Un aspect important à vérifier

https://www.faa.gov/aircraft/gen_av/harness_kits/system_accidents/

Shoulder Harnesses

Aircraft Restraint Systems, Survivable Accidents, & Recommendations

Sur un Virus ou Sinus: WARNING! The safety harness must hold you in your seat securely. This is especially important when flying in rough air, as otherwise you may bump into the tubes and/or spars overhead. Make sure you tighten the bottom straps first, then shoulder straps.

The H (lap and shoulder) harness should be fastened all the time. This significantly improves safety.