The inevitable

[guest]

Did you attach the PC immediately prior to this jump
Yes or no?

No.

Is it attached symmetrically(step on the bridle, pull on and compare the lengths of the load tapes at the skirt of PC) Now?
Yes or no

Yes, as I stated before.

Does the bridle have twists in it relating to the same direction of your 180?
Yes or no?

No, as I stated before.

Is your PC Bias constructed as opposed to Block?
Yes or no?

If Bias = F-111, then yes, as I stated before.
If Bias = something else, then I don't know, please explain.

Thanks
Mike

[space]

Bias constructed means that the reinforcement tape is sewn to the mesh at a 45° angle to the grain of the mesh. Block is parallel to the grain of the mesh.
Let me know and read the link I posted to have a more in depth look into block vs bias..
Take care,
space

[guest]

It is block. I just repacked and checked.

Mike

[space]

The following was pasted from Dropzone.com and was written by the inventor of the hand deploy pilot chute.
It´s highly likely IMHO the cause is due to low seperation velocity because of the lower drag of the block constructed PC.
Take care and buy a new PC from a reputable manufacturer.
space

Reply from Bill Booth:

What happened to you is getting more and more common. Although I hold the patent on the hand deploy pilot chute, I never charged anyone a royality to use it, and therefore never published construction details. I'm afraid this has led to some poorly made pilot chutes as people have copied, but not copied EXACTLY, my original design. As a matter of fact, last Sunday, a jumper came up to me, said that he was having "pilot chute hesitations" on his Vector, and asked me to have a look. His problem, it turned out, was the same one I've seen countless times before...His pilot chute was made by "God knows who", and made incorrectly.

I don't know about you, but one of the the scariest malfunctions I can think of, is a streamered main pilot chute that has enough drag to open your main container, but not enough drag to lift out the bag. What do you do? If you just lie there and wait, the ground may "rise up to smite thee". If you pull your reserve, your main is going to simultaneously deploy, and main/reserve entanglements are rarely much fun either. What to do...Easy, don't jump an incorrectly manufactured or adjusted pilot chute.

So, how can you tell if your hand deploy pilot chute is OK? First, some basic definitions. 1. Apex - The center of the fabric part of your pilot chute. 2. Skirt - Where the mesh and fabric meet. 3. Base - The center of the mesh part of your pilot chute. 4. Centerline - One or two pieces of tape, of fixed length, that lead from the apex to the base. 5. Bridle - A piece of tape, doubled in the case of a collapsable pilot chute, leading from the base to the deployment bag. 6. Kill line - A single piece of line, on a collapsable pilot chute only, that runs from the apex, through the center of the pilot chute, and down through the bridle to the pilot chute attachment point at the bag, or in some designs, to the apex of the canopy. 7. Support tape - 4 pieces of thin tape, sewn to the mesh, leading from the base to the skirt. 8. Bias - Simply put, the direction the mesh stretches the most (a diagonal line, at 45 degrees to the little squares that make up most mesh used in hand deploy pilot chutes). Sorry for all that defining, but if you don't understand those terms, you won't understand what comes next.

OK, now the easy part. If you want your pilot chute to always function properly, simply make sure, in the inflated state, that no part of the skirt is above the apex. In other words, make sure neither your centerline nor your kill line is too short. I pulled the apex on my hand deployed pilot chute for two reasons. 1. It makes them open faster. 2. It yields 11% more drag. However, IF THE APEX IS PULLED DOWN BELOW ANY PART OF THE SKIRT, THE PILOT CHUTE WILL NOT FUNCTION PROPERLY.

How do I check that? First cock you pilot chute like you would during packing. Now hold your pilot chute UPSIDE DOWN by the bridle at the base. Simultaneously pull downward on the apex (handle) and each support tape where it touches the skirt. The apex should be equal to, preferable slightly "below", but never "above" the skirt. (Please remember, the terms "above" and "below", in quotes, refer only to the "upside down" pilot chute you are holding in your hands for this test.) Now look how your support tapes are sewn to the mesh. If they are sewn "on the bias" your pilot chute is properly constructed. If they are not sewn on the bias it means that the mesh halfway between each support tape IS on the bias and will stretch more than enough to allow the skirt to get way "below" the apex. Try it. It's like a round parachute with several different line lengths. It simply doesn't work very well. This extremely common construction error might not let your pilot chute fully inflate, or in extreme cases, inflate at all. If your pilot chute is "borderline" when it is new, then things will get worse and worse as it ages.

