Piper Aircraft is displaying the first flying prototype of its DeltaHawk-powered Seminole DX at EAA AirVenture Oshkosh 2026, less than three weeks after the diesel twin made its first flight. The development aircraft is powered by two FAA-certified DeltaHawk DHK4A180 engines, each producing 180 horsepower and burning Jet A or Jet A-1. DeltaHawk said the aircraft is now undergoing flight testing as the companies expand the flight envelope and co…