Your post is missing a lot of details, it also makes very little sense considering your characters physical qualities.
1. He's falling straight down vertically to my understanding, head first, with one second before impact and moving at a fairly high speed, spotting my character moving and moving the javelin from extended like a lance to pulled back and then thrown would be difficult considering your character's body position, he would also have to significantly change his grip on his weapon, unless he's falling in a different fashion to what I inferred.
2. How he touched down is also incredibly confusing, did he fall on his hands or did he twist in mid-air to land on his feet?
3. Also, is he using any sort of magical ability to hit the very specific point of the moving mech he is aiming for? That seems like a difficult shot considering his circumstances.
Actually, I've had another re-read and the problem is in how you described your fall, you didn't really explain how his attack was being launched other than it being a downwards lunge (I assume you mean thrust, lunge is something very different.) If it is a thrust then it would mean your character was falling face down, where-as if he's trying to carry out some sort of falling stab manoeuvre (which would certainly be less insane) then you may need to edit a little to make that clear. It would still be difficult to transition from that position to a javelin throw though.
Also, if you significantly refute my claims, feel free to call in Rilla to decide what he thinks, might as well make him judge and shit.
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