Di0

unkulunkulu

Why so long posts. Will headwind affect the vertical speed of said aircraft a couple seconds after takeoff or not? yes or no?

Yes, from an absolute point of view *.

Long post was trying to explain what "affect" means. In a certain frame of reference, people that say it does not, are correct. In another, they are not, hence the confusion.
Headwinds helps steeper climbs, therefore they affect the triangle and composition of velocities from a ground perspective (this can't be disregarded by analyzing only relative speeds).

And why what happens to an airplane might not directly transfer 1:1 to a parachute.

When potatoman said equal relative speeds means equal everything else he is also correct, 100%. But to me, that's not the whole picture. IMHO.
Problems are a little complicated and hard to explain sometimes.

* Absolute here meaning Earth Reference.

However, I have to say that what is true from the point of view of an engineer (which sits on the ground) becomes less important from the point of view of the PILOT, whose ass is on the plane/canopy, once you reach a certain equilibrium point (w.r.t airspeed), things don't change anymore.

If horizontal winds would not affect lift, then kiting stuff would not be possible.

airtwardo

Quote

...with big fat student canopies or similarly sized wings the induced and parasite drag of the main canopy are so high that the little parasite drag of the slider won't really matter anyway.

Wanna BET?!

Maybe as a STUDENT you don't notice the difference, but put a few thousand jumps on 'big - fat' canopies & you'll see a definite & marked improvement regarding performance.

I have a few large canopies used for demo jumps...I've gone to removable sliders on most of them. Pull the release handle and as the slider comes off & the drag is gone - & the risers get full spread ~ it's like lighting the afterburner!

Mmmhhhh... yes! I love betting on these things!!!
Eheheh!
But seriously, I wasn't making it up.
When reading about collapsing the slider (since, as said, it was giving me hard times), I remember finding this:
http://www.icaruscanopies.aero/index.php?option=com_content&view=article&id=6&Itemid=652

Coming from Icarus Support, I tend to believe their estimate are quite correct.

Your take off run will be shorter (i.e. another word for faster), since you already "start" at a windspeed of 10mph (let's say) instead of 0. (that's why I said that in general speaking, faster could both mean steeper ascent of faster ascent, they are two different concept in aircraft dynamics).

But I see what you mean when you say "relative speed" you're right, if the relative speed is the same, then the lift and the mechanics are exactly the same.
It's just that a word like "faster" usually is meant in an "external" and absolute reference of frame, to me faster means less time or less runway space.
"Faster" is not relative, that's where the confusion comes from. I do agree that doing 0mph ground speed into an 80mph front wind or doing 80mph with no wind are to a good degree the exact same thing from the plane point of view, however from an external point of view the ascent with head wind is much steeper (i.e. the downward slope is reduced by head wind).
Imagine this: a plane with 0 wind and doing 80mph (ground speed) is flying on a straight line.
The same plane with 40 mph wind still doing 80mph is able to climb because of the head wind, now the relative speed is 120mph so it has an excess of lift, we all agree with this, right?
Yes, you might say: relative speed just changed, but this is EXACTLY the effect of wind and you can't ignore it by saying that it does not affect horizontal and vertical speed of the plane.
That is what I mean when I say that on a plane head wind changes the equilibrium point of flight.

I don't need to ask a pilot, I'm an aerospace engineer.
A pilot might not notice because all he reads is airspeed, but wind speed will change its trajectory w.r.t. to the rest of the world, quite a lot, both vertically and horizontally.




EDIT:
Maybe a site written in proper english will make it more clear, I forgive if my writing kind of sucks, but just google "effects of wind on take off" or something like that:

http://www.experimentalaircraft.info/flight-planning/aircraft-performance-4.php

"Headwind
By taking off into the wind (the wind will generate part of the required lift) the aircraft lifts off sooner and this will result in a lower ground speed and therefore a shorter take-off run for the aircraft to become airborne."

... etc. etc...

Bring this to an extreme, a kite horizontal speed is affected ONLY by headwind.

Very true.
Also, I've had the problem, especially on old-ish and worn risers/handles, that when trying to pass the slider over the brakes to get it behind the neck, it would tangle, tied up, clear one riser but not the other and get stuck there, etc. etc.
Quite annoying, I once had to land using the brake lines themselves to flare, rather than the handles, it was of course and off landing and it wasn't exactly into the wind, so it looked quite horrible. Not too bad since I jump huge canopies and not very loaded, but something to keep in mind.
It's certainly an extra complication

potatoman

Does a plane climb faster flying into wind, or with the wind?

