicated the airplane wants to pitch down and farther increase airspeed/pitch down harder. Is this normal? Sparrow strainers to small for this airspeed? I have the standard pitch trim system. I have been flying my Q since April and now have 62 hours in it. It is a joy to blast around the pattern and it is even a joy to put gas in it after a long cross county. It is just a little too slow in cruise 130 kts. Thank You All. Tim Bryant KUNV N86TB Quickie Builders Association WEB site http://www.quickieb <http://www.quickiebuilders.org> uilders.org Yahoo! Groups Links
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David J. Gall #26183 Paul, Not underneath. On top. It is UNdesirable to have undercambered elevators on canards. It IS desireable to have a slight REFLEX (reverse camber near the trailing edge) on the elevators of canard airplanes. This is one distinct reason that the choice of the LS(1)-0417MOD airfoil was such a POOR CHOICE for a canard airfoil, despite the fact that it has been made to work. IIRC, the LS(1) canard was rumored to be the breaking point between Rutan and the rest of QAC. David J. Gall toggle quoted message Show quoted text ----Original Message---- From: paulbuckley@... Date: Oct 17, 2006 13:28 To: <Q-LIST@...> Subj: Re: [Q-LIST] Flight characteristics questions Dave As a matter of interest, an old method of achieving trim was to 'dope' a length of string along the airfoil trailing edge, varying the length to achieve the desired effect. Do you think that this method could be used underneath the GU elevators as an alternative to camber, if only as a temporary explorative measure? Paul Buckley Cheshire England
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MartinErni@... #26198 Danny, This is not a common problem. In fact yours is the first I have heard of. It sounds to me like something is wrong with you sparrow strainers ( a minor fix). But, I would not fly it until you figure it out. Where are you located? Maybe another builder could help you trouble shot it. Earnest Triq200 960 hours
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Danny Creech <dannycreech@...> #26192 "David J. Gall" <David@...> wrote: >Without sparrow strainers, when the airplane inadvertently goes faster than its trimmed airspeed, the slight undercamber of the LS(1) elevator causes aerodynamic force that pushes the trailing edge of the elevator up. This lets the airplane's nose come down and allows the airplane to accelerate to a yet-higher speed. NOT GOOD! Couple of points here. 1. If the TRAILING edge of an elevator goes up, then the nose of the aircraft goes up. Not down. I re-read David's post several times just to make sure I wasn't missing something. 2. More important though is: Are there any other ways to fix this problem without having to put sparrow strainers on?? They increase drag, stick out being easy to damage from airshow goers, and all in all they look ugly. They look like someone didn't design something right and they had to add a fix. Has anyone came up with some other way to fix this problem? Is this problem only on the LS1 wing or do all of the Q2s and Q200s have this problem? Would making a flush mounted tab (anti-servo or something) into the elevator work? ,___ Capt. Danny Creech ^^ Not an aerodynamic engineer obviously.
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Jim Patillo #26195 Danny, When you pull the stick back on a Q in flight, the elevator is deflected down and the result is the nose goes up. Its a canard. Jim Patillo --- In Q-LIST@..., Danny Creech <dannycreech@...> wrote: "David J. Gall" <David@...> wrote: >Without sparrow strainers, when the airplane inadvertently goes faster than its trimmed airspeed, the slight undercamber of the LS(1) elevator causes aerodynamic force that pushes the trailing edge of the elevator up. This lets the airplane's nose come down and allows the airplane to accelerate to a yet-higher speed. NOT GOOD! Couple of points here. 1. If the TRAILING edge of an elevator goes up, then the nose of the aircraft goes up. Not down. I re-read David's post several times just to make sure I wasn't missing something. 2. More important though is: Are there any other ways to fix this problem without having to put sparrow strainers on?? They increase drag, stick out being easy to damage from airshow goers, and all in all they look ugly. They look like someone didn't design something right and they had to add a fix. Has anyone came up with some other way to fix this problem? Is this problem only on the LS1 wing or do all of the Q2s and Q200s have this problem? Would making a flush mounted tab (anti-servo or something) into the elevator work? ,___ Capt. Danny Creech ^^ Not an aerodynamic engineer obviously.
