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Parachute Aerodynamics

 

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airdolphin  (D 24416)

Aug 19, 2010, 10:24 AM
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Parachute Aerodynamics Can't Post

It's been a while since my AFF course and recently I had a chat with someone who is going through his IAF course. It was a surprise to learn that the course's curriculum hasn't been updated with a treatise on parachute's aerodynamics.

As a commercial pilot and instructor I can assure you that one cannot get any kind of rating without knowing what angle of attack, pitch/yaw/bank, lift, drag, etc. are. So how is it that we, the pilots of flexible wings are not taught what makes them fly, stall, turn and flare?

Especially considering the recent wave of accidents under perfectly good parachutes? Some of those accidents are accidents, but many are due to ignorance and could've been prevented with some training and knowledge!

Some people (such as Brian Germain) have attempted to travel the globe and teach people the aerodynamics of the flexible wing (which is even more complex than that of a solid wing). But not to teach students and require them solid knowledge of this during the IAF course is a serious flaw, IMHO.

Any thoughts on this?

Pavel.


Premier billvon  (D 16479)
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Aug 19, 2010, 10:31 AM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

>So how is it that we, the pilots of flexible wings are not taught what makes
>them fly, stall, turn and flare?

?? I cover that in my course. It's about 10 minutes on the very basics - how moving air causes lift, how drag and lift can cause the parachute to slow down and turn, how lift pulls you into the turn (and thus all of it is no longer acting directly upwards.)

I do it the very first thing in the course, since of all the things they learn that day, canopy aerodynamics is the safest thing to forget.


airdolphin  (D 24416)

Aug 19, 2010, 11:02 AM
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Re: [billvon] Parachute Aerodynamics [In reply to] Can't Post

Bill:

with all due respect, 10 mins is too short. When I teach helicopter aerodynamics, it takes probably several full days to do so... Flexible wing is a bit simpler than things like retreating blade stall and autorotation, but it's still quite complicated.

My point precisely is that it should be in the USPA curriculum and tests for licenses. So, that people don't forget and study.

I kid you not, but a friend of mine made a 90 degree front riser turn at 50 feet while landing out at a small back yard because he heard somewhere that front risers are safer than toggles... Luckily he lived and he is down to "7 lives" now...

Besides, how many people pull their toggles slowly on landing, without getting any pitching action, and then are surprised why they hit hard. That's pure ignorance about how parachutes flare, what makes them pitch, etc...


wrightskyguy  (D 19665)

Aug 19, 2010, 11:55 AM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

Riser turns are already part of student training, and if your buddy doesn't understand their function, this part of training was blown off, or he wasn't paying attention. I think that a 10 to 20 minute lesson covering canopy aerodynamics in the FJC is adequate to get them in the air.


airdolphin  (D 24416)

Aug 19, 2010, 12:03 PM
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Re: [wrightskyguy] Parachute Aerodynamics [In reply to] Can't Post

I would say that most even experienced jumpers don't know what the front risers do and how they work... They may say that if you pull on the right front riser, the parachute will turn to the right and spiral down while accelerating. But few will describe this as: pulling on the front riser effectively shortens the front group of lines (A-B) and thus on that side the angle of incidence (and thus angle of attack) is decreased. Thus the lift on that side decreases as well, so that canopy banks and therefore turns.

A more interesting conversation arises when discussing what happens when that riser is let go. In that case the angle of incidence is restored and therefore the angle of attack is increased, so the canopy's lift increases and that causes (in some cases) the parachute to plane out. There is pitching action that happens in that case, but it's vastly different from the pitching action as a result of a toggle movement.

Another example is what Brian Germain was explaining in his recent workshop - coordinated toggle turns. Most people think that pulling on a toggle is enough, but in reality it causes an uncoordinated turn, and this can be easily seen by looking at the pilot chute trailing behind. If it stays right in the middle, the turn is coordinated. But if it shifts, the parachute is not just turning - it's also slipping. Such turn is uncoordinated. To make a proper coordinated turn one needs to bank the canopy with the harness input in the same direction first, and then add toggle input. In such case the turn will be coordinated...


dninness  (D 19617)

Aug 19, 2010, 12:08 PM
Post #6 of 45 (2916 views)
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Re: [wrightskyguy] Parachute Aerodynamics [In reply to] Can't Post

Having covered parachute aerodynamics with Civil Air Patrol cadets (my evil plan to sneak skydiving into CAP by teaching them about the "aerospace" aspects... yeah!!<GRIN>), I'm with Bill on this one: for an FJC, you only need about 10 minutes on "why the parachute works." Lets face it, your average FJC student really doesn't need to be able to tell me about Bernoulli and "steady state stalls."

