Hi, guys.
I have done two jumps on low altitude in 1997.
First (training) one was at 180 m., second one - at 130 m. (at least for first parachutist in onboard team). Although speed of craft was about 160 km/h. Mi-8 helicopter. Flight info from pilot.
Д-1-5у chute.
Time from exit to landing was something like 12-13 sec. Attention: Even with blank gunfire in the air toward enemies on the ground
It was on some kind of military show. Toy battle and maneuvres for generals.
I would repeat.