A multirotor flight is very critical: if it happens an ESC, motor, propeller, RX failure or even if you get a lot of vibrations in the flight controller, the multirotor will crash. That's why I created a parachute and attached it to the quadcopter. This was the first test I've done with a parachute for quadcopter:
It had a stick so it kept the parachute away from the propellers. The problem is that the CG is difficult to keep in the center of the quadcopter and also because if the quadcopter hits the stick on the ground when it lands it's going to break the stick.
Therefore, I positioned the parachute on the back of the quadcopter without a stick. I've done a "wind tunnel" test (lol ;D) to check if the parachute would open:
As you can see, it seems to work, so I tried it in field:
Although it didn't land well, nothing was broken because the quadcopter arms are foldable and the ground was soft (grass).
The parachute is activated with a receiver channel and a servo. So when I get in trouble I press a button in my transmitter and it will release the parachute.
Currently i'm projecting a parachute launcher with springs, so it will be launch vertically and thus it will open faster. Another option would be using a small rocket/gunpowder to pull the parachute, but i'm still thinking on the positioning to avoid unwanted burn to the parachute and the multirotor