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EFFECTIVITY:
C I R R U S
C O M P O N E N T M A I N T E N A N C E M A N U A L - C A P S
M O D E L S R 2 0
26 Jul 2013
The parachute slows the airplane to a descent speed that is conducive to a safe touchdown. The basic
structure of the parachute assembly consists of the canopy, suspension lines, and the slider; a compo-
nent used to aerodynamically reef the parachute and limit inflation loads.
(1)
Canopy and Suspension Lines
The canopy, which creates the aerodynamic drag, is made up of a series of fabric panels sewn
together to form its desired shape. The canopy has a vent at its center to allow some air to
escape in a controlled manner and thus reduce oscillations and provide a stable descent. Vent
lines are attached to the perimeter of the vent and routed symmetrically across its center to pro-
vide structural support and maintain its shape.
The suspension lines are attached to the “skirt” of the canopy and converge to a riser or set of
risers at the opposite end. The canopy structural integrity is enhanced by a “skeleton” of tapes
and webbings sewn nearly perpendicular to each other to the top surface of the canopy fabric.
Radial bands run from opposite suspension line attachment points, across the top of the canopy.
The skirt band, vent band, and lateral bands run around the circumference of the canopy.
The parachute is fabricated from woven textiles in the form of fabrics, tapes, webbing, and
thread. All of the textile components in CAPS are fabricated from either Kevlar or Nylon and are
woven to military specifications that define specific parameters such as yarn count, yarn twist,
weave type, and finish. To insure good aging characteristics, the only exception to the use of
Kevlar and Nylon is a Teflon cloth buffer on the risers at the suspension line attachment point.
A typical deployment load profile begins with a snatch force which occurs when the parachute
assembly is initially extracted from its container and pulled to full line stretch. When air begins to
fill the canopy, inflation loads result. The parachute is designed to deploy without generating
forces high enough to injure the airplane occupants.
(2)
Slider
To limit inflation loads, CAPS uses a slider to aerodynamically reef the parachute. The slider is a
flat annular shaped fabric panel with metal grommets attached to its perimeter. The parachute
suspension lines are routed through the grommets so that the slider is free to move along the
suspension lines. The slider, which has a significantly smaller diameter than the fully inflated
parachute, is positioned at the top of the suspension lines, next to the canopy skirt, when the
parachute is packed. It therefore limits the initial inflated diameter of the parachute and hence
the inflation loads. During inflation, the slider remains next to the skirt for a period of time that is
dependent on the dynamic pressure acting on the system. This allows the payload to decelerate
to a speed at which the parachute can fully inflate without generating excessive loads.
F. Airplane Attachment Harness
An aircraft harness system connects the parachute risers to the airplane primary structure. The CAPS
aircraft harness consists of two forward harness straps attached to the firewall and a rear harness
attached to the FS 222 bulkhead located directly in front of the parachute enclosure. The CAPS har-
ness system is designed to control the pitch dynamics of the airplane during the deployment cycle by
limiting the aft aircraft attachment harness length until the deployment cycle is complete.
The rear harness assembly has two sections of different length. The shorter section has a mechanical
release mechanism that is activated by two pyrotechnic reefing line cutters. Fuses on these line cutters
are initiated when the line cutter release pin is pulled when the harness is pulled taut during the extraction.
After 8 seconds, the line cutters fire, the longer section of the rear harness takes over and the airplane
assumes its touchdown attitude, approximately ten degrees nose down, to optimize occupant protection.
The release mechanism design is based on a 3-ring release mechanism. This system uses a series of
metal rings routed through each other in a manner that provides a significant mechanical advantage.
For the mechanism to be released, each link must rotate through its adjacent ring or link. Force neces-
sary to hold the small link in its stowed position is considerably smaller than the force that is being
applied as a result of the overall load on the mechanism. On the CAPS system the last link is held in
place by a mini-ring and short length of nylon cord which is severed by pyrotechnic reefing line cutters.
