SMA refines diesel engine

July 11, 2008

Engine manufacturer SMA continues to refine its SR 305-230 aviation diesel engine. Because the European Union is limiting exhaust gas emissions and the EPA has been required to regulate aviation emissions by the Clean Air Act, “avgas will disappear sooner than you think,” said Alain Pierre Deniau, senior vice president of SMA Engines in Grand Prairie, Texas.

SMA believes its vision for an aeronautical piston engine with a low specific fuel consumption, burning Jet A1 fuel—available at most airports around the world—will benefit the environment. In addition, the engine’s slower rotation speed helps to reduce the aircraft’s noise signature.

Improvements to the SR 305-230 include dual turbochargers, with one moved to the side; a new intercooler, improved airflow, and improved engine cooling. The starter, alternator, and air box are new, and the cylinder heads have been upgraded.

The engine’s field experience continues to grow. Currently there are 44 SR 305-230 engines in service; the oldest has been operated 763 hours, Deniau said. A time between overhaul (TBO) validation test is in progress.

SMA continues to work with partners on type certificates and supplemental type certificates to allow additional airframe installations, including the new-generation Cessna 182; Maule M-9; and various Piper aircraft, including the PA-25, PA-28, and PA-34 series. Approvals could be developed for any single- or twin-engine fixed-wing aircraft, from 200 hp to 270 hp, Deniau said.

Mike Collins

Mike Collins | Technical Editor, AOPA

Mike Collins has worked for AOPA’s media network since 1994. He holds a private pilot certificate with an instrument rating.