Head protection – a critical element for any activity where the head may impact another object. This protection helps to deflect and absorb the force of the impact, reducing the damage suffered by both skull and brain.
In an attempt to establish a baseline level of protection, a variety of activity specific standards have arisen. Of interest to us are:
EN966 – Airsports (Paragliding/Hang Gliding).
EN1077/ASTM2040 – Snowsports (Skiing/Snowboarding).
While EN966 has been the accepted norm for paragliding helmets, the cost of development/certification/distribution vs. the small size of the target market has resulted in a limited selection of expensive options.
Many pilots have since resorted to using snowboarding helmets certified under ASTM 2040 and/or EN1077. This practice has become widespread enough that the FAI has since allowed ASTM 2040 for paragliding Category 1 competition events.
All three standards share a common test base -> the dropping of a helmet fitted with a headform from a prescribed height onto a flat anvil. The resulting impact acceleration transmitted through the helmet to the headform is measured and confirmed to be below a maximum acceptable value.
Depending on the test standard, additional tests for peak acceleration and even penetration are performed.
|Drop Test Max Acceleration||250g||250g||250g||300g|
|Flat Anvil Drop Test Height||1.5m||1.5m||1.5m||2.0m|
|Hemispherical Drop Test Height||—||—||—||1.2m|
|Edge Drop Test Height||1.5m||—||—||1.0m|
|Penetration Test Height||0.75m (x2)||0.75m||0.375m||—|
For an example of the testing process, below is a video from Icaro2000 testing a helmet against EN966.
Now that we have an understanding of the what and how of testing – lets explore the ‘why’ (what injuries are they trying to prevent)?
Abbreviated Injury Score
The Abbreviated Injury Score (AIS) is a 7 digit code to describe the type, location, and severity of an injury.
A typical AIS code looks like 123456.7.
|AIS Code Digit Index||Description|
|2||Anatomical Structure – Type|
|3||Anatomical Structure – Specific Part 1|
|4||Anatomical Structure – Specific Part 2|
|5||Level – Part 1|
|6||Level – Part 2|
The Severity Score (digit ‘7’) can have the following values:
|Severity Score||Injury Severity||Probability of Death *|
|2||Moderate||1 – 2%|
|3||Serious||3 – 10%|
|4||Severe||11 – 50%|
|5||Critical||51 – 99%|
* The probability of death is a rough guesstimate and heavily dependant on the reporting region (different regions have different time frame criteria before a death is no longer judged related to an incident).
Peak Acceleration vs. Injury
The relationship between peak linear acceleration of a human head striking a flat solid surface and AIS Severity is as follows (from Examination of Brain Injury Thresholds):
|Peak Acceleration||Injury Severity|
|50 – 100g||1|
|100 – 150g||2|
|150 – 200g||3|
|200 – 250g||4|
|250 – 300g||5|
Remember: a pass for a helmet achieving an EN rating is below 250 g and for ASTM is below 300 g.
The reference for the above table noted that the threshold for a mild concussion is around 98 g. Of note – these numbers are for direct strikes to the head. Strikes that result in rotation or strikes to the face/jaw area can greatly increase the risk of concussion.
In fact, a report by one of the founders of the MIPS helmet system states that it is not the linear impact that causes the concussion but instead an end resulting rotation. Something to remember if one has any sort of protrusion from their helmet (camera or ‘aerodynamic features’ ) that may catch during an impact with the ground and introduce a relative rotation between the brain and the helmet/skull.
Keep in mind that none of the above helmet standards test against injury vs. rotation.
Summing it up
Judgement, Skill, Luck – when all 3 of these fail us, the nets of Insurance comes into play. Passive Safety and Health Insurance are the last to try and catch us before the final floor of Life Insurance.
Helmets are part of our Passive Safety net, hopefully never needed yet welcome when they are. But helmets are not without limitation and knowing that limitation reinforces the importance of not falling through to the net of Passive Safety.
Helmets are important, even critical in paragliding, but even more so is the ability to avoid a situation where a helmet is needed in the first place.
Be safe out there.