Even though GE Aviation introduced America’s first turboprop engines in the early 1940s, rival Pratt & Whitney (P&W) has dominated the turboprop engine sector for small propeller-driven airplanes for decades.
Introduced in 1964, the PT6 turboprop engine from P&W Canada made initial strides with Beechcraft’s line of popular King Air turboprop aircraft, and never looked back. P&W delivered more than 50,000 PT6 engines for more than 130 aircraft models over six decades.
However, the competitive landscape is undergoing dramatic change. A new gunslinger is riding into town. In 2015, after months of secret negotiations, GE Aviation unveiled it would power a plane by Cessna, the largest business and general aviation aircraft builder in the world. The “Advanced Turboprop Engine” – now called GE’s Catalyst, was introduced as the first clean-sheet turboprop engine to hit the general aviation market in more than 30 years.
For GE Aviation’s Brad Mottier, who helped establish GE’s business and general aviation division and integrated systems business in 2008, creating a strong competitor to the entrenched PT6 has been a long journey. Step one in the process dates back more than a decade when GE established its H Series turboprop headquarters in Prague, Czech Republic. This helped to build GE’s turboprop experience in general aviation across the global GE Aviation network.
GE Aviation acquired Walter Engines, a producer of the small M601 turboprop, the previous year. At the time, Walter had seen better days. Of the 37,000 M601s delivered since 1975, only about 1,500 were still flying. The company overhauled M601s, but delivered fewer than ten new engines each year from its weathered, World War II-vintage factory in Prague.
Everything changed with GE’s acquisition. As part of the agreement, GE established a new factory and introduced an improved M601 derivative infused with GE technology from its commercial portfolio. The H Series turboprop, with three variants ranging in horsepower from 750 HP to 850 HP, incorporated new advanced materials, and a blisk design in the compressor to significantly improve fuel burn, power and durability. The H Series turboprop won numerous business, utility and agricultural applications, including the Thrush 510G, the Let 410 NG and the Nextant G90XT.
GE’s Czech operation created a global support network as the GE turboprop engine family expanded. H Series variants were certified through the European Aviation Safety Agency (EASA), an important strategic move for GE Aviation.
However, GE needed a far greater technology disruption to challenge PT6 preeminence. The Catalyst presented the industry not only with a major advance in turboprop technology but a control system that makes flying small prop-driven airplanes easier than ever before.
Eight years ago, the GE team engaged airplane manufacturers and individual operators to be sure a serious appetite existed for a new, clean-sheet turboprop in the 1,000 to 1,600 horsepower class for both current and future airplane models.
“At first, no one took our program seriously, but, by 2014, people were clearly excited,” Mottier said. “Cessna kept pushing us to advance the technology, and that gave us all the encouragement we needed. After all, if we didn’t bring something really different and better to the table, why would airframers ever change to the GE engine?”
Finally, Textron (Cessna parent company) initiated an engine competition for its new Cessna Denali airplane and selected the Catalyst turboprop engine. While four iterations of the Catalyst were designed and evaluated, GE concurrently introduced the Electronic Engine and Propeller Control (EEPC) system for its H Series engine. Most turboprop aircraft have multiple levers the pilot must adjust that control engine and propeller power, pitch and torque. The EEPC system simplifies all of this into a single-lever control. The EEPC became a proving ground for the Catalyst system.
The Catalyst governs engine and propeller pitch with an upgraded full authority digital engine control (FADEC) – technology featured on GE’s larger commercial engines. Like the EEPC, the FADEC allows single-lever control to simplify the pilot’s job. The FADEC provides optimum engine efficiency for any given flight condition while keeping the engine within its limits. Even further, the Catalyst’s fully integrated digital control system collects performance data during each flight and can determine what environment the Catalyst is flying in, the health of the engine during the flight, as well as the health of the controls and accessories.
The Catalyst design has drawn upon GE’s broad technology portfolio. By incorporating 3D aerodynamic design from the GE9X program, the Catalyst has double the pressure ratio of other turboprops in its class, which creates far greater fuel efficiency and power. The titanium compressor, with four axial-flow stages and one centrifugal impeller stage (from the T700 turboshaft engine) feeds air into a reverse flow single-annular combustor. The two-stage HPT blades are made with single-crystal material.
In another sweeping change for GE, the Catalyst is the company’s first all-new “European engine,” incorporating components designed at Avio Aero sites in Italy and Poland, as well as from GE Aviation’s engineering team in Poland. In addition, component and engine design, testing, and final assembly are all performed at the GE Czech complex in Prague.
The Catalyst also has more components designed and produced using the additive manufacturing than any previous aviation engine, comprising more than 25 percent of the overall engine. The additive parts reduce engine weight by five percent and improve SFC.
GE realized that such a technology advance in additive manufacturing requires a significant demonstrator program in advance. In just 18 months, GE secretly assembled and tested a CT7 demonstrator engine with 35 percent of the engine content produced through additive manufacturing.
The CT7 reflects GE’s long history with turboprop engines. The journey began during World War II when GE’s Steam Turbine division in Schenectady proposed the TG-100 turboprop engine later designated the T31, to the US National Advisory Committee for Aeronautics. In 1945, the engine successfully powered the unusual Consolidated Vultee XP-81. It was the first American turboprop engine to propel an aircraft. In addition to a turboprop in the aircraft’s nose, the XP-81 incorporated a J33 GE turbojet in the fuselage.
In 1979, GE’s team in Lynn, Massachusetts, introduced a commercial turboprop engine, the CT7, based on its highly popular T700 turboshaft engine. A year later, Saab Aircraft selected the CT7 for its Saab 340 regional aircraft. The Saab 340 entered service in 1984 and became a highly successful franchise. By the early 1990s, the CT7 powered more than 300 turboprop airplanes, including the Saab 340 and the CASA CN-235 aircraft.
With the Catalyst, GE is aggressively pursuing small aircraft, and progress on the engine briskly continues. In April, the Catalyst ran at full power at the Czech Technical University in Prague. The engine and propeller exercised the pitch system using a FADEC with integrated propeller control.
“This engine is modernizing the cockpit and flight controls like no other engine has done in this marketplace,” says Mottier.