Bridle
Canopy
Pilot chute
Harness
Risers
Container
Lines
Figure 2-6. Round parachute assembly.
mission requirements better than the square parachute.
Poynter’s Parachute Manual, Volume 1, Chapter 8, provides
an excellent discussion of the design parameters and
characteristics of round parachutes for those needing more
technical background.
Construction Concepts and Techniques
TS-100 describes the various ram-air construction methods
such as half-cell chord wise, full-cell “I” beam chord
wise, full-cell interlocking “T” chord wise, and span wise
configurations. When learning the various construction
methods, the beginning rigger can become confused as to how
the seams are folded together. Seeing the schematic diagrams
of the various configurations can help in the repair sequence.
Additionally, there are two basic methods of construction for
the main seam used on modern ram airs. One method is to roll
the adjacent bottom skins with the attendant rib together and
double needle 301 stitch to hold the joint. Line attachment
tabs are then appliquéd over the rolled seam for subsequent
line attachment. The other method is the foil method where
the rib has the line attachment tab attached directly to it and
is flat stitched to the bottom skins allowing the bottom edge
of the rib to be exposed.
Canopy Design
Accomplished design skills are not necessary for the rigger to
properly service parachutes. The skills involved to become a
designer can take several years of training and practice. It is
necessary, however, that the rigger understands some of the
basic concepts to relate the performance characteristics to the
design theory of the components involved. For the average
rigger, these concepts are accepted as those proven and tested
in the finished product. The following are specific areas that the
rigger should understand to determine the identity, function,
and assembly of parachute components and their interaction.
Understanding the sequence and method of deployment is
necessary when assembling components to assure proper
function. Most ram air parachutes are trimmed nose down,
and as such the canopy tries to fly over its nose during
deployment. This flight angle causes the top skin nose of the
canopy to roll over the bottom skin leading edge closing off
the cell preventing inflation. To counter this, the trailing edge
of the canopy is deflected downward to apply brakes during
inflation; this holds the nose up and open allowing air intake.
These are called “deployment brakes” and are implemented
by providing a “brake eye” in the steering line of the canopy
located so as to apply the proper amount of brakes. The
steering line is pulled down through the steering guide ring
on the risers and locked with the nose of the steering toggle
during the packing process. Loss of one or both brakes during
opening will most likely cause a malfunction. Loss of one
causes the canopy to turn into that side as the cells remain
collapsed and the inflated side over-flies the collapsed side.
In flight corrective action is to grab both toggles and apply
both brakes evenly and quickly.
Nomenclature
All riggers should become familiar with Parachute Industry
Association (PIA) Technical Standard 100 (TS-100),
Standardized Nomenclature for Ram-Air Inflated Gliding
Parachutes (See Appendix I). This document is the official
language and terminology used for ram-air parachutes. It
specifies the parts of the parachute, the various construction
methods, and the seam configurations used. This is necessary
for the rigger to understand the manuals and repair procedures
provided by the manufacturers for their products.
Figure 2-6 identifies the components of a typical round
emergency parachute. The nomenclature of this design
has remained constant for several decades with a few
exceptions. While some riggers who skydive think that
the square parachute has replaced it, the round parachute
still has many uses, and in certain instances, fulfills some
Round parachute construction is divided into two primary
techniques: bias and block construction. Bias construction is
most prevalent in the early parachutes and military designs.
It is generally the stronger of the two techniques due to its
ability to stretch more during opening. In bias construction,
the fabric is cut and sewn so that the warp and filler threads
are at 45° to the centerline of the gore. A typical example is
the 28' C-9 canopy.
Block construction is where the warp threads of the panels
are parallel to the hem of the canopy. Block construction
gained in popularity in the lightweight sport reserves of
the 1970s and 1980s. They were easier to build and packed
smaller. An example of this design is the Phantom/Aerostar
canopies, manufactured by National Parachute Industries,
Inc. Additionally lines may run from link to link through the
canopy or from skirt to link using reinforcement tape for the
canopy portion of the radial seam.
