Make your own free website on Tripod.com

Equipment

Home History Equipment Safety & Training Techniques Competitions Media Resources

 

Aerodynamics
CRW Canopies
Packing
Rigging

Introduction

    Following is a diagram indicating the nomenclature and location of major components of a parachute system. For detailed descriptions, refer to the glossaries on this web site.

    

Figure: Components of a parachute system.

Canopy: Diamant. Container: Woomera. Parachutist: Tom Begic - Xtermin8 - Australian 8 Way Speed Team.

Location: Lido Lakes, Indonesia - World Parachuting Championships #6. Photographer: Anthony (Worm) Dorney.


Canopies

    It is possible to do CRW on any deceleration device (parachute). However, there are a many reasons why you should choose CRW specific canopies if you want to do CRW. Whilst it is perfectly acceptable for experienced jumpers to do non-contact or very basic contact CRW (such as stacks) on high performance canopies, the more complex the manoeuvre and the lesser experienced the jumpers, the less acceptable it becomes to use anything but CRW specific equipment. Some reasons why you should NOT use freefall equipment for CRW are:

  • high performance canopies not only perform better whilst everything is OK, but they will also perform more radically when everything is going wrong. In other words, problems are more likely to occur during minor disturbances of formations and canopies, and the affect is likely to be exaggerated compared to a CRW specific canopy. You will descend faster in an entanglement which cuts into your decision and reaction time.
  • most modern freefall canopies have micro-lines. They will cut through flesh given sufficient force and speed. They are also harder to catch and hold because they are smaller in diameter.
  • they usually have cascaded A lines which increases the chance of getting feet caught in lines. This increases the chance of canopy airfoil distortions which in turn increases the likelihood of radical movements. Our aim is smooth, not radical.
  • very few freefall canopies have bridle retraction systems. This means more exposed equipment and a higher likelihood of entanglements.
  • longer suspension lines means its more likely that the suspended load is more likely to rotate if subjected to the appropriate forces. In other words, a side on dock is more likely to lead to spiralling line twists. And this is not that much fun on small elliptical canopies.

    Seven cell rectangular canopies are preferred over nine cell elliptical canopies. This is due to the aerodynamic requirements of CRW canopies. They must be able to maintain adequate pressurisation during docking manoeuvres and when portions of the nose are blocked off by the bodies of other parachutists, re-pressurise after deflation, be more stable when subjected to impact forces or under the influence of turbulence, be responsive enough to be able to respond to inputs quickly but not too responsive such that the slightest distortion will create a massive deviation in its performance, etc.

????? Need more work here! ?????

    If at all possible, each parachutist in the formation should match the following variables with one another:

  • canopy cell structure (standard seven cell preferred).
  • compatibility of all canopies in a formation:
    • airfoil (manufacturer/model/design).
    • aerodynamics.
    • wing loading.
    • plan-form area.
    • cross-porting. Cells should have several cross-ports to promote airflow (hence pressurisation) between adjacent cells. This should be done according manufacturers specifications.
    • brake settings.
    • age and deterioration of canopy material.
    • canopy fabric.
    • bridle length.
    • pilot chute retraction system.
  • flying characteristics (descent rate, forward speed, stall point, etc).
  • flying styles of parachutists in the formation.
    • should spread arms and legs the same such that drag due to surface area is equal.
    • brake input should be consistent throughout the formation.
    • body position is important, especially in large formations.
  • suspension lines
    • direct lines for centre and outer A lines (no cascade).
    • colour coded centre & outer A lines.
    • trim.
    • line length & gauge (thickness).
    • line material.
  • slider dimensions, position and collapsibility after deployment, and style.
  • harness closure (how loose tight, how far apart the risers are spread as this alters the aspect ratio and flying characteristics of a canopy, etc).

    With all that in mind, if you want information about specific CRW canopies, go to the CRW Canopies page.


Deployment & Retraction Systems

Deployment

    CRW jumpers tend to use pullout or throw-out deployment systems. There has also been many other techniques used including the "spit-out" (both toggles in hand, pilot chute in mouth, jump, spit. . . . . . etc).

    The pull-out system: the parachutist grabs the handle and pulls it into the airflow beside him. As he pulls, the container is opened and the pilot chute is pulled out of the container. The pilot chute inflates more rapidly using this method as the pilot chute is correctly oriented to be exposed to the airflow. Unless you drop the pilot chute in your burble, this method promotes a faster deployment. One drawback is that is the handle is usually on the bottom of the pilot chute, the pilot chute cannot be pulled through the rings and collapsed. This can be overcome by relocating the handle on the top of the pilot chute, but then you lose the benefit of immediate pilot chute orientation and exposure to the airflow. The retraction is more important.

