Piper Aircraft has unveiled the Seminole DX, a diesel-powered upgrade to its PA-44 twin, fitted with DeltaHawk’s 180-horsepower DHK4A180 engine. Certification testing begins in November 2025, with deliveries expected in late 2026 or early 2027.

The aircraft was created from a collaboration between Piper and DeltaHawk initiated in 2024. Reservations for production slots opened at EAA AirVenture Oshkosh in July 2025. The new engine offers 40% better fuel efficiency than avgas engines and is compatible with JET A and JET A-1. SAF approval is under review.

Piper will use a company-owned STC to fit DeltaHawk’s firewall-forward kits on the production line. These include counter-rotating engines, three-blade full-feathering propellers and a liquid-cooled climate control system.

“The market has been heard, loud and clear regarding the need for a reliable, cost-effective, heavy fuel, multi-engine training platform,” says Piper Aircraft’s president and CEO John Calcagno. “The new Seminole DX fills that market void perfectly.”

A 20-year Long Term Supply Agreement makes DeltaHawk the exclusive supplier of heavy fuel piston engines for the model.

DeltaHawk CEO Christopher Ruud says: “The installation of our certified DHK engine in the legendary Piper Seminole is a perfect match… creating environmental sustainability for general aviation worldwide.”

The DX variant offers preliminary performance improvements of 35% in fuel burn, 32% in single-engine climb rate and 70% in single-engine ceiling. Piper and DeltaHawk are also exploring future engine integrations for the PA-28 Archer and PA-46 M-Class aircraft.