Something to think about: Round versus Square reserve? There is a distinct possibility of a dual deployment of both parachutes, (main and reserve) during a student jump (or any jump for that matter). The use of a square main and square reserve system poses a very serious hazard for the beginner or very low experienced jumper. According to the accompanying study from Performance Designs, Inc., "intentional cutaways from biplanes showed that the main had the possibility of entangling with the reserve 11 out of 11 times." This means that an inexperienced jumper that has both a square main and reserve, has a long list of scenarios of lifesaving decisions to make in a very short time. Whereas in a square main/round reserve system, the decisions have been made for you. Please read on for the explanations!!
The use of a square/round system minimizes the required knowledge and decision making to deal with a duel deployment scenario, in most cases if no action , or decision is made, the result is an uneventful landing with two deployed parachutes. The use of square/square systems require more advanced knowledge, skills, and decision making, unfortunately in some cases if no action is taken or a poor or improper decision is made, the resulting landing could cause serious injury or in rare cases even death.
The cause of these differences is attributed to the different flight characteristics of square and round canopies. Square canopies by design require forward speed and airflow from the front to stay inflated and flying, while the round parachute is a basic aerodynamic decelerator which requires airflow from underneath to stay inflated, requiring no forward speed and airflow, and lead to the two canopies becoming entangled during this process. With the use of square/round the two inflated canopies require different air speeds and airflow from different directions which removes the occurrence of entanglement.
Please read the study info offered below for better understanding of these type of problems which can occur with the use of both of these systems, and the conclusion of the canopy use studies.
The Dual Deployment: The Dual Round/Square deployment is relatively uneventful. Usually the jumper in these deployments are not aware that the event has occurred. Procedures require releasing the main canopy, and flying the round reserve parachute to the landing area, and performing a good parachute landing fall (PLF).
Entangle although very rare can occur, the procedures are to fly down and land the round reserve parachute with a good (PLF) . Do not release the main canopy, unless you can determine that the release will not interfere with the inflated round reserve. The main canopy usually will fly with a particular inflation and increase angle to the right or left of the jumper on descent.
Common Results of a Round/Square Deployment: The most likely both canopy configurations from near simultaneous deployment is near normal main canopy flight, slower forward speed of the main by drag induced from the round reserve, and a more pronounced angle of attack of the main canopy. This higher angle of attack increases your rate of descent under canopy to a higher degree.
A Very Infrequent configuration is an entanglement of the two canopies. Because the canopies are constructed differently and do not require the same direction and method of airflow, to inflate and maintain flight, this canopy configuration does not require the canopies to "compete" for the moving air which in turn reduces the possibility of canopy entanglement.
Final Conclusions of Round/Square Deployment:
1. Conclusion: The best way to handle any duel deployment is to avoid the situation. Use appropriate and available altitude reporting devices. Follow safety regulations on proper opening altitudes. Insure that AAD's are properly maintained and used.
2. Conclusion: If a duel deployment were to exist with a round/square configuration, release the main canopy, fly and land the round reserve in an appropriate area, and perform a good parachute landing fall (PLF).
3. Conclusion: If a duel deployment of a round/square were to tangle, fly and land with a good PLF the round reserve parachute. Only consider to release the main canopy if you can visually confirm that the release would completely clear the round reserve parachute.
As you can see from the possible occurrences that can result with the use if both types if equipment that the risk, required knowledge, skill, experience and procedures differ greatly.
A very low experienced jumper can initially function to a higher degree of competency and safety with basic equipment allowing the opportunity to gain experience and skills that are needed for use of more advanced gear.
We feel with experience, knowledge and increased safety that a new jumper can obtain through initial static line jumps utilizing a square main and round reserve, will much better prepare them for the system when they go to freefall.
Final note: If a student utilizing a round/square system were to make a poor decision, or take no action at all, the results generally would end uneventfully with a landing at a slightly higher rate of descent.
If student utilizing a square/square system were to make a poor decision or take improper actions, the resulting landing to a much higher percent, could result in serious injury or possibly death. Higher performance equipment requires higher skill, experience, and knowledge to be operated safely.
