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How many seconds would you wait before jumping? Read first!

 

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Poll: How many seconds would you wait before jumpiing?
3 or less seconds 8 / 6%
4 seconds 4 / 3%
5 seconds 20 / 15%
6 seconds 8 / 6%
7 seconds 19 / 14%
8 seconds 9 / 7%
9 seconds 1 / 1%
10 seconds 24 / 18%
11 seconds 1 / 1%
12 seconds 6 / 4%
13 seconds 0 / 0%
14 seconds 1 / 1%
15 seconds 3 / 2%
16 seconds 0 / 0%
17 seconds 0 / 0%
18 seconds 0 / 0%
19 seconds 0 / 0%
20 seconds 0 / 0%
more than 20 seconds 1 / 1%
would not jump 31 / 23%
136 total votes
 
aguila  (B 1009)

Jan 27, 2007, 11:32 PM
Post #1 of 27 (3029 views)
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How many seconds would you wait before jumping? Read first! Can't Post

Hello all. This is for all skydivers with more than 30 Free fall jumps. Imagine your first visit to this DZ and this would be your second jump there.

Scenario:

Drop zone: small. Please see the included picture. The landing area is within the yellow line
Airplane: Cessna 208 Grand Caravan
Jumpers: 17
Winds: no wind said the pilots (do not ask me for wind direction Wink )
Altitude: 13.500 ft AGL
Temperature: 98 F
DZ altitude: 1000 ft ASL
Weather: Sunny wet day with some clouds but there are holes.
Jumprun: from the river along the runway area
Your opening altitude: below 4000 ft

A tandem jumps first just above the red spot showed in the picture. You will follow them.

Now when you are hanging out of the door (You love feeling the wind while taking a look around before jumping) you spot a very big cloud coming right to you. You know you will see nothing but white once you enter the cloud. A few more seconds and you will enter the cloud after jumping.

Question: How many seconds would you wait before jumping after the tandem?

Remember there are 14 more eager tu jump skydivers behind you and pilots hate a second pass.

Please, do not select what you think more experienced people would select. Select what you would do.

Thank you!


(This post was edited by aguila on Jan 28, 2007, 12:09 AM)
Attachments: dzflan.jpg (10.9 KB)


skytash  (D 100388)

Jan 28, 2007, 1:05 AM
Post #2 of 27 (2950 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

I voted that I wouldn't jump. I will always take a 'plane round again if I'm uncomfortable, especially with a cloud coming and a new DZ etc.

If I get bawled out for having done so on the ground, or told I'm not welcome at that DZ again, that's fine. I'm not happy at a DZ where someone considers they have more right to decide on what is safe for me to do than I do. I have no problem if someone has a higher safety threshold than me, eg they won't let me do something I think is safe, but if they want me to do something I don't think is safe - goodbye to that DZ. That can be difficult if there aren't many DZ's in the area I know (been there) but I'd rather spend some time not jumping than being required to do things I consider unsafe.

tash


Squeak  (E 1313)

Jan 28, 2007, 1:24 AM
Post #3 of 27 (2942 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

if you are entering a cloud, at least here we wont jump,


speedy

Jan 28, 2007, 2:31 AM
Post #4 of 27 (2925 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

Here in Germany you are not allowed to jump through cloud. So if I am going to hit the cloud I would not jump and ask for a go around.

Assuming no cloud and no winds I would wait 6-7 seconds. Our pilots on no wind days tend to have a ground speed of 90 - 100 kts. 6 - 7 seconds gives me about 300 meters horizontal separation at opening time which should be enough.


(This post was edited by speedy on Jan 28, 2007, 2:32 AM)


PWScottIV  (B 30429)

Jan 28, 2007, 4:17 AM
Post #5 of 27 (2878 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

Ok, well I know you mentioned you wanted people answering to have more experience than I currently have, but I've recently put in some time researching the subject... So if you'd like to ignore what I say, I totally understand. Likewise, I'd definitely appreciate hearing the opinions of more experienced jumpers if my logic is incorrect...

1. Does anyone find it to be a little strange that the tandems are leaving first? That means probably everyone else on the load has the potential to freefall through the tandems' canopies. Correct me if I'm wrong, but I thought the most important factor in ordering the load was deployment altitude. Followed by average freefall speed (belly, freefly, tracking, etc.), and then group size. Am I totally off here?
2. I agree with everyone else so far that says they'd request a go-around... If I couldn't see below before I needed to jump, I'd just get out of the way to let anyone else by who wanted to jump.
3. Just out of curiosity (because I really don't know), what is the passenger limit for a 208? 17 passengers seems like it would be pretty damn crowded... Maybe even to the point that the CG would be too far back?


speedy

Jan 28, 2007, 5:08 AM
Post #6 of 27 (2855 views)
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Re: [PWScottIV] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

In reply to:
1. Does anyone find it to be a little strange that the tandems are leaving first? That means probably everyone else on the load has the potential to freefall through the tandems' canopies. Correct me if I'm wrong, but I thought the most important factor in ordering the load was deployment altitude. Followed by average freefall speed (belly, freefly, tracking, etc.), and then group size. Am I totally off here?