Yes, helicopter aerodynamics for pilots is FAR more complex (retreating blade stall, anyone? Translating tendency?), and I think that for the most part, helicopter pilots better have a much more firm grasp of aerodynamics than their flexible-wing'd cousins.

But spending more than 10-20 minutes on "this is why / how a parachute flies" in an FJC is probably putting too much extraneous information into their heads when its really not going to help.

However, I do start covering things like "lift, thrust, weight & drag" later when we start talking about riser turns, canopy performance, etc. But again, we're not going to make anybody an expert, but they should be at least familiar enough not to be honking on a front riser in the wrong situation.


TheCaptain  (D License)

Aug 19, 2010, 12:17 PM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

 There is such a thing called information overload, students need to know how a parachute works "basically". They more importantly need to learn how to deal with flying their body, opening the parachute, and identifying and dealling with malfunctions. In the beginning there is alot more important subjects to cover in great detail other than the aerodynamics of the parachute IMHO


airdolphin  (D 24416)

Aug 19, 2010, 12:18 PM
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Re: [dninness] Parachute Aerodynamics [In reply to] Can't Post

Don't you think that "dumbing down" FJC students works against them in the long run (it might be better to study it during the course and not during the boring time of lying in a hospital bed)? My original point was that those who aspire to be fixed/rotor-wing pilots must study aerodynamics and then pass an array of tests to prove that they didn't simply forget it.

We are also pilots (although, luckily, not as much regulated - and I hope it will remain so). So, why wouldn't we also be taught at the same level? It won't make things worse - on the contrary, understanding of flexible-wing aerodynamics will make people safer.

Yes, there are some people who start sweating profusely when they see a lift formula, but they all get through their ground courses. I think FJC students are no dumber than primary heli students and can eventually conquer one formula and a few diagrams.


airdolphin  (D 24416)

Aug 19, 2010, 12:21 PM
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Re: [TheCaptain] Parachute Aerodynamics [In reply to] Can't Post

I would disagree: if we look at statistics (for the last 10 years), it seems that it's quite skewed, and according to it the most dangerous part of skydiving is landing, not dealing with mals or fewer points turned during the freefall or bad body position during the opening. So, I'd make a case that it's much more important to teach parachute flying and landing!

And once again (as in the other post), helicopter primary students deal with the "information overload" and most of them pass their tests and do learn about the retreating blade stall and effective translational lift. So, I believe that the FJC students can spend a bit more time and still study. There is no need to dumb them down, esp. if they realized that their life and health really depends on it!


Bertt  (D 99999)

Aug 19, 2010, 2:29 PM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

As others have said, the FJC is not the time for information overload. For one thing, most students in the first jump course aren't in it for the long run. They need enough information to survive one parachute jump plus a little more to grow with as they continue (if they decide to
continue).
Comparing training for skydivers with training for aircraft is a little misplaced anyway, because on an airplane or helicopter training flight the instructor can demonstrate things then discuss them with the student as they fly along. Can't do that on an AFF level 1 jump.
I would agree that more canopy control training is a good idea, but not in the FJC.


airdolphin  (D 24416)

Aug 19, 2010, 2:46 PM
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Re: [Bertt] Parachute Aerodynamics [In reply to] Can't Post

Perhaps some of the responders are correct, but then another solution is to make a more in-depth course like that mandatory for the B license.

Problem is that once people get out of the FJC, it's a choice for them to learn more or not. Many don't even like flying parachutes and use them only as the necessary evil to get down on the ground. So, although I am not too big on enforcement, I'd be willing to enforce such training here. It may save many bones and lives.

I recently took Brian Germain's course at the Ranch and what was very illustrative is that the only people at the course were jumpers with very few jumps (under or slightly above 100). I was the only one with the number of jumps over 1,000. Perhaps partially it may have been poorly advertised, but I'd expect to see people around 500-800 jumps - one of the most dangerous "phases"...

So, OK, I'll concede to the responders that having students study aerodynamics for the A license may overload them, but why wouldn't this be done for B-D licenses?! It would only make sense.


