Reflex/Normal

[s1buell_wl]

I wanted to open this thread and talk a little about Classes and Speed of the new gliders

How does the reflex wings quickly get into the C class? Someone talked about it before.

PARAGLIDER CATEGORIES

class

A

Paragliders with maximum passive safety and exceptionally forgiving flight characteristics. Very resistant to any deviations from normal state of flight.

Designed for all pilots, including all levels of training.

B

Paragliders with good passive safety and forgiving flight characteristics. Partly resistant to deviations from normal state of flight.

Designed for all pilots, including all levels of training.

C

Paragliders with moderate passive safety and possibly dynamic reactions to turbulence and/or pilot mistakes. Return to normal state of flight may require precise pilot input.

Designed for pilots who know principles of active steering and fly regularly, understanding consequences of using a wing with decreased passive safety.

D

Paragliders with demanding flight characteristics and possible abrupt reactions to turbulence and/or pilot mistakes. Return to normal state of flight requires precise pilot actions.

Designed for pilots flying very actively with considerable experience in turbulences, who understand and accept risk inherent in flying such paragliders.

FLIGHT TEST DESCRIPTION

Flight test report (as described in European Norm 929-2) gives account of 24 manoeuvres. Each of them is ranked as A, B, C, D or F (Failure). There is no percentages here, a paraglider gets as its overall result the lowest mark it obtained at any point. Even a single failure means that a paraglider did not pass at all, i.e. is not conforming to the norm. During flight tests following elements are assessed:

1 - inflation/take-off

2 - landing

3 - speed in straight flight

4 - steering forces and range

5 - pitch stability when exiting accelerated flight

6 - pitch stability using controls while in accelerated flight (any collapses?)

7 - roll stability and damping

8 - stability in gentle spirals and recovery

9 - behaviour in a steeply banked turn (sink rate after two revs)

10 - symmetric front collapse

11 - exiting deep stall (parachutal stall)

12 - recovery from high angle of attack

13 - recovery from a developed full stall

14 - asymmetric collapse

15 - directional control during maintained asymmetric collapse

16 - tendency to spin at trim speed

17 - tendency to spin at low speed

18 - recovery from a developed spin

19 - B-line stall and recovery

20 - big ears: entering, steering, exiting

21 - big ears in accelerated flight (entering, steering, exiting)

22 - behaviour on exit from a steep spiral

23 - alternative means of directional control

24 - any other flight procedure and/or configuration described in the users manual

I'll type some more.... out of time...

[s1buell_wl]

Here we have a normal Class C Paraglider

Sol Synergy Five Class C

It claims 58km +1

[s1buell_wl]

Then we have the Nuc claiming

Speed [km/h] min = 23 ; trim = 37-50 ; max = 62km/h

I think most other reflex gliders claim around 58km/h

Why Bother with Reflex?

[pete_b]

Because they are more stable (resistant to collapse) on full reflex than a normal wing on full speed bar.

Reflex wing, Turbulent air= full reflex

Non Reflex Turbulent air= Off speed bar and actively fly using brakes.

simples.

[s1buell_wl]

I agree to a point but you are just prolonging the breaking point. I see reflex as a good option for speed in stable air for long distance. Cant imagine holding on the speed bar for 1-2h lol. I guess I keep wondering because you are just prolonging the breaking point "if" the canopy did break on full how dramatic would it be?

Good read from Ozone

A Specific airfoil for PPG:

Because of what I have explained above, performance in glide and sink rate for free flying and speed for the motor, it is obvious that wings need developing specially for each category.

Everybody in PPG today has heard about “auto-stable” or “reflex” airfoils. Here is the simple explanation of the benefits of this type of airfoil:

As I’ve said earlier, pilots want to fly fast to cover long distances, so needed in the concept is everything to make a paraglider fly at low angle of attack (to go fast) with maximum stability. The “reflex” airfoil acts as an automatic system that helps the wing to handle turbulence by delaying the point of break (collapse) by positioning the lift forces quite far forward on the profile.

In effect, the more you accelerate, the more effective the reflex is and the more solid your wing becomes: This means it’s more solid, but as I’ll explain bellow, that doesn’t mean it’s safer!

Also, a reflex profile is usually associated with poor aerodynamic performance. In order to achieve maximum speed, a competition reflex wing my require 100% thrust in order to maintain level flight in trimmers out / fully accelerated position. This is the case with the Viper, for instance, which is designed with an emphasis on speed.

So to summarize, reflex profiles have been developed for speed in paramotoring and is the best known solution for speed with a certain amount of solidity and comfort in flight.

The negative sides of reflex airfoils are less often discussed, but are just as important:

The reality of a soft canopy concept, rigged with lines, is that the pilot is always vulnerable to the possibility of canopy collapse. Reflex in the canopy profile delays the point where the collapse occurs, but the risk is ever present.