    The throw-out system: the pilot chute is pulled out of a pocket external to the container (usually BOC) and thrown into the air flow. It re-orientates itself to achieve air flow exposure and pressurisation. Then it pulls the pin on the main container and opens it. The pilot chute can easily be retracted through the rings using this system as the handle is located on the top of the pilot chute. The drawbacks of this system is less reliability with pilot chute pressurisation (very relevant for base-pin height differentials), and the possibility of main pack closure.

    Some teams have placed the handle on the bottom of the pilot chute to promote pressurisation and canopy extraction.

    Several things are important for deployment systems:

  • they must be consistent and reliable in terms of times and heights consumed during the deployment process.
  • the pilot chute must have sufficient drag to get the canopy to line stretch quickly.
  • the bridle must be long enough to clear the burble behind the jumper.
  • they must be fully retractable such that they don't interfere with other parachutists or their equipment and the performance of the parachute.
  • they should be user friendly in terms of packing effort and knowledge and practical use.
  • they should be relatively easy to replace &/or repair in the field.

Retraction Systems

    One of the greatest dangers in CRW is equipment entanglements. If using standard skydiving equipment, the bridle is the most likely piece of equipment to get tangled, especially when one canopy moves behind another. Hence, systems have been developed that retract the bridle and pilot chutes out of the way of other parachutists. These systems also deflate the pilot chute so that it does not affect the flying performance of a canopy.

    Rings are the most common retraction system. They allow the bridle to run through rings placed across the span of the canopy. There are usually four rings. Two are at the centre cell attachment, and there is one each two cells away from the centre cell. The bridle is run from one centre cell ring to one side cell, back over to the other side cell, and then back through the second centre cell ring. The length of the bridle is determined by the distance between these rings when the canopy is fully pressurised in flight. The bridle is usually made a little shorter than the distance described above so that the pilot chute is drawn into the second centre cell ring and therefore collapsed. It is usually shortened a little more than the radius of the mesh material on the pilot chute.

    There are other retraction systems that pull the pilot chute and bridle through the canopy.


Harness & Container

  • large grab soft toggles. Should have a large toggle loop that forces the loop to expand or open so that they are easy to locate and grab. Soft toggles are less likely to get caught around lines and are easier to locate and grab when you are in a hurry moving from one control input to another.
  • larger riser covers. Due to the increased bulk of CRW riser grips (especially the front risers), many standard skydiving containers cannot cover and/or hold the risers in properly.
  • protected reserve flaps and pins. Due to the possibility of lines catching around exposed flaps, it is beneficial to have tuck in and protected flaps on the reserve.
  • do not use containers that have obvious catch points such as cut in lateral harnesses,

Set-up & Configuration

  • Brake Settings
  • Toggle Settings. Its a good idea to get longer toggles with a larger loop (perhaps with two loops). This is for several reasons. The main one is so that they are easier to find whether you are looking at them or not. The second reason is to counteract the affect toggle in hand front risering has on brakes.
  • Riser Grips. Front riser grips are a critical component of CRW equipment. The aim is to be able to grab your front riser and pull down on it as quickly as possible. Depending in your ideal reach whilst under canopy (related to your arm extension, strength, riser dimensions, etc), you should locate the point on your risers where it is easiest for you to grab and that you can get maximum affective leverage. Some form of blocks or grips located at this point will assist with easy gripping. It may be something as simple as an L-Bar sewn into the riser that is covered by grip tape (vet wrap or tennis raquet grip).
  • Front Riser Pulling Aids
    • these are very beneficial for formation jumps where you expect to be occupying one slot for a period if time or for CRW camera persons. Examples include the wing slot and setup positions on large formation jumps. They allow a constant front riser input without much effort. It also means that you wont be pulling down on your toggles at the time. If you have a short toggle to brake setting length, you usually apply some brake by default every time you pull down your front risers (assuming you keep your toggles in hand). This means that your front riser input is less affective as it is counteracted by some braking.
  • Bridle Settings
  • Types of Deployment Systems
    • Throw out
    • Pull out
  • Types of Retraction Systems
  • Tail Pockets. These were developed in lieu of d-bags and tray packing. They make it easier to stow lines and actually assist in improving heading rates. It is less likely for line twists to be induced on opening by a complete canopy spinning than a d-bag. They also make it easier to retract the deployment equipment (bridle & pilot chute) as the obstacle of a d-bag is removed. Bag lock malfunctions are eliminated. But it is still possible but less likely, to get a tail pocket lock malfunction. They also accelerate the canopy extraction and line stretch process which may be a good or bad thing depending on how good your back is.
  • D-Bags. Are generally not used as its benefits (slower openings and making the pack job easier) are far outweighed by the benefits of the tail pocket.

