Basejumper.com - archive

is it possible to BASE Jump head down, to gain speed, and then use the wing suit to steer through aerodynamics and actually start flying back up? Like in the shape of a U?

Do a search in Youtube. If it's not there, it's not possible.

You have to be really good to perform that, if you succeed, usually you will be able to land back at the exit (or close anyways). A good technique to accumulate a lot of jumps.

my < $0.2

/AV

ever heard of anyone making it back the the exit? if they did what kind of suit?

Only one way to find out. Remember to wear lot of cameras.

No. It is currently NOT possible to gain altitude with a wingsuit without some other source of thrust. Everyone who has landed a wingsuit is dead because of it, and it was most likely unintentional.

This topic reminded me of this:
http://www.youtube.com/watch?v=Am-Z-Dyrtkk

Doesn't look like this guy gains any altitude from doing that:

http://www.vimeo.com/wingsuits#5682033

Yeah, I saw a guy get twenty jumps in three minutes doing that.

Thats a pretty nifty jump...I think the record is a 6mph stall in an x-bird? Correct me if I'm wrong.

In a 59 mph descent I 've flared to a 16 ft climb on GPS. Fall rate obviously went negative several MPH, barometric readings on the mudflap showed -28mph or something nearby so I thought worthless at that moment, but GPS showed a few mph climb. I jumped with someone a couple of years back and he was getting a similiar mild climb on an XS, I didn't put alot of time into flying that suit but I had it down to a 5-6mph fall rate on a basic flare from normal flight after a few tries.

In a true head down dive from a plane I get up to about 165-168 mph fall rate with all wings out, 120's next to a freefall jumper carving on my back is much easier on the suit as any tail flutter usually causes rips at the high end of the speed range. Never tried in the biggest suits on the market yet but if anything close to this, the resultant climb would be substantial. Maybe try it this weekend. Imagine getting the suit to climb 100 or 200 ft, imagine diving below something on the edge of a mountain and popping up over it?

Wow, the X-bird has really given the wingsuit world a new level of oppurtunity, can;t wait to see some of this on video!

I can't wait to hear how that goes!

Regardless of the suit one is flying, I don't think a steady state change of direction can cause a gain in altitude.

Let's look at an example from the real world.

High speed exits.
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About 50ft(?) of altitude is gained from roughly 160knots of instantaneous airspeed. One instant you are in the airplane doing 160 knots and suddenly you are doing 160knots in the air.

160knots of instantaneous airspeed is required to power a change in vertical velocity that overcomes gravity for a very short time and causes a gain in altitude of 50ft.

==============

So going head down followed by a change of direction will not create enough force to overcome gravity and the downward momentum to cause a gain in altitude.

you can't rise up above the exit point without the assistance of a strong updraft or other energy.

think about a rollercoaster. the highest point is where the release occurs. that is where you have the greatest potential energy. once you start downward, you will convert the potential energy to kinetic energy. if a jumper flares the wingsuit, they will convert the kinetic energy back to potential energy. friction & drag will constantly steal energy from the system.

to climb above the start altitude, energy must be added that was not there initially. gliders, hanggliders, paragliders, etc. all get that energy from updrafts. wingsuits generally fly to fast to benefit much. find the right wind conditions with the right ridgeline, and it is theoretically possible.

A near-instantaneous change in the relative airspeed upon exit is not, I think, the cause of these 50' gains in altitude. Reference the lift equation:

http://www.grc.nasa.gov/...es/lift_formula.html

In this case we isolate two variables: the velocity variable, v, and, the lift coefficient ('C sub L')

C sub L is determined by complex factors, including the angle of attack (AOA), but for simplicity's sake we might focus only on the AOA and assume the other factors change insignificantly.

If you reproduced a velocity of 160 knots horizontally, and the same angle of attack and C sub L, it doesn't matter how recently you exited the aircraft. In theory, you would achieve the same actual climb.

[Edit to add: of course, your "steady state" assumption would apply to none of the proposed scenarios]

What do you think caused that force(Lift)?

The force(Lift + Drag) is a result of the airspeed that didn't exist when the jumper was in the plane. Let's not split hairs here.


Not the same climb. If that were possible, the jumper will be subject to the same force.

If the jumper arrives at 160 knots horizontal speed with 30 degrees AoA, the force vector is now pointing in a different direction as the AOA is Glide Angle(arctan(D/L)) + Pitch(negative if below horizon). This force has a smaller component pointing vertically up and there is an additional vertical momentum that must be overcome.

What you need is an 'infinite improbability drive'.

I'm working on a suit prototype that might optimize aerodynamics so I can give it a try from a very low jump over water. Sort of a human paper airplane. If nothing else, I think it might make a cool way to jump short jumps without a parachute

Ah, there it is. Red Bull Flugtag?

Yeah, that doesn't have much in common with us.


A cool way to make short jumps into water without a parachute is to get a clean, controlled entry. Kinda difficult to do with a bunch of fabric hanging off each limb ready to scoop up a load of water.

the water is just for the experiment. I plan to develope this suit and see what heights I can jump from.

Video, please.

I'll have a video in about a month. I'm waiting on supplies to arrive from china. If it works I'll put building instructions on the video

Oh yea, just like Ralphie's jumps with custom suit:
http://www.youtube.com/watch?v=cfURx5p9jOY
Needless to say, very ambitious and bold-go for it!

you can't rise up above the exit point without the assistance of a strong updraft or other energy.

A better way to understand it: The force is a function of the jumper's horizontal kinetic energy, which certainly did exist while the jumper was in the plane. By exiting the aircraft, the wingsuit flyer has a chance to convert that kinetic energy into potential energy. Your sum vector is a function of "airspeed," not "rate of change of airspeed."

