2. Discussion of Related Art Parachutes have evolved over the years into highly sophisticated systems, and often include features that improve the safety, maneuverability, and overall reliability of the parachutes. Initially, parachutes included a round canopy. A skydiver was connected via a parachute harness to the canopy by suspension lines disposed around the periphery of the canopy.

Such parachutes severely lacked control. The user was driven about by winds with little mechanism for altering direction. Furthermore, such parachutes had a single descent rate based upon the size of the canopy and the weight of the parachutist. They could not generate lift and slowed descent only by providing drag.

In the mid-1960's the parasol canopy was invented. Since then, variations of the parasol canopy have replaced round canopies for most applications, particularly for aeronautics and the sport industry. The parasol canopy, also known as a ram air canopy, is formed of two layers of material - a top skin and a bottom skin. The skins may have different shapes but are commonly rectangular or elliptical. The two layers are separated by vertical ribs to form cells. The top and bottom skins are separated at the lower front of the canopy to form inlets. During descent, air enters the cells of the canopy through the inlets. The vertical ribs are shaped to maintain the canopy in the form of an airfoil when filled with air. Suspension lines are attached along at least some of the ribs to maintain the structure and the

orientation of the canopy relative to the pilot. The canopy of the ram air parachute functions as a wing to provide lift and forward motion.

Guidelines operated by the user allow deformation of the canopy to control direction and speed. Ram air parachute canopies have a high degree of maneuverability.

Canopies are flexible and stretchable membrane structures, they distort based upon mechanical and aerodynamic tensions, stresses, airflows and pressure distribution. Although a cell is modeled as having a basically rectangular cross section, when inflated the shape distorts towards round with complex distortions. Under canopies of conventional design, the leading edge or nose of the ram air parachute is deformed during flight as is the top profile of the airfoil between the ribs. Additionally, with forward motion, the head-on wind overcomes the internal pressurization of the canopy, and deforms the nose of the canopy. This distortion blunts the nose of the airfoil or even indents it, impairing the aerodynamics of the parachute wing. The parachute flies less efficiently as a result. Therefore, a need exists for a ram air parachute canopy which reduces nose distortion and spanwise topskin distortion.

Inlets are required to inflate and pressurize the canopy to maintain its wing shape. However, the inlets are also the greatest source of drag on the wing which slows forward movement and reduces efficiency. The carrying capacity and glide ratio of the canopy would be improved if this drag could be reduced. Therefore, a need exists for a canopy with reduced drag from the cell inlets.

Typically, in a ram air parachute, suspension lines are attached to every other rib, thus creating loaded ribs (i. e. , ribs to which suspension lines<BR> are attached) and non-loaded ribs (i. e. , ribs which do not have suspension lines attached thereto). The different stresses on the loaded and non-loaded

ribs also distorts the cell shape. Fig. 1 illustrates a cross section of a portion of a typical ram air parachute canopy 500 during flight. Fig. 1 shows two cells formed of parts 501,502, 503,504, with three loaded ribs 510, 511, 512 and two non-loaded ribs 521,522. Suspension lines 541,542, 543 are attached to the loaded ribs 510,511, 512. The top skin 530 and bottom skin 531 tend to arc between the ribs during inflation. Also, the non-loaded ribs 521,522 tend to be higher than the loaded ribs 510,511, 512, which provides a distortion along the span of the canopy. The distortion is aerodynamically undesirable and reduces the efficiency and performance of the canopy.

In order to keep the loaded and non-loaded ribs level and to improve upon the aerodynamics of the canopy, cross-bracing between ribs has been added to some canopy designs. Cross bracing is the use of diagonal ribs in addition to vertical ribs to create more loaded rib-top skin junctions without adding more lines which increase drag and possible deployment malfunctions. Perfection of the top profile of the airfoil is far more important aerodynamically than the bottom profile. U. S. patent 4,930, 927 illustrates such a design. Cross-braced designs suffers from a number of drawbacks.

