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rasmack

Openings and air temperature

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Yesterday I had four great jumps over a totally snow clad landscape. We had to ride the C-206 four times down the runway to clear a path in the snow so the pilot could land again. It was a wee bit cold jumping, though. :)
On all jumps of the day I had extreeeemely slow openings on my Spectre 210 @ 1.14:1. On the first jump I had my hand on the cutaway pillow, and I was hearing my 2000 ft flatline when the slider finally decided to grace me with its presence. At the end of the day I had just worked up a routine to shake the risers rigorously during opening. Still they were slow openings. My jump partner had the exact same experience on his Sabre 170.

Does anyone know of correlations between opening speed and air temperature/humidity or was it just a coincidence that we had these slow openings?
HF #682, Team Dirty Sanchez #227
“I simply hate, detest, loathe, despise, and abhor redundancy.”
- Not quite Oscar Wilde...

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there is a definite difference between cold air and warm air and it is in their densities. cold air is more dense than warm air. it has been noted that hard openings are more likely at higher altitudes where the air is thinner so, there might be a correlation there.
"Don't talk to me like that assface...I don't work for you yet." - Fletch
NBFT, Deseoso Rodriguez RB#1329

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Agreed. It always amazes me how efficient my flare is in the winter. The canopy just stops dead.

Edit to add: I just don't understand the mechanics slowing down / speeding up an opening in relation to air density.
HF #682, Team Dirty Sanchez #227
“I simply hate, detest, loathe, despise, and abhor redundancy.”
- Not quite Oscar Wilde...

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what were your exit altitudes??



5000 ft
4000 ft
4000 ft
13000 ft

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were you at terminal when you pulled???



Good question. Delays on the 4000 ft jumps were ~15 s, so it must have been close. As for the 5000 ft and 13000 ft I am pretty certain we hit terminal. At least the delay on the 5k jump was > 20 s.

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how Cool... ( get it?? cool????? ):o:S:DB|;)
that you were able to make some jumps in january..



Actually it wasn't too bad. I have tried exiting at 13 k @ -25 Celsius (that's -13 F for you Americans). This was nothing like it. Probably not worse than -15 Celsius (5 F) or so.

Edit: Fixed Fahrenheit conversion.
HF #682, Team Dirty Sanchez #227
“I simply hate, detest, loathe, despise, and abhor redundancy.”
- Not quite Oscar Wilde...

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Actually it wasn't too bad. I have tried exiting at 13 k @ -25 Celsius (that's -45 F for you Americans). This was nothing like it. Probably not worse than -15 Celsius (-27 F) or so.



You need to check your temperature conversions as there one rule that is easy to remember -40 F = -40 C

-25 C = -13 F
-15 C = 5 F

If you want confirmation.... try this http://www.onlineconversion.com/temperature.htm
"Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy

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>I just don't understand the mechanics slowing down / speeding up an opening in relation to air density.

There are many parts to this, but the simplest one is that you fall faster in less-dense air; faster fallrate = harder opening (usually.)

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>I just don't understand the mechanics slowing down / speeding up an opening in relation to air density.

There are many parts to this, but the simplest one is that you fall faster in less-dense air; faster fallrate = harder opening (usually.)


Hey! That makes sense. Thanks. :)
HF #682, Team Dirty Sanchez #227
“I simply hate, detest, loathe, despise, and abhor redundancy.”
- Not quite Oscar Wilde...

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Actually it wasn't too bad. I have tried exiting at 13 k @ -25 Celsius (that's -13 F for you Americans). This was nothing like it. Probably not worse than -15 Celsius (5 F) or so.

Edit: Fixed Fahrenheit conversion.



Re: cold weather jumping.Some of the DZ's I frequented,, would run right through the winter, in this rough Western New York State area,, where the Great Lakes tend to lay lots of snow. The paved runways were plowable. So we jumped often in the cold. Seneca Falls, Finger Lakes, Roch...... I had a stretch of 8 or 9 years where I had jumped every month in succession with some of those jumps in real cold. [:/]
I enjoyed flying my canopy on those days and hop and pops made sense..B|
Be careful of the accumulating effect of the cold,, especially if you're doing 2 or 3 60 and 70 second delays..:|
Since dressing against the cold is necessary, try to keep it non-bulky... layers of effective insulation will alllow your "feel" for your rig to be more like you are used to....
Look for gloves which are warm yet thin , to facilitate deployment..
And of course,, be sure to have a warm warm place indoors for between jumps... :);)
-20 C and 0 degrees F.... anytime, is cold
:o:(and when you add wind and in our case substantial AIRSPEED..... that's bonechilling ..
Enjoy the cameraderie of winter time jumping....

skydive softly, skydive often, skydive with friends

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Yes, dress in plenty of light layers.

