A still from video footage shows a Russian helicopter in the sky above the Black Sea.Main Directorate of Intelligence of the Ministry of Defense of Ukraine/Screengrab via TelegramUkraine's naval drones fired missiles at — and hit — three Russian helicopters earlier this week.The first-of-its-kind combat engagement occurred off the coast of Crimea.It's the latest achievement for Kyiv's naval drones, which have been modified to carry missiles.Ukrainian naval drones armed with heat-seeking missiles shot down two Russian helicopters and damaged a third above the Black Sea earlier this week, Kyiv said on Thursday.The unusual combat engagement marked the first known instance of a naval drone firing on and striking an aircraft.