DeltaHawk-Powered Seminole DX Begins Flight Testing

DeltaHawk Engines said this week that the Piper Seminole DX has entered active flight testing following its first flight earlier this month. The development aircraft uses two 180-horsepower DeltaHawk compression-ignition engines that operate on Jet-A.

Initial Test Results

The first flight went for about 30 minutes and took place in 91-degree temperatures at 88% humidity. DeltaHawk said it calculated the density altitude at approximately 3,500 feet and said the aircraft had an initial climb rate between 1,700 and 1,750 feet per minute. The company said both engines operated normally and maintained adequate cooling margins.

The aircraft uses counter-rotating engines connected to three-blade propellers that operate at approximately 2,400 rpm. DeltaHawk reported stable power delivery and satisfactory operation of the propellers and governors during the initial flight. Subsequent flights have focused on handling qualities, cooling performance, engine operation and systems integration.

Certification Program

DeltaHawk is collecting performance and reliability data for a supplemental type certificate that will cover installation of its engines in the PA-44. The company said the test program will continue expanding the aircraft’s flight envelope. The Seminole DX is scheduled to appear at EAA AirVenture Oshkosh, which begins Monday.

Piper and DeltaHawk announced the Seminole DX at AirVenture 2025 as an alternative powerplant configuration for multiengine training operators. DeltaHawk says preliminary data indicates cruise fuel consumption may be approximately 35% lower than a conventional Seminole, although the figure remains subject to confirmation during flight testing.