This is a mechanism in place to launch the X8, when its weight is 5.3 kg. his recovery is done by parachute. http://diydrones.com/profiles/blog/list?user=15tihx7n8mzza
the mechanism is very reliable for heavy winged lanzameinto. unfortunately my x8 fell into a bad spin maneuver and crashed, and I could not keep doing pruenbas with APM.