Cross-bracing results in very complicated construction, high manufacturing costs, and increased packing volume. The standard cross braced design is a 'tri cell'construction with a packing volume approximately 25% larger than an equivalent non-cross braced design. A cross section of a tri-cell canopy is illustrated in Fig. 2. Furthermore, the increased rigidness induced by the cross-bracing creates higher opening forces for the pilot. Typically, large cross porting is used on all of the cells to reduce pack volume, which does nothing to slow the canopy's inflation on deployment. The opening forces can be so severe that they can jar the jumper's body causing discomfort and even injuries. Although designers have implemented"formed"noses, larger

sliders, moved bridal attachment points and modified line trims to try to soften the openings of such cross-braced canopies, it has generally yielded limited improvement.

Sliders used to counteract the large opening forces on a cross-braced canopy often cause premature wear on the suspension lines of the canopy. A slider is a rectangular piece of material with a grommet at each corner.

Grouped suspension lines pass through each grommet. When the parachute opens, the force of the opening canopy and separating suspension lines forces the slider down the suspension lines. Air resistance tends to slow movement of the slider and, hence, restrict opening of the canopy against the spreading foce of the inflating canopy pushing the slider down. The most force on the slider comes from the lines to the outermost cells, which pushes the slider down rapidly caused friction heat. The heat changes the dimension of many standard types of lines (e. g., Spectra, dyneema brand lines). It is not uncommon for outer lines to change in dimension as much as five inches in only a couple of hundred jumps. Accordingly, cross braced canopies are almost exclusively supplied with Aramid based lines (e. g., Kevlar, Vectran, etc. ). These lines do not change dimension with the generated slider-friction heat solving the problem stated above, but suffer from micro-fiber cracking. Accordingly, if over jumped, Aramid lines can break catastrophically with no warning.

Prior art canopies have included formed noses with shaped inlets to limit opening forces. Figs. 3 and 4 illustrate two prior art canopy designs having a formed nose. Fig. 3 illustrates a tri-cell design with an formed nose having an oval inlet 801 by a loaded rib 802. Reinforcing tape 803 is sewn around the oval shape of the nose. Fig. 4 illustrates a formed nose created by extending the top skin 810 and bottom skin 811 around the nose of the canopy to create shaped inlets 812. Again, reinforcing tape 813 is sewn to

the inlet edges. While the fabric tape on the inlet edges of the formed noses in these designs limits wear, the canopy is still subject to span-wise stretching. The entire span of the canopy will stretch during flight and span wise distortion of the nose occurs due to the different stresses on loaded and non-loaded ribs. All prior art canopies with formed noses place the open inlets over a loaded rib. This creates a geometry which, during deployment, presents scoops for inrushing air. The scoop shape results in large opening forces and in substantial drag during flight.

Accordingly, there is a need for an improved parachute airfoil design which provides ram air parachutes with lower spanwise distortion without using crossbraces and with restricted inlet area for softer openings.

Furthermore, a need exists for a canopy design which limits distortion and stretching at the leading edge for improved aerodynamics with formed nose inlets. A need exists for a packable canopy design which provides improved aerodynamics with limited packing volume.

Para-gliders and powered parachutes, which operate with similar designs to ram air parachute canopies, overcome the deformation problem by including"stiffeners"in the nose of the canopy. Typically, the stiffeners are plastic or mylar sheets sewn on the vertical ribs of the canopy into the nose. The stiffeners reinforce the nose of the canopy and help maintain its shape. The stiffeners also function to keep open the inlets of the canopy when not inflated to aid in the launching of para-gliders and powered parachutes. However, the stiff plastic or mylar used in paragliders and powered parachutes is not applicable to skydiving or other freefall deployable parachutes. A deployable system must be packed into a small space and must open efficiently. The stiffeners cannot be compressed as required for packing the parachute. When stiffeners become crushed, they remain creased or bent and create additional deformation of the nose of the

canopy, which hinders proper operation of the parachute. Packing for free fall deployment of such para-glider or powered parachute is not possible due to the stiffeners. Accordingly, there exists a need for a stiffener for use on a parachute to reduce nose-deformation to improve the canopy's aerodynamics, which may be folded and packed as known in the art of deployable parachutes.

