| How
well do you understand flight characteristics
of
high performance canopies?
Jim Slaton explodes a few myths...
A basic
aerodynamic every pilot should understand is LIFT. Canopy pilots
often relate lift only to the flare, because when we flare a
canopy some air is deflected downward resulting in an upward
motion of the wing.
It’s
important to understand that the wing itself produces lift. Wings
are shaped so that air flows faster over the top of the wing than
the bottom, creating lower pressure over the top of the wing,
which
lifts it. Hence, airspeed is crucial to performance. Larger wings
with a bigger aerofoil cross-section create lift at much slower
speeds, whereas smaller wings fly faster and need to maintain
higher airspeeds to produce the necessary lift.
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 |
| All
square parachutes require a certain amount of airspeed to generate
the lift needed to fly and land. Larger wings with thicker
aerofoil sections (accuracy & student type) land efficiently
at slower speeds. Smaller, high performance canopies are
inherently faster but require more airspeed to maintain their
flight characteristics. So under some small, highly loaded
canopies, pilots need to build and maintain a great deal of
additional airspeed to land their wings efficiently. Canopies
capable of flying at high wing loadings are not designed to be
flown slowly. They can be landed with a straight-in approach but
it is not always pretty and not always safe.
Although
smaller wings and higher wing loadings make canopies fly faster,
they have less lifting ability at slower speeds and are very stall
sensitive.
Understanding
this information you can see why skydivers who downsize too
quickly are put in a dangerous situation. Skydivers who transition
to some small, highly loaded, high performance canopies could be
required to generate a great deal of additional airspeed
on every jump
to get productive landings. Added to this high-speed approach is
the reality that not all landing areas – small DZs, off
landings, demos, crowded areas – will be able to provide enough
landing space. Most canopy pilots who downsize too quickly are not
equipped to execute the approach required for an efficient
landing. Consequently they get it wrong.
Skydivers in
this situation have two logical choices. If the canopy pilot is
experienced enough to operate under the landing speeds required by
the wing, they could be a good candidate for canopy coaching
school. With proper instruction they can learn safe,
airspeed-building approaches. But if the pilot does not have
enough experience to perform more than a full flight approach or
is uncomfortable with flying at higher airspeeds there is only one
option, switch to a larger wing. |
|
|
| Contrary
to popular belief, hook turns are not required to land a high
performance canopy. I strongly discourage sharp, snappy final
turns to anyone considering this type of landing. Slow, carving,
front riser approaches have proven to be not only the safest, but
also the fastest and most efficient turns in high performance
flight.
The biggest
misconception in high performance flight is that smaller, highly
loaded canopies are faster so they swoop further. There is a point
with semi-rigid wings where the performance starts to drop off.
Each different wing type will have its own optimal wing loading.
Operating at a parachute’s optimal wing loading gives the pilot
the opportunity to get the most performance from their wing.
Pilots who increase their wing loading above the canopy’s
optimal loading will sacrifice a more efficient control range for
speed. Experienced
canopy pilots searching for better swoops should consider these
important steps. First, operate as close to your canopy’s
|
 |
| optimal wing loading as possible. Second, choose the type of
canopy you think performs best at optimal. Last, don’t feel you
have to downsize to get more performance from your canopy. The
optimal wing loading for most of today’s high performance
canopies is far too great for the average skydiver. Take the time
to learn as much as you can about basic aerodynamics and the
canopy in which you fly.
Knowledge is power and power is
performance.
Words
& swoops by: Jim Slaton
ParaProTour@excite.com
Photos:
Karine Le Blond
Back
to Aug 2001 Contents |
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