People plan to deploy at a certain altitude, however premature deployments or malfunctions can change the height at which they deploy. That is why we should rely on horizontal separation and not vertical.
Freefall speed alters the distance the jumper will drift while falling. The longer the jumper is falling the more they will drift (depending on wind). That is why when the drop run is into the wind it is helpful to put faster fallers out after the slow fallers. If you dropped with the wind you would want the faster fallers out first. With a cross wind drop run the fall rate does not really matter.
No wind means no drift.
In reply to:
2. I agree with everyone else so far that says they'd request a go-around... If I couldn't see below before I needed to jump, I'd just get out of the way to let anyone else by who wanted to jump.
I also agree
In reply to:
3. Just out of curiosity (because I really don't know), what is the passenger limit for a 208? 17 passengers seems like it would be pretty damn crowded... Maybe even to the point that the CG would be too far back?

Our grand caravan 208 can take 20 jumpers. We seldom have that many on a load as we are more concerned with keeping the plane turning than maximizing the number of jumpers on the load.
Yes, 20 is pretty crowded, 17 is OK. There are smaller caravans that take only 15.


piisfish

Jan 28, 2007, 5:13 AM
Post #7 of 27 (2853 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

I would have jumped with the tandem. Angelic

If you don't like the spot, don't jump. If you don't jump, let the others jump.


likearock  (D 24640)

Jan 28, 2007, 6:58 AM
Post #8 of 27 (2785 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

I question whether or not there was no wind at 13,000 feet. There is usually some wind, 10, 15 mph at least. Judging from your description of the original incident, that you waited a full 7 seconds and then almost collided with the preceding tandem, I would say that the winds at 13,000 feet were blowing pretty high. Note that this is completely consistent with a no wind situation on the ground. Bottom line, you should have left more time.

It is critically important when deciding how many seconds to leave for separation to factor in the winds at altitude. Skydive Arizona recently posted inside their aircraft a really good set of guidelines to calculate this. I encourage them to make those guidelines public either on their web site or on these forums.


speedy

Jan 28, 2007, 8:26 AM
Post #9 of 27 (2736 views)
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Re: [likearock] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

Sometimes we have no wind at 13000 ft. In the OP he said "Winds: no wind said the pilots". I would assume, maybe wrongly that the pilots would be referring to winds at altitude.
Maybe aguila just made a track down the drop run? Backsliding is also a possibility.
Looking at the plan he posted it appears the Tandem was dropped short of the DZ ( consistent with a no wind situation) and possibly augila also. It the TM did not hold off before flying up the drop run and aguila stared at the LZ during freefall while backsliding towards the TM ..... that does not help matters.


aguila  (B 1009)

Jan 28, 2007, 9:23 AM
Post #10 of 27 (2701 views)
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Re: [PWScottIV] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

In reply to:
Ok, well I know you mentioned you wanted people answering to have more experience than I currently have, but I've recently put in some time researching the subject...

Thank you! Your point is valid and your vote is welcome! I could not modify the jumps limit and apologize for the inconvenience.

In regard to the Cessna 208 passenger limit it depends on several factors. It is interesting and people should have it mind. Some are:

1- Passengers' weight
2- Luggage and extra weight
3- Are seats and door removed?
4- taking off altitude
5- taking off temperature
6- taking off humidity
7- Pilots' preferences
8- Are the tanks full loaded?
9- Winds
10- Skydivers' stubbornness Wink

I forgot to mention some Caravans have extra space for luggage under the floor. That means extra weight and less passengers

Blue skies!


(This post was edited by aguila on Jan 28, 2007, 11:06 AM)


tombuch  (D 8514)

Jan 28, 2007, 2:08 PM
Post #11 of 27 (2614 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

I would probably give the tandem about 15 seconds and allow myself to slip into the cloud, assuming it's just a small puffy cloud and it easy to clear the airspace under it. If it's more of a cloud than that, I wouldn't jump.

I hate the idea opf a tandem jumping first because there can be a bit of pressure (as in this case) for the next person to reduce the wait time. Keep in mind the tandem pair will be sliding all over the place, and they are sitting ducks.

Doing a go around with clouds and a high opening tandem is a bad idea too.


Premier billvon  (D 16479)
Moderator
Jan 29, 2007, 10:10 AM
Post #12 of 27 (2345 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

>How many seconds would you wait before jumping after the tandem?

