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
- Breakdown of equipment
- ...
All these risks can generally be controlled by adequate training, good equipment (revision), constant vigilance, etc. ...

But in some critical cases, where it is difficult or even impossible to bring your wing back into flying zone, there is a solution: the rescue parachute, which allows you to return to the ground relatively safely ...

The rescue parachute has become an essential part of the modern paraglider's equipment. However, pilots are still not aware of its intrinsic characteristics.
It is not enough to carry a rescue parachute to be safer, because its proper use requires a certain amount of training, and a total involvement from the pilot in case of need.
We will not deal here with its installation and use. We advise you to get in touch with professionals (instructors, SIV instructors) to gather their experience and train you properly with them. You will find a lot of practical information in the FFVL reference document on the rescue parachute (author Pierre-Paul MENEGOZ), which you can download here.

A rescue parachute must be chosen carefully, to best suit each pilot and his or her practice. You may never have to use it, but if that day comes, it is imperative that you can do so without questioning its effectiveness.
We recommend that you do your own analysis by methodically comparing the different models with the help of these few points of reflection.

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 the stability of a model can be directly linked according to certain parameters.

Other parameters can then be taken into consideration, depending on the use you may have:
- Weight
- Volume

The rate of fall

Stability

Arriving gently on the ground under your parachute is good. But arriving in a stable manner is better!
The stability of a rescue parachute is defined by the pendulum amplitude of the oscillations that the pilot will have to undergo when he is suspended below, once the canopy is collapsed and no longer creating disturbances. The lower the amplitude of the oscillations, the more stable the parachute will be. And vice versa ...

This parameter is quite difficult to quantify, and many external elements can degrade this behaviour in real life (canopy re-inflating, parachute "twisted" with the canopy, etc...). We consider here a standard and correct deployment of the parachute.

In general, square (or similar shaped) rescue parachutes are much more stable than hemispherical ones. They stabilize much faster than hemisphericals (1 or 2 oscillations max).
Their construction also makes them much less sensitive to aerological disturbances (turbulence), and allows 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). The sink rate can thus be improved.

Steerability

Your reserve parachute is launched, you lower your canopy by bringing it back in a ball on your knees, you descend gently without oscillations: ... OUF, I am saved!
But the valley breeze invites itself to the party, and pushes you gently (but surely) towards a power line, a cliff, or any other unpredictable delight...
The vast majority of rescue parachutes available on the market do not have any system to maneuver and avoid a potential obstacle or try to get closer to a more favourable area to reach the ground: be it a clearing, or even the trees if necessary Once under the rescue, it is no longer possible to act ...
Some models (few ...) have a system of handles that can act on the canopy to give direction to the parachute. This is not a system of "brakes" as on your paraglider, but simply the possibility of deforming the canopy to make it change course. You can then avoid the obstacle, aim for an open area, or simply face into the wind to slow down the landing.
It is certainly unlikely that you will have to pull your reserve in your life as a pilot, but you can easily understand that having this possibility can be very interesting at the crucial moment.

Other parameters

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

Indeed, a world cup competitor will not necessarily need an ultra-light rescue, unlike the Hike&Fly pilot. The acrobat who multiplies the opportunities to use his parachute (!) will prefer a dirigible rescue to ensure the landing and avoid injury, while the site pilot can let a professional take care of it, ideally twice a year.

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Conclusion

Sink rate and stability are, in our opinion, the 2 major parameters to consider when searching. The ability to steer comes in third but can be quite an advantage over the others. All the other factors can refine your search, but should not take precedence over the first two for safety reasons.

CAUTION :
Reducing the wing loading (by taking a larger size) will theoretically result in a lower sink rate, but may also degrade the stability (especially on the hemisphericals) and make the assembly much more sensitive to turbulence. This decrease in stability may also result in a less interesting sink rate, which is the exact opposite of the desired effect.
To save a few hundred grams, it can also be tempting to choose a smaller parachute size (with the consequence of increasing the wing loading): in this case, the two disadvantages are added together: increased sink rate and increased oscillations (increased instability), with the consequence of a much more violent (too much?) arrival on the ground for the human body!

In case of doubt about the ability to bring the canopy back into the flight envelope, the use of a parachute should obviously 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.