SUMMARY OF THE INVENTION The deficiencies of the prior art are substantially overcome by the canopy design of the present invention which reduces spanwise distortion on the top skin without using cross braces. According to one aspect of the invention, the size of the inlets are changed to reduce drag on the canopy and control the conductance of air inflating the parachute during deployment. according to a first embodiment of the invention, triangular pieces of material are attached to the front edge of the top skin at each of the loaded ribs. The triangular material reduces the inlet size and thus drag on the canopy during flight. The triangular material also tensions the top skin between the loaded ribs and the non-loaded ribs to reduce spanwise distortion. With the addition of this triangular patch on the nose at each rib inlet pack volume is increased by only a miniscule amount, but tension is now transmitted from the suspension line-loaded rib junction through the patch and its reinforcing tape to the top skin of the canopy cell greatly reducing the spanwise distortion of the nose. The distortion is reduced to the same amount present with crossbracing only at the nose of the wing and then tapers back to a usual amount about 1/3 of the way back on the airfoil.

Aerodynamically this is the most important portion of the wing. With equal dimensioned triangle patches on both the loaded and non loaded ribs the nonleaded rib triangles will not tension in the same way than at the loaded

ribs and tend to remain slack. Such a design performs well over prior art but can be further improved by changing the shape of the nonloaded triangles to have a broader angle off the vertical rib so as to overlap with the loaded rib triangles. In this way side they are side tensioned from the loaded rib triangle edges.

According to a second embodiment of the present invention, triangular pieces of material are added to the front edge of the top skin at the loaded and non-loaded ribs. According to another embodiment of the present invention, the top or bottom skin of the canopy are modified to provide the shape of the triangular pieces of material of the other embodiments. The edges of the formed inlet opening are reinforced with woven fabric tape. The resulting configuration looks akin to a triangulated reinforced truss.

According to a third embodiment of the a-line attachment points of the canopy are set back slightly from the tail and the bottom skin cut with a zig-zag or scalloped edge. In this embodiment, the additional inlet area is formed that is only presented during deployment when the relative wind is from below. Once inflated with the canopy in gliding flight the relative wing is from slightly below head on. Prior art canopies use inlets that when their area is projected in the direction of the relative wind have more projected inlet area during flight than during opening. this is reversed from ideal in that more inlet area is required for opening than is required to keep the canopy pressurized for flight. Any additional inlet area than required for flight is simply additional drag. By undercutting the bottom skin the inventive method can ensure proper deployment of canopies with very low drag restricted inlets for flight.

According to another aspect of the invention, a continuous reinforcing fabric tape is attached to the top skin of the canopy along the

leading edge above the inlets. According to another aspect of the invention, the trailing edge of the top skin is also reinforced with fabric tape.

According to another aspect of the invention, at various points along the edges of each cell, the top skin is non-rectangular having a reduced width. When inflated, the areas of reduced width in the top skin have a higher tensions than the surrounding areas. The higher tension in these areas creates a stress pattern to maintain the intended shape of the canopy.

According to one aspect of the invention, the areas of reduced width are located along the leading edge of the top skin. According to another aspect of the invention, the areas of reduce width are located near the apex of the airfoil shape of the canopy. According to another aspect of the invention, the areas of reduce width are located behind the apex of the airfoil shape of the canopy above the second suspension line attachment point.

According to another aspect of the invention, the areas of reduce width are located near the trailing edge of the canopy.

According to another aspect of the invention, flexible stiffeners are attached to the nose portion of the ribs. The flexible stiffeners are wire rings that act as springs to reinforce the nose. The ring springs are formed from a super-elastic metal alloy, i. e. nickel titanium such that they can be greatly deformed during packing and recover without kinking. Such Ni-Ti alloys are over 8 times more deformable than spring steel. The stiffeners may be ring shaped or heat memorized into a formed shape i. e. a D shape during manufacture. Additionally the stiffeners may be attached to the vertical ribs by various methods but preferably by sewing a pocket in the section of the nose to be reinforced and inserting the stiffener ring spring. Additionally the pocket can pre-stress the ring spring into a different shape that it is at rest.

I. e. from a round ring to a D shape to exactly match the leading edge of the

airfoil. This has the added benefit of biasing the spring in the direction of the head on wind that acts to deform the airfoil.

