Here is a video of a premature main parachute deployment on the step of a Cessna 182, first at full speed then at slow mo. The video camera was on the helmet of the first jumper who climbed out. The deployment happened to the second jumper as he climbed out. There are lots of takeaways.
The second jumper sits with his rig against the instrument panel (often called the “student position”). As he pivots and puts his feet on the step, you can see that his yellow pilot chute is on the floor of the airplane, just to his left. Unknowingly, he continues to climb out onto the step, at which point his pilot chute is whipped out the door and begins the deployment. The first jumper sees the deployment and acts by trying to alert the jumper and get him to let go of the strut, but the deployment happens too quickly for any meaningful reaction. Note that the pilot chute goes over the tail of the airplane, but the deployment bag first strikes the tail then goes under it. The parachute quickly inflates beneath and behind the tail and pulls the jumper under the tail. The jumper looked up to find a good canopy. There was no damage to the airplane. Had the deployment bag gone over the tail, we would be seeing a video involving personal injury and aircraft damage.
The jumper checked his pilot chute before he pivoted in the door. The third jumper in back of the plane saw the pilot chute and was yelling at the second jumper, but the visor of his full-face helmet was already closed, and no one heard him. The pilot appears not to have even noticed that it happened.
Takeaways. Jumpers should always check their handles prior to and after maneuvering in the airplane before climbing out. After opening the door, the jump pilot should constantly look toward the door and the jumpers in the door and be ready to contain any parachute component (a loose pilot chute or deployment bag) and restrain the jumper from climbing out. Other jumpers in the plane should do the exact same thing. Anyone who sees a pilot chute or deployment bag should immediately yell "chute out!" If the pilot observes an inadvertent deployment out the door or on the step, he should immediately and forcefully push right rudder to yaw the airplane to the right and swing the tail to the
left and out of the way.
Flying jumpers is just about the most fun way to log time and get paid doing it. But once the jump door is open, it is serious business, and the pilot must be extra-vigilant and ready to react to any inadvertent deployment.