Additionally, another rule of soft canopy aerodynamics is that the faster the airspeed and the lower the angle of attack at the time of collapse, the more dynamic will be the reaction of the glider to the collapse. Because a reflex wing will not deform at the leading edge in turbulence, collapses are generally larger in surface and volume than in a free flight profile, and as a result of this tend to be more aggressive in dive and surge during collapse.

The forces described earlier are - “in a simple way” of explanation – naturally making the airfoil to increase its Angle Of Attack (AOA), even when outside influences are pushing it down, and there are other direct consequences from that :

The altered point of lift on a reflex profile (put simply) naturally encourages the wing to increase its Angle of Attack (AOA), even when outside forces are encouraging it to decrease. There are other direct consequences of this, such as:

Slower inflation / poorer launching. The glider is reluctant to rise and needs to be held with the A’s until overhead otherwise the glider tends to drop back.

Poor flying characteristics at high AOA (slower speeds). Delayed recovery from stall and a short brake range (spin tendency), and poor handling are symptoms of a reflex profile.

Inefficiency: Fuel consumption is noticeably higher.

In pure theory, reflex is actually not the ideal solution for reaching higher speeds. Ideally, a symmetrical airfoil with a Moment as close as possible to zero would offer the highest possible airspeed. In comparison to a symmetrical airfoil reflex is actually slower. Reflex is the solution that fits the needs of our soft canopies when flying at low AOA (high speeds).

Speed is the most popular measure or performance in PPG, and Reflex is the technology currently ‘in fashion’.

There are other answers to increase speed, for example reducing the surface area of the wing dramatically. But like everything else, this must be paid for with higher take off and landing speed, and poor passive safety, which makes it a less than ideal solution for most pilots.

In the future, PPG designers will continue to focus on reduction of energy consumption and performance will center more on glide and sink (efficiency) as well as speed. This is where the limits of reflex become painfully apparent and designer’s skills will be tested when trying to achieve this delicate balance.

[pete_b]

Ask Simon W, he had a full frontal on full reflex and speed bar on the Tip to Tip

[Hemberg]

Reflex or not reflex has been an ongoing discussion for many years now. It seems that reflex wings are generally more accepted now but when it comes to real tests it is absent. I mean certification tests.

I guess it isn't easy to mimic real conditions to see if a glider really is safe and there are difficulties to perform a real test. A damp glider, a used glider, glider with sand in it, high/low settings on the harness and so on, the list can go on. But the level of testing that is done today is simply too poor.

In my opinion I would say that the ppg community accepts reflex as being safe, not just because the manufacturers say so, but because there have been few accidents with reflex wings.

But the discussion if reflex is safe or not should have ended by now. At least some organisation should have done a real test so we have more than anecdotes.

The pulling A-riser test of a ppg wing in reflex and noticing that it is too hard to pull them down doesn't really say much at all. The way ppg wings are tested can be improved I'm sure. Or pg wings for that matter. I liked the dhv test the done not too long ago with EN B gliders, when they used accelerometers and cameras and such.

Can't someone with a bit of cash do a RC ppg and fly it in really crappy weather? If I had the cash I would.

I understand that certification needs to be done in standardized way, but if we can't have that at least we could have something else, a bunch of glider tested just to see what happens.. something.

If it comes to the point when it starting to get too expensive for manufacturers to produce gliders I think it would be better to let some go bankrupt and let the larger ones take the market actually.

[pete_b]

it comes to the point when it starting to get too expensive for manufacturers to produce gliders I think it would be better to let some go bankrupt and let the larger ones take the market actually.

And are you willing to pay another 500-1000 on top of the cost of a glider??.

I am happy flying reflex, I have flown in some of the shittiest weather and was more than happy to be on a reflex wing.

If I had beed on a non reflex I would have landed straight away.

At the end of the day its your choice if you are not happy with the reflex tests then don't fly one, if you are not happy with the non reflex tests YOU are in the wrong sport.

Please check the testing on your rocking chair before sitting down as it may not by suitable for rocking back and forth.

[Hemberg]

No, but I'm willing to have fewer brands to choose between that are better tested.

Larger series, less cost, or same cost if expenses are higher for development.

Or maybe we should make them cheaper by testing them less today?

I think there is room for improvement.

[pete_b]

Always room for inprovement or we would still be using the horse and cart.

[Hemberg]

Btw, I don't think it has to become very expensive to test the gliders.

It's not like we are testing boeings

[pete_b]

Btw, I don't think it has to become very expensive to test the gliders.

It's not like we are testing boeings

But it may do if they have to do more tests = more risk.

[Hemberg]

Or we can see it from another perspective,

How do the manufacturer know that they develop a good glider that are stable and have the specifications they say. Do they guess it is good? Guess that it is stable? Or do they test it, and test to collapse it.

Hopefully they do test it, how would they otherwise know. If they don't then the buyers become the test pilots.

[norbertflyer]

The modern ENC PG wings have very light speed bar operation. I can operate the speed bar on the Ozone Delta with my hands by yanking on the lines just below the pulley. I often steer by this method if I don't have my feet in the speed bar.

