Critical period emerging for new turboprop developments
Turboprop-engine manufacturers continue to develop technologies in anticipation of future demand for new or derivative regional airliners designed to carry approximately 90 passengers, a step up from contemporary aircraft offering around 70 seats. By January 1, Pratt & Whitney Canada hoped to have completed the first phase of a next-generation regional turboprop (NGRT) demonstration program intended to validate characteristics for a main centrifugal compressor. Meanwhile, U.S. competitor General Electric (GE) continues to look for an airframe launch “platform” for the proposed CPX38, which would benefit from its current work to develop the military GE38 turboshaft engine for the U.S. Marine Corps Sikorsky CH-53K.
While the two companies agree that power levels must depend on design cruise speed and aircraft size, both program studies envision the use of eight blades to address higher noise levels otherwise arising from increased tip speeds of ever larger propellers.
“Demand in the regional-turboprop market will only increase,” according to P&WC marketing vice president Richard Dussault, who suggests that the majority of future regional aircraft deliveries will offer at least 70 seats. With detailed design for the new “centerline” NGRT engine under way, the company claims strong relationships with airframe manufacturers and the regional airlines driving future requirements. NGRT technology “could go up to 8,000 shp,” said Dussault.
The Canadian engine firm began testing compressor elements last year. “We’re pleased to say all testing achieved our targets, according to plan,” P&WC told AIN in early December. By the turn of the year, it expected to have completed the NGRT program’s Phase 1, which validates characteristics such as engine component efficiency and pressure ratio.
Aiming to achieve a 20-percent improvement in fuel consumption per passenger and a 30-percent reduction in engine maintenance costs, P&WC has test-run compressor hardware “to the full range of aerodynamic design points.” The next phase of testing, at a partner facility in Germany, is set to begin before April. “During this testing sequence, we will map the full compressor, optimize the rotor match and assess other aerodynamic characteristics [such as compressor airflow, efficiency and pressure ratio],” said the manufacturer.
As part of its technology-insertion process, P&WC also plans to launch the combustion rig demonstration program this year “to validate emission, durability and temperature profile for the hot section,” thereby gauging the level of performance it can provide.
Overall, the company has established a comprehensive testing program for this year. “The primary goal will be to ensure our engine meets all our targets so [that] we’re ready when an aircraft manufacturer launches,” it said. “We are leveraging the latest technologies from UTC Hamilton Sundstrand to offer a fully integrated propulsion system.”
Production planning, typically involving up to 10 NGRT test engines and flight-tests on P&W’s Boeing 747SP, would follow identification of a launch customer.
Meanwhile, GE has scheduled a number of CPX engine or engine component hardware tests for completion this year, including bird/hail ingestion, inlet icing, oil interruption and initial sand-ingestion tests. It also plans durability and endurance runs, according to GE Aviation small commercial engines marketing manager Mary Hussey. Performance in tests up to early last month exceeded expectations, she added.
Last month Hussey told AIN that in seeking a current or future airframe platform on which to launch the CPX38, GE is “looking at all options.”
Speaking at last September’s European Regions Airline Association assembly, GE regional aviation engine operations general manager Allen Paxson said he expects operators to retire some 900 engines between 2012 and 2031, as the fleet (above 30 seats) expands from 1,400 to 3,100 thanks to higher fuel costs, demand from emerging economies and requirements for replacements.
Paxson noted that the CPX38 will benefit from technology transferred from the larger GEnx turbofan, including “a high-efficiency compressor, high-pressure turbine designs and advanced materials.” The company has not defined necessary power output for possible growth versions of current aircraft, nor would it comment on whether or not a common requirement has emerged based on discussions with airframers. Additional parameters for consideration include climb rate, engine rating structure and propeller diameter.