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#11
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On Fri, 25 Feb 2005 13:27:00 GMT, "Dick" wrote:
Thanks for everyones input. Our group was discussing flying in VFR only (no IMC or IFR) and wing leveler only with respect to roll sensitivity of lightly wing loaded, short wing spanned experimentals. Trying to make summer flying in chop somewhat easier. We didn't plan on turning over controls to the device and would still keep a light grip on the stick; just wouldn't have to constantly play the stick. Although we had the impression that a heavier plane would be more stable in chop and require less than continual input by stick, that wasn't much of an option G. Although not discussed among us, I wonder if an increased dihedral result is possible without actually increasing it physically.. Still would appreciate a little discussion that I can pass on for the next non-flying day. Thanks, Dick My Jungster II has zero dihedral, but 15° of sweepback. The wing loading is about 13 lb per sq. ft. It is quite stable in moderate turbulence. While it can be upset it returns to level flight with very little input. That probably won't solve your problem, but it is another factor. Ed Sullivan |
#12
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Morgans wrote:
"Jan Carlsson" wrote in message ... Dick, I think that winglets would improve roll stability, and L/D, climb performance and high alt. performance. Jan Carlsson At the speeds we fly, winglets do little to nothing. They only become useful at higher speeds. But they will look pretty. Dan, U.S. Air Force, retired |
#13
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When I said "I think" I was very humble...
Regarding winglets I am an "expert" (definition of an expert is someone that have read what other have don :-) Peter Masak did a great pioneer work on effective winglets. result was winglets that didn't decrease performance at high speed as the large earlier winglets. Winglets make the wing act like it was of greater span, the improvement is larger then if the wing was lengthened the amount of the winglets height. And the increase in bending moment is smaller then the longer wing will produce. Winglets and longer wings reduce the induced drag (that come from the work of producing lift) that work is harder at low indicated speed, =slow speed at low altitude, low indicated speed at high altitude and getting there. So even an "high speed" jetliner will be helped by using winglets, it spend a long time at high weight climbing to economical cruising altitude, there it cruise at low indicated speed (what pilot see) or more correct low dynamic pressure. Ok, no one here on RAH build jet liner, some fly them, and some build high performance aeroplanes that have the capability to cruise at high altitude, other aeroplanes can benefit from improvements of winglets too, if you fly very long distances and want most economic, you would like to cruise near (high side of) speed for best L/D ( at alt it will still go fast) here winglets will help a lot. other situations is to improve take off and climb and roll stability AND roll rate, better aileron efficiency. In this case Dick want more stability on a ? small big M ? plane, with winglets he get a wing that "think" that the dihedral is grater then it is, and improve the short wings low speed performance. don correct it would not hurt cruise performance. Jan in ME www.jcpropellerdesign.com Propeller and Performance software "Morgans" skrev i meddelandet ... "Jan Carlsson" wrote in message ... Dick, I think that winglets would improve roll stability, and L/D, climb performance and high alt. performance. Jan Carlsson At the speeds we fly, winglets do little to nothing. They only become useful at higher speeds. -- Jim in NC |
#14
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"Jan Carlsson" wrote in message When I said "I think" I was very humble... I also attempt to be humble. You can always find someone smarter, or bigger, or stronger or ..... than yourself. Regarding winglets I am an "expert" (definition of an expert is someone that have read what other have don :-) Perhaps I have more reading to do. Peter Masak did a great pioneer work on effective winglets. result was winglets that didn't decrease performance at high speed as the large earlier winglets. Winglets make the wing act like it was of greater span, This I know. the improvement is larger then if the wing was lengthened the amount of the winglets height. And the increase in bending moment is smaller then the longer wing will produce. This I did not know. Winglets and longer wings reduce the induced drag (that come from the work of producing lift) that work is harder at low indicated speed, =slow speed at low altitude, low indicated speed at high altitude and getting there. So even an "high speed" jetliner will be helped by using winglets, it spend a long time at high weight climbing to economical cruising altitude, there it cruise at low indicated speed (what pilot see) or more correct low dynamic pressure. Do you have any suggestions that I could do some more reading? I hate it when I am wrong! :-) -- Jim in NC |
#15
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My humour doesn't always come to its right in English not even Swedish. Some