Premier billvon  (D 16479)
Moderator
Aug 19, 2010, 3:31 PM
Post #12 of 45 (2839 views)
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

>with all due respect, 10 mins is too short.

It's long enough to understand:

It works on lift, not drag like old round parachutes
You can't stop the parachute or it will stall and drop you
When you turn you descend faster
You can control it and flare it with toggles or rear risers

It's certainly not long enough to understand how to fly a HP canopy, but at the FJC stage the objective is to get them through their first seven jumps safely. After that the learning _really_ starts.

When I did water training regularly I'd put some aerodynamics stuff in there, because at that point they have a better chance of understanding it.

>Besides, how many people pull their toggles slowly on landing, without
>getting any pitching action, and then are surprised why they hit hard.

In my experience, during their first few jumps, not that many. But that's not because they understand that pitching moment is critical in changing the angle of attack momentarily; it's because we go over how fast to flare about a dozen times.


pchapman  (D 1014)

Aug 19, 2010, 6:00 PM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

Compared to learning to fly, we don't really have "ground school". Yes we get 1/2 a day before the first jump typically, but that's it.

In flying, you show up at the airport in they day, brief with the instructor, go fly, and debrief. Same with skydiving.

But in flying you also pay separately for a series of evening classes once or twice a week, a few hours of classroom time to learn all the theory. We don't have that in skydiving.

All we have is some home study from the SIM (in the US) or PIMs (in Canada where I am). Which of course works best for the types who like to study printed material. Aerodynamics seem pretty limited in the SIM, and perhaps a little less so in the PIMs.

So, yes, the emphasis is more on practical considerations rather than the background theory. One can always argue about how much theory is needed for applying to actual jumping.


dninness  (D 19617)

Aug 19, 2010, 6:20 PM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

In reply to:
Don't you think that "dumbing down" FJC students works against them in the long run (it might be better to study it during the course and not during the boring time of lying in a hospital bed)? My original point was that those who aspire to be fixed/rotor-wing pilots must study aerodynamics and then pass an array of tests to prove that they didn't simply forget it.

We are also pilots (although, luckily, not as much regulated - and I hope it will remain so). So, why wouldn't we also be taught at the same level? It won't make things worse - on the contrary, understanding of flexible-wing aerodynamics will make people safer.

Yes, there are some people who start sweating profusely when they see a lift formula, but they all get through their ground courses. I think FJC students are no dumber than primary heli students and can eventually conquer one formula and a few diagrams.

I don't think anybody is suggesting that you don't teach students about parachute aerodynamics, and I do think they get a fair understanding of how the parachute works (from a flying standpoint) during AFF. But jamming complex aerodynamic concepts at FJC students is probably counter productive. For the purposes of FJC, they need to know that its out there, it flies, etc. (there, square and steerable/landable, right?) The rest comes as they go thru the various levels of AFF and learn more about flying the canopy and what it does for them.

But really, considering that many of the variables are just that: variable, it seems to me that the lift formula might be tilting at windmills.


Trae  (Student)

Aug 19, 2010, 6:51 PM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

ibn reply to "with all due respect, 10 mins is too short. When I teach helicopter aerodynamics, it takes probably several full days to do so... Flexible wing is a bit simpler than things like retreating blade stall and autorotation, but it's still quite complicated. "


Considering the relatively high performance of modern canopies available to beginners 10 minutes briefing on how they fly does seem inadequate especially given the high landing incident rate.

So much of the FJC is about minimising information to the student in the hope they won't be overloaded.
And of course most places ust HAVE to fit in all into one day . Many places pride themselves on doin the FJC thing even quicker.
Striking the balance between necessay information and too much forgettable 'rubbish' is part of the job.

Students, if they progress, will be exposed to ever increasing levels of canopy performance. They need to be taught properly how the things fly .

With canopy landing speeds approaching and in some cases exceeding aircraft landing speeds it would seem reasonable to expect the skydivers of today to recieve extra training similar in some respects to pilot training including a good uderstanding of the aerodynamics involved.

The continueing incident rate suggests otherwise .

IMO the skdiving community has been unable to recognise its own inadequacies in dealing with the HP canopy issue. 10 minutes of aerodynamic training says it all.
People presenting such poor trainging standards as acceptable merely perpetuate low industry standards.

