Figure 2-49. Single-side RSL configuration.
Reserve Static Line (RSL) Systems
A RSL system is a backup device for activating the reserve
after a cutaway is performed. It usually consists of a line,
webbing, or cable, which connects one or both main risers to
the reserve handle, housing, or cable. The most common design
used today has a ring through which the reserve ripcord cable
is routed. The riser end attaches to a ring on the riser(s) with
a snap shackle for quick release capability. When the risers
are jettisoned, the lanyard pulls the cable, releasing the ripcord
pin(s), and activates the reserve. This results in a minimum
loss of altitude during the cutaway procedure. The use of an
RSL has saved many lives over the years due to low cutaways.
Though originally developed in 1964, as the Stevens
System, the RSL concept did not become popular until the
advent of student piggyback systems and ram-air canopies.
Through the use of an RSL system, the student parachutist
need only pull the canopy release handle in the event of a
partial malfunction, and the main canopy is cutaway and the
reserve activates. In 1990, the PIA urged manufacturers to
include RSLs as a standard feature on all harness/container
systems. Many did and this resulted in an increase of RSL
use for several years.
Conventional (chest mounted) parachute systems utilized
a cross-connector at the junction of the riser to the lines of
the canopy on each of the front and rear risers. This was so
as to maintain drag if one side release before the other. The
maximum amount of drag available is required to assure
the reserve ripcord activation by the RSL and the release
and separation of the off side riser. When applied to the
piggy back, these cross connectors would hang up on the
bottom of the reserve container preventing separation. Many
manufacturers dismissed this need and elected to provide
a reserve lanyard that was side sensitive (in that it would
activate the reserve if the attached side released and the
opposite side did not release). Others moved the lanyard to
the base of the riser, which required only one cross connector.
This location avoided the possibility of a hang up on the
bottom of the reserve and retained the drag integrity.
In recent years and with the widespread acceptance of newer
types of AADs, many parachutists feel that they no longer
need an RSL. In reality, both systems complement each other.
The AAD functions if the individual does not activate the
main parachute. However, it is altitude and rate of descent
(ROD) dependent. Below a certain altitude, if the ROD
is not met, the AAD will not function. Consequently, if a
cutaway is performed below the activation altitude, it may
take some time for the descending parachutist to reach the
ROD necessary to initiate activation, thereby necessitating
rapid manual activation of the reserve. However, if an RSL
is also installed, it would cause an immediate activation of
the reserve as the main parachute disconnects and moves
away from the parachutist.
In the last few years, as canopy design has resulted in smaller
and more sensitive canopies, many parachutists have elected
not to use an RSL. The rationale is that in a violently spinning
malfunction, which some of these highly loaded canopies are
prone to do, it is preferable to cutaway and regain stability
prior to pulling the reserve. This reduces the chance of an
entanglement with the deploying reserve. While this scenario
has happened, it is a rare occurrence. Statistics show that
many lives have been saved by using an RSL.
RSL Designs
There are four primary design configurations of RSLs in use
today and are listed below:
1. A single-side RSL where the lanyard is attached to
only one main riser, usually the left side. [Figure 2-49]
Only the one side is required to release to activate the
system. This is the most common design in use today
due to its simplicity.
2. A dual side RSL where both main risers are connected
with a cross connector which is the RSL lanyard.
[Figure 2-50A and B] Both risers need to release for
the system to activate.
3. The LOR system developed by the French. This
incorporates two lanyards, one from each riser, that
are attached to individual curved pins that secure
the reserve container with a dual locking loop.
[Figure 2-51] Both risers must be released for the
system to function.
Figure 2-50. A) Dual-side RSL configuration and B) dual-RSL
routing diagram.
Figure 2-51. LOR system.
Figure 2-52. Skyhook® system.
Collin’s Landyard Loop
4. The Collins Lanyard/Skyhook™ system. This design
utilizes a special lanyard that is attached to the bridle
of the reserve free bag. [Figure 2-52] Cutting away
results in the free bag being pulled directly out of the
container by the main risers and results in very little
altitude loss.