Now to "adjusting" a correctly manufactured pilot chute. Kill lines are usually made out of Spectra (Microline). Friction generated during the collapse sequence causes heat, and Spectra SHRINKS when heated. This means that your centerline could eventually get short enough to prevent your pilot chute from inflating correctly. Use what you have learned above to recognize this situation, and correct it.

This is just a BASIC primer on pilot chute construction, and does not address several other important design considerations such as fabric and mesh choices, and how pilot chute size vs. the weight of your main canopy affects seperation velocity, snatch force, opening shock, and malfunction rate. More about these another time.Bill Booth

[guest]

Hi Spacey,

I have a question.

OK, most base pilot chutes have two solid tapes running over the fabric as well as the mesh. The pilot chute is broken into quadrants, or 4 sections. And the orientation of the tapes relative to the little squares that make up the ripstop determines if its bias or block.

What about pilot chutes with 3 solid tapes? There is no clear cut bias or block in that case, from what I see. Do these PCs have rotation problems because of this?

Also, another question about pilot chute rotation causing off-heading openings. Looking from above, why would a clockwise PC rotation cause an opening one direction versus counterclockwise PC roation cause an exactly opposite opening direction?90 right versus 90 left, for example.

Please help! thanks.

[guest]

It's a common, well known fact. With all things being equal or correctly working, and that includes pilot chute and body position, deploying a freepacked canopy in a crosswind will result on average with an opening into the wind. This is most noticable on short delays with strong winds.

What is not so talked about is that crosswinds do have the potential to amplify the bad effects of poor body position.

So a strong wind blowing down the wire combined with a slight dip of the shoulders can quite easily result in a 150 to 180 off heading opening. But as another poster in this thread pointed out, the wind is your friend in this case.

The worst thing on a "short delay strong wind down the wire" jump is to have a more than 90 opening towards the wire. Any residual forward speed of your canopy will be combined with a pendulum effect of you swinging forwards as the canopy has drifted off from being straight above you during deployment, will take you into the wires REALLY FAST. Since you are travelling downwind, contact speed can be pretty high.

So, good body position and deep brake settings are just as important on windy tower jumps as they are on other jumps.

/Lukas

[BASE_689]

>What about pilot chutes with 3 solid tapes? There is no clear cut bias or block in that case, from what I see...

When Space refers to a "bias reinforced along mesh" manufactured PC as a properly built PC, he refers obviously to the situation in which you have reinforcement tapes sewn on mesh only along 2 diameters (or along 4 radiuses).
When you have reinforcement tapes sewn on mesh along 3 diameters (or along 6 radiuses), then that is not any more an issue, because with 3 diameters (assuming you have 1 diameter along one of the two main directions (of the thread) of the mesh), you have the remaining 2 diameters that run along 2 directions at 60° from each other, so comprising (or nearly totally comprising) the "bias direction" of the mesh any way. In the end, in such a way, the distortion of mesh/PC is nearly avoided.

So, to summarize:
1) reinforcement tapes on mesh along 2 diameters: PC must be manufactured with reinforcement tapes along the "bias direction(s)" of mesh, so to have a "bias manufactured" PC.
2) reinforcement tapes on mesh along 3 diameters: PC is automatically manufactured as a "bias manufactured" PC.
3) reinforcement tapes on mesh along 4 diameters: PC is automatically manufactured as a "bias manufactured" PC; in the case of 4 diameters, the PC distortion is really low (btw, my #2 48" ZP PC's have got reinforcement on 4 diameters).

>Also, another question about pilot chute rotation causing off-heading openings. Looking from above, why would a clockwise PC rotation cause an opening one direction versus counterclockwise PC roation cause an exactly opposite opening direction?90 right versus 90 left, for example...

Sorry, I am not an expert about this issue. Space should better to answer us about this issue (how actually a rotating PC can affect asymmetrical extraction of canopy from cantainer and consequent off heading deployment).

