Pratt & Whitney Canada is striving to keep fuel burn on target for its PW307A engine, which will power the Dassault Falcon 7X. Based on results from the first series of engine flight tests, the Longueuil, Quebec-based manufacturer is confident it will avoid the fuel-consumption problem it had on the PW308C for the Falcon 2000EX. P&WC anticipates Transport Canada will certify the PW307A, which has a takeoff thrust of 6,100 pounds (uninstalled, ISA+18.4), late this year.
Compared with the PW308C, which yielded disappointing specific fuel consumption, the development of the PW307A has been “much more rigorous,” Mike Perodeau, P&WC’s vice president for corporate aviation, and Catrina MacKenzie, vice president for the PW307 program, told AIN. The engineers endeavored to get data from every component of the engine, as they wanted to have a clear understanding in modeling performance. “We have done a lot of performance validation through computational fluid dynamics and rig and component testing,” MacKenzie said.
When they evaluated the engine at sea level, beginning in December 2002, the designers knew they were very close to their targets. But they still needed to ensure good performance at altitude, which the flight tests confirmed. As early as its maiden flight, which lasted five hours on July 16, the PW307A was tested to 45,000 feet.
Five test engines are running today. Two more engines were to join the program before this month and another two early this year. One of the ground-test engines has flown on P&WC’s Boeing 720 flying testbed and, by the end of the program, another one or two will fly aboard the testbed, too.
More than 700 hours of ground testing (out of 3,600 planned hours) have been conducted, in the ground test cell including operability, mechanical integrity and performance evaluations. The engine has logged 50 flying hours on the testbed out of the 300 hours planned. Simultaneously, engine subassemblies have undergone 150 hours of technology rig testing (out of 10,000 hours) and 500,000 cycles (out of three million) of fatigue testing in P&WC’s spin pits.
Asked whether the testing program has shown any need for modifications, MacKenzie said, “No.” However, as on every engine under test, “we have performed some optimization on control schedules, tip clearances and exhaust nozzle areas,” she said.
A Family Affair
The PW307A has the same basic architecture as the rest of the PW300 family, which powers the Hawker 1000 (PW305), Learjet 60 (PW305A) and Gulfstream 200 (PW306A). As such, the PW307A has a two-spool architecture. Downstream from the single-stage fan, the high-pressure compressor has four axial stages (the first two with variable-geometry guide vanes) and one centrifugal stage. The high-pressure turbine has two cooled stages. The low-pressure turbine, developed by German-based MTU Aero Engines, has three uncooled stages.
Since P&WC will deliver an integrated powerplant system to Dassault, MHD Nacelle Systems provides the engine maker with the nacelle and thrust reverser. Compared with other members of the PW300 family, the PW307A has a more efficient fan with increased flow capacity. “The advanced shock-management fan is a new concept to control the aerodynamic shock strength and hence reduce the losses and improve the fan performance,” MacKenzie explained.
The Talon combustor has been scaled down from that of bigger engines at parent company Pratt & Whitney. According to MacKenzie, it provides improved maintainability and lower nitrogen oxide (NOx) emissions.
“The high-pressure turbine has disks made of a new powder alloy, which allows us to make disks smaller,” MacKenzie told AIN. This in turn saves weight and allows for more freedom in designing the turbine. Fitted around the turbine is a low thermal expansion housing for better tip-clearance control.
In terms of noise, Perodeau said only that external noise would be “better than Stage 3 and pending changes to noise limits.” He added vibration would be “very low.” In terms of operating costs, P&WC has not yet established any guaranteed rate under its Eagle Service Plan.
The FAA is expected to certify the PW307A soon after Transport Canada, which would give some margin for the first flight of the Falcon 7X, scheduled for the second quarter next year. P&WC anticipates European Aviation Safety Agency acceptance will follow U.S. approval late next year. Dassault has scheduled early deliveries for the Falcon 7X in late 2006. The PW307A should enter service with a 7,200-hour time between overhaul.