Since the early 1990s, most (if not all) manufacturers have
provided an RSL installation on their equipment either as
standard or optional. If the rigger has a system without an RSL
and the owner wishes to have one installed, the rigger should
check with the manufacturer as to the availability of a retrofit
kit or return it to the manufacturer for installation. Because the
installation of an RSL is an alteration to the original design, the
rigger needs approval either from the manufacturer or the FAA.
Because of the nature of the RSL system, it is imperative that
the rigger thoroughly understands the individual concepts.
Unless he or she understands this and has the required
manufacturer’s instructions, the rigger should not attempt
to assemble and pack a system with an RSL installation.
The following describes the basic design and function of a
single side RSL installation on a one-pin reserve container.
Main Riser Attachment
The main risers must have an attachment location for the
lanyard. In this example, a small ring is installed near the lower
hardware end of the riser on the inboard side. [Figure 2-53] It is
Figure 2-54. Snap shackle on RSL lanyard.
Figure 2-53. Main riser RSL ring attachment.
Figure 2-55. Double-ring container installation.
desirable to locate the ring as close to the lower end as possible
so that the pivot arc of the rise does not load the lanyard.
This allows the riser end of the lanyard end to be as short as
possible. If there is excess lanyard, it is difficult to stow, and
it is possible for the lanyard to become snagged and unseated.
It is important that the correct risers with attachment ring be
installed. While many risers have a ring installation, not all
are installed at the correct location. Consequently, the lanyard
length will not match the factory dimensions. This can result
in premature reserve activation when the main is deployed.
Most RSL lanyard designs have a snap shackle or similar release
device mounted at the riser end of the lanyard. [Figure 2-54]
This allows the user to disconnect the lanyard under certain
circumstances. The most common one involves landing in
high winds where the parachutist may wish to cutaway the
main canopy to prevent being dragged. If the lanyard were not
released, the reserve would be deployed as the main is cutaway.
Ripcord Cable Routing
The routing of the ripcord cable from the handle to the pin
determines where the lanyard connects to the cable. Most
RSL attachments connect with the ripcord cable either at the
yoke area or just above the ripcord pin. Generally, there is a
double ring installation where the cable end of the lanyard
is located. [Figure 2-55] On this particular installation, the
connection is at the shoulder yoke area.
RSL Lanyard and Container Mount
These two components are interactive. That is, the design of
the container directly affects the design of the lanyard. Once
the two above locations are determined, then the routing of
the lanyard can be completed. It was originally thought that
the lanyard should have a long length to allow acceleration
during activation to pull the ripcord cable. This has not proven
to be true and most manufacturers keep their lanyards as short
as possible to prevent snagging and easier stowing. The Racer
cross-connector/lanyard is so sized as to not pull the reserve
ripcord until both risers have separated
In the past, a Velcro ® pathway was used for routing the
lanyard. This was either on the shoulder yoke or the reserve
riser. Experience has shown that the use of Velcro® generally
results in high wear and eventual damage to the webbing.
[Figure 2-56] On this design, the lanyard is stiffened with a
short piece of coated cable and stowed in two pockets located
on the yoke area. [Figure 2-57] It is secure and has no wear
points. The ripcord end of the lanyard is routed to the dual
guide ring attachment location and the ripcord cable routed
through the rings. [Figure 2-58] The ripcord cable is then
routed to the reserve closing loop. Figure 2-59 shows the RSL
lanyard and ripcord cable at the moment of riser extension and
just as the cable is loaded. A point that the rigger should be
Figure 2-57. One style of RSL lanyard without Velcro.
Figure 2-58. Ripcord cable routing through rings.
Figure 2-61. Cutaway cable length differential.
Figure 2-59. RSL lanyard extension.
Figure 2-60. Ripcord cable pigtail with broken strand.
Figure 2-56. RSL Velcro riser damage.
aware of is the “pigtail” configuration of the reserve ripcord
that results from the use of the RSL. [Figure 2-60] Because
of the sliding of the ring along the ripcord cable, a curling
effect is imparted to the cable. This is a clear indication that
the RSL lanyard activated the reserve. The rigger should
carefully inspect the ripcord cable for any broken strands.
If any are found, the ripcord should be replaced. If not, the
cable can be straightened and returned to service.
