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wan2doit

Question Proximity Flight

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When flying down the wingsuit's glide slope angle Is it possible to gain altitude if one sees that it is necessary to do so during a wingsuit proximity flight?
Have seen videos of flights that seemed to be within 10-30 ft of ground as the flyer proceeds down a dry creek bed full of rocks and don't know if a person has a chance of corrections for minor miscalculations in terrain vs wingsuit glide angle parallelism.

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Think most, if not all of the experienced proximity wing suit pilots make sure the angle of the line is steeper then their WS glide angle:P Hence they can bail out and seemingly gain altitude by adjusting their angle of attack from a constant dive alongside the mountain to a plane out, still loose altitude compared to sea-level but gaining vertical distance relative ground beneath em.


In this video it appears the pilot gains some altitude just before pulling, but if he was proximity flying, imagine the speed loss and the lack of lift after such a maneuver.
http://www.youtube.com/watch?v=gMkvPDd-8wE

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My understanding is you never gain altitude you only lose altitude at a slower rate. What relatively appears to be going "up" is just within the context of other jumpers who are falling faster, or a mountain side which is angled "down" at a steeper angle than the angle of flight.

In other words: you're always going down, it's just a matter of how fast.

Someone with more experience might be able to explain whether it is possible to actually increase your altitude.

However I would assume even if you managed to momentarily truly gain altitude you would be in danger of an aerodynamic stall fairly quickly, right?

I could be wrong, so I'd be interested in what someone with more knowledge on the subject has to say.

(edited to add: I know exiting a tailgate a jumper in a ws can "pop up" and gain altitude, but I would think the relative wind plus a zero vertical speed allows enough "lift" to gain altitude but once in "normal" flight gaining enough lift to have a negative fall rate would be very very difficult if not impossible... rigid wings and jet engines a la yvess rossy excluded :)

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Thanks 3 Empire,
Another poster WickedWingsuits recommended basejumper.com to me and once there I found this article http://www.flylikebrick.com/articles/flb_fallrate_vs_glideratio.pdf which seems to be quite authoritative and written in pretty plain English.

Looks like down down down except for an almost stall causing flare.

Thanks to all for the help on this.

Frank

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wan2doit

Thanks 3 Empire,
Another poster WickedWingsuits recommended basejumper.com to me and once there I found this article http://www.flylikebrick.com/articles/flb_fallrate_vs_glideratio.pdf which seems to be quite authoritative and written in pretty plain English.

Looks like down down down except for an almost stall causing flare.

Thanks to all for the help on this.

Frank



As mentioned at the end of that PDF that our referenced, As you feel the stall, it does not take much to get going again. A stall is not really like an event, just something to adjust to.
Instructor quote, “What's weird is that you're older than my dad!”

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The111

Correct. Wingsuits don't stall like a plane does because we have non-rigid frames. A wingsuit stall is just a normal freefall.




Correct, but a wingsuit stall while terrain flying would likely be deadly, speed is needed for glide, and the only way to generate speed is gravity. Stall a wingsuit without enough altitude to recover speed and glide or pull, and it's time for a dirt nap.

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3mpire: This is no longer true. Ever since the advent of the Tony suits "Apache" and similar suits, regaining small but significant amounts of altitude went from fantasy and joke to reality. It's not even particularly difficult once you get used to the suit and practice the move. All that is needed is either forward speed or down speed around 100 mph, and the necessary skill.

The attached image is a screenshot from a GPS plot captured during a demonstration of the effect. I managed four of em in one flight. Feels like a roller-coaster complete with zero-G float going over the top, partial stall followed by a shallow recovery drop... when you've got the speed built up, you can repeat it at will once you've got the trick of it. Later tests showed the minimum recharge time is only about 500 feet and you can do it again.