Operational Theory
The rigger must have knowledge of how the parachute
functions. Without this, the rigger may not be able to
assemble the correct components so that they function as
a complete assembly. While the manufacturer may specify
what components are to be used with their particular design,
with the vast numbers of products on the market today,
there are an infinite number of combinations being used by
the skydiving community. While seeming to be compatible
with each other, many designs have subtle differences that
affect their performance and operation. Such differences
include pilot chute drag capability and bag extraction force
requirements. Pilot chutes should not be interchanged unless
the drag capability and container extraction force is known.
Materials
The materials used in construction have changed over the last
several years. This has resulted in better performance and
durability. The use of incorrect materials can have a detrimental
effect on the opening, flying, and landing characteristics of the
parachute. The growth in popularity of the ram-air canopies in
the 1970s required new fabrics for the designs to function. Very
low permeability fabric was necessary for the canopy to remain
inflated and maintain the aerodynamic airfoil shape. To reduce
the drag created by the suspension lines, newer lightweight and
high-strength materials were used. First Dacron®, followed
by Kevlar®, and now Spectra® and Vectran®. While reducing
the line bulk and drag, these materials have introduced newer
problems into the designs.
The ultra-low permeability fabrics inflate faster and have
almost zero stretch. As a result, the opening forces increase
considerably. These effects have contributed to newer packing
and deployment methods to reduce the loads on the parachutist
and harness. These, in turn, affect the design of the container
systems. Using this as an example, the rigger can see the chain
of cause and effect in the design process. Complete coverage
of materials is presented in Chapter 3 of this handbook.
Damage
Damage patterns identified during the inspection of canopies
can highlight problems caused from packing or incorrect use.
By being able to identify these patterns, the rigger can provide
the user with correct technique and, thereby, prevent possible
injury or death. In addition, the rigger can provide valuable
feedback to the manufacturer of potentially serious problems
with new designs once they have been subjected to real world
conditions. While manufacturers conduct extensive testing
programs before releasing new products to the market, very
often, subtle problems do not arise until the parachute has
been in the field for an extended period of time.
Containers
The container component assembly of the parachute system
is that part which encloses the canopy(s) and lines, the
deployment device (if used), and the pilot chute unless it is
externally mounted as on a “pop top.” It is held closed by
the use of cones or loops, which are secured by ripcord pins
or locking pins such as are used on hand deploy systems.
Containers may consist of single units as are used on pilot
emergency systems or multiple units such as are used on
skydiving piggyback systems. The term “pack” is used
interchangeably with container. The harness and container
assembly may be called the pack and harness. The term
“packtray” is used to refer to the bottom panel or section of
the container where the lines may be stowed during packing.
Early containers were simply a bag-shaped unit that the
canopy was stuffed into and then tied closed. The parachute
was static line deployed and the parachutist simply fell away
from the balloon or aircraft allowing the canopy to deploy.
With the advent of manually deployed free fall systems, the
need for a more secure and tailored design became evident.
Originally, the parachute systems were identified by the
position at which they were located in relation to the body
of the user. These were the back parachute, seat parachute,
chest parachute, and lap parachute. The containers were
usually rectangular in shape with four closing flaps. These
configurations were primarily dictated by the need to fit the
assembly into the flighdeck of the aircraft.
With the growth of skydiving, the container configurations
and the associated terminology changed. The original
location of the main parachute on the back and the reserve on
the chest became known as the “conventional” configuration.
[Figure 2-7] The original tandem configuration with both
Figure 2-8. Piggyback containers.
Figure 2-7. Conventional container.
Figure 2-9. Tandem container system.
the main and reserve on the back became known as a
“piggyback,” and the introduction of a two-person parachute
system became the new “tandem.” [Figure 2-8 and 2-9]
Configuration
When canopies were packed into early bag-type containers,
they always wanted to assume a spherical or round shape.
