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#11
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drake wrote:
Hi, there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c) which, when attempting a stall, does not pitch down correctly. Instead one of the wings (either port or starboard (50/50)... no gyro problems due to engine) almost always drops, and this genreally results in the a/c entering a spin (which the rookie pilots are unable to handle, generally). There is no inherent imbalance in the c.g. location due to the fuel tanks ot fuel flow. What could be causing such a wing drop while stalling? Is it soem inherent instability in the roll axis? Sounds like a good rudder trainer. |
#12
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Lars,
Fit wedges on the leading edges at the wing roots to force a root stall. Some WW2 era military trainers tip stalled to enhance training experience and the root wedge fix is used to remove the characteristic (and surprise) for civilian warbird use. Albert (drake) wrote in message om... Any help/advice/recollection of previous such problems and what you did to fix it will be greatly appreciated. Lars |
#13
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On Sat, 10 Jan 2004 00:03:57 GMT, john smith
wrote: drake wrote: Hi, there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c) which, when attempting a stall, does not pitch down correctly. Instead one of the wings (either port or starboard (50/50)... no gyro problems due to engine) almost always drops, and this genreally results in the a/c entering a spin (which the rookie pilots are unable to handle, generally). There is no inherent imbalance in the c.g. location due to the fuel tanks ot fuel flow. What could be causing such a wing drop while stalling? Is it soem inherent instability in the roll axis? Sounds like a good rudder trainer. Sounds like my Debonair. And...no it doesn't have wedges on the wing roots although it does have the little 1/4 inch stall strips about 6 inches long. I don't think the first 60 or so had any washout either, but I'd have to dig deeper on that. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
#14
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Ditto Chuck's response. On one of my experimental gliders, I designed a
delta-wing using a reflex airfoil (M-178 I think.) However, I did not wash out the tips, and I used wingtips that terminated in a sharp points. Big mistake. When tested at high AOA's, massive tip stalls caused the wing to roll 45 degrees and yaw 180 degrees about every 3 seconds. Curiously enough, the Wright boys (yep, them again) used washed out wingtips on the 1902 glider. Harry "flies under polyethylene too" Frey PS: Funny what you can learn from watching the (stress) hawks fly. Isn't it? |
#15
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#16
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Dave Hyde wrote:
Wright1902Glider wrote: When tested at high AOA's, massive tip stalls caused the wing to roll 45 degrees and yaw 180 degrees about every 3 seconds. Was this a model or was it piloted? Dave 'bowling balls' Hyde Yea, that'd be heck in a dog fight. You could fly a tight landing pattern, though. Nafod "nafod" 40 |
#17
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Hi all,
Thanks for your replies. The a/c in question is: http://www.bharat-rakshak.com/IAF/Im...nt/Deepak.html The wingdrop problem has been solved (some years back). Just learnt that all the engineers did was to replace the counter-sunk flat top rivets on the wing-top (holding the skin to the ribs) were replaced by protruding pan-head rivets, which apparently energised the flow (made it more turbulent?). There were rivets all over the wing, but more towards the wing-root side. This solved the wing drop problem i.e. the wing drop while stalling was then gentle enough to be handled by novice pilots. I still am not completely satisfied with the turbulence explaination... why should a more "energised" flow make the wing drop less violent? One character who worked on this kite several years ago said that the stall actually started mid-wing, and progressed very quickly, so that one wing (entire wing, not just the tip or root) stalled and dropped. Dunno if he was farting or not. Has anybody used the protruding rivet approach before to solve wing aerodynamic problems before? Quite a minimalist solution! Drake Lars |
#18
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drake wrote:
Hi all, Thanks for your replies. The a/c in question is: http://www.bharat-rakshak.com/IAF/Im...nt/Deepak.html The wingdrop problem has been solved (some years back). Just learnt that all the engineers did was to replace the counter-sunk flat top rivets on the wing-top (holding the skin to the ribs) were replaced by protruding pan-head rivets, which apparently energised the flow (made it more turbulent?). There were rivets all over the wing, but more towards the wing-root side. This solved the wing drop problem i.e. the wing drop while stalling was then gentle enough to be handled by novice pilots. I still am not completely satisfied with the turbulence explaination... why should a more "energised" flow make the wing drop less violent? Sounds like the round head rivets are acting like turbulators. If the boundry layer is not attached to the surface, none of the "energy" in the flow is transfered to the surface. Basically, tickling the boundry layer like that causes it to reattach to the surface. That's what they mean by "energizing" the flow. Make more sense? Richard (the new improved)Lamb Hi ya'll! |
#19
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Separation bubbles?
OT: BTW, my experimental glider was a full-sized HG, and I tested it both clipped-in and unclipped. The second method was preferable, as the first allowed the glider to drag me all over the beach at Kitty Hawk. I should note that when I designed this machine, I had very little understanding of the fine points of non-rigid delta-wing aerodynamics. There's a photo of it on my website. Its the "Stormy Petrel 3" photo. The "Stormy Petrel 2A" was a modified "Batso" glider and flew fairly well. Harry http://hometown.aol.com/wright1902/page3.html |
#20
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Todd
Further on your experience. A number of model airplanes I have seen had very rapid roll off as the airspeed was reduced approaching the stall. On landing this caused the wing to drop and bird cartwheel. One solution was to glue a piece of string along the crown of the air foil. Another was to put a wedge shaped piece of balsa on the wing leading edge near the fuselage. Both seemed to work ok and made the birds flyable by new bees. Same techniques will work on full size aircraft. Big John Pilot ROCAF On Thu, 15 Jan 2004 14:51:10 -0500, Todd Pattist wrote: Richard Lamb wrote: Sounds like the round head rivets are acting like turbulators. My glider uses a strip of tape that looks like Dymo labeling tape with a string of periods punched into it to turbulate the flow. Todd Pattist (Remove DONTSPAMME from address to email reply.) ___ Make a commitment to learn something from every flight. Share what you learn. |
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