danwayland 0 #1 April 2, 2003 1st of all, let me just say that I am not encouraging anybody to try and land a bird suit. However, I think it's interesting to discuss whether or not that might be possible. I heard about these "Ground Effects" from a glider pilot friend of mine who says they can use gound effects to get back to their runway if they've accidentally flown outside of the "wind cone." He said his instructor intentionally had him fly too far away from the airport to glide back given the winds that day, at which point he thought, "Great, now we're landing in a field somewhere, good idea." The apparently $hit hot instructor then took the controls, hook turned the glider, and zoomed very low across a field for a long ways using the efficiency of ground effects to maintain enough speed to climb up to 300', back into the "wind cone" at the end of the field. He was then able to land on the runway. Wing in Ground Effect is an aerodynamic principle which states that lift to drag ratio of a wing increases greatly when the wing is at an AGL altitude equal to approximately half its width. http://home.mira.net/~radacorp/ground_effect.html Would that perchance mean that a 6' tall bird man would have much more efficient lift at 3' than at 3000'? Maybe enough lift to stay aloft at a slow enough forward speed to land in water? Or on the ground? Again. Not encouraging anyone to try this. I just think it's interesting.-- Dan Wayland http://www.danwayland.com Quote Share this post Link to post Share on other sites
kevin922 0 #2 April 2, 2003 I still think a big airbag at least half the length of the runway would make a birdman landing doable. I have felt my GTI "stall" in flight after picking up speed and popping my wings not sure what my forward speed was like at the time though. was thinking about buying the timex gps watch pedometer which uses a gps strapped to your body to wirelessly talk to the watch your wrist and give you info like your forward speed, distance travled, etc. Quote Share this post Link to post Share on other sites
quade 3 #3 April 2, 2003 QuoteWould that perchance mean that a 6' tall bird man would have much more efficient lift at 3' than at 3000'? Maybe enough lift to stay aloft at a slow enough forward speed to land in water? Or on the ground? Define your terms. By "land" do you mean one that is possible to walk away from? As in, "Any landing you can walk away from is a good landing." Anyway, the reduction in drag created by ground effect in flying a wingsuit close to the ground would be minimal at best. Yes, there -would- be a reduction in drag, but in the very short time you'd have to play with it, it wouldn't help you out.quade - The World's Most Boring Skydiver Quote Share this post Link to post Share on other sites
Hooknswoop 19 #4 April 2, 2003 QuoteWing in Ground Effect is an aerodynamic principle which states that lift to drag ratio of a wing increases greatly when the wing is at an AGL altitude equal to approximately half its width QuoteWould that perchance mean that a 6' tall bird man would have much more efficient lift at 3' than at 3000'? Width, not length. Ground effect for a wing suit would probably happen at about 1 1/2 feet off the ground and would help cushion the impact only a little. I still think a wing suit will be intentionall and successfully landed someday. Hook Quote Share this post Link to post Share on other sites
danwayland 0 #5 April 2, 2003 I dunno.... I heard through the grapevine that Yari (pardon me if that's misspelled, and pardon me if this is just gossip) has a little GPS thingy that has indicated he's actually been able to climb during freefall. That is, dive 300' to build up enough speed to climb a few feet. If that's possible at altitude, and if you 'hook turned' your Birdman suit to build up speed, and if the lift to drag coefficient was signifcantly improved by ground effect, and if you did it over water, and if you decreased your weight by not wearing a rig (man is that a no sissies allowed statement or what!)... never mind. Forget I mentioned it. I'm sorry I even brought it up.-- Dan Wayland http://www.danwayland.com Quote Share this post Link to post Share on other sites
kevin922 0 #6 April 2, 2003 QuoteQuoteWing in Ground Effect is an aerodynamic principle which states that lift to drag ratio of a wing increases greatly when the wing is at an AGL altitude equal to approximately half its width QuoteWould that perchance mean that a 6' tall bird man would have much more efficient lift at 3' than at 3000'? Width, not length. Ground effect for a wing suit would probably happen at about 1 1/2 feet off the ground and would help cushion the impact only a little. I still think a wing suit will be intentionall and successfully landed someday. Hook I still say airbag.. and I think I would be willing to try it from small heights.. (to start off with) i can see a giant airbag running half the length of a runway, flying the cessna a few hundered feet up (where it is safe to just jump onto the airbag and be okay.. much like a jumping from the top of a building stunt) i know you wouldn't have much time to get the suit up to speed and whanot but to see what landing on an airbag in a suit would feel like.. seems somewhat safe to me. Quote Share this post Link to post Share on other sites
kevin922 0 #7 April 2, 2003 QuoteI dunno.... I heard through the grapevine that Yari (pardon me if that's misspelled, and pardon me if this is just gossip) has a little GPS thingy that has indicated he's actually been able to climb during freefall. That is, dive 300' to build up enough speed to climb a few feet. If that's possible at altitude, and if you 'hook turned' your Birdman suit to build up speed, and if the lift to drag coefficient was signifcantly improved by ground effect, and if you did it over water, and if you decreased your weight by not wearing a rig (man is that a no sissies allowed statement or what!)... never mind. Forget I mentioned it. I'm sorry I even brought it up. I'm not positive about the positive rate of climb, however I'm pretty sure he's got it down into the single digits.. but if your timing is off you're fawked... Quote Share this post Link to post Share on other sites
quade 3 #8 April 3, 2003 QuoteWidth, not length. To be more accurate SPAN. Ground effect is generally consider to begin at a height above the surface equal to 1/2 the wing span of the aircraft.quade - The World's Most Boring Skydiver Quote Share this post Link to post Share on other sites
ManBird 0 #9 April 3, 2003 The span would actually be maybe 2½' feet, if anyone cares. You definitely can hook the suit. I've had my GTi down to 21 MPH (per ProTrack, so accuracy is questionable, but low-mid 20's a number of times) after 270ing and diving the suit. In a Skyflyer/S3, I wouldn't doubt that fall rate could become extremely minimal. However, as you lose fall rate after a hook, you gain forward speed, and as you shave off forward speed, you gain fall rate, and there really is no "stall point" that would make it safe. Maybe survivable on certain surfaces with PERFECT timing, but definitely not safe. As someone on this site was saying, what kills you is your internal softness. You stop, and you may have minor external injuries or abrasions and that's it, but your brain, heart, etc are just floating around in your body, held by very soft things. They'll stay in motion even when your body is stopped and could tear out of place. That's why some high-speed accidents (impact, swoop, etc) leave the body apparantly unharmed, but result in fatality. If you heart is going 10 MPH in one direction, but you're not moving, it could break away, and you're done. Ground effects on today's wingsuits are probably not quite enough to prevent a fatal fall rate. Not yet, anyway."¯"`-._.-¯) ManBird (¯-._.-´"¯" Click Quote Share this post Link to post Share on other sites
nacmacfeegle 0 #10 April 3, 2003 Definitely an interesting discussion for me, I've been curious about ground effect flight for a while. Geeky I know...Try a google search for Ekranoplane, Caspian Sea Monster, WIG flight, etc etc.... The Russians built some HUGE 'aircraft' like this, mostly experimental though.... -------------------- He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson Quote Share this post Link to post Share on other sites