As a side effect of mastering this trick you no longer need a true "High speed exit" to gain altitude from a tailgate aircraft, either. "High speed exit" used to mean firewalling the engines, 160-200+ knots, or as close to Vne as the pilot will give you. Last time I exited a skyvan I was given a warning that they were not slowing it down and we'd all be getting a 120mph exit. The pilot had refused to give me a "real" high speed exit when requested about a year prior, because he had flown a suit, once, a decade ago, and was convinced "You'll rip your arms out at the shoulders" and no amount of "I've done this at least 30-40 times at over 200 knots without harm in the biggest of suits" would convince him otherwise. When people decide to hold opinions out of ignorance it is futile to argue with them so I did not bother. He was our pilot. Sometimes it is better to be diplomatic than to be "right" or win an argument.

However I got the last laugh because I no longer require that kind of speed to climb, anyway. A mere 120 in a heavy Apache-class suit was FAR more than enough to produce the effect. The resulting video from my helmetcam looked like I'd been shot almost straight up from a slingshot. I was looking way, way down at the skyvan within about 4 seconds.
-B
Live and learn... or die, and teach by example.

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With the glide ratio, I think technically if you're climbing you're beyond 'glide ratio' territory. High GR is still a downward sloping flight path path. 2:1, 3:1, 5:1, 100:1 are all approaching a straight horizontal flight path but you're still descending. But once you cross over that horizontal (climb up even briefly) your GR will spike off the chart.

Having said all that, and looking at the graph again, there are some instances where it peaks, but not off the chart. I'm no expert on how the data is compiled in these devices so someone else may have some more informative comments. :)

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I have to admit I had never given much thought to it until today but after some quick googling I believe once you're talking about truly "flying" as opposed to "gliding" you start talking about lift-to-drag ratio instead of glide ratio. Wikipedia says that for gliders and wingsuits the glide ratio and lift-to-drag ratio can be the same when speed is constant but with varying speed the two can diverge.

I'm not sure if it is "correct" to represent a negative glide ratio or once you cross that threshold you just switch to lift-to-drag...?

Links:

http://en.wikipedia.org/wiki/Lift_to_drag_ratio
http://en.wikipedia.org/wiki/Gliding_flight#Examples

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If you think the technical data is a hoot, you should see the visual effect when you do it on a cloud. Scooting UP the side of a cloud and clearing the top will blow, your, mind. For just a few seconds, the cloud and landscape below it are receding. At the top, during the +...0...- transition you get 5-7 seconds of total silence and a reacceleration curve equivalent to a still-air BASE or balloon exit.

I've been mapping the physics of this for about a year and a half now. Establishing a working fallrate range in the negative numbers. The instrumentation gets flaky this far outside design parameters... there's a huge amount of slop built in. On the borderline, a weak climb, my alti and GPS often disagree... sometimes the alti reports a climb, GPS reports a 0mph planeout, and sometimes the exact opposite, GPS shows solid climb, alti shows fallrates in the low single digits.

There's also error in the GPS software. If you really look close at that graph you'll see the plot technically contradicts itself in several places... the red "altitude" curve shows 4 distinct climbs, one of which barely qualifies... probably got 20-40 feet at best... but the fallrate display only shows one spike to a solid "-5" mph the rest show around zero give or take 3-5 mph.

But when you do it dramatically enough, the instruments will disagree as to the magnitude of the climb but both will agree that a climb happened. GPS will report +75 feet, fallrate -5mph, Altitrack will playback a -29 mph climb and show a regain of more like 150+ feet. Watching the Altitrack playback the altitude and fallrate in realtime is surreal... altitude loss slowly tapers off to zero, then the numbers start ticking back up for a few seconds.

Both instruments have hard-to-measure inaccuracies inherent to their nature. GPS is most inaccurate on the Z axis, and an altimeter can be somewhat fooled and its results exaggerated or muted by airflow transients, so neither can be taken as an absolute, but combined and then compared to actual freefall time from video gives a very solid idea how roughly accurate it actually WAS.

Last all-out flight I did, Altitrack showed freefall time 4:21 exit to opening from 13.5-2800-ish. I kinda doubted this till I played back the video... which showed exactly 4:21 till the canopy stood me up. So although there's slop and inaccuracy, that inaccuracy is limited and a certain amount of faith can be placed on it.

So when you see BASE guys claiming to outfly impossible-looking terrain, they ain't lyin'. They've got short burst glide ratios available that spike out the same way that graph does. I'm far from the only bird to be able to do this. It has become almost common, now.
-B
Live and learn... or die, and teach by example.

