You nailed the countdown theme with this one. I really like the self-aware humor, like “my face was experiencing a strange reorganisation by the wind.” The tension really ramps up when the parachute fails to come out.
The technical terms are interesting, but to be honest, something which the reader will probably skim over. It’s hard to know what those values mean, but if you can put the speeds in context (say, x times the speed of a cheetah, for example), it makes it more relatable to the reader.
Also, reading this felt somewhat more like reading someone’s journal than reading a story. It has the countdown theme, it has a climactic occurrence, but there is no decision on the part of the main character, no choice he has to make to reach the climax. It all seems to happen to him, in a way. If, for instance, something had happened to the instructor and he was left in charge of pulling the parachute, this would force the character to act, which is what makes for a strong story.
You have a lovely writing style, and I hope you keep writing!
This is a well-written story, with all the factual elements added giving it more sense of realism. As the MC prepares to jump, then does so, the protagonist’s doubts and fears are well-shown. The views and experience of free-falling also described well the situation.
What I think lacked for me is perhaps a sense of danger in the story. There is no indication until the end that something could go wrong. Perhaps if a hint was given early in the story, I would be mentalized that this wonderful experience could go terribly wrong.
While the technical information gave the story credibility, I think it might have been better to keep it to a minimum, and use the available word count to emphasize more the potential dangers.
The ending did indeed almost end in tragedy, but there wasn’t too much sense that the protagonist’s life was in danger, or great panic from him.
By enhancing that sense of urgency or panic, a good story can be so much better. Good luck