WS Altitude change after high speed pass

[mnskydiver688 0]

For those who have done a high speed pass out of a tail exit, how high above the plane do you think you got? I was having a discussion with another jumper about this.

Sky Canyon Wingsuiters

[mccordia 73]

Video (unless its 1st person) is a poor judge of height.

If you look at someone staying on level with the airplane, from the perspective of a flyer who is doing a normal 'drop' (exiting earlyer)then on video it looks like the person is climbing way high above the plane, while actually he is staying on level.

I had a few (lower speed) exits where on video of others it looked like I was way, way, way above the airplane, just keeping on climbing. While from my own perspective, I never got above the airplane..

But viewer perspective aside..doing a proper exit, body at about 45 degrees on the airstream, opening op smoothly, and pushing yourself 'up' on the relative wind in a maximum flying position, you can get a good amount of 'free' extra altitude.

The key is good 'climbing' exits is the smooth opening up.
If you just exit all open, then the blast of the wind will only push you back, or even demolish and tear your wings.

On most high speed passes, you easily get 10 to 30 meters above the airplane. In some extreme cases (exits of around 140 knts) Id guess up to around 200 or so meters would be possible.

So roughly 500 Ft of extra altitude would be my guess...testing and trying for more..

JC
FlyLikeBrick
I'm an Athlete?

[mnskydiver688 0]

That video is where my question originates. The other jumper didn't believe that ~500ft was possible on a high speed pass and that the wide angle lens was throwing me off. At what speed would you have to worry about blowing apart you or the suit?

Sky Canyon Wingsuiters

[mccordia 73]

There is a little distortion due to a (moderate) wide-angle lens, but the height you see here is pretty much what it looked and felt like in person.

Honestly...inside I was stuck in between "OOH DAMN THIS IS COOL" to actually being a little scared and worried about the height (sounds silly..I know)

Costyn and I shot a lot of exits like these during a boogie at Spa (Belgium) last year. And we also have some cool video on exits like these shot from inside the plane.

The pilot loved playing with exit speeds.
We slowly increased the exit speeds from 100 knts to 145 knts. And there wasnt too big a difference between anything over 130 knts.
Next time we meet the pilot/plane, we'll try and see how fast (and as a result of that; high) we can take it.

If you browse through skydivingmovies or look on our website at the (full)video for the Hercules Boogie 2004 also has a segment on high speed exits (set to Robie Williams "Radio") with some amazing footage from Vesa and Andy Ford (even barrelrolling on exit)

There are some exits shot from a (fighter)plane flying next to the hercules. Also clearly showing the climbing (sadly not following the wingsuits out all the way)

Blowing your suit apart is not about the speed. Its about the technique.
Though proper construction does help of course.

You need to exit closed, and smoothly (in half a second or so) open up, and 'push' yourself up into full flight (climb)
Exit completely open, and you'll just get pushed back or hear a big "BANG!" and find yourself in normal freefall with nylon confetty hanging from your body (seen it happen to a friend of mine)

JC
FlyLikeBrick
I'm an Athlete?

[chrisgray 0]

250+ feet of gain is not uncommon at an exit speed of 130 knots.

It is quite the rush to do a high speed exit the first time.

WSI-6 / PFI-55
The Brothers Gray Wingsuit Academy
http://www.myspace.com/cgwingsuitpilot
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[mccordia 73]

And on a safety related side-note:

People who skydive with a BASE pouch for their pilotchute (notice the word 'BASE' in there, its not called the 'SKYDIVE' pouch) should not/never/ever attempt any high speed exits (or backflying, or flying with un-experienced other flockers), unless they have a severe interest in killing themselves or their fellow jumpers..

A premature deployment would in all situations be a potential hazard to anyone flying close or behind you.

When the plane is doing 130+ knts, its even possible to stay on level with the tailgate plane in a normal 'tracking' (without a wingsuit) when done properly..

Jarno gives you the big thumb up!
Its up to you where you put it (just pimping my new avatar)

JC
FlyLikeBrick
I'm an Athlete?

[mnskydiver688 0]

Oh I am sure. I have to learn to fly one though first! I'm sure it's one of those few times in skydiving where you do feel your stomach in your throat.

Sky Canyon Wingsuiters

[Skyjester 0]

hi,this time is the first time I ask before I try...do you think it,s possible to fit a 30m nylon rope with certain safety quick release stuff for last ws-pilot connected to tail-exit plane\chestbelt+flying above the aircraft for long time and distance---behind a offshore boat with my manta(inflatable wing 1,5²m) it works,so why not up there.?

don´t pester the jester . . or better: WHY SO SERIOUS ? ?

www.pralle-zeiten.de

[LouDiamond 1]

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hi,this time is the first time I ask before I try...do you think it,s possible to fit a 30m nylon rope with certain safety quick release stuff for last ws-pilot connected to tail-exit plane\chestbelt+flying above the aircraft for long time and distance---behind a offshore boat with my manta(inflatable wing 1,5²m) it works,so why not up there.?

