Dropzone.com Article:
"AirLock"
Posted Mon November 8,
1999
There is a considerable amount of chatter about
“valved” parachutes going around these
days. Many skydivers believe that airlocked parachutes
are the way of the future, while others see the
introduction of this new technology as a temporary
fad. In this article I will discuss the pros and
cons, as objectively as I can, to this new development
in parachute design.
Simply put, an “Airlock” is a system
designed to contain the internal pressure of a ram-air
canopy, and therefore its airfoil shape. In short,
the air goes in, but it doesn’t go out. If
the wing’s shape is not reliant upon the relative
wind (created by airspeed), then the performance
range is consequently expanded and enhanced in every
respect. In addition, the theory holds, such a self-contained
airfoil will not distort or be otherwise adversely
effected by turbulent flying conditions.
Parachute designers have worked towards the goal
of a valved parachute since the very birth of the
ram-air canopy. Domina Jalbert, the man to whom
credit is given for developing the world’s
first ram-air canopy, was among the first to design
such a system. Although his “valve”
didn’t exactly revolutionize the industry,
the spirit of Jalbert’s concept of a self-contained
airfoil continued to possess (and obsess) the minds
of inventors worldwide. Some twenty years later,
I too got enthralled with this quest.
I got involved with the airlock project as the
result of a near-fatal collapse of my paraglider
in 1993. From my wheelchair, I began designing various
systems to keep the air in the wing, with mixed
success. I built scores of miniature parachutes,
experimenting with every type of valve I could imagine.
I discovered that regardless of the type of valve,
I had to retain the leading edge “scoop”
of the airfoil in order to maintain adequate internal
pressure. I realized that there are many ways to
achieve this end, but found only one method that
stood head-and-shoulders above the rest. So I brought
my idea to the only person I could think of that
might be crazy enough to actually build it: Tony
Uragallo. He hired me on the spot.
Tony and I did extensive research on the valve
concept over the course of three years. Some of
our designs were incredible, while others weren’t
worth the fabric we built them out of. It was an
age of synthesis, a time of wild creative genius
and misdirected insanity. We eventually developed
a product that we were proud of, and marketed it
as “The Jedei”. As expected, the market
received it with mixed emotions. Now that there
are literally hundreds of these canopies flying
all over the world, the pros and cons of valved
parachutes have become much more readily observable.
The safety and performance advantages of the design
seem to be very well received. Pilots of valve parachutes
have observed significantly longer landing surfs,
even without dangerous acceleration maneuvers. This
is due to the lack of “wing shrinkage”
as the airspeed decreases. Furthermore, owners report
that the wing feels far more stable in turbulence,
exhibiting little or no spanwise compression, even
in the nastiest of conditions. The most exciting
news is what has not been reported: there have been
no documented canopy collapses due to turbulence
whatsoever...Not One.
Clearly the primary objective has been achieved.
Consequently, a valved-parachute “cult”
has formed; a sector of the skydiving population
that refuses to jump anything that isn’t valved.
Supporters of the movement shun the use of “open-celled”
parachutes in much the same way as early Zero-P
jumpers avoided F-111 canopies. Although the supporters
are adamant, they all have reported similar shortcomings
to the airlocks.
The disadvantages to the design seem to be born
of the same attribute that attracts airlock customers
in the first place... the air doesn’t come
out of the wing, whether you like it or not. For
instance, after landing on an excessively windy
day, you may be in for a bit of a fight if you haven’t
developed a technique for “downing”
the parachute. No one has reported any injuries
as a result of being dragged after landing, and
the hassle is something the owners seem to be willing
to trade for the performance gains. The bottom line
is: "would you rather have a bit of struggle
with getting the air out on the ground, or a whole
lot of struggle getting it back in during flight?"
The drop zone packers usually have a bone to pick
with the airlock concept as well. As the air tends
to stay inside the wing longer, the airlocks sometimes
require an extra step in the packing process. Most
packers have adapted a technique of laying the parachute
in a side-pack configuration, and then rolling their
bodies across the canopy from tail to nose. Once
most of the air is out, the parachute packs up the
same as any Zero-P canopy. Although the packers’
gripe is valid, one must keep in mind that if it
were solely up to the packers, we’d all be
jumping F-111 parachutes.
Lastly, there is the issue of cutaways. It is true
that a few people have lost their valved canopies
after cutaways. An undeniable side-effect to the
airlocks is that the parachute can sometimes drift
further after a cutaway than an “open-cell”
canopy. This is usually not the case, but the possibility
does exist. Interestingly, all of the despondent
owners have replaced their lost parachutes with
new valved canopies, an unarguable sanction of the
technology.
The final question still remains: “Is it
all worth it?”... Is the theoretical safety
margin afforded by parachute valve systems worth
the new problems that they create? The fate of the
airlock parachute remains in the hands of the skydiving
community... the future is still to be decided.
The airlock may be just another passing facet of
the “Techno Fad”, or a permanent feature
of the sport that will develop into the industry
standard. As always, the direction and nature of
the accepted technology is determined solely by
the consumer, not the inventor.
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