Reflection on the rescue parachutes ...

Introduction

Paragliding is a "risky" activity.
There are a number of risks that can lead each pilot to a multitude of critical situations:
- Lack of training
- Insufficient experience
- Bad weather analysis
- Collision with other aircraft
- Breakage of equipment
- ...
All these risks can generally be controlled by adequate training, equipment in good condition (servicing), constant vigilance, etc. ...

But in certain critical cases, where it is delicate or even impossible to return your wing to the flight envelope, there is a solution: the rescue parachute, which can enable you to return to the ground relatively more comfortably...

The rescue parachute has become an essential part of modern paragliding equipment. However, pilots are still too unfamiliar with its intrinsic characteristics.
Carrying a reserve parachute is not enough to ensure safety, as its proper use requires a certain amount of training, and total involvement on the part of the pilot in case of need.
We won't deal here with its installation or use. We advise you to get in touch with professionals (instructors, SIV instructors) to gather their experience and get the right training from them. You'll find a wealth of practical information in the FFVL reference document on rescue parachutes (author Pierre-Paul MENEGOZ), which you can download here.

A rescue parachute must be chosen with care, to best suit each pilot and his or her flying style. You may never have to use one, but if you do, it's imperative that you can do so without questioning its effectiveness.
We recommend that you carry out your own analysis by methodically comparing the different models, using these points to help you think things through.

Il existe aujourd’hui sur le marché de nombreux modèles et de nombreuses formes : hémisphérique, carré, Rogallo, octogone, pentagone, …
Chaque fabricant propose une conception propre, avec son lot d’avantages mis en avant par un marketing adapté. Tous sont certifiés et ont passés avec succès les tests d’homologation (EN et/ou LTF). Ces tests permettent de vérifier différents aspects du parachute (Source : EN 12491) :
– Taux de chute (doit être inférieur à 5.5m/s pour un modèle non dirigeable, et 4.4m/s pour un dirigeable)
– Stabilité (Evaluation visuelle)
– Temps d’ouverture (<4s)
– Résistance (Shock test à 40m/s, le parachute doit résister à 2 tests successifs sans détériorations)

The most important parameters (in our opinion) when choosing your parachute are:
- Fall rate
- Stability
- Steerability
The fall rate and stability of a model can be directly linked depending on certain parameters.

Other parameters may then be taken into consideration, depending on your intended use:
- Weight
- Volume

Fall rate

Stability

It's all very well to land smoothly under your parachute. But arriving stabilized is better!
The stability of a rescue parachute is defined by the pendulum amplitude of the oscillations the pilot will experience when suspended below, once the canopy is collapsed and no longer creating disturbances. The lower the oscillation amplitude, the more stable the parachute. And vice versa...

This parameter is very difficult to quantify, and many external factors can degrade this behavior in a given situation (canopy re-inflating, parachute "twisted" with the canopy, etc.). Here, we consider a standard, correct deployment of the parachute.

Generally speaking, square (or similar-shaped) rescue parachutes are much more stable than hemispherical ones. They stabilize much more quickly than hemispherical parachutes (max. 1 or 2 oscillations).
Their construction also makes them much less sensitive to aerological disturbances (turbulence), and enables them to maintain good stability throughout the descent.

Some models can even be used with a lower wing loading, while remaining just as stable (unlike hemisphericals). This can improve sink rate.

Steerability

Your reserve parachute is launched, you lower your canopy into a ball on your knees, you descend gently without wobbling: ... OUF, I'm saved!
But the valley breeze invites itself to the party, and gently (but surely) pushes you towards a power line, a cliff, or some other unpredictable delight...
The vast majority of rescue parachutes available on the market have no system for maneuvering and avoiding a potential obstacle, or for trying to get closer to a more suitable area to land: be it a clearing, or even the trees if necessary. Once under the canopy, there's nothing you can do about it...
Some models (few in number...) feature a system of handles that allow you to move the canopy to give the parachute direction. This is not a "brake" system like on your paraglider, but simply the possibility of deforming the canopy to make it change course. You then have the option of avoiding the obstacle, aiming for an open area, or simply facing into the wind to slow down the landing.
While it's unlikely that you'll ever have to pull your reserve in your flying life, it's easy to see how having this option can be very useful at a crucial moment.

Other parameters

Your type of practice may also require you to compare other parameters, such as weight, volume, folding method, ...

Indeed, a World Cup competitor won't necessarily need an ultra-light rescue, unlike the Hike&Fly pilot. The acrobat who uses his parachute more than once (!) will prefer an airship to ensure the landing and avoid injury, while the site pilot can leave it to a professional, ideally twice a year.

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Conclusion

In our opinion, fall rate and stability are the 2 most important parameters to take into account when searching. The ability to steer comes in third, but can represent quite an advantage over the others. All the other factors can be used to refine your search, but for safety reasons they must not take precedence over the first 2.

ATTENTION:
Reducing the wing loading (by taking a larger size) will theoretically result in a lower sink rate, but it may also degrade stability (especially on hemisphericals) and make the assembly much more sensitive to turbulence. This reduction in stability may also result in a less attractive sink rate, which is exactly the opposite of the desired effect. This reduction in stability may also result in a less attractive sink rate, which is the exact opposite of the desired effect.
To shave off a few hundred grams, it may also be tempting to choose a smaller parachute size (with the consequence of increasing the wing loading): in this case, the 2 disadvantages are added up: increased sink rate and increased oscillations (increased instability), resulting in a much more violent (too?) landing for the human body!

If you have any doubts about your ability to bring the canopy back into the flight envelope, use of the parachute should be preferred to the more random "that'll do!"
We recommend that you seek professional advice, and carefully analyze the characteristics of the various models on the market.