In this 2nd brace position, should your head lean against the seat in front? Air Crash Investigation: M1 Plane Crash (S14E01) motivated this question, the relevant timestamps for which I greened. Neither the audio or picture below (in which the hands are hiding the front of the head) explicitly resolves: For maximal safety, in the 2nd suggested brace position (on the right, timestamped at 42.10), should the head touch or rest on the seat in front?
I know nothing of physics or aerodynamics, so please explain in as simple English as possible. The original video appears too dark, so I did enhance the originals (using Gamma Correction):
The head should be against the seat in front of you. The reason is that if the plane crashes, your head and upper body will be thrown forwards until they hit something. If you're in a normal sitting position, your head will be moving pretty quickly by the time it smashes into the seat in front of you, leading to serious injury or death. Moreover, as your torso and head are moving forwards in an uncontrolled way, you can get injured by your head essentially flopping around. Since your head is going to end up against the seat in front of you anyway, putting it against that seat before the crash means it doesn't smash into it during the crash, and that it's not flopping around on its way to the seat.