With the single side RSL, it is imperative that the main
riser with the RSL attachment leave after the opposite
riser. If the opposite riser stays connected while the RSL
deploys the reserve, there is the possibility of a main/reserve
entanglement. To ensure the correct staging of the cutaway,
the release cable of the RSL side must be longer than the cable
on the opposite riser. A minimum of 1 inch is the standard
differential. [Figure 2-61] If non-compressible housings are
not used, the staged separation is not reliable.
Joint Efficiency
Joint efficiency is the percentage of the measurement of
strength when applied to the junction or fabrication of two
or more materials. An example is the cross seam in a canopy
gore where two panels of fabric are joined. The strength of
the seam needs to be greater than the strength of the fabric.
To achieve this, there are several factors that need to be
considered in the design. These include the following:
• Fabric—the weight and weave of the fabric affects
the type of junction used.
• Thread type—this is affected by the weight of the
fabric. Generally, the lighter the fabric, the smaller
the thread used. Accordingly, a smaller needle is used
in order not to damage the weave of the fabric.
• Stitch type—this is determined by the type of seam
needed for the design. For the French fell seam
normally used in joining the panels of a canopy, the
301 straight stitch is used.
• Stitches per inch—this has a direct correlation to the
size of the thread used and the stitch type. There is
a fine balance between the security of the seam and
overstitching. Too many stitches per inch dramatically
affects the strength of the seam by perforating the
material. The number of rows of stitching also affects
this. While more rows generally increase the strength
of the seam, too many perforate the material as well.
• Thread tension—as lighter fabric and thread are used,
the thread tension balance becomes more important.
• Reinforcing—the addition of reinforcing through
the use of tapes, cords, etc., adds to the strength of
the seam. However, their use may also reduce the
elasticity of the seam at the same time.
Some of the previous factors also can affect heavier materials,
such as tapes and webbings. In working with webbings in
harness design, most construction methods have tended
to overbuild the junctions. This has been done primarily
because the materials have readily accepted heavier threads
and stitch patterns.
An area that needs to be addressed is that of re-stitching
webbing. Until recently, there was not much study done
to determine how much strength is lost in this process.
G.S. Dunker, a parachute engineer, conducted a study that
evaluated the variables introduced when re-stitching webbing
junctions. Some of these variables included the following:
• The treatment or conditioning of the webbing.
Condition R webbing has a resin treatment to make it
stiffer as opposed to condition U or untreated webbing.
• The size and condition of the needle used in the
sewing. Larger needles make larger holes. A blunt
needle or one whose point is damaged, will do more
damage to the webbing and weaken it.
• The size of the thread used.
• The stitch pattern used and length. A W–W pattern is
stronger than a box X pattern.
• The number of times the webbing is re-sewn.
All of these affect the ultimate strength of the webbing junction
or stitch pattern.
Chapter Summary
It is important to know the history of parachute design in
order to move forward technologically. The old saying,
“Those who don’t know history are destined to repeat it.” Is
especially applicable to parachute design and manufacture,
where a relatively small, esoteric group of individuals who
are loosely controlled and turn on a dime, churn out designs
that some eager young test jumper is willing to try. This is
not necessarily a bad thing. The civilian led sport parachute
market is responsible for just about all the newest innovations
in the industry over the past 45 years. But it should be kept
in mind that a new design generally takes about ten years’
wringing out in the field to discover it’s failure modes and
make it safe and reliable.
Materials
Chapter 3
Introduction
The correct identification and use of the various materials in
parachute manufacturing and repair are of vital importance to
all riggers. Just as important as acquiring knowledge of tools
and machines, knowing and using the correct terminology
for materials is essential to the rigger’s job comprehension.
In doing repairs or alterations, the rigger must be able to
identify the types of materials used in order to duplicate the
original manufacture and to ensure the correct level of safety
necessary. Some materials may look similar, but there can be
subtle differences between them that make a major difference
in their strength or durability.
It is not the intent of this chapter to present information on
every type of material or hardware ever used in parachutes.
For very detailed specifications on a broader range of
materials used in current production parachutes, as well as
obsolete and military surplus parachutes, there are additional
reference sources, such as “The Parachute Manual” by Dan
Poynter. The purpose of this chapter is to present as much
information on the essentials of modern materials seen in
today’s parachute systems.