Climbs exactly the same.

Keyword: Relative, not cousin.

Wrong analogy. A plane will have to push into the wind to create lift, therefore -fact well known to a pilot - going against the wind will increase the horizontal component of the speed and, leaving all other factors untouched - generate lift "faster". Although we might disagree on what we mean with the word "faster" (in general language, I see how it could both mean steeper ascent or fastest ascent).
That is why airplane always want to takeoff and land INTO the wind.

As for the parachute, I am sure a round canopy would not be affected in its descent by horizontal wind speed whatsoever, as all its lift (or rather, "vertical drag") is purely a matter of shape factor and passive air resistance, as said by pretty much everybody, there is no way for a round canopy to know which direction it is going with respect to the ground, it's just "carried around". It's a completely passive object that would act the same and always have a 0 relative component to the wind, as in itself it does not produce any forward speed and there is no ROTATION of air flow around a profile moving forward in the wind.
The opposite is true for square canopies, I think.
I am not so entirely sure the same is true for a square canopy, which also uses its profile to create lift, in that case more air passing around the canopy should create more lift, similarly to when a bigger mass of air passes around an aircraft rigid wing (more lift is produced at bigger relative speeds, again leaving all other factors untouched).
Now, is the effect secondary compared to others, namely to the main effect of a steady head wind, which is to slow down your horizontal speed, rather than affect your vertical one?
Probably.
But my intuition tells me that for any body that generates lift using a wing profile (as modern canopies do, although very partially), a small effect from head wind vs tail wind on the descent rate should be theoretically present (although maybe not enough to make a difference from a piloting point of view).

less drag, although the effect is becoming noticeable only at higher wingloads/smaller canopies, with big fat student canopies or similarly sized wings the induced and parasite drag of the main canopy are so high that the little parasite drag of the slider won't really matter anyway.

Then also what skydiverek said. Plus less damage on the slider itself from flapping. Final point, it looks cool.

I find wasting food that could be eaten (and a real pie is food) for a "prank" personally disgusting.

Cheap whipped cream, I am totally OK wiht (it's not much and it's chemical for the most part, and it's not that you can "eat" whipped cream if you're hungry), but wasting a couple of good "real" pies for this, honestly would upset me. Of course, shaving cream is fine, whatever. It's the gesture that matters to me, not the material item that gets in your face.

Maybe it's just me being anal, maybe it's not a big deal for everybody else, but that's how I was raised and it really-really-really-really bothers me. If I were in the "buying committee", I would personally oppose buying real pies for a pieing ceremony.
I think it can be called pet-peeve, right?

Hellis

I don't believe thousands of lives would be saved.
My general feeling, meaning I don't have any statistics on it, is that most car crashes with fatalities are not in 60+ mph nor in sportcars.

It would have saved Paul Walker. Which is all the statistics I need.

Joking aside aside, I am pretty sure there is a direct correlation (and causation) with the the speed at which an accident happens and the chance of dying vs surviving the accident. In a cars like in skydiving. The thing is that modern cars developed a lot of active and passive safety mechanisms that keep the passenger relatively safe(ish) from impacts belove 60 mph, either preventing the crash (ABS, Stability Control...) or greatly reducing the damage of the impact (seat belts, airbag, frame studied to dissipate energy etc.).

In skydiving we have no passive safety backups (except for very ineffective helmets), so I personally see the benefits of bundling up with every possible active device people can come up with and is proven to be effective (within reason).


But we are digressing, my point was another, my point was that forcing everybody to use NAV240s would effectively take the fun and the interest from the sport and the industry, same way forcing everybody to drive volvos with prius engines would do to car industry and car enthusiasts.
Forcing everybody to use safety backups as RSLs and AADs on regular jumps would not take away any of the fun and leave the industry for the most part intact as we know it.

I'm not saying it would be right choice or that I think it should be done, I'm highlighting the difference (or what I think is the difference) and why one thing might happen and the other might not.

faulknerwn

I think the biggest difference is the use. It is a rare skydiver who gets to a thousand jumps without having a malfunction. It is a very rare skydiver who has a legitimate AAD save. That is the big difference,

My question for those who want AADs mandated - do you want to ban small canopies? That will save far far more lives than mandating AADS. Heck not just from swoop landings - but simple things like line twists are typically non-events on big student canopies but are a dangerous high speed malfunction on tiny ellipticals - which also leads to low cutaways and late reserve pulls.

So rather than mandate AADS, mandate that everyone jump >200 square foot squares. That would save far more people. And heck, large slow canopies are cheaper too than cross braced canopies so rather than causing people to spend an extra $1400, you will actually be saving them money. How could anyone complain about that?

