SMA SR305-230
| Industry | Aerospace |
|---|---|
| Products | Aircraft diesel engines |
The SMA SR305-230 represents a horizontally opposed, four-cylinder, air/oil-cooled diesel piston engine with a four-stroke cycle, delivering . Produced by SMA Engines, this model stands as the firm's only offering and is available as a retrofit package for the Cessna 182 aircraft.
Design
Equipped with turbocharging and direct fuel injection, the SMA SR 305-230-1 employs an electronic CPU to continuously regulate the fuel-to-air ratio. Should the CPU malfunction, a mechanical fallback system enables the pilot to manually manage fuel delivery and safely complete the flight.
At full throttle near sea level, it achieves manifold pressure, which it can sustain up to . Unlike many aero engines that restrict maximum power output to brief takeoff durations, this engine supports continuous full-power operation. Typical cruise settings operate at , while an economical cruise mode utilizes manifold pressure.
The STC conversion for the Cessna 182 includes a modified cowling designed to accommodate the engine and enhance cooling airflow. Cooling is divided between direct airflow over approximately one-third of the cylinder surfaces and oil cooling through heat exchangers mounted on the sides. The oil circulation system targets high-temperature areas within cylinder heads and barrels, transferring heat efficiently to the oil coolers.
By early 2008, SMA had supplied over 50 conversion kits mainly across European markets, with fewer installations in North America—generally completed by independent installers.
Cost savings from the conversion become apparent when avgas prices surpass those of jet fuel; at cruise, the diesel engine consumes roughly 10 gallons (38 liters) per hour compared to 13.5 gallons (51 liters) consumed by the original gasoline powerplant.
In 2014, SMA aimed to deliver 90 units and was advancing development on a six-cylinder SR460 model producing between .
Applications
- SMA SR305-230: Cessna 182 (STC conversion)
- SMA SR305-260E: Diamond DA50
- SMA SR305-230: ATLS GS-301 Batoor
In July 2012, Cessna revealed plans to offer the Cessna 182 equipped with this engine as an official factory option, targeting deliveries in Q2 2013. Initially intended to replace the traditional avgas engine entirely, this approach was later discontinued. As of 2023, the Cessna 182 remains available solely with the Lycoming IO-540-AB1A5 gasoline engine.