Diving after another jumper

[Mockingbird 0]

If you have to dive out a minimum of 100 feet after another jumper, how long should you wait to exit? (This is one of the requirements on the yellow card for 'A' license.)

Blue skies & happy jitters ~Mockingbird
"Why is there something rather than nothing?"

[rasmack 0]

Quote

If you have to dive out a minimum of 100 feet after another jumper, how long should you wait to exit?

However long your instructor tells you to.

Serious reply: Assuming you mean 100 ft vertical separation it would be 2-3 seconds.

0.5*g*t^2 = 100 ft <=> t = sqrt[200 ft / g] ~ 2.5 s

Factor in air resistance and it's another ball game but as an estimate it probably holds water at this stage of the jump. If, however you are referring to absolute separation (horizontal and vertical combined), one second should be plenty.

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

[Mockingbird 0]

Thanks, rasmack. What I had in mind was one of the requirements on the yellow card for an 'A' license. It says: "Dive a minimum of 100 feet after another jumper and dock safely without assistance from the other jumper (two times)."

When I did this jump with a coach, I was told to leave at the same time, and as it turned out (once I got stable and looked for her), she did seem to be at least 100 feet away. On another jump, it was suggested that I wait one second. My exit wasn't very good and I flipped, which took a few seconds to recover from, so I don't know if the other jumper woulda' been 100 feet away or not if I'd had a stable exit.

So ideally speaking, and based on the requirement as stated on the yellow card, if my exit is stable, how long would I need to wait after the other jumper leaves?

Blue skies & happy jitters ~Mockingbird
"Why is there something rather than nothing?"

[AFFI 0]

I believe that the spirit is this requirement on the card it so teach, no, introduce the “Dive Swoop Dock” maneuver to teach the fundamentals of safely diving down to a formation and docking on it without injury, death or even worse – taking out the formation.

I could be wrong...

Mykel AFF-I10
Skydiving Priorities: 1) Open Canopy. 2) Land Safely. 3) Don’t hurt anyone. 4) Repeat…

[tombuch 0]

Quote

Serious reply: Assuming you mean 100 ft vertical separation it would be 2-3 seconds.

0.5*g*t^2 = 100 ft <=> t = sqrt[200 ft / g] ~ 2.5 s

Factor in air resistance and it's another ball game but as an estimate it probably holds water at this stage of the jump. If, however you are referring to absolute separation (horizontal and vertical combined), one second should be plenty.

The easy answer is to exit a little less than a second after the first jumper.

I'm going to approach the math from a slightly different perspective than rasmack, and do so without crazy symbols that those of us educated a long time ago in the American school system may not quite grasp. I'll discuss 100 feet of horizontal separation because it's an important concept to understand for general safety.

Lets assume the airplane is a Cessna moving over the ground at about 80 miles per hour. There are 5,280 feet in a statute mile, so the airplane is covering 422,400 feet per hour (80 x 5,280). There are 60 minutes in an hour, so the airplane is covering 7,040 feet per minute (422,400 / 60). There are 60 seconds in a minute, so the airplane is covering 117 feet per second (7,040 / 60). So, if you wait about a second you will be just over 100 feet horizontally from the first jumper.

Horizontal separation is an important concept to understand because horizontal separation is necessary to keep groups far enough apart so that they don't conflict with each other at opening. As you can see from the above example, a second doesn't provide much separation. Additional time will provide additional separation.

Hopefully your instructor has already discussed how long to wait between groups to provide a safe buffer area. The actual time will vary depending on the airspeed of the plane, the wind (which defines ground speed), and the size/type of groups. I wrote an article for the S&TA area of The Ranch web site that discusses waiting between groups, and the distance an Otter will cover when traveling at 90 mph of airspeed in various wind conditions. It is available as article 15 at http://theblueskyranch.com/STA.php, but the graphics are not displaying correctly, so I've attached it as a Microsoft rtf file.
.

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

[rasmack 0]

For the record my above post is not to be taken in any way as advice on separation between groups. That is a much bigger question.

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

[SethInMI 174]

Quote

There are 60 minutes in an hour, so the airplane is covering 7,040 feet per minute (422,400 / 60). There are 60 seconds in a minute, so the airplane is covering 117 feet per second (7,040 / 60). So, if you wait about a second you will be just over 100 feet horizontally from the first jumper.

Tom, I think that statement ignores the "forward throw" of the exiting jumper. And I changed the underlined "second" from minute.

Seth

It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

[leapdog 0]

Quote

If you have to dive out a minimum of 100 feet after another jumper, how long should you wait to exit? (This is one of the requirements on the yellow card for 'A' license.)

Not to take away anyhting from the more experienced instructors here, but simply a second or less will do just fine. The coach should show you a nice stable way to dive if you don't already know how. The purpose is to swoop and dock as in a formation. All the info here is good but for now just keep it simple.
Don't cloud what you are trying to accomplish and learning the basic with all the technical stuff just yet.

Gunnery Sergeant of Marines
"I would like it if I were challenged mentally at my job and not feel like I'm mentally challenged." - Co-worker

[tdog 0]

Quote

If you have to dive out a minimum of 100 feet after another jumper, how long should you wait to exit? (This is one of the requirements on the yellow card for 'A' license.)

The way I do this with people I am working with... I rear float and give a freefly arm exit count. They are inside diving. We go at the same time...

If they tumble, they get a large distance on both horizontal and vertical axis. If the exit nicely and are too close for the learning, I backslide/fall fast until I like the gap from a learning perspective.

