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 collect data for certification.
“From Piper’s perspective, we were thrilled to see the prototype complete its maiden flight on July 2 and to have it here on display at EAA,” Piper President and Chief Executive Officer John Calcagno said during a press conference at AirVenture on July 20.
The aircraft completed four traffic-pattern circuits during its first flight, according to Calcagno. Preliminary data showed a climb rate of about 1,700 feet per minute and fuel consumption roughly 35% lower than the standard avgas-powered Seminole, he said.
Piper estimates that fuel costs on a 700-nautical-mile mission could fall dramatically compared with the avgas-burning Seminole.
“On a 700-nautical-mile mission, it translates into the estimated trip fuel cost dropping from about $670 to around $320, cutting the fuel cost of a training flight by more than half,” Calcagno said.
Piper’s published preliminary figures show the Seminole DX burning 15.1 gallons per hour at 75% power and 6,000 feet, compared with 23.3 gallons per hour for the avgas-burning Seminole. The manufacturer also projects a 32% improvement in single-engine climb performance and a 70% increase in single-engine absolute ceiling.
Piper introduced the Seminole DX at AirVenture 2025 and said at the time that certification was expected during the third quarter of 2026. Deliveries of 2027-model-year aircraft were expected to begin in late 2026 or early 2027.
The manufacturer has said the Jet-A-powered aircraft is drawing inquiries from flight schools in markets where avgas is expensive or difficult to obtain.
“Interest in the Seminole DX has been very good since its announcement at last year’s AirVenture,” Calcagno said. “Inquiries have been especially strong in the European and Asia-Pacific flight training markets.”
Skyborne Airline Academy placed the first US order for the Seminole DX in September 2025, signing for five aircraft for its training operation in Vero Beach, Florida.
Based in Racine, Wisconsin, DeltaHawk manufactures FAA-certified Jet A compression-ignition piston engines. Its current certified four-cylinder DHK engine family produces between 180 and 235 horsepower for general aviation aircraft, while the company is also developing smaller two-cylinder engines aimed at light trainers, unmanned aircraft and military applications. DeltaHawk says its engine architecture is also being adapted for hybrid-electric propulsion systems.
Piper also announced at Oshkosh a fleet agreement with ATP Flight School covering a firm order for six aircraft and options for 25 more in 2027.
The firm order includes three Archer TX aircraft scheduled for delivery within 30 days and three conventional Seminoles due in 2027. ATP uses the Archer for single-engine instruction and the Seminole for multi-engine training across more than 85 training centers.
Piper separately announced plans to build a new factory service center at its headquarters in Vero Beach.
The facility will include more than 33,000 square feet of indoor space and 11,000 square feet of outdoor service area on two floors, with seven indoor aircraft bays and four outdoor bays. It will support customers across the eastern United States, the Caribbean, Mexico and Central America.
Construction is scheduled to begin later in 2026, with the center expected to open during the fourth quarter of 2027.