( and no I am not suggesting this - but it is no more absurd than the mandating AAD arguments)

Well, to continue the parallelism: for the same reason for which we allow fast sport cars instead of forcing every car maker to only build cars that can go at 60mph max. This would save thousands of lives every year.
But it would also a) destroy the industry as we know it and take away the very reason for the industry to exist and develop new stuff (car industry or canopy industry) b) it wouldn't be "fun". And "fun" is a big deal for human beings, even if it sounds stupid.
That's the main reason we are here talking, we not only want to have fun. We NEED to have fun, it's what makes us what we are.

Therefore, it's better to keep you selling high performance cars with backup mechanism (say, an airbag, it's your responsability not to crash in a wall, but the airbag might save your sorry ass if you do) or high performance canopies (again, it's your responsability not to chop low if you need to, but a skyhook might save your sorry ass if you do).

We are leaving the realm of skydiving to venture in the lands of human nature, why do we strive and look for faster things, higher performances, push limits and so on? It's in our nature, but it's also our nature to try to mitigate the risks with backup devices and technology. Again, if we were in the business of saving lives alone, banning skydiving would be the most effective decision. Also, banning skis, motorcycles, fast cars and acrobatic planes would help.
But I think here we are discussing the best compromise between our right/need to have fun with safety devices that are not directly taking your fun away (you wouldn't argue that an airbag or a seatbelt makes a porsche any less fun to drive, same way an AAD doesn't make my rig any less fun to jump).

I personally jump only rigs with AADs and Skyhooks.
It's my decision, it comes from a bunch of considerations, mainly being an engineer and deciding to trust other engineers but also since I never had a cutaway, I think I want all the assistance possible when it'll happen.

Oh, but it's my responsibility to pull all the handles in the right order. Sure thing, so it is your responsability to know how to properly steer or brake on a car, and yet the ABS, ESC and TC save a lot of asses every day.
So it is your responsibility to learn how to work on a power circuit if you need to, yet circuit breaker save lives daily.

The main concept of a BACKUP device is that, if something can go wrong it will go wrong, if there is room for a mistake, somebody will make a mistake at some point.

The argument "it's your responsibility to save yourself by doing this or that" is honestly completely pointless when talking about backup and safety devices, which are there for whem that doesn't happen, and whose job is exactly to do something when the human fucked up (and everybody can fuck up, being sure that it's always the other person that will do the mistakes is a great way to kill ourselves).

Would I force AADs or RSLs if I were the Emperor of The World and the only one to have the power to decide?
I don't know, probably ultimately not, because I don't like people and I think mankind has every right to try to thin itself. With sports cars, with skydiving, with alcohol, with skiing, with rock climbing, with extreme hiking, all fun things I love to watch or do, and that kill people "unnecessarily".

But it's human nature, we wouldn't be here if we didn't feel the urge to see what's out there or how it feel when going that fast.

JeffCa

Should somebody be allowed to jump without a reserve? Why or why not? They're expensive, they're heavy, they can kill you if they deploy at the wrong time, and I know plenty of people who have never used theirs. Is it only a nanny state that would force a reserve on us? (Am I correct that reserves are mandatory at every DZ on Earth?)

Is the issue just that the older jumpers see an AAD as an add-on, but many newer jumpers see it as a vital part of a rig? I don't consider a rig to be "complete" if it doesn't have an AAD. When I see ads for a "complete rig", I expect it to have an AAD, but it often doesn't. What should be the definition of a "complete rig"?

Out of curiosity, are there places where altis aren't mandatory? I haven't been around enough to know, but I do know that some old-timers insist that their eyes are their primary alti.

Because over time, after they became mandatory, they also became "socially accepted".
It happened with every single safety device in history: when seat-belts were made mandatory, people complained, people didn't use them for a while anyway, they're uncomfortable, they can strangle you, I am a safe driver, blahblahblah, now pretty much everybody accepts their use.
Mandatory helmet to ride a motorcycle? People bitched, then eventually in a few years accept them as "normality", and later they would consider you a "unnecessary risk taker" if you don't wear one.
The "nanny state" argument was made and eventually disregarded for what it really is.
Airbags? Same stuff, expensive, not worth it, they kill more people than they save, blah blah blah, all bullshit, nowadays I think nobody would ever buy a new car without them.

If they'll ever make AAD or RSLs mandatory, people will scream, people will yell, people will complain and cry. Some of them will cheat and find ways to not use them. Most of us won't and will just comply.
In a few years, they would look back at "those crazy days that rigs didn't have mandatory AADs" the same way we look at old cars without seat-belts.

