Small engines may spawn a new class of turboprops

 - October 4, 2006, 5:07 AM

The so-called “father of very light jets,” Eclipse CEO and president Vern Raburn, knows this new class of small jets wouldn’t even be possible without suitable engines from Pratt & Whitney Canada, Williams International and GE-Honda Aerospace. Simply, these lighter, more efficient, lower-output turbofans have opened the door to new possibilities for jet aircraft designers.

History could soon be repeated, except this time it’s the turboprop market that could see a new class of smaller aircraft–very light turboprops, if you will–thanks to the efforts of a fledgling company called Innodyn. The Osceola Mills, Pa.-based company is developing lightweight, fuel-efficient, low-cost 200- to 300-shp turboprop engines, as well as a 500-shp “TwinPack.”

Innodyn was founded in 1997 as Affordable Turbine Power by Chuck and Charlie Nearhoof, the company’s president and vice president, respectively. Last year, after securing financing to start engine production, it changed its name to Innodyn.

The brothers–both experimental aircraft enthusiasts and pilots–have considerable experience in many aspects of manufacturing and assembly, having spent the last 30 years working on an array of manufactured products and manufacturing processes through their successful machining business, Nearhoof Industries. Together, they have designed the mechanical and gearing systems for the Innodyn turbines, in addition to a patented digital fuel-control system that is perhaps the most important part of the engine.

But the brothers are hardly alone in their endeavor. Kevin Pearce, Innodyn’s director of engineering, has been instrumental in the development of the fuel-control system and, along with the Nearhoofs, is named on the patent. Chief technical consultant Dr. Boris Glezer, who contributed to several improvements in fluid machinery during the past 35 years, heads the company’s new product development and technical risk assessment.

Penn State University aerospace engineering professor Dr. Cengiz Camci, a leader in the field of turbine aero-thermal development, is a “key member” of Innodyn’s R&D team. Penn State is listed as one of the company’s “partners.”

Unique Systems

According to CEO Gregory Grose, the patented fuel-control/ management system is what makes Innodyn’s turbines so efficient and eliminates the throttle-to-power lag time associated with turbine engines. Basically, there are two key parts of this system–the fuel-monitoring computer and fuel-delivery components.

The system’s computer monitors fuel consumption five times per rotation, which at first glance seems simple. However, Innodyn’s turbines spin at 60,000 rpm, meaning the computer must process 300,000 readings per minute (or 5,000 per second). Using these precise readings, the computer constantly adjusts the fuel/air mixture to an optimal setting.

Carrying out the commands from the computer is the fuel-delivery system, composed of an “innovative” fuel nozzle and a “pulse width modulation” fuel pump, which Grose said pulsates 42 times a second. Working in tandem they create small fuel pellets that burn completely–at 360 degrees–when ignited.

“This means the fuel burns cleaner, faster and more efficiently,” Grose noted. “We also believe that emissions are reduced, which will soon be verified by independent testing.” Innodyn’s flight data shows that the small turboprops consume approximately seven gallons of jet-A per 100 shp per hour.

Grose said the fuel-control system could be applied to any turbine engine. As such, Innodyn is considering licensing the technology to other engine manufacturers for their powerplants.

As for the engine itself, Grose told AIN that each of Innodyn’s light turboprops has only 13 parts, the majority of which are gears. The only moving part is the shaft. (The company’s engines are single-shaft turbine designs.) A prototype 255-shp engine has been flying aboard an RV-4 experimental airplane for “several years.”

Building on this work, Innodyn has developed the 500-shp TwinPack, which combines two of its 250-shp turbines through a common gearbox. The two-engines-in-one powerplant is estimated to consume about 35 gph at full power, about the same as 500-shp versions of the venerable Pratt & Whitney Canada PT6A. Testing of a prototype TwinPack is scheduled to start later this year, according to Grose.

The TwinPack weighs in at about 330 pounds, which is slightly heavier than a 500-shp PT6A at 286 pounds. However, the Innodyn engine is more compact, with dimensions of 29 inches long, 24 inches wide and 14 inches high. The PT6A is only 19 inches wide but 62 inches long, requiring a much longer engine compartment. This can especially be a problem when re-engining aircraft with the P&WC engine.

Grose said the TwinPack, which made its public debut at EAA AirVenture in Oshkosh, Wis., last month, would be a suitable replacement for a six-cylinder piston engine. Besides the redundancy benefits, he added that–in some applications–both engines could be used for climb, and when cruise is achieved one side could be shut down for added fuel efficiency.

Production Plans

Innodyn recently finished building 10 production engines and is currently evaluating them to ensure they meet stated performance specifications. Following the successful conclusion of these tests, the company plans to begin shipping light turboprop engines later this year for use in experimental aircraft. Prices range from $26,000 for a 165-shp engine to $34,500 for a 255-shp powerplant.

The 500-shp TwinPack could enter the market later next year, if scheduled engine tests start by year-end and progress as expected. The company has not yet set a price for the TwinPack powerplant.

Grose said Innodyn has plans to certify the engines, and it is seeking a strategic partner with experience in FAA certification to under- take the process. There is incentive to have FAA-certified powerplants, he said, since several established aircraft manufacturers have expressed strong interest in the small powerplants.

“Things at Innodyn are progressing fast–we will be making several important announcements in the coming months,” concluded Grose.