FAR's and wingsuit landing w/o a parachute?

[Hooknswoop 19]

If he landed on a slope equal to his glide ratio, wouldn't the impact be zero? All he would have to worry about then is sliding to a stop, which is done by motorcycle racers all the time. ????

Derek

[AndyMan 7]

Motorcycle racers are usually on flat, smooth, paved surfaces... Not bumpy hills of varying pitch.

Secondly, the airplane landing on the runway is very close to having his glide match the runway, but often times the pilot errors which results in a hard landing.

It'd be extremely difficult for a wingsuit jumper to perfectly match the angle of the hill, since that hill will almost invariably change its pitch throughout the run, never mind accounting for human error. The wingsuit jumper should not plan on hitting it 100% right on, since that is nearly impossible, certainly implausible. Any plan for landing a wingsuit succesfully must have a margin of error.

_Am

__

You put the fun in "funnel" - craichead.

[billvon 2,427]

> If he landed on a slope equal to his glide ratio, wouldn't the impact be
> zero?

Well, you can't land on a slope equal to your glide ratio. You'd never touch it. You have to land on a slope that's slightly less than your glide ratio, or purposely lower your glide ratio to descend to the slope. So there will always be an impact of some sort.

>All he would have to worry about then is sliding to a stop, which is done
>by motorcycle racers all the time.

It is unusual for motorcycle racers to impact with more than a few feet per second of vertical speed; they start out two feet above the ground. So their impact is guaranteed to be very low.

Now, if you wanted to achieve the same sorts of speed with a wingsuit landing, you'd have to make the final approach at a speed of, say, 2fps relative to the slope. So you'd lose 2 feet per second, or 120 feet per minute. If you stabilize your final approach 20 feet above the slope (which I think is really low!) you'd need 1600 feet of runway before you even start slowing down.

[kallend 1,647]

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> If he landed on a slope equal to his glide ratio, wouldn't the impact be
> zero?

Well, you can't land on a slope equal to your glide ratio. You'd never touch it. You have to land on a slope that's slightly less than your glide ratio, or purposely lower your glide ratio to descend to the slope. So there will always be an impact of some sort.

>All he would have to worry about then is sliding to a stop, which is done
>by motorcycle racers all the time.

It is unusual for motorcycle racers to impact with more than a few feet per second of vertical speed; they start out two feet above the ground. So their impact is guaranteed to be very low.

Now, if you wanted to achieve the same sorts of speed with a wingsuit landing, you'd have to make the final approach at a speed of, say, 2fps relative to the slope. So you'd lose 2 feet per second, or 120 feet per minute. If you stabilize your final approach 20 feet above the slope (which I think is really low!) you'd need 1600 feet of runway before you even start slowing down.

Another data point. I am a glider pilot. The seat of a typical glider has minimal padding, maybe none on a trainer (sit directly on the plywood or sheet metal seat). There is no "suspension", the wheel is unsprung. The compliance in the tire and your gluteus maximus is the only "give" between your spine and the ground. Most gliders land on turf runways, which are far from smooth. Off-airport landings can be on very rough ground, and are common.

Yet glider pilots walk away uninjured after the vast majority of landings.

...

The only sure way to survive a canopy collision is not to have one.

[billvon 2,427]

>The compliance in the tire and your gluteus maximus is the
> only "give" between your spine and the ground. Most gliders land
>on turf runways, which are far from smooth. Off-airport landings
>can be on very rough ground, and are common.

Ah, but your butt can still take a lot more impact than your chest can, and your torso is set up to take loads from that direction. Look at the tandem butt-slide. Add six inches of compliance and you're in reasonably good shape. Add another six inches from structural deformation in a crash, and it's no wonder most pilots walk away from even hard landings. (Not just glider pilots either.)

But a chest impact, with no padding - there's a reason a great many motor vehicle impact deaths were dissected aortas before airbags came into vouge. You just can't take much deceleration trauma there.

[darkwing 4]

It can be both fun and frustrating to listen to a bunch of people with just enough knowledge to sound expert discuss technical issues, in this case, physics.

There are a couple of current threads with lots of physics in them, and it regularly happens to various degrees, where there are plenty of expert-sounding posts, from people with varying experience levels. It is a reminder to me that on issues where I am not expert I have to be very careful in evaluating expert-sounding postings. Having lots of jumps doesn't make anyone an expert in physics. Heck, I'm living proof that it doesn't even make you a good skydiver.