For the container to remain flat, it was necessary to tailor the
fabric and then use frames or bow stiffeners to keep it flat
and compress the pilot chute. Back designs utilized multiple
cones and pins, usually three or four to maintain the length
and width. Seat containers were usually more square and
thicker since they were held in place by the seat pan. Most
use two cones and pins for closing. The same was used for
chest and lap parachutes. Many military systems still utilize
these basic configurations today.
With the introduction of skydiving in the 1960s, most
equipment was of modified military designs, and the first
generation of commercial products was simply colored
versions of these designs. In the 1970s, skydiving canopies
had progressed to ram-air designs, which were smaller
in volume and had different deployment requirements.
Container designs evolved to meet these requirements. The
introduction of the hand deploy pilot chute was probably the
Figure 2-10. Modern military container.
Figure 2-11. Square reserve hesitator loop configuration.
Figure 2-12. Non-restrictive container corners.
most influential concept in the evolving container design.
Cones were replaced by fabric closing loops, and main
ripcords and pins were replaced by hand deploy bridles and
locking pins. It was no longer necessary to compress the
spring-loaded pilot chute inside the container. Thru closing
loops were used to compress the pack and make it thinner to
conform to the body shape. The use of deployment bags and
other devices helped provide shaping to the container. This
was true for both square and round canopies.
Today, most modern container designs have completely done
away with frames and bow stiffeners. This has resulted in
smaller, more flexible, more comfortable, and more efficient
container designs. Instead of metal stiffeners, nylon plastic
is used to reinforce the container flaps for backing the
grommets. The nylon is lighter, easier to work with, and
cheaper. Many of the modern military designs now follow the
design concepts pioneered by the sport industry as they have
proven better and more cost effective. Figure 2-10 shows a
modern military container.
Modern Design Concepts
The containers of today do more than simply enclose the
canopy and deployment device. Sport containers in particular
need to be designed so that they contribute to the deployment
needs of the specific parachute. Piggyback designs have
separate requirements for the main and reserve containers.
The reserve container is generally small, tight, and mostly
wedge-shaped. Virtually all popular sport systems are
designed around the use of a ram-air canopy. The deployment
method of choice is a Type 5 deployment bag. In the early
days of the ram-air reserve, there were certain container
design requirements specified by the manufacturers which
are listed below:
1. A hesitator loop configuration secures the bridle
and holds the bag in until the reserve pilot chute is
deployed and under drag. [Figure 2-11]
2. Nonrestrictive corners to allow the bag to be lifted
off by the bridle in the event of a horseshoe-type
malfunction. [Figure 2-12]
Change 1 (December 2015)
Figure 2-13. Modern aerodynamic container design.
These requirements were adhered to for many years. Today,
containers achieve the required holding and deployment
needs through design tailoring. The bottom corners of the
reserve container are designed so that the bag is held in place
while the pilot chute and bridle deploy and then releases the
bag, rotating it out of the container top to bottom into the
airstream. At the same time, the bag can still deploy quickly
in the event of a horseshoe-type malfunction.
The main container is less restrictive than the reserve in
holding the main canopy in place during deployment. This is
important so that there is no tendency for the bag to twist or
be unstable on deployment. With many of the main canopies
used today, if the bag is unstable, it results in the main
canopy opening unevenly and causing spins and possible
malfunctions. Along with the main bag, the main risers must
be able to deploy evenly for the same reasons.
In the early days of skydiving, the primary body position
was a stable, face-to-earth position. This resulted in the main
container being behind the parachutist out of the airflow. One
of the primary problems faced during those days was the high
incidence of pilot chute hesitations. This was the result of poor
training and lack of understanding of that air flow. Eventually
skydivers learned to sit up during deployment causing the air
to flow over their back sweeping the pilot chute into the main
stream. Hand deployed pilot chutes were developed to make
packing easier and eliminate the need for a metal ripcord.