It's that simple.

gowlerk

***I can't believe anyone would make the argument that their own life is not worth $300.

Neither can I. Do you know someone who does? What kind of life preservation device are you referring to?

I think he was referring to people that don't use a skyhook because "that damn thing costs a whole 300 dollars!!!".
Then they spend just as much in customized stripe colors and embroideries.

ridebmxbikes

so is skydiving safe or not?! i came into this sport thinking it was dangerous, then i find out its safe, then during my aff I'm told its dangerious, then once i got my license I'm informed its safe... but i keep getting all these mixed opinions if its safe or not! well, which is it?!

Well, if you don't know if something is safe or not, then it's not. Easy as that. :)

Skydiving ends up in a death every 100,000 jumps, in other words an average fun jumper that jumps 2000 times in his life has a 2% probability of ending up dead at some point.
This is consistent with the other statistics: 30000 active skydivers in the US and about 30 deaths a year, i.e. 1 out of 1000 skydivers will die every year, in 10-20 years of activity you have 1-2 % chances of dying.

2%, it's certainly not suicidal, but it's not my definition of "preferred activity for all those safety conscious people out there" either. Know your risks, accept them.

stemartin72

Read this: 'The fatality rate for skydiving is around 1 death per 100,000 jumps' 'For BASE jumping it is closer to a roughly estimated 1 death per 500-1000 jumps so is, roughly, more than a hundred times more fatally prone to risk than skydiving.'. Yes. There is definitely a need for regulation.

Now, about how a sponsor like RB encourages some people to take unnecessary risks:
http://www.ibtimes.co.uk/red-bull-stunt-marketing-extreme-sports-death-464619
And Victor Kovats was probably #8.

Those stunts are planned between the sponsor and the stuntman, who ultimately has the last word.
I mean, look at how RB sponsored Baumgartner and their project, it didn't seem to me the work of a bunch of cowboys and kids with gopros: there was some serious work and they made everything they could to make it safe.
Yesterday, in Dubai, Icarus canopy sponsored Ernesto Garcia in a project to land a 35sqft canopy setting the new world record.
EpicTV sponsors Base Jumpers and WS Proxy Flier to get new videos and documentaries on human flight.

All of these are extremely risky projects, all of these can end up with deaths, and did at some point before. And they will again.
But all of these involve very experienced jumpers, among the most experienced in the world, perfectly aware of the risks, they accept it, they write a will and they know that their next jump has a good chance of being their last.
They don't recruit kids from high school with the promise of sex, money, drugs and rock and roll to use them, unbeknownst of the risk, to shoot an awesome video (or an awesome death) because nobody aware of the risks in their right sets of minds would accept the gig.
That's not how it works.


All the professional WS fliers and pro base jumpers that died recently accepted the risks, they did it with their own free will, and the sponsors only gave them money and support to do something they would have done anyway, one way or the other.

I guess this was exactly the niche market that Mirage was trying to cover with their new double parachute BASE system that is TSO'd, introduced a few months ago. I don't remember the name.

A lot of people that want to do proxy flights from a heli would find much more legal ground to do so, if they board the plane with a "legal" rig.

Then again, if WS proximity fliers keep killing themselves at the rate they are, there might not be too much of a market in a few years.

AhahahAHAHAH!

Yeah, that's a nice hole. Actually, I didn't know about the story of Benld Meteorite, thanks for sharing the link! :)

That being said, not to sound immodest but I am an aerospace engineer and I have studied the topics of atmosphere reentry, supersonic aerodynamics and fluidynamics, compressible and rarefied flows, shock-wave formation, for long enough. :)
So I was quite sure of what I was saying. But no problem, it just happened to be my cup of tea!

sundevil777

When an object is originally moving as fast as a meteorite would be moving, then I am not at all sure that it can be expected that the energy would be "exhausted" as you say.

Something that small toward the end?
Yep, it would. We jump in the last km of atmosphere, a meteorite has a good 100km at least to start the deceleration. A meteorite that, after the burnout part, remains that small, it would decelerate pretty quickly and be at at a normal terminal velocity by the time it is in the part of atmosphere we live in.
It simply has a very small inertia, which means it looses speed very fast, the inertia of a "stupid" rock, it doesn't matter where it comes from. And thus it slows down with the exact same characteristics of a rock. Friction, especially when at higher speeds, would be the leading force VS gravity attraction (the opposite is true for a big rock).