One reason we have jump numbers and rigger ratings in the profiles is so we can use them to make credibility value assignments to the poster's comments. Although such simple pieces of information in the profiles are not unflawed, they are better than nothing. Unfortunately, lots of people can make physics-talk sound correct, and we have little, if any, way to assess their actual expertise.

So, when I'm watching mountain climbing (for example, since I know nothing about it) on TV, and there is a lot of serious, technical sounding commentary, I just hearken back to all the RealTV episodes about skydiving that sounded authoritative, but were laughably, absurd.

-- Jeff
My Skydiving History

[kallend 1,647]

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>The compliance in the tire and your gluteus maximus is the
> only "give" between your spine and the ground. Most gliders land
>on turf runways, which are far from smooth. Off-airport landings
>can be on very rough ground, and are common.

Ah, but your butt can still take a lot more impact than your chest can, and your torso is set up to take loads from that direction. Look at the tandem butt-slide. Add six inches of compliance and you're in reasonably good shape. Add another six inches from structural deformation in a crash, and it's no wonder most pilots walk away from even hard landings. (Not just glider pilots either.)

But a chest impact, with no padding - there's a reason a great many motor vehicle impact deaths were dissected aortas before airbags came into vouge. You just can't take much deceleration trauma there.

I doubt anyone will survive a chest-first bad landing of the same magnitude that would crush a glider's structure. Question is, can he survive a chest first good landing? How good does it have to be.

...

The only sure way to survive a canopy collision is not to have one.

[mjosparky 3]

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I doubt anyone will survive a chest-first bad landing of the same magnitude that would crush a glider's structure. Question is, can he survive a chest first good landing? How good does it have to be.

I think the only way to know the answer to that question is obvious. This could be really interesting.
Sparky

My idea of a fair fight is clubbing baby seals

[billvon 2,427]

>Question is, can he survive a chest first good landing? How good does it have to be.

That is indeed the question. Along with -

How does a wingsuit fly in ground effect? Will it result in a pitch-up or pitch-down tendency?

How will the aerodynamics of the suit change as contact is made? Will it still be stable as contact is made?

What sort of protection do you need to survive a 70mph face-first chest-down slide down a mountain?

[goose491 0]

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Motorcycle racers are usually on flat, smooth, paved surfaces... Not bumpy hills of varying pitch.

Someone made a reference to speed skiiers and the amount of effort and work that goes into snow preperation and the building of the slope itself.

You are grasping... the hill does not have to be bumby... nor of varying pitch.

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It'd be extremely difficult for a wingsuit jumper to perfectly match the angle of the hill,

Jean Loic did it. It's called the "Mountain Swoop"... check it out sometime.

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since that hill will almost invariably change its pitch throughout the run

There you go again. I'm pretty sure Jeb's going to make sure the pitch is constant... and that most of the "bumps" are smoothed out. The "slope" that he will land on... well that can be built to his specific dimentions... it's truly not an issue.

My Karma ran over my Dogma!!!

[goose491 0]

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Motorcycle racers are usually on flat, smooth, paved surfaces... Not bumpy hills of varying pitch.

Someone made a reference to speed skiiers and the amount of effort and work that goes into snow preperation and the building of the slope itself.

You are grasping... the hill does not have to be bumby... nor of varying pitch.

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It'd be extremely difficult for a wingsuit jumper to perfectly match the angle of the hill,

Jean-Albert did it. It's called the "Mountain Swoop"... Check it out

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since that hill will almost invariably change its pitch throughout the run

There you go again. I'm pretty sure Jeb's going to make sure the pitch is constant... and that most of the "bumps" are smoothed out. The "slope" that he will land on... well that can be built to his specific dimentions... it's truly not an issue.

My Karma ran over my Dogma!!!

[AndyMan 7]

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Jean Loic did it. It's called the "Mountain Swoop"... check it out sometime.

I've seen Loic's hill swoop. Actually, I think that's a great example of the dificulty of the stunt. It also gives a practical indication of the speeds involved. Note that the hill was bumpy, and of varying pitch. What's being discussed here is an order of magnitude more dificult.

The problem with landing a wingsuit on a hill is clearly not just getting close, it's touch-down and managing the "landing roll slide".

I'm doubtful that a perfectly flat, perfectly straight hill of sufficient length currently exists. I presume building one is outside the budget constraints.

