Simply put, it is an aerofoil which – in case of decreased angle of attack – automatically tends to
have it increased again. In other words, it always stays in neutral position regarding its load. On
drawings it's an aerofoil that has its tail turned upwards :)
One of the most distinct features of the paragliders equipped with reflex airfoil as opposed to
classic paragliders is their substantially increased stability on high speeds.
As always in nature, nothing is for free. In case of longitudinal self-stability you pay for it with lesser
lift coefficient. It means that in order to get good glide ratio you have to choose proper wing shape
and aerofoil thickness. With paragliders there comes additional problem, namely big forces needed
to steer it. These are main reasons why you don't find full reflex aerofoils among free-flying
paragliders. In our designs we solved these problems through carefully adjusted rigging as well as
introducing several new solutions like ALC and TST systems.
With PPG or PPC canopies worse glide ratio is not that problematic, because there is always an
engine to help, while self-stability means that even in turbulent air you can feel completely safe
(and fly with hands in your pockets :) Considering limited manoeuvrability of a glider burdened
with paramotor this is an extremely desired feature. Last but not least, with such big margin of
stability reflex canopies can be safely flown at much higher speeds than classic paragliders.
airfoils
In reflex-airfoil paragliders releasing trimmers and activating speed system results in shifting
pilot’s weight towards leading edge, so that A and B rows carry almost all of it while C and D rows
get relieved.
The opposite happens in classic paragliders – with increasing airspeed load on the A and B rows
decreases, while more is carried by C and D lines. In some extreme cases full acceleration can
lead to total unloading of the A risers, with subsequent frontal collapse (frontstall).
The important quesiton is, how to discern a reflex paraglider from a classic one? Currently
there is quite a number of paraglider available claiming to be partially or semi-reflex, and no one
knows for sure what does it exactly mean.
Sometimes such names are a mere marketing tricks, aimed to use established position of fully
reflexed designs. However, there is a way to prove if there is a reflex attitude present or not.
In 2006 an idea was born within Dudek Paragliders concerning effective measurement of variable
loads occuring at individual risers.The idea was brought to life by a Swiss test center Air Turquoise
(http://www.para-test.com), while detailed technical solutions were prepared by École
Polytechnique Fédérale de Lausanne.
The project included sample flights absolved on a reflex and classic profile paraglider. The reflex
paragliders were represented by Dudek Action (its characteristics well proven by its long presence
on the market) and as a classic sample we used a Sky Paragliders Atis (thanks to the company for
the measurement reports).
The results are accessible below.
It is worth noting that in case of classic profile no measurement was done for the max speed
configuration (released trimmers + full speed bar), where even more unloading of A and B rows
would be observed.
Diagram of forces occuring at reflex profile Dudek Action 27
Diagram of forces occuring at classic profile Sky Paragliders 2
The diagrams confirm that in accordance with theory there is a distinct increase in load of A and B
rows while accelerating a reflex profile paraglider.
Similar tests have been performed for the Nucleon and Synthesis paragliders (see below).
safety
