"lfk f; \"A Lt. - Airborne Systems

Figure The LeMoigne Parachute
High-Glide Parachutes
The term high-glide refers to parachutes with glide
ratios greater than 2.0. These parachutes are characterized
by airfoil type canopy cross-sections end wing
tyoe planforms. A wing- I i ke shape with low porosity
material creates a rathsr flat single or double membrane
canopy. Typical high-glide parachutes are the
Parawing, originated by Rogalla , the Parafoil
invented OY Jalbert and further developed by
Njkolaides the Sailwin9 developed by Barish
and thE VolpJane developed by the Pionee' Parachute
Company.
The Parawing and. Sailwing are single membrane
canopies. The Parc:foil has a ram-air inflated , double
memb ane airfoij cross-si?ction. .A. PP'oxi-nately onethird
of the chord length of the Vol plane is a double
membranc, ram-air inflated, airfoil leading edge. All
high-glide parachL. tes are equipped for steering by
means of wing tip or trailing edge lines. Pulling :he
lines cI'eates either aileron or spoiler effects, or wi1gtip
angle of attack changes. A certain amount of
glide control for steeoenin9 or flattening the 91 ide
104
path and for fiare-out is r.racticed by sport jumpers.
To obtain such modulation with remote steering
with a fully automatic navigation and landing system
has proven difficult. The control forces and control
line movements are high ccmpared to aircraft type
con trois and are in the rarge of 4 to 6 perce'lt of the
total r8sul:ant aerodynamic force acting on the canopy.
Such forces can be handled easily by jumpers
but require considerabie electrical pOWel", control ;jne
movelnm s and a weight penalty for large high-giide
parachutes used with veh ides of SEvera I thousand
pounds weight. Refererce 220 which describes the
development of a ground con:rolJed high-glide parachute
system for the landing of a 6000 Ib spacecraft
points out SO'le of tile difficulties involved.
Another characteristic of high-glide parachutes '
the high peak opening force caused by the low porosity
material used for the canopies. Wi nd tunnel tests
show opening ioads are nearly 50 percent higrer than
those ex perienced witr solid c rcu lar flat parachutes.
Control I ing peak forces usually requires multiple reef-
ing for large systems in order:o stay within allowable
lirrits of vehicle load and parachute weight. Many
sport jUl"pers USE reefing for dec'easing the oper,ing
force even at relatively low jump soeeds.
A'rcreft wi ng terminology has been adooted for
high performance gliding parachutes. It is convenient
to relate the aerodynamic for':es to the flat planform
area of t18 lifting sur ace,
Since includes the
w-
area of all fabric surfaces in the canopy. the ratlc
5", is indicative of the effectiveness witl' which
the fc:bric is IJsed to create the liftirg surface. The
weight of the canopy tends to be proportional to tl16
inverse ratio
Aspect ratio is a significant parameter affecting
the aerodynamic performance of gliding parachutes.
Aspect ratio is a measure of slenderness of the wing
planform, determined bylhe equation
AR
where '" wing span. An increase in aspect ratiQ of
the canopy increases "the glide ratio of a gliding parachute.
Increasing the aspect ratio also introduces
deployment ar,d canopy opening complexities, especially
on large parachutes.