Some FJC's used to run night school as a way to provide necessary information in a proper learning environment .

Teaching aerodynamics as a necessity might scare away the dummies and that might be a good thing.


davelepka  (D 21448)

Aug 19, 2010, 8:37 PM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

Quote:
with all due respect, 10 mins is too short. When I teach helicopter aerodynamics, it takes probably several full days to do so... Flexible wing is a bit simpler than things like retreating blade stall and autorotation, but it's still quite complicated

Here's where you miss the point - the level of complexity and the amount of fine control you have over a helicopter requires an in-depth knowledge of the aerodynamics, the control systems and the how the two work together.

A modern z-po student canopy loaded at .75 to 1 is a bit simpler. Left turn, right turn and flare. That's about all a student needs to know in realtion to the operation of the canopy. You can have a successful canopy flight including a stand up landing using nothing but those three inputs.

Of far more importance to the student is knowing where to fly the canopy, and how to get it there. Their time is far better spent learning the effects of the wind with realtion to ground track, flying a landing pattern, and how to select a landing area (the DZ is the obvious choice, but when that is not an option, knowing about power lines next to roads/buildings and that corn can be 8 feet high can make the difference between a safe landing and not).

At some level you have the correct idea, that new jumpers are being shorted in terms of what they learn in the way of canopy control, and some of that includes the aerodynamics. Something should be done, but certainly not until they have a grasp of making a basic skydive and are ready to take on the additional information. This is why students jump student canopies, because their size and design makes their operation simple and forgiving.

In a perfect world, there would be continuing education connected to earning advanced liceneses and being allowed to jump smaller or higher performance canopies (actually there is a world like that, it's called Switzerland). In the US, however, the powers that be have chosen to take a pass on that sort of idea, and left it all up to guys like Brian Germain, and their optional, for-profit courses.


MrDree  (Student)

Aug 20, 2010, 5:13 AM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

In Switzerland, in order to get the A license you need to pass a written exam divided in 5 parts: Gear knowledge, "Jumping procedures", Aerodynamics, Meteorology, and Legislation.

Is there something similar in other countries? Just curious.


timmyfitz  (D License)

Aug 20, 2010, 6:14 AM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

In reply to:
I recently took Brian Germain's course

I now understand why you are posting and pushing this.


kallend  (D 23151)

Aug 20, 2010, 7:56 AM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

In reply to:
I would disagree: if we look at statistics (for the last 10 years), it seems that it's quite skewed, and according to it the most dangerous part of skydiving is landing, not dealing with mals or fewer points turned during the freefall or bad body position during the opening. So, I'd make a case that it's much more important to teach parachute flying and landing!

OK, but knowing anything about aerodynamics will not prevent a canopy collision at 100ft or a hook turn started too low, which appear to be the predominant causes of landing accidents.

And yes, I DO know helicopter aerodynamics, in fact I wrote a very successful helicopter flight simulator, and still I agree with Bill.


JohanW  (D 86318)

Aug 20, 2010, 8:09 AM
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Re: [MrDree] Parachute Aerodynamics [In reply to] Can't Post

In reply to:
In Switzerland, in order to get the A license you need to pass a written exam divided in 5 parts: Gear knowledge, "Jumping procedures", Aerodynamics, Meteorology, and Legislation.

Is there something similar in other countries? Just curious.
It's in 4 parts, but we have similar exams for A, B and C in the Netherlands.

It's been a while, I don't remember the exact subjects, there is no Aerodynamics part as such, but I think the subject is in there somewhere.


airdolphin  (D 24416)

Aug 20, 2010, 8:29 AM
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Re: [timmyfitz] Parachute Aerodynamics [In reply to] Can't Post

In reply to:
In reply to:
I recently took Brian Germain's course

I now understand why you are posting and pushing this.

I am not sure what you are insinuating by your post, but my post was mostly a result of the conversation with someone going through the FJC. He knew nothing about parachute aerodynamics and when we discussed a little bit of, light bulbs seemed to light up in his head. His exact words were - "so, now I understand why when I was flaring slowly I still hit the ground relatively hard".

I then simply compared two disciplines - helicopter flight training and skydiving training and questioned why it is mandatory to pass aerodynamics in the first case and the FJC students don't even get their feet wet in the second. I believe that knowledge is power (though not a substitute for practice), and it may help people stay safe rather than try to fly "by feel only".