According to another aspect of the invention, the heights of the ribs in the canopy are not uniform. Non-loaded ribs are shorter than loaded ribs at least at the front edge. This forms cells that are slightly trapezoidal in shape. The tension across the bottom skin is transferred-to and pulls down the non-loaded ribs. This tensioning keeps the top portion of the non-loaded ribs from rising as much above the top portion of the loaded ribs. Thus, the top skin remains relatively even, reducing spanwise distortion and improving the aerodynamics of the canopy.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross section view of cells in a non-cross braced canopy of the prior art; Fig. 2 is a cross section view of cells in a tri-cell canopy of the prior art; Fig. 3 is a front view of a first formed nose of the prior art; Fig. 4 is a front view of a second formed nose of the prior art; Fig. 5 is a front view of a ram air parachute according to an embodiment of the present invention; Fig. 6 is a perspective view of portions of two cells of a ram air parachute according to an embodiment of the present invention; Fig. 7 is a front view of a portion of a ram air parachute according to a first embodiment of the present invention; Fig. 8 is a front view of a portion of a ram air parachute according to a second embodiment of the present invention; Fig. 9 is a front view of a portion of a ram air parachute according to a third embodiment of the present invention.

Fig. 10 is a side cross sectional view of the canopy according to an embodiment of the present invention.

Fig. 11 is a bottom view of the canopy according to an embodiment of the present invention.

Fig. 12 is a top view of a top skin panel for a single cell of a canopy according to an embodiment of the present invention ;

Fig. 13 is a side view of a vertical rib of a canopy illustrating areas of increase tensioning.

Fig. 14 is a side view of a vertical rib of a ram air parachute according to an embodiment of the present invention; Fig. 15 is a side view of a ring shaped stiffener according to an embodiment of the present invention; and Fig. 16 is a side view of an applied stiffener according to an embodiment of the present invention.

Fig. 17 is a cross sectional view of two cells of a ram air parachute according to an embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 5 is a front view of a ram air canopy according to an embodiment of the present invention. The canopy has a top skin 121, bottom skin 122, and a plurality of vertical ribs 131,132, 133. The top skin 121 and bottom skin 122 are separated at the leading edge to form inlets 140 for the cells of the canopy. Fig. 6 illustrates parts of two cells 42,43 of the canopy according to a first embodiment of the present invention. Each portion 42,43 is formed by a portion of the top skin 21a, 21b, a portion bottom skin 22a, 22b, and two vertical ribs 32,32, 34. The top skin 21 and bottom skin 22 are partially open at the front edge of the canopy to provide an inlet. A triangular member 60 is attached between the bottom skin 22 and the top skin 21 at the loaded rib 33. Additional triangle members 70a, 70b are attached between the top skin 21 and bottom skin 22 at the non-loaded ribs 32,34.

The triangular pieces 60,70a, 70b creates two reduced size inlets 25a, 25b between themselves, the top skin 21 and the bottom skin 22. The triangular members 60,70a, 70b may be a separate piece attached to a front

edge of the top skin 21 or may be formed as an extension of the top skin 21.

Fig. 7 is a front view of a cell between loaded ribs 31,33 according to the first embodiment of the present invention. Fig. 6 illustrates the angles of the triangular members 60,61 and tensioning on the canopy when inflated. As is typical of the airfoil shape of the ram air parachute, the top skin 21 extends up from the inlet at the front edge. The non-loaded rib 32 is visible through the inlet, between the two inlet portions 25a, 25c. Line 32a illustrates the position of the non-loaded rib 32 attached to the top skin. The triangular members 60,61 extend part of the way along the leading edge of the top skin 21 from the loaded ribs 31,33 to the non-loaded rib 32.

Preferably, the triangular members 60,61 are dimensioned so that the edge facing the inlet portions 25a, 25c are tensioned when the canopy is inflated.

Furthermore, the triangular members are dimensioned so that the top skin is also tensioned along lines 60a, 61a from a top point 65 of non-loaded rib 32.

The tensioning of the triangle member 60,61 and top skin 21 restricts upward motion of the non-loaded rib relative to the loaded rib, without the use of cross bracing. A second triangle member 70 is positioned in front of the non-loaded rib 32. The second triangle member 70 is dimensioned so that the upper two vertices meet the top skin at the same location as the vertices of the first triangle members 60,61. As with the first triangle members 60,61, the second triangle member may be formed as a separate piece attached to the front edge of the top skin or as an extension of the top skin. According to the second embodiment of the present invention, the second triangle member 70 is dimensioned to reduce the inlet without changing the tensioning of the first triangle members 60,61 or the top skin 21. The improved nose structure of the present invention has aerodynamics similar to that of cross-braced canopies without the added weight or packing volume.