Containers

  • AAD's should be considered carefully. Whilst it is acceptable to use
  • no SOS systems.
  • no RSL systems.

Accessories

  • Hook Knife is compulsory - multiple knives are preferred - consider mounting locations. Most likely to be used in an entanglement.
  • Altimeter (Visual, Audible) provides valuable information for emergency decision altitudes, break off height, docking decisions, etc.
  • Headgear (allow for hearing)
  • Timing Device
  • Tertiary Parachute
  • Weights
    • Jacket
    • Pouch
    • Clip on (tertiary / D ring mounted)
  • front riser trim tabs to assist with controlling descent rate and forward speed.
  • cross connectors are useful when building planed formations, especially large ones. They are not necessary for offsets and stacks or faster CRW disciplines such as rotations. They should be connected between front suspension lines and rear risers.

Jump Attire

    The critical factor is protection of body parts from abrasion from rapidly rubbing suspension lines. The hands and feet are most commonly affected. The climatic conditions, and altitude must also be considered. CRW jumpers spend more time in the air than free-fallers, this is especially relevant at high altitudes in cold climates.

  • Jumpsuits
  • Shoes
    • ensure no catching components such as hooks are exposed.
  • Socks (ankle covers).
  • Gloves
  • Goggles / Sunglasses

Spotting Aids

  • Measurement devices contained within the aircraft
  • Altimeter
  • GPS
  • Air Speed Indicator
  • Compas
  • Maps / Aerial Photographs
  • EYES
  • Wind Socks & Other Wind Indicators (clouds, trees, water, smoke, WDI, etc)

?????


Aircraft

  • Exit Airspeed
  • Centre of Gravity
  • Stall Speeds
  • Forward Throw
  • Turbulence from Prop Blast
  • Dead Air on Tailgates

Following are notes & other ideas relevant to this section that require further development. Please ignore.

  • there should be no protrusions that may catch onto equipment whilst performing CRW, this includes hooks on boots, devices mounted on the arms (watch, altimeter, jewellery), jewellery, etc.
  • adequate limb coverage should be worn to prevent friction burns and damage to lines (socks, boots, gloves, long sleeves, etc)
  • e. cross connectors 
    • (1) A secure foothold at the top of the risers is essential for building planes, which can develop greater tension as they grow larger.
    • (2) Cross connectors should be attached between the front and rear risers only, not from side to side.
    • (3) Side-to-side cross connectors can snag on the reserve container during deployment and cause a dangerous entanglement.
  • section on basic knots required in CRW
  • how to connect & disconnect gear
  • how to do a line check
  • how to untangle lines

Riser grips - front and rear

AAD's - comments on types, RSL's and other safety equipment, 

whatever system you use, you have to ensure on headings as the risk of opening collisions can be high. People have died from collisions on opening.

Graphics of equipment and components.

  • finding root cause of problems
    • pilot chute hesitation
    • low snatch force
    • excessive opening shock
    • controlling opening shock
    • off headings
      • body position
      • worn toggle/riser velcro leading to premature release
      • tripped on way out of the plane by other people or aircraft components
      • turbulent prop blast
      • lines packed hard up against reserve in pack tray
      • worn or uneven stowage bands
      • erratic or chaotic pilot chute inflation and canopy extraction (i.e. spinning p/c)
      • asymmetrical deployment equipment (p/c attached off centre to bridle)
    • premature toggle release
    • line dump
    • pilot chute in tow
    • end cell closure or slow pressurisation
    • trouble shooting guide
    • canopy incompatibility when wing loading is similar
      • age difference = variable porosity & line trim
      • brake settings
      • flying style
      • variable materials (different batch) used in construction - a serious team should use the same material if possible
    • in built turns
    • uneven pressurisation -> off headings and turns
    • varying response to similar 

Hit Counter

 

Home Contents Site Admin Feedback Search

This site is developed and maintained by Tom Begic. Send mail to Tom with any feedback.
Copyright 2005 OzCRW. Last modified: May 16, 2005