I agree that, assuming weight stays unchanged, and thrust remains zero, the sum force equals lift + drag. the lift component of that equation is based on the lift equation which i mentioned previously. drag is the sum of induced drag and parasite drag. None of the above anything to do with the rate of change of airspeed in this case.

not splitting hairs here... it's just physics!

What is the airspeed of the jumper at the peak of their climb, after stepping off the tailgate? It's not 160 knots any more...



i feel like you are intending to talk about a force, but are actually referring to the rate of change of a force.



I would define AOA for a wingsuiter as the angular difference between the angle of the velocity vector of the jumper, and the angle of the mean aerodynamic chord of the jumper. Therefore, AOA is not directly a function of glide angle. In a straight, unaccelerated glide, it is permissible to use pitch and glide angle to get a very good estimate of AOA. But they are not the true determinants of it.

in the case of "this additional vertical momentum" (which I assume you mean in the downward direction), then we are not talking about an object in level, horizontal flight. instead, you are talking about an object that is descending. You are merely describing that the jumper who immediately exited the C-130 has a velocity vector with components of 160 knots horizontally and zero knots vertically. and for the hypothetical jumper in mid-flight, I take it that you are proposing them to have a constant 160 knots horizontal component as well as some downward component as well. This is where we are not on the same page, it seems.

You are talking about a jumper in mid flight, gliding 160 knots in unaccelerated, descending flight. I am talking about a jumper in mid flight, gliding at 160 knots in decelerating, level flight. Trading his airspeed to maintain altitude.

(level in this sense means not climbing or descending, as opposed to "not in a turn")

Theoretically, if the jumper has enough kinetic energy, he can trade it for potential energy.

theoretically. All i'm saying is that there is nothing in the laws of physics that could prevent a properly designed wingsuit, flown by a skilled-enough flyer, from physically (and momentarily) gaining altitude after a dive.

"jus' sayin"

And since we're talking about a C-130...

The T.O. airspeed limitation for a "slick" C-130 with the ramp and door open in flight is 150 knots. Jump run would be at 130 (or possibly 140) knots most likely

Now that's splitting hairs

Sure, it is theoretically possible.

Thanks for the links you PM'd me.

Equations and theory notwithstanding, I'll make it clear (if it isn't painfully evident already) that I have zero actual wingsuit experience.

I searched the DZ.com forums as you suggested. Thinking like a pilot (not a wingsuit jumper) got me fixated on classical laminar concepts of aerodynamics. But a wingsuit is not a glider.

I was introduced to a concept utterly foreign to me-- significant lift, at AOAs far in excess of the critical AOA (see link #1)

I got the impression from the DZ.com thread below (#2) that: jumpers exiting the tailgate on a high-speed jumprun, to climb above their exit altitude, were doing so at an AOA apparently far in excess of critical AOA. (i.e. 30-45 degrees) Is this true? Could someone educate me on the typical AOA experienced during the middle of a wingsuit jump? (I tried googling it but google wasn't a useful friend today)

And I'm definitely willing to tentatively accept Yuri's estimate of 3.567 as the "magic" L/D for level flight, considering I have nothing else to go on and his arugment seems quite reasonable. I also have the impression now that the best L/D achieved in practice is in the low to mid 2's? Is that correct?

This is making me re-think the whole thing...

(1) http://www.aerospaceweb.org/...irfoils/q0150b.shtml

(2) http://www.dropzone.com/...rum.cgi?post=3083486

too tired, i'll leave it at that for now. Thanks for the education!

so much in life is better understood with experience. (just go to a dz and talk to the tandems before they jump. they ask what's it like, and want a clear answer. after landing, they understand, but can't explain it either.)

the best thing is to go, get a wingsuit, and jump out of a plane. see what YOU can do. skill level and body shape will change the performance YOU get. take it slow. work things out. calculations can be a poor substitute for judgment. engineers frequently multiply results by a safety factor; it provides a margin for error.

modern physics constantly works to resolve differences between theory and experiment. trust, but verify!

ps

look at videos of birds. see what they can do, without flapping. especially look at the videos of a falcon diving and pulling up. if they CAN'T do it, neither can you.

I really think the aerodynamics is fairly moot and not particularly important. the limiting factor will be strength. pulling out of a dive generates a lot of forces. I doubt anyone can maintain the rigidity required in their abs and arms to "pull" that one off.

How much WS experience do you have?

At this point I can actually chime in on experience- not for being a bird, but for training hawks & falcons for 7+ years... falcons and other birds most certainly do pull up out of glides/dives all the time, without batting an eye (or a wing).

Maybe you're not trying to say what I think it sounds like you are saying?

Or did you think you knew everything about falcon flying just from watching a youtube video, like i do with wingsuiting

It will be an impressive day when someone finally pulls off what we've been debating in this thread, but i've no doubt it will happen...eventually

Ive logged speeds (vertical) of 8 mph after heavy diving (around 200mph) in my wingsuit.
I know finish Visa has logged climbing of a few mph. Being heavier than me, his dive builds more speed/momentum for the flare that follows.


I wouldnt want to try landing this with the body position and forward speeds involved though...
But for sure....climbing is possible.,,

climbing is not possible

Impossible is only an opinion.
I think it is possible to climb in a wingsuit, One just has to sort out the the ladder on the A.
Take care,
space
ps I still have that hat for you. send me an address.

It actually is JT, though I doubt the diving altitude/speed needed is available in a base enviroment. But done and proven in the skydive enviroment (on a carpet sized wingstuit).

this is a classic.

http://www.youtube.com/watch?v=-vfLDIvBGXE