Reflex paragliders can be tested in flight as the classic paragliders are, by traditional, wellestablished European Norm procedures. However, tests are performed with only fully closed
trimmers (slow settings). The reason is, with released trimmers (fast settings) some manoeuvres
routinely done during trials are impossible to execute or unreliable when attempted on reflex
paragliders. This does not mean that a reflex paraglider is unsafe when flown with released
trimmers – quite the contrary: for example it is so much tuck-resistant, that it can’t be properly
tested with traditional methods. Such a situation happens only when the paraglider is a truly reflex
one, and that can be proven by measuring in-flight loads of individual risers (link).
Dudek Paragliders performed such tests in case of Action/Reaction models (see above) as well as
Nucleon and Synthesis.
Nucleon:
Synthesis:
Both paragliders demonstrated definite reflex features.
History
Reflex profiles have been known in the aviation from its early times, and they are to be found in
many publicly available profile catalogues. They have been tried in hanggliding and paragliding
too, initially with little success. Especially paragliding application proved to be a hard task – lack of
rigid elements, low wing loading and high steering forces discouraged many of the designers.
After many attempts, the first serially produced paraglider with really working reflex profile was
created: it was the Traper of Dudek Paragliders.
Traper aroused high interest and won a high acclaim among competitors when it was shown at
European PPG Championship (Hungary, 2002). It was there that Michael Campbell-Jones saw it
and he couldn’t believe his eyes, seeing a practical realisation of an idea he tried to introduce for a
couple of years. That galvanized him to enter close cooperation with our company. Michael
significantly modified steering scheme in order to make it easy and smooth (hard steering is an
inborn feature of reflex wings), and doing that he became a coauthor of Traper’s follower – the
Action. Regrettably our ways soon parted, as Michael started promoting the Action as his own
development without endorsing Piotr Dudek’s part, to the degree of concealing the very fact of
manufacturing the Action by Dudek Paragliders. To this day you can find texts praising Michael as
a father of reflex profile – which is absurd, since it was known almost for a century now and was
never patented by anyone. Similarly, it is not true that he designed the Action.
In our following reflex designs (the Reaction, Synthesis, Plasma and Nucleon) we perfected
steering scheme of the profile with several novel ideas, arriving at a reflex paraglider which is easy
to launch, amiably at steering and exceptionally safe.
Achievements
Our designs remain popular with pilots all over the world, dominating both the quantity (on average
half of the competitors are using Dudek wings, with rest of the cake divided among several
companies) and quality statistics, confirmed by numerous top places and world records. Here are
some of the results:
Competitions
:
2010 British National league (1st leg): 1st, 2nd, 3rd
2009 World Paramotor Championships: 1st PF1, 1st PL1, 2nd PF2, 3rd PL2
2009 Polish Paramotor Nationals : 1st, 2nd, 3rd...
2009 British Paramotor Open: 1st, 3rd, 1st (women)
2009 Spanish Paramotor Championships : 1st
2009 France Paramotor Open: 2nd
2008 Euro Paramotor Championships : 1st PF1, 1st PL1
2008 Japan Paramotor Nationals : 1st, 2nd, 3rd...
2008 Polish Paramotor Nationals : 1st 2nd 3rd...
2008 French Paramotor Open: 1st (women), 2nd, 3rd, 4th, 5th
2008 German Cup: 2nd PF1, 2nd PL2, 3rd PL1
2008 UK Paramotor Nationals : 1st, 2nd, 3rd, 4th...
2007 World Paramotor Championships: 1st PF2, 2nd PF2, 2nd PL1, 3rd PF1
...and many more.
World Records:

