The Discovery Channel robbed a 15-year-old girl of her father ... when he perished in a helicopter crash while filming a reality show for the network -- this according to a new lawsuit.
Sonya Joubert -- the mother of 15-year-old Sofia Donatelli -- just sued Discovery on her daughter's behalf ... claiming the 2013 chopper accident that killed 45-year-old Michael Donatelli was the result of Discovery's shocking lapse of judgment for allowing a very dangerous flight plan.
Michael Donatelli -- a Special Forces veteran -- was a passenger in the helicopter when it inexplicably crashed just north of L.A. a year ago.
He was starring in an unnamed military-themed reality project for Discovery at the time. The helicopter pilot and a cameraman were also killed in the crash. The show never made it to air.
Aside from the flight plan ... the suit claims Discovery allowed the chopper to fly at low altitudes, over hilly terrain, with low light, poor visibility, and in frost conditions. The lawsuit also claims Discovery should have known the pilot was "unfit" to operate the helicopter.
We've reached out to Discovery, so far no word back.