In the face-to-earth position, the primary purpose of the
container is to hold the canopy and pilot chute closed, and
then allow it to open during deployment. Today, body
positions experienced during free fall range from head-down
to feet-to-earth and everything in between. Where speeds
formerly experienced ranged from 110 miles per hour (mph)
to maybe 140 mph, today speeds in a head-down position can
exceed 200 mph. This has changed the container dynamics to
ensure a more secure system and increased protection from
the wind blast. These changes have resulted in more secure
and streamlined configurations to accommodate these new
requirements. Figure 2-13 shows a modern container design
shaped to meet the high-speed airflows of today.
An additional area that needs to be addressed when designing
piggyback systems is the main riser covers. In the early days
of sport piggyback designs, the main risers were held in
position by webbing keepers. As the sport progressed, the use
of fully enclosed main riser covers became the norm. In their
attempt to protect the main risers during high-speed free fall,
some designs tend to restrict the deployment of the reserve
container in the event of a “total” main pack malfunction.
When this happens and the main container remains closed,
the main riser covers do not open. Because of this, there is
additional restriction over the upper corners of the reserve
container. This contributes to higher reserve bag release
forces. In severe cases, this can result in a reserve pilot chute
in tow with potential serious consequences. The balance
between sufficient main riser protection and the requirement
for unhindered reserve deployment is a critical design feature.
Most modern sport parachute containers have housings of
some sort to accommodate ripcords and riser release cables.
These flexible metal conduits come in 3 basic types in varying
diameters: non-compressible, relaxed, and non-extendable.
The housing type is critical to provide proper protection
and function for the usage. Non-extendable is used for most
ripcord housings, except on Navy seat packs. Relaxed refers
to the ripcord housing that is not completely compressible.
Non-compressible housing is the correct type to use for 3-ring
cutaway systems so the compression does not cause the sides
to release unevenly.
Harness Design
According to Poynter’s Parachute Manual, “the harness is
an arrangement of cotton, linen, nylon, or Dacron® webbing,
which is designed to conform to the shape of the load (usually
the body), to be carried in order to secure it properly so that
the opening forces and the weight of the load are evenly
distributed during opening and descent.”
Figure 2-15. Super swooper harness.
Figure 2-14. Military harness.
The earliest harness was nothing more than a swing seat
that the parachutist sat on and then held onto the risers
or suspension straps. It soon became apparent that if the
openings were in any way uneven, it could be very precarious
for the parachutist. While the sling seat worked for the ride
down, it was necessary to add additional straps to secure
the parachutist. These straps included the leg, back, and
chest straps. The standard harness configuration is equipped
to secure a torso, head, arms, and legs with straps. Others
have been added over time for additional purposes, such as
survival kits or cushions. Figure 2-14 shows a basic military
style harness. This harness configuration has seven points of
adjustment to allow fitting of most military personnel.
Most of the early parachute systems had the harness detachable
from the containers. This allowed interchangeability for
various models. In the 1970s, skydiving systems began to
integrate the harness into a true harness/container assembly.
This was accomplished by sandwiching the harness between
the container and backpad and sewing them together.
Figure 2-15 shows one of the earliest custom systems called
the “super swooper.” This harness was the precursor of
today’s sport harnesses.
As skydiving and the sport parachute industry has grown,
most of the equipment is now custom-built for each
individual. The standard piggyback harness configuration of
today is a fixed main lift web with adjustments only at the
chest and leg straps. [Figure 2-16] Elimination of the extra
hardware and webbing has resulted in a dramatic reduction
in weight of modern systems. Along with this has been an
increase in comfort and flexibility. One of the most innovative
designs adopted in recent years is the “articulated” harness.
This design incorporates metal rings at the hip junction and
the chest-strap attachment. [Figure 2-17] These rings allow
a full range of motion both in the air and on the ground and
increase the fit and comfort of the harness. Note however that
hardware incorporated into the main lift web or junction of
a harness should be equal in strength to the webbing or at
least the certification of the harness. Type 7 harness webbing
is 6,000 pounds tensile. Type 13 harness webbing is 7,000
pounds tensile. The stainless steel “RW-8” is certified to
3,500 pounds. The stainless steel 5010 Harness Ring is
certified to 5,000 pounds.