The flip side of that is that sometimes an extra pair of socks make your toes COLDER because they restrict blood flow.

So start with extra large boots and gloves, so that you will have enough room for extra socks, but still maintain circulation.

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I have a really really really really indepth lesson saved to my PC from my canopy coach.

If your still intrested in density altitude and how it applies to our wings both swooping and not, i can forward it to you.

Its fairly complicated, but he did a great job of breaking it down.


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>wouldnt it also provide less "grab" for your canopy to provide a hard opening?

Nope. Problem there is that the _percentage_ change in speed is the same but the _absolute_ change is much higher. As an example, if you're falling at 150mph at 20,000 feet, and open your parachute, you'll slow down to (say) 15mph. If you're falling at 120mph at 2000 feet, you slow down to (say) 12mph when you open there. But in the first case you still have to lose 135mph in X seconds; in the second case you have to lose 108mph in X seconds. Even if everything else was the same (and it isn't) a 2 second opening will be softer in denser air.

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At the end of the day I had just worked up a routine to shake the risers rigorously during opening. Still they were slow



OK, lets refine that technique a bit. Grab only the rear risers, and give them a symetrical tug, maybe an inch or two (your canopy may need more, but start small). This will 'encourage' the slider to come down.

It works at any temp or altitude.

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I have a really really really really indepth lesson saved to my PC from my canopy coach.

If your still intrested in density altitude and how it applies to our wings both swooping and not, i can forward it to you.

Its fairly complicated, but he did a great job of breaking it down.



Well, yes please. My e-mail is in my profile.
HF #682, Team Dirty Sanchez #227
“I simply hate, detest, loathe, despise, and abhor redundancy.”
- Not quite Oscar Wilde...

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Hey Ras.

Jumped this weekend as well - as you know in close to identical conditions you were jumping in.

On my normal canopy (Katana-97) I didn't experience any kind of longer opening - just the usual quick and snappy opening. Did have some funky off-heading openings but I attribute that to packing/body position.

My friends Katana-107 had very soft opening compared to the -97.

While I am sure air density is a factor, I'd think canopy design and packing are greater factors.

Don't they remove snow from the runway at your DZ? They do it here B|.

Unfortunately, our hangar doors had frozen solid and the snow was piled up high outside it. Took a while to get that removed. Then we had that layer of ice somewhere in the middle of the snow. Made for some interesting landings (i.e: don't drag your foot when you swoop B|).

Video coming up on the flying gnu soon.

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On my normal canopy (Katana-97) I didn't experience any kind of longer opening - just the usual quick and snappy opening...



OK, we didn't have anyone jumping handkerchiefs that day. :)
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While I am sure air density is a factor, I'd think canopy design and packing are greater factors.



It's just funny that the guy working manifest was commenting on our slow openings.

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Don't they remove snow from the runway at your DZ? They do it here B|.



Did I say runway. I meant grass strip. I am sure we could pay the farmer to clear it, but hey the Cessna does a good job all by itself. :)
HF #682, Team Dirty Sanchez #227
“I simply hate, detest, loathe, despise, and abhor redundancy.”
- Not quite Oscar Wilde...

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It's quite hot down here at the moment.

Last Saturday I jumped in 43 C ~ 110 F. Did not notice any difference in opening, but a) the flight to altitude took much more time b) the landing speed much faster c) interesting thermals and d) absolutely exhausted after only 3 jumps and packs....
---------------------------------------------------------
When people look like ants - pull. When ants look like people - pray.

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It's quite hot down here at the moment.

Last Saturday I jumped in 43 C ~ 110 F...



I'm not jealous! I'm not! :P



No reason to be. It's a public holiday tomorrow and I was planning to go to the DZ but the temperature will be up there again and it's just too damn hot. I have jumped when it was minus 10 C on the ground (in Denmark actually) and know how unpleasant that is. But trust me, jumping in extreme heat is bad too and actually can be quite dangerous. Easy to run into thermals low and being smacked into the ground... So I will spend the time i my pool instead.
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When people look like ants - pull. When ants look like people - pray.

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