Enough to clear the cloud. Minimum exit timing would be 7.3 seconds for 1000 feet separation with the following assumptions:

1) No winds at exit or opening (which would be odd.)

2) 70kt jump run.

3) No tracking during the jump.

Under the conditions I am guessing existed during your jump, I'd give them more like 12-14 seconds.


(This post was edited by billvon on Jan 29, 2007, 10:12 AM)


speedy

Jan 29, 2007, 11:34 AM
Post #13 of 27 (2303 views)
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Re: [billvon] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

Quote:
Enough to clear the cloud. Minimum exit timing would be 7.3 seconds for 1000 feet separation with the following assumptions:

1) No winds at exit or opening (which would be odd.)

2) 70kt jump run.

3) No tracking during the jump.

I am curious about the .3 part of the 7.3
I assume that the 70kt is IAS.
TAS = IAS + [(IAS2%)(ALT/1000ft)]
Which at 13,000 ft gives 88.2 TAS = 148.8 ft/sec (note the DZ was at 1000 ft msl and at 13,500 AGL the TAS would be actually higher)
7 sec would give you 1041.6 feet separation at opening time. Is the .3 an extra margin of safety? Tongue
Or is something wrong with my calculations?


sundevil777  (D License)

Jan 29, 2007, 2:05 PM
Post #14 of 27 (2246 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

It would depend on where the bottom/base of the cloud was. If you're going to fall out of it in a few seconds, then I would proceed as if it wasn't even there. If it was a lot thicker, I might be tempted to get out quickly and keep the tandem in sight the entire time, maybe track back towards them but well off the the side (off jump run direction). This gives a chance to do an aggressive track and flare out, which is fun. This assumes that I was planning a solo jump. I am very confident in my ability to follow tandems without being dangerous, and I would probably still never get within about 200 feet of them horizontally, and slightly above so they couldn't see me to be distracted by my presence. After the jump, I'd let the TI know what happened and that I wasn't being totally reckless.

I like jumping through and near clouds. Of course I wouldn't like to hit something while doing it, but...it is a lot of fun.


(This post was edited by sundevil777 on Jan 29, 2007, 2:06 PM)


aguila  (B 1009)

Jan 31, 2007, 1:51 PM
Post #15 of 27 (1995 views)
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Re: [PWScottIV] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

In reply to:
...

1. Does anyone find it to be a little strange that the tandems are leaving first? That means probably everyone else on the load has the potential to freefall through the tandems' canopies. Correct me if I'm wrong, but I thought the most important factor in ordering the load was deployment altitude. Followed by average freefall speed (belly, freefly, tracking, etc.), and then group size. Am I totally off here?

There is an official statement supporting your arguments: http://72.14.209.104/...06.pdf+tandem+exit+o but this was a real case and you might find yourself in such situation. That is the reason for this poll (I just found the document yesterday)


Premier PhreeZone  (D License)
Moderator
Jan 31, 2007, 2:19 PM
Post #16 of 27 (1974 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

USPA makes recommendatiosn but they are ignored all the time. Take for example Skydive Arizona. The are one of the largest and busiest DZ's i nthe world and their landing direction is east or west only, NOT into the wind despite the USPA recommending landing into the wind. For the longest time Skydive City in Z-Hills used to put freefliers out first desipte the USPA recommending something else.

Seperation needs to be done based off accurate winds aloft. That or if you can look staight down and spot you need to wait until the plane has traved 1000-1500 feet forward from the last group's exit point.


PWScottIV  (B 30429)

Jan 31, 2007, 5:29 PM
Post #17 of 27 (1945 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

In reply to:
In reply to:
...

1. Does anyone find it to be a little strange that the tandems are leaving first? That means probably everyone else on the load has the potential to freefall through the tandems' canopies. Correct me if I'm wrong, but I thought the most important factor in ordering the load was deployment altitude. Followed by average freefall speed (belly, freefly, tracking, etc.), and then group size. Am I totally off here?

There is an official statement supporting your arguments: http://72.14.209.104/...06.pdf+tandem+exit+o but this was a real case and you might find yourself in such situation. That is the reason for this poll (I just found the document yesterday)

Yeah, that's what I thought... I know others have made a strong argument for almost the opposite order... But I wonder what the safest method is? I've been attempting to create 1000ft (1500 for groups) horizontal separation based on estimating the horizontal clearance between myself and the last jumper/s. I've been trying to do that by looking back and forth between straight down and the jumper/s. It also does seem to end up being somewhere between 5 and 10 seconds. The 45deg rule doesn't seem to work though, because I've never seen a jumper move fast enough backwards to ever get near 45deg, maybe 30 or so, but never 45, yet... I only have 21 jumps though, so I'm just about as inexperienced as they come...


aguila  (B 1009)

Jan 31, 2007, 8:35 PM
Post #18 of 27 (1902 views)
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Re: [PWScottIV] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

In reply to:
In reply to:
In reply to:
...

