let's say the helicopter is going down at 125 mph (~= 200km/h , close to human terminal velocity because i'm lazy), you would then need to be able to jump with enough strenght to completely couteract that speed,
which means you need to jump at a similar speed.
According to random sources, a height of 15 meters with a starting speed of 0 is a 50/50 chance of dying
surviving probably means being crippled permenantly/ for a long time
15 meters means you hit the ground at around 60 km/h (~=37mph)
Can you imagine doing a jump where you instantly go 140km/h (~=87mph) upwards?