sentences:  It was subsequently fitted with a laminar flow wing and attained 793 km/h (428 kn, 493 mph) at 4,350 m (14,270 ft) with the motorjet functioning.On 15 June 1945, the Klimov VK-107A piston engine was damaged beyond repair in flight.Following acquisition of another VK-107A, flight testing continued until 18 October when the engine reached the end of its service life.