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EPS diesel passes testsEPS diesel passes tests

Graflight 8 engine demonstrated for U.S. Air Force

A Wisconsin company developing an eight-cylinder aviation diesel engine from the ground up has demonstrated to the U.S. Air Force that the Engineered Propulsion Systems Graflight 8 can handle a variety of propellers and missions.
The Graflight 8 is undergoing testing for FAA certification, and recently passed a vibration test demonstration for the U.S. Air Force. Photo courtesy of EPS.

Engineered Propulsion Systems was founded by automotive engine designers who saw opportunity in an aviation market where diesel engines were adapted from automotive engines.

“It was ludicrous,” EPS CEO Michael Fuchs states on the company website, describing the practice of modifying engines made for cars and trucks for use in airplanes. Fuchs, who founded the company in 2006 with EPS Vice President Steven Weinzierl, designed their aeronautical engine around a block made of compacted graphite iron, a material which allows the engine to produce more power at a given weight. It is a material that Fuchs had experience with in automotive engines. Patents were secured, prototypes built, and in 2014 Dick Rutan, following a test flight in a Cirrus SR22, declared it “a new paradigm in aviation propulsion.”

The company has been testing and modifying since, and hopes to achieve FAA certification of the engine for use in general aviation aircraft this year

The U.S. Air Force also has taken an interest, awarded a development contract, and the company announced June 29 that ground tests to measure propeller vibration with a variety of Hartzell propellers demonstrated the engine is capable of running both aluminum and composite propellers in various configurations without need for additional vibration dampening. No other aviation diesel engine, the company states, has passed vibration tests for such a wide variety of propellers.

“The benefits of a clean sheet design and the new technologies incorporated in the Graflight 8 have substantially advanced diesel compatibility with all forms of high horsepower propellers,” Fuchs said in a news release. “We are pleased to have satisfied this part of our Air Force contract award and look forward to continued success with the program.”

The Air Force is probably eyeing the fuel-efficient, FADEC-controlled engine for use in unmanned aircraft, though that has not been spelled out in so many words. Recent tests coordinated with Hartzell Propeller Inc. were reported on by a drone publication, and the tests were similar to those conducted for the Air Force and announced more recently in that multiple propellers were tested in configurations up to and above 350 horsepower. The engine can potentially exceed 400 horsepower, and do so with high fuel efficiency. Like other modern engines, software can be modified to produce a range of power output levels.

The company is eyeing a broad swath of the aviation market, manned as well as unmanned, and hopes to achieve FAA certification of the engine this year. A pre-production version of the Graflight 8 performed well in ground testing, the company announced in February. The V-8 configuration flown by Rutan in 2014 has become a “flat vee” 8, with the steel cylinders housed in more horizontally opposed banks of four than the previous designs.

Jim Moore

Jim Moore

Editor-Web Jim Moore joined AOPA in 2011 and is an instrument-rated private pilot, as well as a certificated remote pilot, who enjoys competition aerobatics and flying drones.
Topics: Technology, Power and Fuel

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