_Am

__

You put the fun in "funnel" - craichead.

[goose491 0]

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I'm doubtful that a perfectly flat, perfectly straight hill of sufficient length currently exists. I presume building one is outside the budget constraints.

You wouldnt' have to build one.. you'd just have to smooth the bumps and inconsistencies out of one that already exists.

Are you going to tell me that on this vast rock, there is not one slope that is long enough that can be worked into a nice smooth surface? Again, you are grasping. Again, you are focusing on the wrong aspect.

People are arguing the physics in here (and that's not even the topic of the thread btw).



Edited for respect

My Karma ran over my Dogma!!!

[AndyMan 7]

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Are you going to tell me that on this vast rock, there is not one slope that is long enough that can be worked into a nice smooth surface?

Within reasonable budget constraints, yes.

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Again, you are grasping

And you're being disrespectful.

_Am

__

You put the fun in "funnel" - craichead.

[billvon 2,427]

>you'd just have to smooth the bumps and inconsistencies out of one that
>already exists.

I think perhaps you underestimate the difficulty of preparing a smooth surface on a very steep hill that does not change its slope over the course of a thousand feet or so. Ski places will occasionally do it over a smaller distance (a few hundred meters) for ski jumping - we're talking about something much longer and much flatter.

I have no doubt that this will eventually be achieved. It will NOT be achieved by someone who just smooths out a few bumps on a mountain and figures they can land there.

[goose491 0]

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>2)The man is still landing on a slope, a privilege the Jet does not >have.
>(vectored forces)

Again, doesn't matter. It's the distance he has to decelerate in. If his approach speed to the surface is X just before contact, then X is the important number no matter what angle the surface is (even upside down.)

Landing on the slope absolutely makes a difference Bill!!

We have a perfect example of how landing on a slope makes a difference to your deceleration trauma. Extreme Skiers! They jump off of cliffs at heights NO human could ever survive. But because they are landing on a slope, and because they carry forward motion, they survive the great falls because deceleration does not all have to occur in the "5 milliseconds" that you provide.

It is comparable to a NASCAR driver... if he plows head-on into a wall at full speed, his car must decelerate to Zero mph in the short distance provided by the 'crumple' of his car (the compression of the ribs). The distance is too short, so the value of 'a' in f=ma is so great that we all know 'f' is far to great as well. Too much FORCE... he will not survive.

If the same driver hits the wall with the same speed, but this time he hits it at an angle, there are two vectors to the FORCE that will decelerate him. One perpendicular the wall, the other parallel it. The Force Vector perpendicular the wall is met by an equal but opposite force from wall to car. Some kinetic energy is absorbed by the crumpling of his car at the corner and a slight deceleration is manifested as a result. But more importantly, it redirects the car so that the rest of the FORCE used to decelerate it is the FORCE of friction... parallel the wall. He rides along the wall... the rest of his speed is bled off... he survives.

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Doesn't matter. Deceleration is the key issue, not mass.

So which is it now Bill? What's gonna hurt you? Is it the distance, the Deceleration?... it's the FORCE that will get you and I see your argument... but you have him decelerating in such a short distance and time that there is no hope for him. See here:

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That is the crux of the matter. How much deceleration distance is there? Let's take an example:

15mph, 3/4 of an inch compression on your chest before your ribs break. D=.5AT^2, so you decelerate in 5 milliseconds. Total G-force? 137 G's.

Perhaps you can compress your chest 3 inches before your ribs break. If that's the case, you will see 31 G's. That's a lot of stress on that vessel.

... you are assuming the jumpers entire downward vector of 15mph will be decelerated by the compression of his ribs... and in 5 milliseconds. Truly you must be aware that this is not the case as the jumper will continue to slide down the hill after initial impact.

As far as the Physics are concerned, they are sound. A wingsuit can be landed.

The surviveability is this stunt is arguable only by the length of the landing area (because it will have to be loooonnnng) and the jumpers ability to stay stable once he/she has touched down (because it will be faaaaaasssst). The jumper will NOT experience a traumatic impact upon said touchdown. The biggest risk assumed would be that once sliding on the ground at crazy-breakneck speeds, he/she is unable to maintain directional stability and begins to roll or flip.

My Karma ran over my Dogma!!!

[goose491 0]

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Again, you are grasping

And you're being disrespectful.

