In July 2025, Piper Aircraft, Inc. announced the new Piper Seminole DX. A diesel-powered PA-44 Seminole featuring DeltaHawk’s FAA-certified, DHK4A180 180-horsepower, heavy fuel, compression ignition engine. The Seminole DX was born from a successful collaboration between Piper and DeltaHawk announced in early 2024.
The liquid-cooled, 180HP turbo-charged DeltaHawk engine produces turbine performance at 40% better fuel efficiency versus reciprocating avgas engines, while also achieving a significant reduction in cost of ownership due to fewer moving parts. The engine is approved for JET A and JET A-1 fuels, with Sustainable Aviation Fuel (SAF) approval pending. Piper will use a Piper-owned STC to integrate DeltaHawk’s firewall-forward kits into the Seminole production line. The kit includes counter-rotating DeltaHawk engines and three-blade, full-feather propellers. Additionally, the aircraft will have an advanced cabin temperature control system utilising the engine’s liquid cooling to ensure a comfortable flight experience in diverse conditions.
“The market has been heard, loud and clear, regarding the need for a reliable, cost-effective, heavy fuel, multi-engine training platform,” said John Calcagno, President and CEO of Piper Aircraft, Inc. “The new Seminole DX fills that market void perfectly. Based on interest received since our MOU announcement last year, we anticipate global market demand for the Seminole DX to be between 25 to 40 aircraft per year over the next 10 years. The DeltaHawk team has been a pleasure to work with over the past 16 months as they epitomise quality and customer focus. Future collaborations are in process as well.”
A 20-year Long Term Supply Agreement (LTSA) designates DeltaHawk as the exclusive heavy fuel, piston engine supplier for the Piper Seminole. Certification flight testing begins in November 2025, with FAA certification expected in Q3 2026, followed by certifications from Transport Canada, EASA, and India’s DGCA. Deliveries of the 2027 model year Seminole DX aircraft are anticipated to begin in late 2026 or early 2027.
“The installation of our certified DHK engine in the legendary Piper Seminole is a perfect match with our industry-unique features to provide the lowest cost of ownership and the simplest and safest multi-engine training platform ever,” said Christopher Ruud, Chief Executive Officer of DeltaHawk Engines. “Just as important, we see this new 20-year agreement not just in terms of engines, but also as a wonderful step by Piper, utilising DeltaHawk’s powerful innovation, while creating environmental sustainability for general aviation worldwide.”
The Seminole DX offers significant performance enhancements* over the current PA-44 Seminole, including a 35% reduction in fuel burn, a 32% increase in single-engine climb rate, and a 70% higher single-engine absolute ceiling.
* Note: Performance metrics are preliminary and subject to final certification testing.
Piper and DeltaHawk are exploring further engine applications for both the PA-28 Archer and PA-46 M-Class platforms, strengthening their partnership for future innovations.