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that is way cool that you are able to get that performance even with the instrumentation variation. I hadn't thought about the sound that has to be like being suspended in mid air, I can only imagine how cool/weird that has to seem.

I'm obviously not a BASE jumper though I try to learn as much as I can about it out of intellectual curiosity.

I noted up thread you said you needed about 100 MPH vertical speed to generate enough lift to hit that sweet spot where you start to climb.

What kinds of vertical speeds are common on a BASE flight?

I'm sure even at lower vertical speeds where you're not actually climbing you can flatten your glide angle enough to have a wide envelope to operate in. But looking at the graph and the altitude I'm not sure I'd try that maneuver so close to the ground :D

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lurch

Feels like a roller-coaster complete with zero-G float going over the top, partial stall followed by a shallow recovery drop... when you've got the speed built up, you can repeat it at will once you've got the trick of it.



That sounds ridiculously fun!

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Its fun beyond all ability to communicate. The most fun part of it is the swoopy "going over the top" soaring, launched-from-a-cannon feeling that goes with it. First time I did one of those I -knew- I'd just got the suit to climb even before I saw the alti and GPS results. If you've never experienced it, there's just no way to really describe it, but when you get it, oh, BOY do you know it. Its a very visceral, "WHOA, HOLY SHIT!!!" sort of feeling you can't mistake for anything else.

You can get the eerie silence at speeds around 29 and below... maintain it and all you get is a very quiet hissing sound in your ears... no windblast at all. Its tricky to get the suit to hook up properly and stabilize under 30 mph but when it does, things go quiet and STAY quiet and you're just floating around up there all day. I love it... :)-B

Live and learn... or die, and teach by example.

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That's a great question. When proxy flying you have to dive the suit below the suits trim angle in order to generate speed ,which can then be converted into glide when needed.There are a few different ways to dive the suit that I use - raking the arms back , lowering the chest by bending at the waist, lowering the chest by bending at the waist and then matching the leg wing angle to the chest angle.
The one thing that proxy videos don't show very well is just how steep the terrain that is being flown actually is.

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in reply to "So when you see BASE guys claiming to outfly impossible-looking terrain, they ain't lyin'. They've got short burst glide ratios available that spike out the same way that graph does. I'm far from the only bird to be able to do this. It has become almost common, now. "
.......................................................

hi there lurch,

Just to clarify this statement ...are you saying some base fliers are now using actual (relative to true horizon) climbing flight to clear obstacles ? ( ps I have no doubt modern wingsuits are capable of climbing flight)

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lurch

Its fun beyond all ability to communicate. The most fun part of it is the swoopy "going over the top" soaring, launched-from-a-cannon feeling that goes with it. First time I did one of those I -knew- I'd just got the suit to climb even before I saw the alti and GPS results. If you've never experienced it, there's just no way to really describe it, but when you get it, oh, BOY do you know it. Its a very visceral, "WHOA, HOLY SHIT!!!" sort of feeling you can't mistake for anything else.

You can get the eerie silence at speeds around 29 and below... maintain it and all you get is a very quiet hissing sound in your ears... no windblast at all. Its tricky to get the suit to hook up properly and stabilize under 30 mph but when it does, things go quiet and STAY quiet and you're just floating around up there all day. I love it... :)-B



Haha wow, I'm only just starting out, but wingsuiting has always been something I've been keen on working towards. Your description of it has sold me on it for sure. Any tips for skills in particular to focus on developing in my first few hundred jumps if I want to wingsuit one day?

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Start focusing on tracking jumps in the last 50 jumps or so before you get into wingsuits. Start getting used to thinking of a skydive as a 3d flight path where you're going somewhere. Where you got out where you're going and where you want to be when you open. Keeping track of that at all times throughout the skydive is a critical foundation skill especially for wingsuit flying.

Beyond that, just have fun your first few hundred jumps. Even for people focused just on getting to wingsuits, your first few hundred jumps you're still just working on general education in skydiving.