That way I have more control of the gap...

[justinb138 0]

Quote

Tom, I think that statement ignores the "forward throw" of the exiting jumper. And I changed the underlined "second" from minute.

Seth

Both jumpers will experience the forward throw from the plane, so it's not really a factor.

[billvon 3,080]

>If you have to dive out a minimum of 100 feet after another
>jumper, how long should you wait to exit?

If you wait about a second (i.e. "one one thousand go") you will end up about 100 feet away.

[Mockingbird 0]

Right. I wasn't asking about separation.

But I'll hold on to Tom's explanation for reference!

[Mockingbird 0]

Thanks, tdog. This is what I was inquiring about.

[kelpdiver 2]

Quote

>If you have to dive out a minimum of 100 feet after another
>jumper, how long should you wait to exit?

If you wait about a second (i.e. "one one thousand go") you will end up about 100 feet away.

As I recall that jump, the natural delay I made initiating the exit right after my instructor left proved to be quite sufficient.

[billvon 3,080]

>As I recall that jump, the natural delay I made initiating the
>exit right after my instructor left proved to be quite sufficient.

Yep. If you say "OK, ready?" and then leave as soon as they nod, it will take them nearly a second to process the information and dive out after you - thus accomplishing the same goal.

[indyz 1]

Quote

>As I recall that jump, the natural delay I made initiating the
>exit right after my instructor left proved to be quite sufficient.

Yep. If you say "OK, ready?" and then leave as soon as they nod, it will take them nearly a second to process the information and dive out after you - thus accomplishing the same goal.

That's what I've been doing when I coach. I've found (in my limited experience) that if you tell somebody to "wait one second", they tend to wait too long.

[Fast 0]

Quote

Quote

>As I recall that jump, the natural delay I made initiating the
>exit right after my instructor left proved to be quite sufficient.

Yep. If you say "OK, ready?" and then leave as soon as they nod, it will take them nearly a second to process the information and dive out after you - thus accomplishing the same goal.

That's what I've been doing when I coach. I've found (in my limited experience) that if you tell somebody to "wait one second", they tend to wait too long.

yeah!


If I asked a student to wait 2 seconds in the door after I jumped out, it would be the last time I saw them that skydive cause they would never get down to me. Sometimes people have a hard enough time with going at "near" the same time. Its a learning thing! They get it eventually though!

~D
Where troubles melt like lemon drops Away above the chimney tops That's where you'll find me.
Swooping is taking one last poke at the bear before escaping it's cave - davelepka

[dragon2 2]

Watch this video, it has 2 people in it doing the delay. More or less The first one waits too long (count how long that is!) the 2nd goes unstable.
http://www.skydivingmovies.com/ver2/pafiledb.php?action=file&id=3754

ciel bleu,
Saskia

[Reginald 0]

When I'm working with students on this item I have them dive and I rear float. I have the student give the count “ready, set, go” with body motion not verbalized. I leave on “set”. The student dives on “go” the difference is about 1 second and produces approximately 100 feet of separation. Works like a charm.

"We've been looking for the enemy for some time now. We've finally found him. We're surrounded. That simplifies things." CP

[Mockingbird 0]

Quote

Watch this video, it has 2 people in it doing the delay. More or less The first one waits too long (count how long that is!) the 2nd goes unstable.
http://www.skydivingmovies.com/...ion=file&id=3754

Thanks, dragon2. As so often happens with .wmv's on my computer, it buffers, plays for a while, stops, indicates that it's buffering again, and then goes black. It looks like it was going to be a really helpful video, too! I'll keep trying.

Blue skies & happy jitters ~Mockingbird
"Why is there something rather than nothing?"

[bob.dino 1]

Download VLC. It plays pretty much anything, and plays it pretty decently too...

[Mockingbird 0]

Actually, I have VLC; I guess I need to check the preferences so it'll play whatever I download.

Blue skies & happy jitters ~Mockingbird
"Why is there something rather than nothing?"

[mnealtx 0]

Quote

Quote

Watch this video, it has 2 people in it doing the delay. More or less The first one waits too long (count how long that is!) the 2nd goes unstable.
http://www.skydivingmovies.com/...ion=file&id=3754

Thanks, dragon2. As so often happens with .wmv's on my computer, it buffers, plays for a while, stops, indicates that it's buffering again, and then goes black. It looks like it was going to be a really helpful video, too! I'll keep trying.

Right click the movie and save it to your computer...THEN play it...

Mike
I love you, Shannon and Jim.
POPS 9708 , SCR 14706

[kallend 2,112]

Quote

Quote

There are 60 minutes in an hour, so the airplane is covering 7,040 feet per minute (422,400 / 60). There are 60 seconds in a minute, so the airplane is covering 117 feet per second (7,040 / 60). So, if you wait about a second you will be just over 100 feet horizontally from the first jumper.

Tom, I think that statement ignores the "forward throw" of the exiting jumper. And I changed the underlined "second" from minute.

Seth

But the following jumper has forward throw too, so that (to a good approximation) cancels out.

...

The only sure way to survive a canopy collision is not to have one.

[Mockingbird 0]

Hi, Mike. Yeah, thanks. I figured that out late last night. (I have a Mac, so for me it's actually "Control-Click" your signature? You'll be back then? I'm definitely thinking about going. Neat ad about it in Parachutist.

Blue skies & happy jitters ~Mockingbird
"Why is there something rather than nothing?"