Stay safe out there
Blue Skies and Soft Walls
BASE #689 :D

[crwper]

I've noticed something a bit different re: crosswinds on static line jumps. Looking at video of a jump in about 5 mph wind from the right, two jumpers, it was pretty clear that the canopy moved to the left as it opened (because it is lighter and has much higher surface area than the jumper, so it is accelerated more quickly by the wind). The result is that the bottom skin is presented to the wind, the canopy is tilted to the left, and it turns left to recover (the situation is basically the same as if I had been in a left turn to start and then let the toggles go).

It seems to me there are two competing forces here: there is the tendency of the canopy to turn into whatever tilt it has, which is what we noticed on this static line jump; and there is also the fact that when the canopy is pulled to the left, the right risers are loaded first, and that should result in a turn to the right. Possibly the second one is dominant in freefall jumps, which is what most of the discussion on this topic seems to have focused on.

I'd like to hear other people's experiences.

Michael

[space]

4 diameter PC note.
I inspected a canopy with this type of construction for the PC in an accident investigation. The long loops at the base of the PC (to allow airflow?) enabled the jumper to have the PC 7.5cm/3in assymetric.
On to other aspects.
According to Bill Booth, If the skirt can be pulled up(at some reasonable force) past the pulled down apex, The drag factor changes to less. Seperation Velocity between one and the PC is the envelope.

IMHO, Too slow and the canopy dances around during line stretch, Too fast and and you get center cell extraction leading to endcell whipping, assymetric means that if the PC is orbiting as opposed to spinning in place. As an analogy, If you have flown steerable kites, the greatest force is when the kite is directly flying thru the down wind horizontal, any flying away from this point is reducing the amount of applied force to the lines. It can be explained trigonometrically better by somebody else than I.
As for what an orbiting PC can do I will give an example of what I could do, As a deckhand navigating the Mississippi locks and dams, I routinely orbited a rolling 180 in the lock lines to free them from the timberheads 20ft or sometimes higher above where I stood. An easy test would be to hang a rig by the legstraps high enough to swing the upside down hanging canopy around by the 2.3m bridle and see if one can induce line twists.
I wish to state that I don´t think that Mike´s 180 was due to this effect. and also that material considerations will have an effect, like type of mesh
and it´s bias/block elongation ratio and porosity vs surface area ratio. the slope of permeability increase of the f-111 vs use parameters.
hope this helps,
feel free please to add.
take care,
space

[guest]

I disagree slightly. Assuming you exit between the wires, the worst case scenario is wind going only 60 degrees from your exit heading. The canopy will favor opening downwind - with the tail facing the wind - toward the wire if its blowing that way. I frequently jump in these conditions on antennas and I cannot recall a 180 you describe in all the antenna jumping I've done for many years. If the winds are 90 degrees off, then its easily conceivable the canopy will open upwind, with the nose facing into the wind. I've jumped into the non-ideal sections of an antenna with winds not at the back but from the side and have experienced the canopy opening into the wind as you describe.

An obvious awkward scenario is the 90 degree opening toward the wind-favored wire. Let's say its the wire on the left, for example. If you open 90 degrees to the left, its relatively easy to hit the wire. My personal preference, depending on the winds and the specifics of the site, is to turn left toward the tower and face into the wind, and continue turning left to eventually face fully away from the tower and midway between the guy wires. If I turned right, it's very easy to build up a lot of speed and cruise right into a guy wire.

take care
;-)

[guest]

About disagreeing, it was not to crwper's post but to Lukas'

[guest]

I think my explanation of angles etc might have been too concise. We basically agree on most points. But I am still convinced about a canopy wanting to open into the wind, all other things equal. I have seen this so many times, ie if the wind is blowing down the right wire, the canopy will have a tendency to open towards the left, as long as the pilotchute behaves and body position is straight. A lot of experienced body flyers will rotate in freefall away from the windprone wire, just like you say.

As for jumping into anything but the downwind sector, the statistics on doing that are so bad. I won't dare. Almost all my friends wire touches or pass thru's are from jumping in those kind of conditions. Winds down the wire are not good, but winds in another sector are worse. If you get twists, watch out ! I think at Petronas there were 6 cases of twists in about 600 jumps. Go figure !

Enjoy your steel,

/Lukas