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När är en flygskärm inte en flygskärm?

22 DEC 2009 17:35
Efter PWC i Italien har det uppstått en debatt om vad som definierar en flygskärm. Det var en skärm med bara 2 linor och kolfiberförstyvningar som var överlägsna alla andra tävlingsskärmar. Nu har PMA, Paraglider Manufacturer Association haft ett möte och vill delge sin syn på Vad är en skärm?
  • Skapad: 22 DEC 2009 17:35

Paraglider Manufacturers Association

press release 2009-12-21

The discussion about the FAI definition of paraglider


The current FAI definition of paraglider is:

Class 3: Hang gliders having no rigid primary structure (paragliders), and which
are able to demonstrate consistent ability to safely take-off and land in nil-wind
conditions.

The decision by the Paraglider Manufacturers Association to regard about 70cm
long, 1.5 mm diameter carbon rods, which are tensioned like a bow and sewn to
the profiles of a paraglider as “rigid primary structure” rather than as “flexible
and secondary” was not taken easy. It was preceded by very intensive
discussions, which took several weeks:

On one side there is yellow, on the other side is red, in between we have orange.
The question which we had to answer was: How much orange is still yellow and
when does it start to become red?
There are two possible extremes of a wing with a pilot who is suspended below
this wing by lines: A very simple paraglider just consisting in cloth and lines
without any Mylar or other reinforcements and an Atos-type wing under which
the pilot is suspended in a paragliding harness by 2 lines, holding 2 or 3 other
lines in his hands to control the wing. Somewhere in between these two
extremes we had to draw a line, which defines where a flexible paraglider ends
and where another type of aircraft starts.

The PMA sees the Ozone BBHPP as the first “tentative step over this line". Soon it
will be followed by machines which will be maxing out the principle of the rigid
primary structure. These wings will differ much more from the principle of the
traditional, flexible soft-paraglider than the Ozone proto is doing it today.

The decision by FAI to limit the FAI-Class-3 22 years ago, when the FAI definition
was introduced, is still a valid decision today. It helps to preserve the simplicity
of the simplest flying machine existing. Most of the success of the paraglider
comes from the fact that it is simple and easily accessible.

If a new FAI-Class for paragliders with rigid primary structure will be introduced,
depends on you, the pilot who wants to fly it and on designers and
manufacturers who want to design and produce it. It will not be dictated by FAI
or PMA or anybody else. It will be decided by the market. What had to be
decided is a definition for “rigid primary structure” because as the long
discussions in the PMA working group showed the FAI definition for FAI-Class-3 is
too vague to be understood in the same way by everybody.

The proposal for a revised definition of FAI-Class-3 was voted upon by all PMA
members. The vast majority, 76% of the 27 PMA members choose the following
definition:

1) Hang gliders having a flexible structure (paragliders), and which are able
to demonstrate consistent ability to safely take-off and land in nil-wind
conditions.
Flexibility is defined by the ability of a component to be bent around a
radius of 1cm by 180° without being damaged. This test of flexibility will
be executed in at least two perpendicular planes and will be performed
when the component is integrated into the glider.
Note: all rigifoil materials and all Mylar reinforcements as used up until
today in certified gliders will fit inside this definition.

Pilots, designers and manufacturers will choose to decide to introduce or not to
introduce a new class of paraglider, which will give room for more rigid
structures. This will not only give the “new developments” room, but also
protect the proven and very successful principle of the classic paraglider.

Until now nobody knows if the repeated attempt to equip a paraglider with rigid
structures will be successful this time. Look at the several attempts in the history
of our sport: from the rod-wings of André Bucher and Karl Bauer to the
revolutionary mono-sail up to the last designs of Laurent de Kalbermatten, the
Pantair etc.
In contrast to the principle of the classic paraglider, where all components are
only loaded by tension, these rigid materials are able to receive compression
loads. This is not only opening the doors to new possibilities, it is also causing
some new risks. At least now something can crack as well, not only rip.
Obviously this changed demand on the materials is causing the need of a
different treatment of the machines (also in the certification process).
If there would not be a differentiation in between these basic principles of
construction in competitions, everybody would be forced to follow the new trend
to be competitive in performance. But some designers don't want to do this,
because they like the brilliantly simple, straight forward principle of a classic
paraglider which has proven to be suitable for the masses and which has been
successful because of that. By limiting the classic paraglider design as it has
been done until now in FAI-Class-3, this principle has still a chance to survive,
also in competitions.

Finally this discussion regarding the "rigid primary structure" and a new, better
defined and clear FAI definition of a paraglider is only a side issue. The
competition sport is moving more and more away from the focus of attention of
the normal pilot. This tendency is already developing since many years now.
In the beginning, when the competition sport was still interesting for every pilot,
all competitors were flying with the same, serial and certified wings as every
other normal pilot as well (AilesdeK Big-X).

Then we flew the serial canopies with just thin lines (Edel Racer, UP Katana,
Nova Sphinx etc).
After all there arrived the first machines of the new Open Class (Xenon,
Boomerang). These machines were still produced in big series and were available
for everyone to buy and flyable by many.
The latest development is to build very complex prototypes which are individual
constructions and which are not sold anymore, because a normal leisure
competition pilot is not able to handle them. Therefore more and more "normal
pilots" will lose their motivation to compete in an environment which does not
offer fair and equal chances for all pilots. And also more and more manufacturers
will give up their open class engagement because of the huge effort and costs
involved (at the moment only about 1/3 of the more than 40 manufacturers who
sell internationally are active in competition with open class wings).
Actually the PMA working group "competition gliders" is discussing solutions to
this crucial question. We hope, that we can offer some good proposals to CIVL
soon.

A short excursion to what would happen if paragliders with “rigid primary
structure” would be developed to be certified and sold as Serial Gliders:

The testing laboratories agree on the fact, that paragliders with rigid primary
structure cannot be tested following the existing EN-926.

The FAI definition of a paraglider also is the definition of a paraglider in EN-926.

EN-926-1 does not contain any tests for components in paragliders which are
exposed to compression loads and which can not only rip but also break.
To make a front collapse of 30-40% as described in EN-926-2 already is difficult
with some of the 3-line wings. It’s impossible to do on a 2-line wing, where
perhaps 80-90% of the load is on the front row of lines. The quality of an
asymmetric collapse which is caused by pulling one front riser is completely
different to the one of an asymmetric collapse on a glider where a major part of
the load is carried on the 2 or 3 remaining rows of lines.

New testing criteria for paragliders with components, which are exposed to
compression loads and/or with only 2 rows of lines would have to be created.

The refined, precise definition of FAI-Class-3 (paraglider) is important for all
pilots, designers and manufacturers, competition organizers and juries in
competitions and last but not least also for the testing laboratories to know what
is a FAI-Class-3 paraglider and where exactly are it’s limits.

 

Ytterligare info från PMA:

The PMA has put some answers to frequently asked questions to the PMA decision towards FAI-Classes of paragliders on the PMA website.

 

 

Skribent: Sune Cullberg

 


 

fai

FAI betyder "Fédération Aéro- nautique Internationale", det franska namnet på det internationella flygsport­förbundet, i vilket vi är medlemmar genom Svenska Flygsportförbundet.