[billvon 2,427]

>They jump off of cliffs at heights NO human could ever survive. But
>because they are landing on a slope . . .

Again, it doesn't matter that they're landing on the slope. If you hit a 45 degree slope going straight down at 30mph, the impact is the same as if you had hit a flat slope going 30mph at a 45 degree angle. It's the closing rate, not the angle, that matters. Since mountains have handy slopes that allow slow closure rates, skiers use them.

>So which is it now Bill? What's gonna hurt you? Is it the distance, the
> Deceleration?

The deceleration. The distance you have to decelerate gives you a minimum deceleration you will see. If that deceleration is greater than that which you can survive, no fancy padding/slope/angle in the world is going to help you.

>... you are assuming the jumpers entire downward vector of 15mph
>will be decelerated by the compression of his ribs... and in 5
> milliseconds. Truly you must be aware that this is not the case as the
> jumper will continue to slide down the hill after initial impact.

Of course. But that doesn't matter. He could be going 100mph or standing still; it's the closure rate perpindicular to the surface.

15mph represents about a second and a half of freefall, or roughly 30 feet. If you can survive a chest-first fall onto a flat surface from 30 feet, you can survive a 15mph closing speed landing.

>As far as the Physics are concerned, they are sound. A wingsuit can
>be landed.

Well, drop an elephant out a skyvan and I can 100% guarantee you that he will land. The big question is what shape the elephant will be in afterwards.

>The jumper will NOT experience a traumatic impact upon said
>touchdown.

Again, that depends upon closure speeds. If they are low, then he will not experience much of an impact. If they're high, he will.

[itllclear 1]

If I missed this somewhere earlier in the thread sorry, but --

Does anyone have the details on the horizontal sppeds of the ski jumpers on the 90 meter jump?

It may be that we're trying to re-invent the wheel, and there are people who already are landing on slopes at speeds (horizontal and vertical) close to what a wingsuit can provide.

P.S. -- I'll watch ... from a distance.

Blue Skies!

Harry

"Harry, why did you land all the way out there? Nobody else landed out there."

"Your statement answered your question."

[darkwing 4]

Here is a link to the official requirements for a ski jumping hill. Look at page 36 and beyond. I'm too busy to do the calculations now, but they won't be difficult, at least to get some reasonable numbers. Note that ski-flying hills are "badder."

-- Jeff
My Skydiving History

[goose491 0]

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Again, it doesn't matter that they're landing on the slope.

directly contradicts:

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Since mountains have handy slopes that allow slow closure rates, skiers use them. (this in reference to jumping from unsurvivable heights whilst skiing and landing it on a downhill slope)

The wingsuit cannot sustain horizontal flight. The sloped landing area matters... it is crutial.

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If you hit a 45 degree slope going straight down at 30mph, the impact is the same as if you had hit a flat slope going 30mph at a 45 degree angle.

This is pretty much obvious. But it's not what we are dicussing. Our daring wingsuit pilot is not hitting a 45 degree slope coming straight down nor is he hitting a flat slope at an angle.

He is going to match the angle of the landing areas slope... and then make his angle slightly steeper.

He's coming in at 43 degrees on your 45 degree slope (where "up" is 0degrees and we are counting clockwise).

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It's the closing rate...

Precisely! Matching your 45 degree slope for example lends itself to a situation where "He will never land" as you said yourself. Adjusting your sink rate by a little bit will have your glide slope become slightly steeper... sligthly

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It's the closing rate...

Precisely. But the closing rate between what? The glide slope and the landing area's slope right?. So how is it that one of those two angles "doesn't matter" ?

The wingsuit has limitation. It will not be able to make a "slow closure rate" unless he has a sloped landing area to match his glide slope to... then can adjust said glide slope accordingly.

(Don't forget that when the two slopes are matched, you may be traveling at 18-30mph, Down, relative to the centre of the earth, but you are traveling ZERO miles per hour down relative to the landing area.)

My Karma ran over my Dogma!!!

[billvon 2,427]

>The wingsuit cannot sustain horizontal flight. The sloped landing area
>matters... it is crutial.

For the final time, IT DOESN'T MATTER what slope the landing is from an impact attenuation point of view. If your speed PERPINDICULAR to the surface is 15mph at impact, the impact will be the same no matter what the slope.