Speed over a closed circuit of 50 km without landing (RPF1Tm): 65.4 km/h

Speed over a closed circuit of 50 km without landing (RPF1Tf): 45.14 km/h

Speed over a closed circuit of 100 km without landing (RPF1Tm): 51.9 km/h

Distance with Limited Fuel (RPF1Tm): 110.161 km

Speed over a straight 15/25 km course (RPF2T): 37.4 km/h

Distance over a closed circuit without landing (RPF1Tm): 343.6 km
Closer look for WORLD RECORDS and MEDALS
Reflex-profile paragliders: actsand myths
Reflex profile paragliders have been produced for many years now. There must be a dozen
thousands of them flying in the skies, and the number of flights absolved cetainly is a seven-digit
one. With growing confidency more and more pilots go flying in even more difficult conditions, yet
there are no reports of accidents allegedly caused by reflex-profile characteristics.
How is it then that so many pilots still consider reflex wings to be evil and traitorous? Popular
meaning says they are docile in easy weather, but can get really nasty when struck by some bad
mood. As usual, fear is a child of ignorance. And when there is no solid knowledge around, myths
come in handy.
That’s why we decided to give short shrift to several most persisting of them, which grew over
years.
Myth #1: hard to take off a reflex wing"
A reflex-profile paraglider (RPP) takes off differently than a classic paraglider (CP). RPP needs to
be launched with one smooth pull, quickly arriving over pilot’s head. You can’t pull up the wing too
slow or have a break in-between, as many pilots do. According to their CP experience they think it
is safer to pull it up reluctantly than to go with full zeal and then brake it when it wants to overtake
the pilot. This is all wrong – with RPP there is no possibility of overshooting: once the canopy is
filled up and stays in the airflow (be it due to the wind or pilot’s movement), RPP firmly stays
overhead and simply waits for you to take-off. This is one of its fundamental advantages.
Is such a start a difficult procedure? Well, it depends. To be frank, green pilots who started their
training on RPPs under guidance of an instructor conscious of reflex technology have a lot less
problems than seasoned classic wings pilots, who just switched to reflex.
Fact: A reflex-profile paraglider takes off differently than a classic paraglider. Problems can be
caused by handling a RPP with CP habits, or by misjudging trim settings (in relation to wind
speed). Pilots who do it properly have no problems with taking off on a reflex wing.
Myth #2: "It is hard to steer a reflex wing"
Harder handling is not caused exclusively by the reflex profile peculiarity; there is also a simple
fact that RPP’s fly faster than CP’s (steering a classic wing at 60 km/h would require a lot of
strength too). Should an RPP be steered with technologies similar to CP, you would really need a
strongman to handle it at high speed.
However, ongoing design improvements finally worked out solutions that practically eliminate this
problem. In latest wings brakes act more like “pulling in” than “pulling down”, thus bringing comfort
to steering RPP at low speeds. At high speeds (open trimmers + speedbar) there is additional set
of steering handles connected directly to wingtips (TST - Tip Steering Toggles), allowing for easy
and effective handling.
Fact: Modern RPP design features more effective classic steering techniques at lower speeds,
and alternative handles set (TST) for higher speeds.
Myth #3: "Dynamic RPPs reactions to collapses induced by test-pilots
proves that the paraglider can be very dangerous when flown in
turbulence.”
Test pilots are forcing collapses (frontstall, 50% asymmetric, 75% asymmetric) by pulling A-row
lines or risers. Typically it’s an easy job for the test pilot, since classic paraglider’s inherent
vulnerability to collapses (especially when accelerated) requires but a slight pull on the lines to
cause a massive frontstall.
Quite the contrary for the reflex paragliders. Due to considerable resistance to collapses of a reflex
profile, test-pilot has to pull with all his might for several seconds. Meanwhile, already fast-flying
RPP accelerates even more, as pulling A-row diminishes wings’ angle of attack. At last a large and
sudden collapse occurs, then reopens spontaneously and dynamically by the paraglider on its
own. While unassisted reinflation is a welcomed behaviour, the dynamic exit is regarded as a sign
of instability of the wing and thus disapproved.
Such judgement is wrong for two reasons.
First: any wing (including those considered very safe) flying at 50 or 60 km/h will exit the collapse
dynamically, therefore gaining considerably worse marks – even as it would be still the same, safe
wing.
Second: in real flying a collapse is caused by a stream of sinking air (turbulence) entered by a
paraglider. Even at hypothetic 35 km/h speed (and RPP’s fly much faster than that) and theoretic
maximal chord of 3.5 m (in reality much less, especially at wingtips) we have only 1/3 of a second
between the leading edge entry in turbulence and the moment when entire profile is covered with
it. It means that in real life aerodynamical force is acting on leading edge for tenths of a second
only, since later on it engages entire canopy and is rather subduing that collapsing it. Moreover,
we have to remember that the reflex-profile is automatically adjusting its angle of attack all the
time, further limiting the exposition.
Fact: RPP’s reaction to collapses induced by test-pilots during certification procedures or SIV
courses does not reflect real behaviour of the paraglider. A wing of fully reflexed profile will
acknowledge even strong turbulence by slight acceleration and upsurge (when faced head-on) or
a swing and slight turn when it is hit distinctly on a side.
Attention: another situation occurs when a paraglider enters rising air. There is not much difference
between reflex and classic profile behaviour – a violent turbulence can “stop” a paraglider in flight
and bring it to parachutal stall. Testing such a case would require simulating it on highest possible
AoA (slowest trim setting). Usually such stall is entered by a slow letting out of a full or B-stall, and
then time is measured in which the paraglider returns to normal flight – the sooner the better of
course.
All in all, certificating of modern RPPs is a broad topic which deserves an article of its own, if not a
number of them.
Myth #4: "All RPPs behave exactly the same"
Each year the offer of RPPs is getting broader. Each year new designers come to try the reflexwing concept, enriching it with their own ideas and experiences. “Old” designers are playing with
new trends. In effect we have several types of reflex-profile paragliders:

fully reflexed wings,

“half-reflexed” paragliders (i.e. with profile showing limited reflex behaviour),

semi-stable paragliders (i.e. with profile displaying only some features of typical reflexprofile)

partly reflexed paragliders (for example with reflex profile in central part of the canopy
only).
When additionally we’ll take into consideration changes brought to profile by trimmers and speed
system, we will have:

reflex behaviour in full speed range,

reflex behaviour at middle and high speeds.
To sum it up, we arrive at quite a number of possible RPPs. All these wings can (and usually do)
behave differently, depending on their design and current trim/speed system configuration. Fully
reflexed profile is hardest to exploit, but it is the one most welcomed by pilots wishing to fly as fast
and safe as possible. Compromises offering limited reflexivity bring some features typical for
classic paragliders (lower speeds or easier handling), but it is invariably with a loss of several
welcomed reflex-profile features.
Fact: All RPPs flying in full-reflex mode feature increasing stability with increasing speed. But not
all of the RPPs available are fully reflexed at every trim/speed system setting, and that’s why they
can behave differently.
Myth #5: "Reflex-profile paragliders are said to be immune to
turbulences.”
RPP is not a flying broom nor does it possess any magic powers of casting spells on weather.
Turbulences won’t disappear simply because the flight is done on a RPP. Pilot will experience
them as sequence of jolts, felt harder with increasing speed.
The truth is, an RPP is very resistant to turbulence-induced collapses. That’s why their pilots have
considerable less work to do (if any at all) when controlling stability of the wing flown through rough
air areas. And as we already know the faster he flies, the safer it will be (this concerns fullyreflexed paragliders only).
Fact: RPP does not erase unpleasant feelings in turbulence, but it is very resistant to turbulenceinduced collapses.
Myth #6: "Reflex-profile paragliders can be flown only by experienced
pilots."
We have to discern two notions: experience and education. The first is gained through practice,
the latter by training. A pilot with considerable airtime gathered exclusively on classic wings can
experience difficulties when he starts flying RPPs, thus perceiving them as potentially dangerous.
Flying with brakes slightly pulled in is by far not the only one, but decidedly most widespread error.
As (hopefully ; ) known, this technique while perfectly suited to CP will cause an unpleasant feeling
of instability when applied to RPP.
Speaking generally, RPP’s range looks pretty similar to CPs: there are competition wings with high
aspect ratio and sophisticated trimming as well as simple recreational wings. Competition
paragliders require much experience, while recreational ones can be flown much easier. Still, flying
both of them it is absolutely necessary to know and understand peculiarities of reflex-profile wing
operation. There are following points to be learned:

influence of brakes, trim and speed system on flight parameters and safety

take-off and landing techniques, applicable trim settings and landing approach calculation

handling of a paraglider in specific flight stages.
Fact: Flying a RPP absolutely requires knowledge and understanding of its specific demands
(besides all general paragliding knowledge of course). An educated pilot even with negligible
experience will be perfectly right on his recreational RPP.
As you can see, most of the myths concerning RPP has its roots in treating RPPs from classic
paragliders point of view. It his highest time to underline that reflex profile paragliders are different
than their classic counterparts! The difference is important enough to justify additional training
before flying a RPP. Be it brief, but in its crucial points it is indispensable.
To simplify the matter: it is better to think of a reflex-profile paraglider as of a paraglider with
several features of an aeroplane. And conscious RPP pilot must learn these “aeroplane”
characteristics of his wing, for otherwise he will be restricted to… mythology.
Epilogue
Recently there was a famous case of two American car thieves, bagged when trying to steal a
Toyota Avensis. The police got them before they were able to drive away from the spot, since they
could not operate the manual gearbox. All their previous driving experience concerned cars
equipped with automatic gearbox only.
Basing on these facts, journalist George Rubber of local newspaper came to conclusion that
Toyota Avensisis is a car which is incredibly hard to drive.
After further contemplation on plight of the hapless thieves (a prison term), George Rubber arrived
at another one priceless deduction:
Under certain circumstances Toyotas Avensis can be very dangerous cars.