I jumped back in 1978 before tandem jumping. They had a tether connected between the parachute and plane's strut. When I'd dropped enough the tether opened the chute. We trained for 3 hours on how to jump, learning to check the chute so, if it didn't properly open, we could open the reserve chute.
Well...I must have passed out. The opening of the main chute brought me to conciousness but I never checked it to make sure it was opened properly. It was quite an experience. One of our group broke his leg on landing.
We were ready to do it again the next week but it was too windy for newbies so we planned to do it again in the spring. By then, I'd had enough time to think about it and never did it again. I'm glad I did it but I must have been crazy.