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Skydiving General Ignorance

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grizzly
98884.  Tue Oct 03, 2006 8:25 am Reply with quote

I'm assuming that this could have something to do with the fact that if a chute isn't packed properly it wont work. Since a reserve chute is used less often the probability that it has been put back (in fact it may never have been put back, I don't know) incorrectly is lower than that of the main chute (which is obviously always used).

Maybe, however, I am just wrong. I am not an expert.

 
mr2mk1g
99379.  Wed Oct 04, 2006 11:32 am Reply with quote

dr.bob wrote:
Is a reserve parachute designed differently from a normal one to make it less likely to fail? If so, what are the differences, and why are normal parachutes designed to be less likely to fail as well?


Yes actually, there are a number of important differences between main and reserve parachutes which significantly affect their relative malfunction rates, (with reserves being far less likely to fail).

Reserves are more square in shape than main parachutes which are more rectangular in shape (when looking straight down on the top). This simple difference makes reserves open more reliably. It also makes them more docile and less fun to fly.

Many main parachutes are also fully or slightly elliptical at the wing tips making them more responsive whereas reserves are very boxy (think Spitfire wing vs. Hurricane wing). This also increases the malfunction rate of main parachutes relative to reserves.

The trade off is of course that main parachutes are far more fun to fly. Failing every 1/1500 is probably safe enough for a main parachute where you have a backup – it’s not acceptable for a last chance reserve where enjoyable flight characteristics are far less important than reliability.

There are also differences in the way in which reserve and main parachutes open. Reserves use a mechanism which actually jettisons part of the deployment system – this wouldn’t be cost effective for main parachute as jumps would cost several hundred pounds in lost equipment per go, but for a reserve it doesn’t matter – safety is paramount.

Reserve parachutes must comply with certain minimum standards regarding their manufacture and the manner in which they open. There are maximum weight loadings and tolerances mandated by national bodies. You or I on the other hand could build a main parachute out of our bed sheet and jump it if we were silly enough.

And that is just the basic differences… there are many others.


Last edited by mr2mk1g on Wed Oct 04, 2006 11:36 am; edited 1 time in total

 
mr2mk1g
99382.  Wed Oct 04, 2006 11:35 am Reply with quote

grizzly wrote:
I'm assuming that this could have something to do with the fact that if a chute isn't packed properly it wont work.


Yes there are important differences in the way they are packed.

Reserve parachutes must be packed by riggers who are extremely experienced in packing parachutes, have obtained specific qualifications in this field and are regulated by the national aeronautical bodies, (CAA in the UK, FAA in the US for example).

Reserves must be opened and inspected every 6 months and receive what is effectively a full MOT. Their use is accurately recorded and they are retired when they have been used as few as 25 times. Main parachutes on the other hand may be used well in excess of a thousand times; they may be packed by anyone, with few or no qualifications and their inspection/maintenance is left up to the individual skydiver.

A reserve is also folded differently to a main parachute and it is done in a far more exact manner. It takes much, much longer, (30 minutes), to pack a reserve parachute vs 3-5 minutes to pack a main – a time concession which is probably acceptable with a main failure rate of around 1/1500 and you have a backup, but not when it’s your last chance.

 
grizzly
99415.  Wed Oct 04, 2006 2:01 pm Reply with quote

very insightful stuff there :-)

 
Oldogsrbest
1067614.  Sat Apr 05, 2014 8:35 pm Reply with quote

Tas wrote:
Quote:
Q6. What should a skydiver do if their reserve parachute fails?


Aren't you supposed to put your arms out (in a star shape) to increase air resistance and thus slow your descent?

(Although landing like that may be a tad painful, I'd have thought).

There is a QI bit somewhere about an RAF Lancaster crewman who bailed out without a 'chute (as it had been destroyed by flak). The Lanc' was on fire, so he thought it'd be a better way to go. He ended up falling through a tree, and landing in a snow drift. Broken leg and arms (along with cuts and bruises) from a fall of 10000 feet plus. Not too bad, I guess!

:-)

Tas


That was Nicholas Alkemade.

His grandson, also an Alkemade, was in a Brit doco about training grandchildren of Lanc aircrew to crew a Lancaster. The young Alkemade was a chef. May still be... Name POSSIBLY LUKE? I think I spotted an entry on fb of his, when a parachutist asked how he might contact him, but I don't 'do' fb, so just reported it back for him to approach.

I THINK the Brit doco was called Bomber Crew, BUT I think there are SEVERAL docos/poss dramas, too, with same name, so if one sounds wrong, keep digging

A sad tale of WW2 and parachuting, involves the death of ERNEST SALWAY, & his aircrew pal, who risked his life to help him. (Survived & won medal).
Far better to let you search, then U get a longer, fuller tale & photo of him. I've been telling his sad tale for 5/10 yrs. Probably I'm LOATHED by parachutists

The first Lancaster bomber aircrew I researched had 6 of 7 aircrew seen by Dutch farmer & family, to jump from plane, fall to their deaths, with no parachute opening. So early on in research, it deeply shocked me. I presume they were too low. The 7th lad, a wireless op was found UNDER the fuselage, 2 weeks after the rest of the crew were buried. I will always wonder if his 'chute had been destroyed. Sadly, with results being the same, will never know

 
Feralcat
1281355.  Sun Apr 15, 2018 6:29 pm Reply with quote

I found this all fascinating, tho I knew about Nicholas Alkemade and Ernest Salway - and others...

I did know a parachutist who had done thousands of jumps and witnessed 3 parachute fail jumps resulting in death.

He was very black humoured about it all.

I had also not ever really thought about it, but he said with the planes set up to jump out of, on the way up, there is a LOT of farting, with first timers often mortified and sniggered at, by the more juvenile minded and the long termers letting rip with not a thought

He also told me - and this is VERY dark - warning - if you are in that situation, if you want to make it easier for those who will be cleaning up, to go in face down.

I had thought that would be worse, thinking of the result of faces etc BUT he said that going in face first, you are a mess but your ribcage tends to hold the mash together. On your back, you tend to explode in the belly region.

Its a conversation I havent been able to forget.

 

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