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

area
'" (R/ /2Jf2(J-sin
:= g.,
The projected area in Plane B- B is
Z(A,+A2)s;n')
The local differential pressure is
FIAK
:95
where is the pressure coefficient from an estimated
ressure distribution curve, e. c.p/q, Fif;. 7. 18 and
K' is the integration factor, a function of the shape of
tne pressure distribut"on curve and the geQmetric
porosity .
Equil i brium of Typical Horizontal Element.
From a summation of forc::s in direction R, the unit
tension in a horizor, tal member is
fc pR (nIZ) Isin
The arc length is
'"
.. 2(3 R r sin (1fIZ;/s;n (3
The length of the horizontal member is
ef.(1 + fH)
where eJ. is tho unstretched length. A value for (J
found by itcration to givo
eH 100
The unit tension in each horizontal member is resolved
into three mutually perpendicular components:
1. Tangent to the meridional member
M'R sin (rrIZ) cas "I
2. Normal to the meridional member in a plane
which includes tre ceMral axis
102
(CO$ f3 sin (3 sin a/eos a.)
flv fe (sin picas a si'n a
(CDS sin 13 sin a/eDS a)
3. .f' circumfe ental force
f1r fe cos (l1/Z)
(CDS (3 I- sin sin a/eDs a.)
101
7103
Equilibrium of a Segment of a Meridional Member
(/:h).
fRl2f'r
where the load in one meridiO'al member starting at
the ski r1 is
fR FIZsin"l 104
and the number of gores
the number :if suspension
lines. At subseqJent stations fFi is computed
by subtt acting the accumulated /:fli from the initial
val ue. Since the ends of two horizontal me.Tlbers are
acting on each meridional memoer, the l::ad at station
360
= f'R(j- 1)-
/2) (j-1)-
105
/2) j
and the length of segment
Mf(1 HR) 7- 106
where c.hj is tt'e unstretched or manufactured length.
For complete delails, see Reference 221
Solution Algorithm. A flow diagram f:r the digital
computer program is presented in Figure 7- 19A. A
user s manual which includes a lis-:ing of the program
will be found in Reference 532
Eqv8tions 7.84 and 7.85 are solved simultaneously
by the method given in Figure 7. 198 for the uMeefed
para::hute. Equatiens 7-86 and 7-87 through 7.91 are
resolved simultaneously by the method given in Fig.
ure 7. 19C for the reefed parachute. The remaining
equations 7.92 through 7- 106 are resolved simultaneously
by the method given in Figs 7. 19B or 7 19C.
Input data include:
Parachute geometry (reefed and unreefed)
Meterialload-strain curves
= =).
Pressure :jisulbllian curves (ree ed and un.
reefed I
Main riser load, (reefed and unreefedi
One of the basic assumptions of the slotted cano.
py analysis is that the horizontal sails or ribbons arch
outward with t'le warp yarns tying In planes normal
to the radial or meridional -nernbers. But it was ob.
served that the vertical me-nbers of the ribbon and
ringslot canopies introduced 0 pronounced distortion
near the skirt that prevented the horizontals from
bulgin normally by plClling them upward. As a result,
the verticel members pick up a component of
the grid pressure ; oad and transfer it to the radial
members. This is generally analogous to the stressstrain
relationships of the solid cloth canopy II.lstratad
in Fig. 7. 15 except for the 45 degree displacement
of warp and fill axis.
The e"18ct of the vertical members on the internal
load distributicn o the canopy was ac:;ounted for in
an analvsis based on the following assumptions.
Meridional curvature is constant over each !Jh segment
of the canopy, and cun/Dtvres EIe tangent at
the junction between adjacent segments. The hori-
zontal ribbons have simple curvature
The vertical members act as equivalent fill yarns
uniformly distributed across the gore.
The edges of a horizontal ribbo!1 lie n planes at an
angle to norrral plane C (Fig. 7. 17)
The projection of a horizontal ribbon on normal
plane C is a circular arc.
The additional equations required are not develop-