Following Dassault’s surprise disclosure of another engine-related delay to the Falcon 5X here at NBAA, Safran says it has identified the problems with the Silvercrest and is poised to discuss a range of potential fixes with the airframe manufacturer.

Despite Dassault hinting that the latest problems may force it to consider an alternative engine, Safran says it is striving to minimize further delays and insists the baseline architecture of the Silvercrest is sound. However, according to Safran commercial engines VP Cedric Goubet, the length of the delay will depend on which particular set of fixes is selected, and he adds that the revised schedule will be known well before the end of the year.

“The Silvercrest is an all-new engine, but with proven technologies, and is aimed at reaching performance levels that are unrivaled for this market segment. However, it’s been a challenge – and, truth be told, more challenging than we thought initially,” says Goubet. The unexpected problems cropped up in September during flight tests of the latest configuration of the Silvercrest incorporating improvements destined for the service-entry standard on the -5X.

“We had made a lot of progress, and solutions to most of our previous difficulties were validated and verified during the tests of this new configuration. But then this issue appeared, and clearly it was very disappointing,” says Goubet.

During tests on the company’s Gulfstream II flying testbed, the high-pressure compressor (HPC) suffered acceleration, deceleration and stall issues at high altitude and low speed conditions. The GII is capable of flying at 45,000 ft. and was investigating the potential for additional efficiency gains when the problems hit.

Unusually for an engine in the 11,000-lb.-plus thrust range, the compressor combines a four-stage axial unit with a single centrifugal stage. “The issue is with the axial part, not the centrifical,” confirms Goubet, who adds the “problem has nothing to do with the overall architecture of the compressor.”

“We have to optimize the settings of the compressor and maybe introduce some modifications to really recover all the [surge] margin we need to operate as expected across the flight envelope,” he says. “However, we have enough knowledge to know it is unlikely that it will be sufficient to only optimize the settings, the control laws and positioning of the VSV [variable stator vanes]. That will help to achieve a portion [of the losses], but not all the way. We may look at some flowpath modifications, but we want to minimize that and we will not add stages or vanes,” Goubet says.

The engine, meanwhile, continues to fly a restricted flight envelope on the GII, and data continues to help guide Safran’s engineering team as to the best solution. The engine can also continue to be used in its current configuration for several certification tests, says Safran.

Striving to strike a balance, Goubet says the latest flight-test discovery “is bad, but it is not a catastrophe. There is no doubt in our confidence to achieve what we set out to do with this engine. Despite this issue, we remain confident in the progress we have made with this engine over the past two years and the fact we will get there with a competitive engine in this market segment.”