I also use this set-up http://shop.flybubble.co.uk/ronstan-win ... -lines-kit They make keeping the speed bar on with just the weight of a foot.

I remember flying the old Action PPG wing against my old Aspen1 PG wing in the mid 2000's and could not maintain level flight on full revs with the Action at full speed, yet I only needed 80% of maximum revs with the Aspen1 at full bar. (The Action was 1 or 2 kph faster though, but a slightly smaller wing, yet uncertified).

Richard

[s1buell_wl]

This for me it’s not about if you like to fly Reflex or not but the Paradigm we seem to be in with the technology. Paragliding has come a long way. I’ll have to dig up the pic’s of the 1989-90 glider I took for a flight (wow talk about things going tight!). I love to understand the technical “how”

Think back a few years…. The word Reflex hit the market and at the time paragliders were getting 18-20km/h max speed bar. This new “reflex” foil raised the bar to around 40km/h. This was enough to raise a ton of interest and a ton of skepticism (Dell seen this and with his evil ways seen a marketing opportunity).

The Paradigm;

This sport has always been about how do we get these slow gliders going faster? This is the million dollar question. It can be done but safety goes out the window.

But as with Cars the faster you go the more kinetic energy you build up thus if your crash the car the worse the impact

With gliders (reflex/normal) the faster you go the same applies.

I think this answers my question:

“Reflex Profiles have more stability in accelerated flight than a normal free-flight wing”. This, I can understand free flight wings reduce the AOA to gain speed. However this really leaves the wing highly susceptible to full frontal with any minor turbulence".

Or you can overweight the normal paraglider to gain the speed. In this situation the collapse would be equal or worse.

I see the Roadster has passed EN certification at full speed on the 12cm accelerator range. You can see the reflex is here to stay the foil developers are working hard to blend speed and safety. Dudek at high speeds becomes hard was a rock when accelerated.

Edited July 6, 2012 by Guest

[s1buell_wl]

On the testing I also found this (From Ozone)

I’m guessing all the big players are working on this

This is great (Ozone is currently working in concurrence with several other paramotor manufacturers and Air Turquoise (An EN testing) to set up a specific certification for the sport of paramotoring). I think this would take some of the mystery out of the accelerated flight, would be interesting that's for sure!

Certification

Currently there are only 2 types of certification for paragliders (DHV and EN), and one dedicated to PPG wings which is recognized only by the German authorities (DULV).

The DHV and the EN certification are very similar and after years in use have become a recognizable standard for paragliders, with the flying public well acquainted with the categories of each system.

The DULV is inspired by the DHV. The DULV test pilot performs a selection of DHV flight tests with and without motor. The categories have been reduced to a simple pass / fail, so in the end the wing has DULV certification or not.

As ‘auto-stable’ airfoils become more popular in paramotor wings, there is an obvious problem with the certification of these wings with the current tests.

The current tests only measure the effect of a collapse, but not the ability of the wing to resist collapse. Paramotor wings with ‘auto-stable or reflex airfoils will fail all current flight tests. The reasons are explained above: the high resistance of these airfoils at low angle of attack cause very dynamic reactions to collapse.

Ozone is currently working in concurrence with several other paramotor manufacturers and Air Turquoise (An EN testing) to set up a specific certification for the sport of paramotoring.

The idea would be as follows:

First, the wing should pass the EN tests in a defined configuration (let’s call it ‘neutral’ position), to be sure the flying characteristics and the behavior during maneuvers fit into a category of safety. This category, like the current EN tests, will be defined by European Community Law.

Second, a measurement would be taken to give a figure representing the amount of reflex, such as a percentage point, that would define the amount of reflex at full speed and / or untrimmed flight.

With this measurement pilots would know how much reflex there is in each wing. Today, apart from what the manufacturer says and the feed back from the pilots that have flown the wings, it’s impossible to know what a wing is like in terms of amount of reflex. The current definitions of no reflex, semi reflex, and ‘reflex’ are inadequate.

This measurement won’t be a stamp of approval or a measure of safety for flight at full speed, but it will be information for pilots and a reference to compare between wings.

To return to what was explained earlier, a high amount of reflex will describe a wing with higher resistance to collapse but stronger side effects, while a lower figure will show a wing with less resistance to collapse but less trouble in other flying characteristics.

Whether or not a wing has reflex doesn’t mean it’s safe, or unsafe. This is why we think it is an important point that a PPG wing for most pilots should be treated like a paraglider and be tested as such. The brake range, the behaviour at high angle of attack (spin tendency, stall exit, big ears, etc), the spiral, collapse behavior, etc… need to be tested to show that it is suitable for that level of pilot.

We don’t simply launch and go into the full speed or untrimmed flight mode to turn the reflex ‘ON’ and then hope we’re safe!

Flying requires the pilot to go through various stages and making sure the wing will behave within the defined categories during all stages of flight is a much greater warranty of safety for pilots.

Disregarding this and only measuring the amount of reflex in a wing would be disregarding over 20 years of research and experience of paraglider testing.

[Hemberg]

Great news!