A second embodiment of the present invention is illustrated in Fig. 8.

As in the first embodiment, the third embodiment of the present invention includes triangle members 60,61 for limiting the inlet and for tensioning the top skin 21 to maintain an aerodynamic shape. The third embodiment further includes second member 71 disposed in front of the non loaded rib.

The second member 71 is in the form of a non-regular pentagon or simply overlapping triangles with broader angles from the vertical rib. The edges of the second member 71 from the lower skin 22 connect to the first triangle member 60,61 at points below the front edge of the top skin 21. As with the other embodiments of the present invention, the second member 71 can be formed as a separate piece attached to the top skin 21 or as an extension of the top skin 21. Additionally, the second member 71 and the first triangle members 60,61 may be formed as a single piece and jointly attached to the front edge of the top skin 21. The second member 71 is dimensioned so that additional tension is provided between the first triangle members 60,61 and the bottom skin 22 at the non-loaded rib 32. The extra tensioning provided by the second member 71 helps maintain the aerodynamic shape of the nose of the canopy.

Fig. 9 illustrates a third embodiment of the present invention. In the third embodiment, the vertex of the triangle member 72 at the non-loaded rib is set back from the bottom skin. This allows additionally tensioning of the nose of the canopy and an increased inlet area.

Inventive canopies have been constructed where the upper edge of the triangles are stitched along the length to the top skin and the apex or downward point is attached not to the bottom skin, but to the edge tape of the vertical rib using a bar tack.

The embodiments of the invention as set forth above disclose members for limiting the inlets to cells of the ram air parachute. All of the members disclosed in these embodiments have substantially straight edges reinforced with tape. The objectives of the members are to tension the nose and top to maintain an aerodynamic shape lower in distortion and to restrict the inlet area. The improvement realized in the present invention is an increased efficiency of the canopy, and an increased ability to control the inflation of the canopy for reduce opening shock. In addition, using the nose-patterned modification on a standard canopy allows the canopy to fly faster since the drag on the nose is greatly reduced and greatly increased efficiency and max wingload capabilities. Canopies of the inventive design have been flown up to ten pounds per square foot and landed up to 4.5 pound per square foot.

The triangular members 60,61 reduce the area of the inlet which reduces drag on the parachute during flight. The reduced inlets also limit entry of air in the cells during deployment, which slows deployment and limits opening forces. However, deployment may be excessively slowed.

Fig. 10 illustrates the effective projected area of the inlet in both flight (A)

and deployment (B). The dotted lines in Fig. 10 represent the bottom skin 22', suspension line 51a', and inlet 80'for a standard canopy. The effective inlet area (B) during deployment, when the parachute if falling is much smaller than the effective inlet area during flight (A) when the parachute is moving forward. When the inlet area is reduced as in the present invention in order to reduce drag during flight, it may become too small for efficient deployment. In a fourth embodiment of the present invention, the suspension line 5 la and bottom skin 22 are moved back from the front edge of the canopy. This embodiment of the invention is represented by the solid lines in Fig. 9. The modification increases the effective area (C) of the inlet during deployment without substantially changing the effective area during flight. Accordingly, the canopy can be efficiently deployed and flown.

The design of the present invention, creates a zig-zag front edge to the bottom skin 22 as illustrated in Fig. 11. The difference between the loaded and non-loaded ribs varies depending on the intended design.

Inventive sport canopies have been made with an offset of 1", but offsets may be in the range of 1"to 3", or even up to 6". Existing ram air canopies have more projected area for flight than for deployment, which is opposite what is needed for deployment and flight of the parachute. Accordingly, the present invention addresses this problem, and offers more projected inlet

area for deployment than for flight, resulting in smooth, beautiful openings with slower progression of inflation and reduced drag in flight.