E-mail Felix B., he can tell you all about doing that

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[mccordia 73]

Felix tried it and spent some time spinning behind an airplane. Tearing part of the tail off. Much like a single-rope kite trailing behind a running child. Not too succesfull.
The video used to be on skydivingmovies. Maybe someone can dig up the link.

Joe Jennings also performed that stunt, bodysurfing behind a c172 on tow-rope in his camera-suit. That was succesfull and looked like a lot of fun..

JC
FlyLikeBrick
I'm an Athlete?

[vesatoro 0]

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You need to exit closed, and smoothly (in half a second or so) open up, and 'push' yourself up into full flight (climb)
Exit completely open, and you'll just get pushed back or hear a big "BANG!" and find yourself in normal freefall with nylon confetty hanging from your body (seen it happen to a friend of mine)

I think the suit ripping apart comes more from the wrong exit angle (combined with open wings) than having all wings open. I think the key for not losing the speed given by the plane is to exit in as shallow angle as possible, more at about 30 degrees than 45 degrees, and spread the wings more or less immediately. And if not exiting in shallow angle, trying to make the angle shallower just after the exit at the beginning of the "climb". At about 30 degrees angle of attack you're much nearer the angle of attack of efficient flight, thus creating as much lift and as low drag as possible.

Vesa

"Fear is the path to the Dark side"
(Master Yoda)

[yuri_base 1]

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At about 30 degrees angle of attack you're much nearer the angle of attack of efficient flight, thus creating as much lift and as low drag as possible.

Even for most efficient wing profiles with infinite span the maximum lift at AoA of 10..15 degrees before the stall is about equal or less than the lift at approximately AoA=45 degrees (see this article). Most wings - and more so us in wingsuits - generate maximum lift at about 45 degrees - at 10..15 degrees or 30 degrees it's only a fraction of that of at 45.

For climbing above the plane, it's the lift that matters, since initial speed is purely horizontal, so the drag which is opposite to speed, plays no role in your climb.

Therefore, 45 degree pitch angle is the most efficient technique for the climb.

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[tr027 0]

A+ on the hypothesis! Experience however, should intuitively (only if you fly enough and I realize it's winter) remind you that wingsuits don't fly at 45 AOA; they stall much sooner (as do parachutes), even at the slightly higher jumpship airspeeds. Perhaps with your new instrumentation, and jumpship GPS synched with WS GPS, get some actual comparison data on this.

"The evil of the world is made possible by nothing but the sanction you give it. " -John Galt from Atlas Shrugged, 1957

[Skyjester 0]

thanks , I didn`t knew that . . .Jarno,your example about the running kid is sweet see no problem and Yes,we do video

don´t pester the jester . . or better: WHY SO SERIOUS ? ?

www.pralle-zeiten.de

[yuri_base 1]

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wingsuits don't fly at 45 AOA

You're talking about efficiency (maximum or at least decent L/D), which in this case - climbing above the plane as high as possible - is not... efficient (no pun). What is necessary is to maximize the force that pushes you up. Since in the first few seconds of high-speed exit your speed is almost entirely horizontal (the vertical speeds during the climb - 10-20mph are still much less than horizontal ~120-160mph), that force is lift.

For most bodies - be it a superefficient glider, a slab of wood or a brick, the lift is maximum at around 45 degrees (+/-5 degrees).

Stall is a significant drop of lift when AoA exceeds certain value (usually 10-15 degrees). After passing through the minimum, lift goes up again with increasing AoA and reaches maximum at ~45. And that's what we need for the climb.

By the way, because our body dampens the lift/drag characteristics of the wings so much, overall we do not have that dramatic drop of lift (if at all) as airplanes do. The lift simply monotonically (although not as a straight line) increases from 0 at AoA~0, reaches maximum at ~45 and goes back to zero at ~90 degrees.

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they stall much sooner (as do parachutes), even at the slightly higher jumpship airspeeds

Stall has nothing to do with airspeed. You are confusing powered level flight (where AoA to maintain level flight depends on speed) with nonpowered gliding. Stall is a function of AoA only.

And "wingsuits don't fly at 45 AOA" is a 666th reason why flocking sucks, since that's typical AoA for most flocks (L/D=1).

Yuri

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Windows only: WS Studio

[tr027 0]

I'll be very interested in seeing data from any experiments on this topic if any are ever done, because all the firsthand observations I have in my wingsuiting experience (watching many exits from various jumpships) say otherwise.