1. Does anyone find it to be a little strange that the tandems are leaving first? That means probably everyone else on the load has the potential to freefall through the tandems' canopies. Correct me if I'm wrong, but I thought the most important factor in ordering the load was deployment altitude. Followed by average freefall speed (belly, freefly, tracking, etc.), and then group size. Am I totally off here?

There is an official statement supporting your arguments: http://72.14.209.104/...06.pdf+tandem+exit+o but this was a real case and you might find yourself in such situation. That is the reason for this poll (I just found the document yesterday)

Yeah, that's what I thought... I know others have made a strong argument for almost the opposite order... But I wonder what the safest method is?

You know the answer. For the same scenario remove the tandem and put a 3-way opening at 3K ft instead. How long would you wait to jump? Easy or hard selection?


speedy

Feb 1, 2007, 12:14 AM
Post #19 of 27 (1871 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

Quote:
For the same scenario remove the tandem and put a 3-way opening at 3K ft instead. How long would you wait to jump?

For the 3-way group I would wait slightly longer than for the Tandem. Say I was waiting 7 secs for the tandem, then I would wait 11 seconds for the 3 way group.


Premier billvon  (D 16479)
Moderator
Feb 1, 2007, 11:41 AM
Post #20 of 27 (1760 views)
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Re: [aguila] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

>You know the answer. For the same scenario remove the
>tandem and put a 3-way opening at 3K ft instead. How long would
>you wait to jump?

Depends on who the 3-way was and what the uppers actually were (as opposed to the pilot just thinking they were zero.) Truly zero uppers and Dan BC, Bill Binder and Christy? 8 seconds. Mark Brown and two newbies, with what looks like average uppers? 12 or so seconds.


kallend  (D 23151)

Feb 1, 2007, 11:47 AM
Post #21 of 27 (1759 views)
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Re: [billvon] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

In reply to:
>You know the answer. For the same scenario remove the
>tandem and put a 3-way opening at 3K ft instead. How long would
>you wait to jump?

Depends on who the 3-way was and what the uppers actually were (as opposed to the pilot just thinking they were zero.) Truly zero uppers and Dan BC, Bill Binder and Christy? 8 seconds. Mark Brown and two newbies, with what looks like average uppers? 12 or so seconds.

Why pick on Mark?Shocked


Premier billvon  (D 16479)
Moderator
Feb 1, 2007, 11:51 AM
Post #22 of 27 (1753 views)
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Re: [kallend] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

>Why pick on Mark?

Dan BC tends to do 4-way training jumps where people practice staying in their slots. Mark's jumps are more often with newbies, and he often has to "fetch" them after they backslide 500 feet, go low or do something else unexpected.


rhys  (D 95)

Feb 3, 2007, 6:14 AM
Post #23 of 27 (1640 views)
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Re: [PWScottIV] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

>Does anyone find it to be a little strange that the tandems are leaving first?

yes. i would have told the load organiser that the tandems should jump last unless somebody is opening higher than 5000'.

there is no reason for a tandem to jump before a sporty other than the safety being comprimised for the sake of faster turn around times.

pretty damn stupid if you ask me!


(This post was edited by rhys on Feb 3, 2007, 6:14 AM)


likearock  (D 24640)

Feb 3, 2007, 6:44 AM
Post #24 of 27 (1628 views)
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Re: [rhys] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

In reply to:
there is no reason for a tandem to jump before a sporty other than the safety being comprimised for the sake of faster turn around times.

pretty damn stupid if you ask me!

If you feel so strongly about it, you might want to talk to the WFFC organizers. Tandems go first as a rule there among thousands of fun jumpers. As far as I know, that hasn't led to any special problems.

Regardless, the main point of this thread was that the near collision in freefall had much more to do with exit separation than exit order.


rhys  (D 95)

Feb 3, 2007, 7:04 AM
Post #25 of 27 (1616 views)
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Re: [likearock] How many seconds would you wait before jumping? Read first! [In reply to] Can't Post

>If you feel so strongly about it, you might want to talk to the WFFC organizers. Tandems go first as a rule there among thousands of fun jumpers. As far as I know, that hasn't led to any special problems.

and what was the logical reason for that other than comprimising safety for faster turn around times?

I have never jumped at a dropzone that puts tandems out first and if i did... yes i would question the reasoning because i cant think of another reason other than turn around time, another jumper opening higher than 5000' or a bird person!

many have said they wouldn't go to the WFFC because of the safety record there. i am not schooled up enough to make a comment myself about it but yes it still seems like a dumb idea. even though cool people are diong it!


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