According to another aspect of the invention, spanwise spreading of the canopy is controlled on the formed nose canopy. Typically, a formed nose canopy includes reinforcing tape only around the inlets. According to the present invention, as illustrated in Fig. 4, a continuous, structural fabric tape 100 is stitched along the entire leading edge of the top skin above all of the formed inlets. The structural fabric tape 100 is woven, cut and oriented to minimize stretch along the leading edge of canopy. During flight, the ram air canopy tends to stretch along it span. Since the structural fabric tape 100 is a continuous piece it limits the span-wise stretch. Using a structural fabric tape in a line across the top skin at the nose of a ram air parachute, the aerodynamics of the parachute canopy are improved. The reduction in span- wise stretching from use of the structural fabric tape maintains the designed airfoil shape of the canopy. Also, the added strength along the front edge of the canopy helps to prevent nose deformation from front wind and span-wise distortion from differences in loaded in non-loaded ribs. Furthermore, a canopy changes performance over time as the fabric stretches and wears.

The leading edge of the top skin suffers significant stretch and wear, which limits the useful life of the canopy. The structural fabric 100 along the leading edge of the top skin limits stretching and slows wearing, which allows the parachute to substantially maintain its performance and to extend its service life.

Reinforcement of other edges of the canopy also assists in maintaining a proper shape, improving performance and extending the useful life of a canopy. Structural fabric tape may also be sewn along the trailing edge of the top skin to prevent stretching and spreading of the rear of the

canopy. The span-wise reinforcement of the leading and trailing edges of the top skin helps to maintain the desired airfoil shape of the ram air canopy without the need for extensive cord-wise cross bracing. Thus, the weight and pack volume of the canopy is significantly reduced.

Fig. 4 is a top view of a top skin piece 121 of a canopy according to an embodiment of the present invention. The top skin piece 121 corresponds to a single cell of the canopy. A plurality of top skin pieces 121 are connected together to form the top skin 21 of the entire canopy.

As illustrated in Fig. 12, the top skin piece 121 is substantially rectangular having a constant width along its entire length from the leading edge 131 to the trailing edge 132. However, reduced width areas 141,142, 143,144 are strategically located along one or more areas on the length of the top skin piece. The reduction in width is slight. For a nine cell, ten foot canopy, having top skin pieces with widths of approximately thirteen inches, the reduction in width may be 1/4 to 1 inch, along each side. The reduced width areas 141,142, 143,144 are positioned to correspond to specific parts of the airfoil shape of the canopy. Fig. 13 illustrates various locations of reduced width along a vertical rib of the canopy according to an embodiment of the present invention. A first area of reduced width 141 corresponds to the leading edge 151 of the top skin of the canopy. A second area of reduced width 142 corresponds to an position 152 near the apex of the airfoil shape. This position 151 starts substantially above the connection point for the leading suspension line 51 and extends towards the trailing edge of the canopy. A third area of reduced width 143 corresponds to a position 153 behind the apex of the airfoil shape. This position 153 is substantially over the connection point for the second suspension line 52. A final area of

reduced width 144 is located at the trailing edge of the top skin 21 corresponding to a position 154 at the trailing edge of the canopy.

During flight, the cells of the canopy are inflated by air passing into the inlet at the leading edge and exiting at the trailing edge of the canopy.

The inflation tensions the flexible fabric forming the top skin 21, bottom skin 22, and vertical ribs 31, 32,33 and deforms the cells from an ideal rectangular cross section. Additionally, head winds provide additional forces on the leading edge of the canopy and further distort the shape. Also, pressures from air passing over and under the canopy create forces which can cause distortions in the ideal shape. The areas of reduce width 141,142, 143,144 on the top skin pieces 121 create areas of increased tension on the top skin 21 at predetermined locations in the air foil shape. The increased tension on the top skin 21 at these locations limits the distortions caused by inflation, headwind, and air movement forces. Thus, the canopy of the present invention better maintains the ideal air foil shape and has improved performance. Of course, the present invention is not limited to the specific areas of reduced width 141,142, 143,144 and corresponding positions 151, 152,153, 154 along the airfoil shape. The location of areas for tensioning of the top skin will depend upon the specific design and performance characteristics of the canopy.

Other mechanisms could be used for tensioning the top skin of the canopy other than variations in the straight edges of the top skin pieces. For example, in a canopy having reinforcement tape along the leading edge of the canopy, the reinforcement tape could be selectively tensioned during assembly to provide tensioning of the top skin. Similarly, reinforcement tape on any seams may be selectively tensioned to achieve the objectives of the present invention.