Of course, different story is for massive meteorites with bigger inertia and with bigger gravity attraction forces, but as far as a rock like that is concerned, I am positive it has to fall at a regular terminal velocity shortly after the initial shocks, even if we accept the "meteorite theory".

There is also another reason, the smallest canopy you find on rental gear are 190s, and I only know of one place around herethat offers 170s down to 150s.
Maybe there are more, I don't know for sure, that's what I stumbled upon reading websites of DZs, no serious "research", but for sure it's hard to find anything smaller that "big-fat" canopies.
I find flying "MY" canopy so much more rewarding than flying a borrowed canopy that is different every time.

I rented gear until I was comfortable going one size smaller than the smallest canopy they had at my DZ, that I think is the best use of money I could make without waiting too long.

Oyinko

Lucky man!

http://www.nrk.no/viten/skydiver-nearly-struck-by-meteorite-1.11646757

Well no, truth be said from my perspective: he would have been the unluckiest man to be HIT by a meteorite. :D

sundevil777

My first reaction is that I would have thought it would be moving much faster if it were a meteorite.

Not by the time it's so close to earth and it exhausted all the extra speed during the entering into the atmosphere (the part when they "burn") and subsequent descent through it.
At this point it would be the exact same speed of a rock of the same size thrown by the aircraft, for example. Terminal speed is not influenced by your past "history" too much. :)

Deimian

This has been discussed before, but I personally don't think that pulling the slider down AFTER you have release the brakes is a good approach. Pulling it down with the brakes released looks to me far more complicated, time consuming, distracting and error prone than doing it with the brakes stowed. Also, why would you want to loosen your leg straps? I understand that being in a seated position is more comfortable, but we are not hanging for that long......

Agreed with this.
It's just so more natural and cleaner to have the brake lines out of your slider grommets that way (which I prefer).

Andy9o8

Having never, ever been anything other than a weekend warrior with an intermediate canopy, I am the last jumper in the world who'd ever have a skygod attitude (when it comes to skydiving, at least). A novice with 9 jumps and no other exposure to the skydiving industry does not yet have a foundation to express an "opinion" to another novice such as he expressed here. I could have been snarky to him, but I'm satisfied I made my point indirectly, and politely. If that's the sort of thing that prompts you to fire away at me from your keyboard, then bite my ass.

The funny thing is that the novice with 9jumps expressed a quite similar opinion to those of riggers with thousands of jumps in this thread. Jumping very old gear can make people "uncomfortable", if you're a newbie even more so.

Take for example me, since I have been in the sports for only a year, I don't know all the service-bulletins, recalls, problems and modifications that have been made in the last 20 years. Some, I've heard of. Some I certainly haven't.
Which is a good enough reason for me to not buy "ancient" gear and stick to newer designs.
I also wouldn't feel comfortable jumping gear that is older than me (I'm 30 though so that's hardly up for debate ).
Mainly because, being an engineer, I know that this type of gear is a result of a long trial-and-error process and, honestly, if I can, I'd like to take advantage of past people's errors when it comes to it.

Priceless.
However, the original wiki-how has a very intersting tips & warnings section that wasn't reported:

http://www.wikihow.com/Cope-With-a-Double-Parachute-Failure

Quote

Tips
* Your reserve chute should have been packed by a certified rigger and is moderately less likely to fail; therefore, it may be helpful to focus your efforts on opening your reserve parachute.
* Some humans who have, for various reasons, become aware of their impending death, develop psychological coping strategies to deal with this; for instance, the Kubler-Ross phases of grief. Since your own death approaches far more quickly, this is unlikely to be of any use to you.



* Water landings: if you have successfully attached to a companion whose chute opens, keep in mind that both your arms may be broken or dislocated, and you may be unable to swim or tread water before your chute fills and drags you under.
* If, after total chute failure, you land on something soft, it is possible that instead of being killed outright, you may be permanently paralysed due to spinal injury. If you have a strong aversion to this outcome, aiming head-downward before impact in the manner of an Olympic diver may ensure the destruction of your cranium and your immediate demise.

I think this does not belong here, since it's clearly a BASE related accident.

skymama

It's the accent.

It works all the times.
Down south, even more so!

SIM, section 6-8 (pag. 140) on the 2014-1015 version.

Two main reasons: entanglement and distraction factor (both before and during the jump).

The most bugging thing is: if you have to do it, why in hell- why!- would you place your damn camera right in front of that struct, so that it pretty much cover you and all you see is a weight bar going up and down?!?
STUDY YOUR DAMN FRAME!
That's all.