As older generations of regional turboprop airliners continue in service, new technology solutions are coming on stream to assure additional decades of life even as low fuel costs are deferring regional jet retirements. OEMs and MROs are taking notice, given the numbers.
According to data from CAPA Center for Aviation, a Sydney-headquartered aviation industry intelligence organization, turboprops and regional jets held an equal 14% share of the 27,114 global commercial fleet—for just under 3,800 aircraft each—in 2015. Many turboprops, in fact, are barely at mid-life. One example is the 30-36-seat Saab 340.
Dale Dennis, CT7 turboprop product leader for GE Aviation, reports that the Saab 340 fleet stands at 360 worldwide, including 97 aircraft parked or transitioning between operators. GE sees opportunities with that type through upgrades of the CT7-5A and CT7-9B, which respectively power the Saab 340A and B models. Those upgrades are targeting extended time on wing.
“Within the last three years, we have achieved a 25% increase in on-wing time, with a 30% improvement expected by mid-2018—for both the CT7-5A and -9B,” says Dennis. “Today, we are at on-wing time of 7,000 flight hours and 8,000 cycles. When we reach 30%, it will be 8,000 flight hours, and 9,000 cycles.” The average cycle time of a Saab 340 is 52 min., he adds.
GE is accomplishing this by leveraging the technology incorporated in the newer CT7-8 into the more mature -5A and -9B. Among the enhancements is a new output drive assembly that provides for better lubrication and reduces the chances of an unscheduled maintenance event, while extending individual part lives. Also leveraged from the CT7-8E is a new axis BB integral seal, which, Dennis reports, has reduced gearbox oil leakage. “We have made multiple improvements as the CT7-5A and CT7-9B engines have matured,” he says.
Dennis estimates that the Saab 340 fleet should remain in service for another 30 years, with the Saab 340A continuing to carve a niche as a dedicated freighter and the 340B likely to remain in passenger transport. “At about 36,000 hr., the fleet is at the halfway point of its remaining life,” he explains. “Since its introduction in 1983, the airframe life has been extended from 45,000 to 60,000, and currently, to 80,000 flight hours.”
In another advance in turboprop engines, Pratt & Whitney Canada announced its new PW150C in July 2014, for the 70-seat MA700 regional airliner under development in China by Avic Xian Aircraft Co., and slated for certification in 2019. The newest member of the Pratt & Whitney Canada PW100 family, the PW150C offers some enhancements over the PW150A, reports Fred Lefebvre, the OEM’s vice president for marketing.
“The PW150C’s core is essentially the same as the PW150A, but we have made some adjustments to the compressor section’s aerodynamic profile,” he says. “Along with the latest material technology, in the form of more durable metallic alloys, we have also integrated an additional power turbine stage.”
Both engines are three-spool powerplants incorporating a high- and low-pressure spool, and a power turbine spool. “There are two stages to the power turbine spool in the PW150A,” he adds. “We’ve added a third stage to the PW150C’s power turbine spool, which will improve fuel burn and the engine’s overall operating temperature. This translates into longer component life.”
In addition, he notes, the engine has been designed with a modified reduction gearbox to support the MA700’s larger-diameter propellers and an optimized low-pressure compressor.
“The engine will produce up to a 5% better fuel burn, increased time on wing, and improve operating costs, given its newly designed gearbox and power section,” Lefebvre says.
There also could be some aftermarket benefit for PW150A operators. Some of the PW150C technologies could be retrofitted into the PW150A. “At this point, there is interest in this, but it will be up to our customers to decide,” he says. “The retrofitted modifications would result in increased efficiency and temperature margin for better fuel consumption and reliability.”
Extending the useful lives of turboprops involves more than engines. With the Automatic Dependent Surveillance-Broadcast (ADS-B) “Out” mandate looming in 2020, operators need to bring aircraft into compliance. This often involves modifications to the flight management system’s (FMS) software for compatibility with the FAA NextGen air traffic control system, and other ADS-B Out-equipped aircraft.
“If the aircraft has been built within the past five years, it won’t necessarily require an upgrade for ADS-B Out, but legacy aircraft will,” says Tobin Shackelford, director of special missions at Field Aviation’s Toronto facility, specializing in commercial airliner modification work. “Our focus is on the Dash 8 and Q400, and Bombardier has been very much ahead of the game on preparing for compliance with the NextGen ATC system.” He notes that for some older-production models, the navigation boxes will have to be replaced with new ADS-B Out-compatible equipment, such as a Mode C transponder.
According to Shackelford, Field Aviation was one of the first companies to provide a flight deck modernization program for the Dash 8, which was developed under a Field Aviation supplemental type certificate (STC)and approved by Transport Canada, the FAA and European Aviation Safety Agency in 2013.
“We have replaced the Dash 8’s legacy mechanical cockpit instruments with a Universal EFI-890 four-panel LCD flat display system,” he says. “Over the past three years, we have done five upgrades on Bombardier Dash 8-200 and Dash 8-300 aircraft. We have a backlog of eight at this time.”
Another Field Aviation STC, approved in 2011, was for additional wing-mounted long-range fuel tanks, which increase the fuel capacity of the Dash 8-100 and -300 series by 80%. This, says Shackelford, came about as a result of special-mission modifications the MRO was doing for Dash 8 military and government operators. “Commercial operators, especially the international ones flying over remote areas, have made inquiries. They want the extra fuel.”
Reed Chase, general manager of Empire Aerospace in Hayden, Idaho, reports that for MROs with a turboprop airliner focus, cockpit upgrades represent major opportunities. The company’s FAR Part 145 certificate includes the ATR, Dash 8, and Saab 340 families.
Most upgrade work performed on these older aircraft models, says Chase, involves avionics retrofits. “For example, we are installing a digital, plug-and-play, four flat-panel Esterline 100-604045-002 flight instrument display system which is certified for the ATR series. It replaces the current Honeywell 7003110-912, which is CRT-based,” he explains. “The replacement will be lighter weight and more reliable.”
Empire Aerospace, Chase adds, is also offering an ADS-B Out package for the ATR 42 and ATR 72, under an STC from Garmin.
According to Jessica Koss of Garmin International, the OEM holds an FAA STC for installation of the package, consisting of a dual GTN 725 Wide Area Augmentation System-ADS-B position source on those aircraft, and is in the process of amending the STC to approve installation of dual GTX 3000 Mode S/ADS-B transponders. “That will leverage the GTN 725s as the approved WAAS-ADS-B position source,” she notes. FAA approval of the amended STC is expected in January 2017.
Notable & Quotable
“We expect continued growth in the turboprop MRO market. There are still a lot of turboprops out there, and they are definitely more economical to operate than regional jets,
especially on shorter cycle
—Calvin Tuitt, senior vice president of business development-MRO, C&L Aviation Services
“At the request of their mainline air carrier partners,
regional airlines are upgrading cabins with business-class cabins, seatback displays and inflight connectivity. This is now flowing down from the regional jets to the turboprops, even though most turboprop flights are under an hour.”
—Tobin Shackelford, director of special missions, Field Aviation
“The Saab 340 is probably the best example of a turboprop airliner with many years ahead of it. Most are not even close to their airframe cycle time life limits, and they continue to serve a very special niche, particularly among smaller commuter and regional operators.”
—Reed Chase, general manager, Empire Aerospace