Many riggers operate quite successfully with a basic level
of material knowledge in their proverbial tool kit. There are
certain materials that are commonly used on most parachute
systems, and in dealing with these on a regular basis, the
rigger becomes very familiar with their characteristics and
proper application. It is fundamental that the rigger know
their correct type, nomenclature, strength, and common use.
In dealing with other riggers, manufacturers, and suppliers,
the rigger is then able to identify the referenced material in
order to obtain the appropriate repair part or describe the use
of the material to others. All of this is part of the parachute
rigger’s lexicon, required to communicate their needs and
accomplish the required tasks.
Specifications
All certificated parachute systems built under government
approval programs require most, if not all, materials used
in their construction to have some form of specification
approval. The most common of these systems is the military
specification (MIL-SPEC) system. In addition, there are other
government specifications, such as Federal Standards, and
commercial specifications in use. The MIL-SPEC system
is the one with which most riggers are familiar. Contrary
to popular perception, not all materials for use in parachute
manufacturing must be MIL-SPEC. Any specification may be
used, provided that the manufacturer can prove compliance
with this specification, and that the specification is acceptable
to the Federal Aviation Administration (FAA) for use in
the parachute system. As a rule, the MIL-SPEC system has
proven the most readily available and accepted method.
In recent years, the government has been accepting more
commercial specifications in lieu of MIL-SPEC items. In
2002, the Parachute Industry Association (PIA) adopted
approximately 270 parachute-related specifications, drawings,
standards, and test methods. The PIA takes responsibility for
the continued maintenance and revision of these specifications.
As the specifications are revised, they keep their original
identification number, but the PIA prefix precedes them.
For instance, MIL-W-4088 webbing becomes PIA-W-4088.
Through the involvement of the PIA Specifications Committee,
the revised specifications, including new digital drawings, are
made available to the industry.
The MIL-SPEC or PIA-SPEC system of identification
consists of the initial letters MIL or PIA with a middle letter
such as W for webbing or wire, then the identification or
serial number of the specification. In addition, there may be
a revision letter, such as A, B, C, D, etc. In the case of PIA-
W-4088D, this is the fourth revision.
The materials and hardware listed herein are only a small
part of those available, but the most commonly used in
the majority of today’s rigging profession. By learning
the specifications and uses of these materials, the rigger
establishes a sound basis for the repair and maintenance of
modern parachutes.
To promote the latest specifications, the PIA nomenclature
is called out unless otherwise noted. In the past, the common
method to denote the various types of webbings, cords, etc.,
was to use the Roman numeral for the type (e.g., Type VIII
for Ty-8, Type XVII for Ty-17). For this handbook, the
standard is the Arabic numeral (e.g., Ty-7).
Many of the figures in this chapter use a neutral background
with an XY grid for reference. The numbers are in one-inch
increments for a proportional reference.
Fabrics
Nylon is the predominate fabric used in the manufacture
of parachutes. Chemically speaking, nylon is made of
repeating units linked by amide bonds and is frequently
referred to as a polyamide (PA). It was invented in the late
1930s by Wallace Carothers while conducting research
at DuPont. There are many different kinds of nylon and
some of the major differences include the weave, weight,
and finish. The various types of materials include canopy
fabric, pack cloth, tapes, webbings, mesh, elastic fabrics,
stiffener materials, and foams.
Canopy fabrics are primarily ripstop nylon. Ripstop weave is
a plain weave with heavier threads woven into the material at
right angles resulting in a boxlike pattern. The heavier thread
and the unique weave results in ability of the threads to slide
over one another inhibiting the tearing process and results in
stronger fabrics. [Figures 3-1 through 3-6]
The composition of most containers is from either nylon duck
(Para-pack) or Cordura®. Para-pack has a smooth somewhat
shiny finish; Cordura has a matte, more rugged appearance.
Both are sturdy and long lasting. Most sport containers also
utilize a thin foam lining on the inside of the flaps to smooth
out the fabric and absorb wear and tear. Other fabrics, such
as mesh, Spandex ®, and ballistic fabric, serve specialized
purposes. [Figures 3-7 through 3-16]