Ram-air Parachute

a united states navy parachute team leap frogs jumper landing square ram-air parachute.

personal ram-air parachutes loosely divided 2 varieties – rectangular or tapered – commonly called squares or ellipticals , respectively. medium-performance canopies (reserve-, base-, canopy formation-, , accuracy-type) rectangular. high-performance, ram-air parachutes have tapered shape leading and/or trailing edges when viewed in plan form, , known ellipticals. taper in leading edge (front), , in trailing edge (tail).

ellipticals used sport parachutists. have smaller, more numerous fabric cells , shallower in profile. canopies can anywhere elliptical highly elliptical, indicating amount of taper in canopy design, indicator of responsiveness of canopy control input given wing loading, , of level of experience required pilot canopy safely.

the rectangular parachute designs tend square, inflatable air mattresses open front ends. safer operate, because less prone dive rapidly relatively small control inputs, flown lower wing loadings per square foot of area, , glide more slowly. typically have lower glide ratio.

wing loading of parachutes measured of aircraft, comparing exit weight area of parachute fabric. typical wing loading students, accuracy competitors, , base jumpers less 5 kg per square meter – 0.3 kilograms per square meter or less. student skydivers fly wing loading below 5 kg per square meter. sport jumpers fly wing loading between 5 , 7 kg per square meter, many interested in performance landings exceed wing loading. professional canopy pilots compete wing loading of 10 on 15 kilograms per square meter. while ram-air parachutes wing loading higher 20 kilograms per square meter have been landed, strictly realm of professional test jumpers.

smaller parachutes tend fly faster same load, , ellipticals respond faster control input. therefore, small, elliptical designs chosen experienced canopy pilots thrilling flying provide. flying fast elliptical requires more skill , experience. fast ellipticals considerably more dangerous land. high-performance elliptical canopies, nuisance malfunctions can more serious square design, , may escalate emergencies. flying highly loaded, elliptical canopies major contributing factor in many skydiving accidents, although advanced training programs helping reduce danger.

high-speed, cross-braced parachutes, such velocity, vx, xaos , sensei, have given birth new branch of sport parachuting called swooping. race course set in landing area expert pilots measure distance able fly past 1.5-metre (4.9 ft) tall entry gate. current world records exceed 180 metres (590 ft).

aspect ratio way measure ram-air parachutes. aspect ratios of parachutes measured same way aircraft wings, comparing span chord. low aspect ratio parachutes, i.e., span 1.8 times chord, limited precision landing competitions. popular precision landing parachutes include jalbert (now naa) para-foils , john eiff s series of challenger classics. while low aspect ratio parachutes tend extremely stable, gentle stall characteristics, suffer steep glide ratios , small tolerance, or sweet spot , timing landing flare.

because of predictable opening characteristics, parachutes medium aspect ratio around 2.1 used reserves, base, , canopy formation competition. medium aspect ratio parachutes have 7 cells.

high aspect ratio parachutes have flattest glide , largest tolerance timing landing flare, least predictable openings. aspect ratio of 2.7 upper limit parachutes. high aspect ratio canopies typically have 9 or more cells. reserve ram-air parachutes of square variety, because of greater reliability, , less-demanding handling characteristics.

general characteristics

roadside chai shop made of old parachute in ladkah, india.

main parachutes used skydivers today designed open softly. overly rapid deployment problem ram-air designs. primary innovation slows deployment of ram-air canopy slider; small rectangular piece of fabric grommet near each corner. 4 collections of lines go through grommets risers (risers strips of webbing joining harness , rigging lines of parachute). during deployment, slider slides down canopy above risers. slider slowed air resistance descends , reduces rate @ lines can spread. reduces speed @ canopy can open , inflate.

at same time, overall design of parachute still has significant influence on deployment speed. modern sport parachutes deployment speeds vary considerably. modern parachutes open comfortably, individual skydivers may prefer harsher deployment.

the deployment process inherently chaotic. rapid deployments can still occur well-behaved canopies. on rare occasions deployment can rapid jumper suffers bruising, injury, or death. reducing amount of fabric decreases air resistance. can done making slider smaller, inserting mesh panel, or cutting hole in slider.