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Figure 1-5.—Suspension lines on 28-foot canopy | Up
Aircrew Survival Equipmentman 2 - Aviation theories and other practices | Next
Figure 1-8.—Vent |
Figure 1-6.-Close-up view of a gore.
by the letters A, B, C, and D (fig. 1-6), starting
with the bottom section. Figure 1-7 is a flat view
of the entire canopy, and the note in the figure
shows the relationship of the gore in figure 1-6
to the rest of the canopy.
Most woven cloth has two types of threads—
warp and filling. These two types are identified
by their relationship to the selvage edge. A selvage
edge is a finished edge on two sides of a piece of
fabric to prevent raveling. This finished edge
sometimes has a narrow border of different
threads or sometimes it may have a different
weave. Warp thread runs parallel to the selvage
edge of cloth and runs lengthwise down a roll of
fabric. Filling thread runs perpendicular to the
selvage edge or crosswise across the width of the
cloth.
The sections used in a parachute canopy are
cut at a 45-degree angle to the centerline of the
gore. This is called a bias construction and
provides the maximum strength and elasticity. The
radial and diagonal seams are double lapped for
security. The suspension lines are enclosed in the
channel produced by stitching the radial seams.
Figure 1-7 shows a flat view of this bias
construction of the 28-gore canopy. Stenciled on
the top center gore (section A of gore 28) in letters
one-half inch high and about 12 inches from the
bottom of the canopy are the NAVAIRFAC order
number, date of manufacture, serial number, and
the manufacturer’s mark or trademark. Stenciled
on the diametrically opposite gore (section A of
gore 14) is the date of manufacture and serial
number.
If you should have to add markings to the
canopy, the marking fluid you use should be in
accordance with Specification MIL-I-6903A,
Amendment No. 1.
Note the vent pictured in figure 1-8. This vent
acts as a relief valve and relieves the high internal
pressure within the parachute at the instant of
opening. Without this vent, an opening at high
speed could result in a dangerous rupture of the
canopy. The skirt (not shown) and vent hems are
reinforced with 1-inch tubular nylon webbing with
a tensile strength (T/S) of 4,000 pounds, to aid
in preventing tears from completely separating the
canopy.
All machine stitching, except zigzag, should
conform to Type 301, Federal Standard 751, and
should be not less than 8 nor more than 10 stitches
per inch. Ends of all tape, webbing, and lines must
be seared to prevent fraying. No waxes should be
used. For sewing diagonal seams, either size B or
E nylon thread may be used. Use size E thread
for all other seams, zigzag stitching, and repairs.
Removable connector links provide a quick
attachment for the canopy and suspension lines
to the lift webs.
1-8
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