"The evil of the world is made possible by nothing but the sanction you give it. " -John Galt from Atlas Shrugged, 1957

[RJmoney 0]

yeah i think the best pops i see and get are when they people are facing straight into the wind blast. the 45 degrees makes complete sense in my head but whenever i get pushed near that by not exiting with my legs bent and together i don't get a good pop. (unless its the jet, i messed that one up and still got a helluvan exit)

word to your mother,
RJ$$
BASE 1117

[mccordia 73]

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unless its the jet, i messed that one up and still got a helluvan exit

The type of aircraft has less to do with this, its 100% the airspeed its doing at the moment of exit. If a plane flies fast enough, even after a shoddy exit, you can still 'climb' back up to way above the plane.


All the math aside...what I do (and also what I seem to see most other people do) indiciates roughly a 45 degree angle works best.

The flatter you are, the less altitude you seem to win. Instead you then seem to use the throw of the airplane to maintain (closer) the same speed as the plane..When you're more upright, you only get pushed 'back' by the oncoming wind.
If you're a bit headlow, the wind pushes you on the back or top of your wings, and actually throws you down (or into a spin)

If you check Vesa's exit (attached pic) in the Hercules Boogie 2004 video, seen from the side, you can see the rough angle at which the body is, relative to the plane. And that is excactly 45 degrees.

JC
FlyLikeBrick
I'm an Athlete?

[tr027 0]

Thanks for the picture. Looks like the other two in the picture who are at the same AOA also got way above the plane. Nice work.
and with that I've exceeded my postings limit for the month (3 in last 2 days) so will go back to lurking.

"The evil of the world is made possible by nothing but the sanction you give it. " -John Galt from Atlas Shrugged, 1957

[RJmoney 0]

yeah that picture explains it well.
and i'm not an idiot i know the jet isn't what gave me the boost, it was the airspeed.

word to your mother,
RJ$$
BASE 1117

[yuri_base 1]

As a humble father of the new exciting sport - Theoretical Wingsuiting - I must say that I'm delighted to learn that my predictions work without the need to hurl myself from 'em perfectly good airplanes. You guys are my heroes - and you, Jarno, are the Number One - testing my theories without even realizing it, risking your life for the sake of my baby - Wingsuit Science!

That said, look at the picture and rotate it clockwise 45 degrees, you'll see a 3-way flock.
Suppose that you do a high speed pass at 160mph at the same AoA and body position. The total aerodynamic force will be increased proportionally to the square of the airspeed increase, or (160/85)^2 = 3.6 times. That's the force of the blast you expect to feel when you exit: 200lbs*3.6 = 720lbs! As before, lift and drag are equal and are L' = D' = 720lbs/sqrt(2) = 509lbs. 500lbs pushes you up above the plane and 500lbs pushes you back, away from the plane. You are jerked up at 1.5G acceleration, and just in 1s your upward speed is increased from 0 to 50ft/s!

Man, you take some beating or what! While I'm happily drinking cold silver Sapporo on my magic wingsuit couch wearing an invisible nanotube wingsuit on the naked body.

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[vesatoro 0]

OK, Jarno and others, maybe it just feels "flatter" than it really is :D

"Fear is the path to the Dark side"
(Master Yoda)

[yuri_base 1]

Another illustration of the simple and beautiful physics of non-powered flight:

What jumprun speed do you need to start climbing above the plane - with or without wingsuit (in tracking position)?

To start climbing right after exit, you need lift be greater than your weight: L' > W (here prime denotes high-speed pass values). If in sustained tracking or wingsuit dive your total speed is v and lift is L and you do high-speed exit at speed v' at the same AoA and body position, L' will be increased by the factor of the speed squared:

L' = L*(v'/v)^2

In sustained flight,

L = W*(L/D)/sqrt(1 + (L/D)^2)

Combining everything, we get this condition:

W*(L/D)/sqrt(1 + (L/D)^2)*(v'/v)^2 > W

or

v' > v*(1 + 1/(L/D)^2)^(1/4)

For example, if you can track at L/D = 0.8 with total speed of 115mph (90 down, 72 forward), you can go above the plane at the jumprun speed of 145mph. If you fly wingsuit during flocking at 60 down, 60 forward (total 85mph), you need the minimum of 101mph to start climbing. If you're a heavier jumper with 70 down, 70 forward, you need 118mph.

Anybody climbed above the plane without wingsuit in tracking position at 45 degrees?

Android+Wear/iOS/Windows apps:
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iOS only: L/D Magic
Windows only: WS Studio

[willpower 0]

climbed above a herc c130 the other day - awesome feeling to look down on the plane. anyway, i felt that keeping my legs only slightly bent and shut until the relative wind hit my arms helped to maintain the head-up angle... then just hold out on the arms and open the leg... and voila

things are not as they appear, nor are they otherwise

[VectorBoy 0]

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As a humble father of the new exciting sport - Theoretical Wingsuiting

Or what wikipedia refers to as mental masturbation with reference to nylon. BTW not a sport.