Fig. 14 illustrates a vertical rib 31 of the canopy having a stiffener 100 according to an embodiment of the present invention. The stiffener 100 is in the form of a ring and provides reinforcement to the leading edge shape of the nose 71 a of the rib 31. The stiffener can be formed and attached to the rib in various ways. The stiffener is formed of an elastic alloy, and preferably a super-elastic alloy such as Nitanol (nickel-titanium alloy). The super-elastic alloys can be bent more than normal metal alloys without creasing or deforming. They are self-annealing at their designed operating temperature range. In addition to nickel-titanium, copper-zinc, copper- aluminum-nickel, and nickel-titanium-copper are known super-elastic alloys.

Such alloys have different properties with various temperature range requirements. The alloy for the stiffener must be usable at the temperate ranges in which the parachute is to be used.

According to one embodiment of the invention, the super-elastic alloy is formed into a predetermined shape for fitting a particular nose shape of a canopy. The super-elastic alloy is then treated with heat to retain the desired shape of the stiffener 100. The stiffener 100, in the desired shape, is attached to the rib of canopy. Different methods can be used for attaching the stiffener 100 to the canopy. Preferably, a pocket 110 of a flexible material is stitched on the nose 71 a of the rib 31. The stiffener 100 is placed in the pocket 110. The pocket 100 may be correspond in the desired shape of the stiffener 100, as illustrated in Fig. 14 or could force the ring spring into a different shape. Alternatively, stitching could be used to attach the stiffener to the rib. A second embodiment of the stiffener 101 is illustrated in Fig. 15. In the second embodiment, the stiffener 101 is formed of a straight wire length of super-elastic alloy. The two ends of the wire are connected together to form a circle, but the alloy is not heat treated. The stiffener 101 is inserted in a pocket 111 on the rib. The pocket 111

maintains the desired shape of the stiffener 101. As illustrated in Fig. 16, the pocket 111 may be formed such that a back side of the stiffener 104 is bowed to provide a spring bias. Preferably, stiffeners 100 are used on all of the ribs of the canopy. However, they may be used on only some of the ribs, if desired.

During-packing of the parachute, the stiffeners 100 are crushed and deformed. However, since the stiffeners 100 are formed of a super-elastic alloy, upon deployment, they return to the desired shape, either as heat treated or as controlled by the pocket. The desired shape provides forces on the nose of the canopy to maintain the shape at each of the ribs and to prevent deformation of the nose due to head-winds. The reduction in deformation greatly improves the efficiency of the parachute wing.

Fig. 17 illustrates the structure of a canopy according to an embodiment of the present invention. A cross section of a cell 41,42 is shown in Fig. 4. However, the same structure would apply to all of the cells of the canopy. The cell 41,42 is formed by two loaded ribs 31,33 and unloaded rib 32, and portions of the top skin 21a, 21b and bottom skin 22a, 22b. Suspension lines 51a, 51b are attached to the loaded ribs. As illustrated in Fig. 5, the loaded ribs 31,33 are of the same height. The unloaded rib 32 is shorter in height than the loaded ribs 31,33. The bottom skin 22 is not flat, but is angled between the loaded ribs 31,33 and the non- loaded rib 32. The cell has a trapezoidal shape rather than the rectangular shape of conventional cells. During flight, a portion of the force applied

from the suspension lines 51a, 5lb to the loaded ribs 31,32 is transferred via the now angled bottom skin portions 22a, 22b to the non-loaded rib 32. The load transfer results in an improved load distribution and reduced span-wise distortion of the top skin.

The design of the present invention reduces the spanwise top skin distortion of the canopy caused by the non-loaded ribs rising further above the loaded ribs. Thus, the canopy has reduced drag and improved aerodynamics. The design of the present invention is able to achieve a portion of the benefits of cross-braced canopies without the negative aspects caused by cross bracing.

While the present inventions have been described with a certain degree of particularity, it is obvious from the foregoing detailed description that one skilled in the art may make one or more modifications which are suggested by the above descriptions of the novel embodiments.

Furthermore, all of the features of a canopy according to the embodiments above do not have to be implemented to achieve improvements in performance. Any of the features, or combinations thereof, can be implemented separately.