I think you are confusing vertical speed with closing speed perpindicular to the surface. Take someone who hits a flat surface and an 80 degree slope while in freefall. The guy who hits the flat surface is going to see a closing speed of (cos 0)*120mph, or 120mph. The guy who hits the 80 degree surface is going to see a closing speed of (cos 80)*120 or 20mph.

>He's coming in at 43 degrees on your 45 degree slope (where "up" is
>0degrees and we are counting clockwise).

Now that we can work with! At a forward speed of 100mph, an 88 degree angle away from the perpindicular will give you a closing speed of about 4mph. or about 5fps.

>The wingsuit has limitation. It will not be able to make a "slow closure
> rate" unless he has a sloped landing area to match his glide slope to...
>then can adjust said glide slope accordingly.

Right. And choosing that slope will be critical. Let's say it's the same as his best glide. He may still not be able to land; once he enters ground effect his L/D increases and he climbs away from the slope. Let's say it's _less_ steep than his best glide. Now he will be able to land, but not bail on an aproach (unless he can stay in ground effect until he goes over the edge or something.)

[AndyMan 7]

Consider a jet on approach to O'hare.

The runway is level and flat. You could say that it has a pitch of zero degrees.

An heavy DC11 is on approach. It's descending on a 5 degree slope.

At touchdown, the DC9 "colides" with the runway at a 5 degree angle. The landing gear easily absorb the shock, and the captain taxi's whats left of the airplane back to the loading gate.

Now consider a wingsuit flyer.

The jumper spends 10 million bucks to build a flat and stright ski slope with a constant pitch of 45 degrees.

The wingsuit flyer is on approach to the hill, doing his best to match the slope. However, since he's tired, the best he can do is a pitch of 40 degrees.

At touchdown, the wingsuit flyer "colides" with the hill at a 5 degree angle. Rescuers attempt to find his head.

Whether it's 40 vs. 45, or 0 vs. 5, the force of impact is exactly the same.

The difference in the gravity vectors is irrelevant, because it's energy is relatively insignificant compared to that of the jumpers kinetic energy at 40 degrees.

_Am

__

You put the fun in "funnel" - craichead.

[mjosparky 3]

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If I missed this somewhere earlier in the thread sorry, but --

Does anyone have the details on the horizontal sppeds of the ski jumpers on the 90 meter jump?

It may be that we're trying to re-invent the wheel, and there are people who already are landing on slopes at speeds (horizontal and vertical) close to what a wingsuit can provide.

P.S. -- I'll watch ... from a distance.

Blue Skies!

Harry

Harry,

Ski jumpers land on their feet with big long skies. The wingsuit pilot is going to land on his face. If he lands in a bowl of jello at any angle, he is fucked.

Sparky

P.S. ---- I am the guy standing next to Harry, at a distance.

My idea of a fair fight is clubbing baby seals

[goose491 0]

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If your speed PERPINDICULAR to the surface is 15mph at impact, the impact will be the same no matter what the slope.

This is my point. Your speed is not 15mph PERPENDICULAR to the surface. It's 15mph PERPENDICULAR the horizon. Gravity pulls you to the centre of the earth... not perpendicular whatever slope you happen to be on. Gravities force upon you is vectored as well when you are on a slope... that's how skiers ski.

Your speed is ZERO perpendicular to the surface as you have matched the glide slope.

Your speed PERPENDICULAR the surface will be a funcion of the smallest increment you can ajust your sink rate by.

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Right. And choosing that slope will be critical.

"Ah", We're getting somewhere....

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Let's say it's the same as his best glide. He may still not be able to land; once he enters ground effect his L/D increases and he climbs away from the slope.

Groud effect will take place only for a height equal to the wingspan of the vehicle... that's not very high off the ground... and it's ADDED lift.

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Let's say it's _less_ steep than his best glide. Now he will be able to land, but not bail on an aproach (unless he can stay in ground effect until he goes over the edge or something.)

Golly! Where have I heard that before? I think it might have been in one of MY posts!

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The surviveability is this stunt is arguable only by the length of the landing area (because it will have to be loooonnnng) and the jumpers ability to stay stable once he/she has touched down (because it will be faaaaaasssst). The jumper will NOT experience a traumatic impact upon said touchdown. The biggest risk assumed would be that once sliding on the ground at crazy-breakneck speeds, he/she is unable to maintain directional stability and begins to roll or flip.

So your argument is still that the angle of the landing area doesn't matter (For the final time) ?

My Karma ran over my Dogma!!!