Textron has put the future of the largest Cessna-branded business jet on hold until it knows whether Safran can resolve a problem detected in October with the Silvercrest engine during high-altitude testing.
Textron Aviation launched the 12-passenger Cessna Citation Hemisphere with 4,500nm range in 2015, promising to achieve first flight in 2019 with an aircraft powered by two 12,000lb-thrust Silvercrest engines.
The business case for the Hemisphere relies upon the unique fuel efficiency of the Silvercrest engine, says Textron chief executive Scott Donnelly, speaking to analysts on a fourth quarter earnings call.
“To make that aircraft be what we want it to be, that’s the engine that makes it work. So if you go to a larger engine then you have to go to a larger aircraft and that’s a path that we’re not going to go do,” Donnelly says.
Another Silvercrest customer, Dassault, has already cancelled the Falcon 5X as a result of doubts about the engine’s future. The French business jet manufacturer has re-launched the Falcon 5X as a larger aircraft that will enter service in four years with Pratt & Whitney Canada PW800 engines.
Unlike Dassasult, Textron Aviation currently doesn’t build any aircraft larger than the Hemisphere.
“If the [Silvercrest] engine is not there, then you do a step back and go, okay guys, what do we want to do?” Donnelly says. “Going bigger doesn’t make sense to us, so we would have to evaluate a change in our strategy. It’s all predicated on where the engine is and we just don’t know yet.”
Safran has been wrestling with the high-pressure compressor in the Silvercrest engine for a few years. The engine features an axial-centrifugal architecture in the high-pressure commpressor, which means the airflow passes straight through the blades of the first stages of the compressor before curling around the fixed tips of the last stage.
Such architectures are common in engines below 7,000lb-thrust, but are rarely seen in the 10,000-12,000lb-thrust class of the Silvercrest, due to the complexity of managing pressure losses in the airflow around the final, centrifugal stage. If it works, however, Safran believes the Silvercrest will represent the most fuel efficient turbofan engine in a usually neglected market segment.
First, however, Safran has to resolve the problem with Silvercrest at high altitude. In tests at high altitude on Safran’s flying testbed, the Silvercrest was found to be slow to accelerate or decelerate upon command.
Dassault reacted strongly to the news at the NBAA convention in October, saying the Falcon 5X problem was under review. Two months later, Dassault announced the Falcon 5X would be cancelled and replaced with the larger model.
Textron Aviation officials have always adopted a more patient approach with the Silvercrest. The company’s executives have agreed with Safran that the high-pressure compressor problems identified during testing for the Falcon 5X would be resolved by the time the engine was needed for the first flight of the Hemisphere in 2019.