R 99 wrote:
"377, what is your estimate of the g's during the opening at 180 MPH of a round canopy?"It depends on what kind of opening you get. I have had so called "slammer" openings on squares that have popped a few suspension lines that were in excellent condition. On C9 rounds I'd guess 9Gs max at 180 mph deployment. C 9s don't often give abrupt openings. Note the gentle squidding on the 727 SAT Thailand jumps.
See: You are not allowed to view links.
Register or
Login The speed limits on chutes are real. They can fail if exceeded.
"All of the [modern commercial] canopies open significantly faster than the military 28ā canopy ā with some canopies of this general type
capable of producing 20 gās or more at only 180 knots. While this quicker opening is a great benefit at low speeds and/or low altitudes (such as skydiving cutaways) it is definitely a mixed blessing in the bailout environment. It must be further noted that smaller canopies inherently open faster than larger ones (due to the smaller internal filling volume)."
"Based on my qualitative feel for the overall experience of the tests that I've conducted, some of the small, very lightweight canopies (NPI/FFE) in use today have in excess of 50% catastrophic failure rates at speeds of 130 to 150 knots. These same canopies would almost certainly exhibit a 100% failure rate at speeds over 180 knots."
Here is some info on FAA canopy standards (TSO C23) See pg 22/64 You are not allowed to view links.
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LoginTSO C23b was based on testing a military C9 round canopy,which at the time was considered a state of
the art canopy.Standard category equipment had to demonstrate the ability to withstand a 5000
lb shock load with no damage. No specific speed or weight was required for structural testing.
This testing was adequate for most skydiving applications when all canopies were round and were built
out of relatively high permeability fabric and high elongation Nylon lines.
With new technologies such as low permeability fabric and new canopy designs like ram-air canopies,
this standard was no longer adequate. Some canopies could generate the 5000 lb shock loads at relatively
low weights and speeds while others would not generate 5000 lbs at speeds and weights far
higher than what was required with a C9.
Parachute equipment produced under TSO C23b has no required placarded maximum weight or
speed. However, this is very misleading. All parachute equipment has a maximum weight and speed
combination above which failure is likely.
In most cases it is significantly easier to pass the 5000 lb shock load of C23b than to
pass the minimum testing requirements of TSO C23C or TSO C23D.
The next revision of the TSO,TSO C23c, provided a solution to the lack of specific weight and speed
testing and placarded limits.However,TSO C23c had a major limitation in that it only provided for
certifying equipment up to 254 lbs exit weight.This meant that anyone over about 230 lbs could
not legally use this equipment.
TSO C23d fixed this limitation by providing a means for certifying at higher weights and higher
airspeeds.
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