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Paul Buckley #26200 Not this elevator.........it's at the front! toggle quoted message Show quoted text ----- Original Message ----- From: Danny Creech To: Q-LIST@... Sent: Wednesday, October 18, 2006 6:13 PM Subject: RE: [Q-LIST] Flight characteristics questions >"David J. Gall" <David@...> wrote: >Without sparrow strainers, when the airplane inadvertently goes faster than its trimmed airspeed, the slight undercamber of the LS(1) elevator causes aerodynamic force that pushes the trailing edge of the elevator up. This lets the airplane's nose come down and allows the airplane to accelerate to a yet-higher speed. NOT GOOD! Couple of points here. 1. If the TRAILING edge of an elevator goes up, then the nose of the aircraft goes up. Not down. I re-read David's post several times just to make sure I wasn't missing something. 2. More important though is: Are there any other ways to fix this problem without having to put sparrow strainers on?? They increase drag, stick out being easy to damage from airshow goers, and all in all they look ugly. They look like someone didn't design something right and they had to add a fix. Has anyone came up with some other way to fix this problem? Is this problem only on the LS1 wing or do all of the Q2s and Q200s have this problem? Would making a flush mounted tab (anti-servo or something) into the elevator work? ,___ Capt. Danny Creech ^^ Not an aerodynamic engineer obviously. ------------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.408 / Virus Database: 268.13.4/480 - Release Date: 17/10/2006
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Jon Finley <jon@...> #26194 Not on our airplanes.... Elevator trailing edge up = nose down. Elevator trailing edge down = nose up. David wrote it correctly. This plus the fact that stick left = right roll and vice versa are the reason that these planes are so hard to fly. ;-) (kidding about the roll thing) Jon Finley N90MG - Q2 - Subaru EJ-22 Legacy http://www.finleyweb.net/Q2Subaru Mid-Valley Airpark, Los Lunas, NM toggle quoted message Show quoted text -----Original Message----- From: Q-LIST@... [mailto:Q-LIST@...]On Behalf Of Danny Creech Couple of points here. 1. If the TRAILING edge of an elevator goes up, then the nose of the aircraft goes up. Not down. I re-read David's post several times just to make sure I wasn't missing something.
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Danny Creech <dannycreech@...> #26199 Darn if your not right! As soon as you responded I thought about it and it only makes since! Sheeesh. I guess that is why I leave all the design to the engineers and I just fly them. <GRIN> I just know I'm going to get drug through the mud for making that statment! I guess I'm just not used to the tail being upfront where it belongs. Your a funny guy Jon. Danny Creech >Not on our airplanes... . Elevator trailing edge up = nose down. Elevator trailing edge down = nose up. David wrote it correctly. This plus the fact that stick left = right roll and vice versa are the reason that these planes are so hard to fly. ;-) (kidding about the roll thing) Jon Finley N90MG - Q2 - Subaru EJ-22 Legacy
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Danny Creech <dannycreech@...> #26201 Yeah, stupid me. I knew I was going to get it on this one. GRIN Danny Creech Jim Patillo <logistics_engineering@...> wrote: Danny, When you pull the stick back on a Q in flight, the elevator is deflected down and the result is the nose goes up. Its a canard. Jim Patillo --- In Q-LIST@..., Danny Creech <dannycreech@...> wrote: "David J. Gall" <David@...> wrote: Without sparrow strainers, when the airplane inadvertently goes faster than its trimmed airspeed, the slight undercamber of the LS(1) elevator causes aerodynamic force that pushes the trailing edge of the elevator up. This lets the airplane's nose come down and allows the airplane to accelerate to a yet-higher speed. NOT GOOD! Couple of points here. 1. If the TRAILING edge of an elevator goes up, then the nose of the aircraft goes up. Not down. I re-read David's post several times just to make sure I wasn't missing something. 2. More important though is: Are there any other ways to fix this problem without having to put sparrow strainers on?? They increase drag, stick out being easy to damage from airshow goers, and all in all they look ugly. They look like someone didn't design something right and they had to add a fix. Has anyone came up with some other way to fix this problem? Is this problem only on the LS1 wing or do all of the Q2s and Q200s have this problem? Would making a flush mounted tab (anti-servo or something) into the elevator work? ,___ Capt. Danny Creech ^^ Not an aerodynamic engineer obviously.
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Allan Farr <afarr@...> #26203 David, The elevators on my GU canard appeared to me to have been put on upside down by the original builder as the trailing edge curved up. I have gone to alot of trouble flipping them over so that the t/e curves down - do you think I should have left them as is? Allan Farr Q2 P.S. On fast taxi runs with the elevators as they were (t/e curved up), the canard didn't want to fly. I need all the lift I can get up front, and that is one reason why I flipped the elevators over. toggle quoted message Show quoted text ----- Original Message ----- From: david@... To: Q-LIST@... Sent: Wednesday, 18 October 2006 13:11 Subject: Re: [Q-LIST] Flight characteristics questions Paul, Not underneath. On top. It is UNdesirable to have undercambered elevators on canards. It IS desireable to have a slight REFLEX (reverse camber near the trailing edge) on the elevators of canard airplanes. This is one distinct reason that the choice of the LS(1)-0417MOD airfoil was such a POOR CHOICE for a canard airfoil, despite the fact that it has been made to work. IIRC, the LS(1) canard was rumored to be the breaking point between Rutan and the rest of QAC. David J. Gall ----Original Message---- From: paulbuckley@... Date: Oct 17, 2006 13:28 To: <Q-LIST@...> Subj: Re: [Q-LIST] Flight characteristics questions Dave As a matter of interest, an old method of achieving trim was to 'dope' a length of string along the airfoil trailing edge, varying the length to achieve the desired effect. Do you think that this method could be used underneath the GU elevators as an alternative to camber, if only as a temporary explorative measure? Paul Buckley Cheshire England