Have patience. Get used to the idea that 200 jumps is just getting started, 200 wingsuit jumps is also, just getting started -again-, and it is going to take probably 4-700 wingsuit jumps just to start getting a really clear picture of whats going on, on any given jump. When I hit 1000, I started feeling like maybe I knew what I was doing. By 1500, I was certain I didn't. Another 1000 jumps later, I have more to learn than ever.

Fly an oversized, docile canopy. I stuck with a Sabre 2 170 loaded at about .9 for my first 700-something jumps at least. Best decision I ever made. Security blanket saved my ass more times than I could count. Let me get away with all kinds of mistakes until I didn't make them anymore. Got so I could put it anywhere I wanted it in any weather.

First and foremost focus especially if you wanna be a bird has to be on awareness and survival skills. Doing cool stuff is pointless if you're doing it stupidly and only surviving on lucky breaks.
Never, ever let your guard down.
-B
Live and learn... or die, and teach by example.

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No. To my knowledge nobody is betting on climbs yet.
But there's a bunch of terrain flying going on now that is visibly betting on short term glide ratio where if you didn't set it up right you aren't gonna be flying flat enough to clear the obstacle.

Valerii Salcutsan showed me some spectacular footage from what I think was a recently opened line in Romania somewhere. It involved crossing a gap and then clearing a ridgeline. From the exit, that ridgeline looks flat-out impossible to reach, let alone clear. At the start of the video, the camera was looking at it, but I didn't believe they'd go for it, till they did.

If you don't get the setup right and turn the last half of the approach into the ultimate planeout from hell you will not clear the ridge and if you're lucky, you figure it out in time and bail to the left. The visuals are breathtaking.

-B
Live and learn... or die, and teach by example.

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lurch

Start focusing on tracking jumps in the last 50 jumps or so before you get into wingsuits. Start getting used to thinking of a skydive as a 3d flight path where you're going somewhere. Where you got out where you're going and where you want to be when you open. Keeping track of that at all times throughout the skydive is a critical foundation skill especially for wingsuit flying.

Beyond that, just have fun your first few hundred jumps. Even for people focused just on getting to wingsuits, your first few hundred jumps you're still just working on general education in skydiving.

Have patience. Get used to the idea that 200 jumps is just getting started, 200 wingsuit jumps is also, just getting started -again-, and it is going to take probably 4-700 wingsuit jumps just to start getting a really clear picture of whats going on, on any given jump. When I hit 1000, I started feeling like maybe I knew what I was doing. By 1500, I was certain I didn't. Another 1000 jumps later, I have more to learn than ever.

Fly an oversized, docile canopy. I stuck with a Sabre 2 170 loaded at about .9 for my first 700-something jumps at least. Best decision I ever made. Security blanket saved my ass more times than I could count. Let me get away with all kinds of mistakes until I didn't make them anymore. Got so I could put it anywhere I wanted it in any weather.

First and foremost focus especially if you wanna be a bird has to be on awareness and survival skills. Doing cool stuff is pointless if you're doing it stupidly and only surviving on lucky breaks.
Never, ever let your guard down.
-B



Awesome post. Certainly adjusted my expectations in terms of the number of jumps it will take to progress in this sport. It's all about the journey though I guess. I'm looking at buying a used rig soon, tossing up between a 170 at 1.06 and a 190 at 0.95. As much as I think I want to fly a smaller canopy, I also value being alive in order to do so. In some way I also like the idea of buying a larger docile canopy and just flying the hell out of it. Anyway, thanks again for the detailed posts :)

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Quote

Start focusing on tracking jumps in the last 50 jumps or so before you get into wingsuits.

Quote



This, I disagree with. Amongst other stereotypes, people that have been hard trackers for many jumps before they put on the wingsuit frequently turn out to be the worst students. I'd prefer to have students that stay on their bellies and do RW with their buddies. They're more aware of their bodies vs learning (usually bad) habits that don't really apply to wingsuiting.



Start getting used to thinking of a skydive as a 3d flight path where you're going somewhere. Where you got out where you're going and where you want to be when you open. Keeping track of that at all times throughout the skydive is a critical foundation skill especially for wingsuit flying. ***

This.

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