The “stepped” harness is not as strong as the continuous
horizontal harness [Figure 2-18]. If point loading occurs on
a stepped harness, stitching may break, and the junction can
Figure 2-17. Fully-articulated harness.
Figure 2-18. Stair-stepped harness (aka stepped harness) junction
warping.
Figure 2-16. Standard piggyback harness.
fail with disastrous results. With a continuous horizontal, if all
the stitching were to fail, the wearer would still be wrapped
in webbing and restrained in the harness.
In recent years and with the increasing popularity of vertical
skydiving or “free flying,” greater speeds are experienced
with corresponding higher loads on the harnesses. For many
years, harnesses were overbuilt as they were basically copies
of military designs. As the sport has progressed, equipment
has been made lighter and smaller.
Bridles and Deployment Devices
In the early days of parachutes, the lines and canopy were
stowed in the container. During the deployment process, the
canopy was extracted first, followed by the lines. This was
known as a “canopy first” deployment. If the canopy inflated
before tension was applied to the lines, a malfunction was
highly likely and a hard opening shock a certainty. Over the
years, it was learned that the deployment process needed to
be controlled to prevent malfunctions. Hence the introduction
of deployment devices that changed the deployment sequence
to “lines first” by preventing canopy skirt from spreading
until the lines were fully extended.
At the start of the World War II, with the advent of airborne
paratroops, the main canopy was deployed from a direct
bag static line system. In this system, the main canopy was
packed in a bag that was permanently attached to the static
line. After deployment, the bag and static line remained
with the aircraft. This system is still used today with some
modifications. For emergency parachutes, the military
adopted the “quarter bag” in the 1950s for use with high-
speed emergency systems. [Figure 2-19] This was fairly
complicated to pack but effective in controlling the parachute
during opening. In the early 1960s, the sleeve was developed
Figure 2-19. Quarter bag.
Figure 2-21. Type 1 deployment—T-7A reserve.
Figure 2-20. A) Non-collapsible slider and B) collapsible slider.
and soon became popular for sport parachuting or skydiving.
With the growth of skydiving and the increased use of the
reserve parachute, it soon became obvious that the reserve
parachute needed to be controlled more. In the mid 1970s,
the two-stow diaper was developed for use with emergency
and reserve parachutes. This design was soon followed by
the three-stow diaper and the piglet-style diaper invented by
Hank Ascuitto. During this time period, the deployment bag
became the preferred method of deploying the increasingly
popular ram-air or square canopies. In 1977, Para-Flite, Inc.
introduced the first ram-air reserve canopy, which utilized
the “free bag” deployment system. This design continues
to this day virtually unchanged as the preferred method of
deploying square reserve canopies.
Reefing devices slow down and stage the opening sequences
of canopies, resulting in lower opening forces. This is
particularly critical at higher speeds where the excessive
“G” forces experienced may injure or kill the user. The
most common reefing device used today is the “slider.”
[Figure 2-20A and B] This device consists of a piece of
fabric with grommets or rings at the corners through which
the line groups pass. This restricts the inflation of the canopy
and slows down the opening. While other methods have been
developed for military or aerospace applications, the slider is
the preferred method of reefing ram-air canopies. Without this
device, skydiving would not be as developed as it is today.
Deployment Types
There are currently six different types of deployment
methods, which are listed below.
Type 1: Canopy First Deployment
With this method, the lines are stowed vertically or
horizontally in the container. Examples of this method are the
T-7A chest pack or the B-12 back parachute. [Figure 2-21]
Type 2: Two-Stow Diaper or Half Diaper
This method utilizes split line groups. Two stows from one
line group lock the diaper, compensated by offsetting stows
of the other line group in the container with the remainder of
the lines stowed in the container. Examples of this method
are the early Strong 26' Lo-Po and the Pioneer “K” series
reserves. [Figure 2-22]