Considering the other point that the majority of accidents and fatalities occur under functioning parachutes (and frequently due to ignorance), it only made sense to raise the question.

But now I am repeating myself.


(This post was edited by airdolphin on Aug 20, 2010, 8:30 AM)


toolbox  (D 18778)

Aug 20, 2010, 9:01 AM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

If your buddy really made a 90 degree turn of any kind at fifty feet(front riser,rear riser,or toggle) he must have forgotten what all 1st jump students should know without all the technical mumbo jumbo you are trying to complicate newbies with.
Low turns without time for full recovery to flat and level flight will end badly.
A properly trained student should know that they should not make anything but small corrections in direction of flight below 200 feet,and at fifty feet they should be flying hands all the way up preparing for plf if needed and ready to flare.
More advanced instruction comes later when they have already learned the basic survival skills.
Remember KISS


dninness  (D 19617)

Aug 20, 2010, 9:13 AM
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Re: [toolbox] Parachute Aerodynamics [In reply to] Can't Post

In reply to:
If your buddy really made a 90 degree turn of any kind at fifty feet(front riser,rear riser,or toggle) he must have forgotten what all 1st jump students should know without all the technical mumbo jumbo you are trying to complicate newbies with.
Low turns without time for full recovery to flat and level flight will end badly.
A properly trained student should know that they should not make anything but small corrections in direction of flight below 200 feet,and at fifty feet they should be flying hands all the way up preparing for plf if needed and ready to flare.
More advanced instruction comes later when they have already learned the basic survival skills.
Remember KISS

This.


riggerrob  (D 14840)

Aug 21, 2010, 10:07 AM
Post #24 of 45 (2582 views)
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Re: [kallend] Parachute Aerodynamics [In reply to] Can't Post

In reply to:
In reply to:
I would disagree: if we look at statistics (for the last 10 years), it seems that it's quite skewed, and according to it the most dangerous part of skydiving is landing, not dealing with mals or fewer points turned during the freefall or bad body position during the opening. So, I'd make a case that it's much more important to teach parachute flying and landing!

OK, but knowing anything about aerodynamics will not prevent a canopy collision at 100ft or a hook turn started too low, which appear to be the predominant causes of landing accidents.

And yes, I DO know helicopter aerodynamics, in fact I wrote a very successful helicopter flight simulator, and still I agree with Bill.

......................................................................

I am also backing Bill.

I turned wrenches on Sea King helicopters .. back when I was young and beautiful ...

First jump courses are about MUST KNOWS needed to survive the first few jumps.
Over-loading FJC students just clutters their minds with distracting information. Information and theories that they will not grasp until they have hung under a canopy a few times.

SHOULD KNOWS should be introduced as they progress to faster canopies, after they have earned their A Certificate.

Which is why I prefer CSPA's system of requiring progressively more-detailed understanding of canopy aerodynamics for each successive certificate

Only the most curious/theoretical/analytical (followers of Brian Germaine) skydivers listen to NICE TO KNOW information. Unfortunately the finer points of aerodynamics are lost to the general skydiving population.
IOW Save your breath.


erdnarob  (D 364)

Aug 22, 2010, 9:42 PM
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Re: [airdolphin] Parachute Aerodynamics [In reply to] Can't Post

Being a skydiver, a physics teacher and a pilot as well, I found your idea very interesting. I was giving some basics of aerodynamics of an airfoil like a parachute to my first jump students for about 10 minutes too. It is maybe not enough from a scientific point of view but you have to consider the priority of the matter to be taught for such a course. First jump students do not have to get the full explanation right away but if one of them asks the question, the instructor should be ready to answer. Later when students get their first license, aerodynamics of a parachute can be part of a seminar.
Once I have made a program on my HP 48 GX graphing calculator to calculate the spot taking in account the speed and direction of winds aloft (given by a pilot forecast source) at every 3000 feet from ground to 12000 feet. I tested my program by making the calculation "by hand" and by using actually the calculated spot. When I tried to convince the people at the DZ to use that program at least for the first load, very few people were interested and some said my program was useless. As always, people are relying on the performances of their canopy to bring them back for landing until after a cut away they will lose their 2000.00$ canopy. We are doing a very technical type of sport but the skydivers really interested by the aerodynamics of a parachute are not part of the majority.


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