people recognise it as humor. :-) There was an article by Peter Masak on the net some years ago, I have saved it on the puter at my office. As an Captain you can always ref. to §1= Captain is always right. or §2=if Captain is wrong, §1 is what rules. (not a good one in a plane) Jan www.jcpropellerdesign.com "Morgans" skrev i meddelandet ... "Jan Carlsson" wrote in message When I said "I think" I was very humble... I also attempt to be humble. You can always find someone smarter, or bigger, or stronger or ..... than yourself. Regarding winglets I am an "expert" (definition of an expert is someone that have read what other have don :-) Perhaps I have more reading to do. Peter Masak did a great pioneer work on effective winglets. result was winglets that didn't decrease performance at high speed as the large earlier winglets. Winglets make the wing act like it was of greater span, This I know. the improvement is larger then if the wing was lengthened the amount of the winglets height. And the increase in bending moment is smaller then the longer wing will produce. This I did not know. Winglets and longer wings reduce the induced drag (that come from the work of producing lift) that work is harder at low indicated speed, =slow speed at low altitude, low indicated speed at high altitude and getting there. So even an "high speed" jetliner will be helped by using winglets, it spend a long time at high weight climbing to economical cruising altitude, there it cruise at low indicated speed (what pilot see) or more correct low dynamic pressure. Do you have any suggestions that I could do some more reading? I hate it when I am wrong! :-) -- Jim in NC |
#16
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Jim,
In addition the to article I mentioned earlier, http://www.soaridaho.com/Schreder/Te...lets/Masak.htm, take a look at the series posted on http://www.soaridaho.com/Schreder/Te...ts/PSU_Ref.htm Wayne http://www.soaridaho.com/Schreder "Morgans" wrote in message ... Do you have any suggestions that I could do some more reading? I hate it when I am wrong! :-) -- Jim in NC |
#17
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Morgans wrote:
Do you have any suggestions that I could do some more reading? I hate it when I am wrong! :-) I thought I was wrong once, But I was mistaken!. John |
#18
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From the model airplane world here is a product that controls both
pitch and roll. http://www.futaba-rc.com/radioaccys/futm0999.html It operates by optically referencing the horizon. So your day VFR application would be a coincident limitation. I don't know how current autopilots mechanically couple to the flight controls but there are very large hobby servos that could probaby be powerful enough to nudge the controls back and forth in response the the control unit. You could either just use their sensor and build your own controller or attempt to use their controller. BTW- The vibrating piezo gyros used for RC helecopters have some slow drift so you can't use them directly but they do have a lot of promise still for a stabization system. In the hobby application they act more as dampers than absolute references as the horizon would be for the earlier mentioned method. So the hobby gyro could counteract bumps but the steady state error would have to be maintaned by the pilot. Regards Dick wrote: Sitting around the hanger and discussing the possibility of somehow using off-the-shelf electronic/computer components or gadgits for semi-automatic wing leveling on lightly loaded, short wingspans. Not being computer guys, the current thought is that something should be out there that is available cheaply and modifiable to use a simple wing leveler. Having heard someplace that automotive computers, as an example, sense data millions of times leads us to believe that sensing the wing tip initial movement and counteracting very very quickly would be a good thing. As an example: One fellow pictured a rolling ball bearing inside a tube somehow activating a magnetic switch which in turn pulses a dc linear motor to operate the aileron minutely. We are not sure how to detect the very earliest initial wing tip movement or drive the small trim type motor and would appreciate some thoughts or site recommendations to investigate. Thanks, Dick |
#19
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Ah. You might consider pursuing developing a "rate damper". This would be
much simpler than trying to control attitude, as it would only require sensing of rate. This would not act as a wing leveler (well, not exactly, but it might provide some attitude stabilization without correcting for drift), but it would respond to bumps. You'd still fly attitude, but the damper would handle the transients due to turbulence, etc. Being a flight controls engineer, I won't advise you further on this project (not willing to assume any liability on a project I don't control), but I will provide the following advice: (1) Incorporating such capabilities on an aircraft is LOADED with very serious potential hazards, all of which can be mitigated by a very careful and conservative system buildup. These include: - PIO susceptibility - runaway servos that can make it difficult/impossible for the pilot to fly the airplane - high transient electrical loads - high mechanical loads on your airplane (2) Set things up so that you can always turn it off quickly and revert to a normal airplane (i.e. no mechanical load on flight controls from an unpowered servo. Set it up so you can always mechanically trim out what you get from a stuck, hard-over servo. (3) Instrument the system thoroughly during development and test so that you know how hard you're working your airplane. Check with some R/C modelers to get the idea on how to set something like this up. "Dick" wrote in message m... Trying to make summer flying in chop somewhat easier. We didn't plan on turning over controls to the device and would still keep a light grip on the stick; just wouldn't have to constantly play the stick. |
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