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Doug Humble <hawkidoug@...> #26204 Allen - can you take some photos and post them to the photos folder? Doug "Hawkeye" Humble A Sign Above www.asignabove.net Omaha NE N25974 toggle quoted message Show quoted text ----- Original Message ----- From: Allan Farr To: Q-LIST@... Sent: Wednesday, October 18, 2006 4:39 PM Subject: Re: [Q-LIST] Flight characteristics questions David, The elevators on my GU canard appeared to me to have been put on upside down by the original builder as the trailing edge curved up. I have gone to alot of trouble flipping them over so that the t/e curves down - do you think I should have left them as is? Allan Farr Q2 P.S. On fast taxi runs with the elevators as they were (t/e curved up), the canard didn't want to fly. I need all the lift I can get up front, and that is one reason why I flipped the elevators over. ----- Original Message ----- From: david@... To: Q-LIST@... Sent: Wednesday, 18 October 2006 13:11 Subject: Re: [Q-LIST] Flight characteristics questions Paul, Not underneath. On top. It is UNdesirable to have undercambered elevators on canards. It IS desireable to have a slight REFLEX (reverse camber near the trailing edge) on the elevators of canard airplanes. This is one distinct reason that the choice of the LS(1)-0417MOD airfoil was such a POOR CHOICE for a canard airfoil, despite the fact that it has been made to work. IIRC, the LS(1) canard was rumored to be the breaking point between Rutan and the rest of QAC. David J. Gall ----Original Message---- From: paulbuckley@... Date: Oct 17, 2006 13:28 To: <Q-LIST@...> Subj: Re: [Q-LIST] Flight characteristics questions Dave As a matter of interest, an old method of achieving trim was to 'dope' a length of string along the airfoil trailing edge, varying the length to achieve the desired effect. Do you think that this method could be used underneath the GU elevators as an alternative to camber, if only as a temporary explorative measure? Paul Buckley Cheshire England
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David J. Gall #26206 Cap'n Dan, They look like someone didn't design something right and they had to add a fix. BINGO! Well, not quite. Airfoil choices are a compromise and sometimes a band-aid is needed to make a particular choice work in a particular application. The LS(1) airfoil wasn't the only choice at the time, but it had a goodly amount of marketing hype propelling it along in the early '80's. We've since learned that its not such a hot GA airfoil after all, but for a high wing loading (like on a Q200 canard) it is one of the "good" choices. Unfortunately, its trailing edge is curved just the wrong way for a canard elevator. Strainers are one possible solution to fix such a problem, but not the best for the hangar-rash issues you mention, among others. The advantage of the strainers is that they have a long leverage arm behind the elevator hinge line. You could use a fixed trim tab instead, but it would have to be pretty large since it would be closer to the hinge line. See the Long-EZ "new" canard with the Roncz 1145MS airfoil for the correct way to do it. Roncz essentially designed a fixed trim tab into the airfoil along the entire span of the elevator. Most people don't even notice that it is there, but it is. It is "tweaked" so that the elevator's natural "floating" angle of deflection is appropriate for a low cruise speed for the airplane without any trim system or control system forces being applied. Your strainers should be adjusted similarly, if the designers and builders did their jobs right. Meanwhile, since no one has adapted the Roncz airfoil to the Q-birds, I recommend that you keep the strainers and follow the advice offered on this list, especially the advice to have some experienced sets of eyes look over your plane. I suspect you've got a problem with your strainers or maybe even with the construction of your elevators. David J. Gall P.S. an anti-servo tab could be adapted, but it would only be flush at one elevator deflection, likely close to full "up" elevator (trailing edge down). Tabs, by their very nature, are not "flush." -----Original Message----- From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of Danny Creech Sent: Wednesday, October 18, 2006 10:13 AM To: Q-LIST@... Subject: RE: [Q-LIST] Flight characteristics questions < snip! > 2. More important though is: Are there any other ways to fix this problem without having to put sparrow strainers on?? They increase drag, stick out being easy to damage from airshow goers, and all in all they look ugly. They look like someone didn't design something right and they had to add a fix. Has anyone came up with some other way to fix this problem? Is this problem only on the LS1 wing or do all of the Q2s and Q200s have this problem? Would making a flush mounted tab (anti-servo or something) into the elevator work? ,___ Capt. Danny Creech ^^ Not an aerodynamic engineer obviously.
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David J. Gall #26205 Allan, I don't think there's supposed to be any curve at all in the GU elevators. My plans don't show any. David J. Gall toggle quoted message Show quoted text -----Original Message----- From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of Allan Farr Sent: Wednesday, October 18, 2006 2:40 PM To: Q-LIST@... Subject: Re: [Q-LIST] Flight characteristics questions David, The elevators on my GU canard appeared to me to have been put on upside down by the original builder as the trailing edge curved up. I have gone to alot of trouble flipping them over so that the t/e curves down - do you think I should have left them as is? Allan Farr Q2 P.S. On fast taxi runs with the elevators as they were (t/e curved up), the canard didn't want to fly. I need all the lift I can get up front, and that is one reason why I flipped the elevators over.
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