Snecma Silvercrest Engine To Feature OEI Rating

Snecma’s in-development Silvercrest turbofan, which will power the Dassault Falcon 5X twinjet, will feature a one-engine-inoperative (OEI) rating for extreme hot days. To accommodate the rating, the FAA has issued a special condition called “rated 10-minute OEI takeoff thrust at high ambient temperature” (rated 10-minute OEI TOTHAT). The French engine manufacturer says this marks the first use of an OEI power rating, commonplace for helicopter turboshafts, on an airplane. The additional takeoff rating raises the exhaust gas temperature limit to augment OEI takeoff thrust in hot conditions for a maximum of 10 minutes. Thus, the maximum takeoff thrust of 11,450 pounds at sea level will be available up to ISA+20, five degrees C. above the usual ISA+15 reference temperature.

The feature is being incorporated into the Falcon 5X’s automatic takeoff thrust control system. Using it will require notifying pilot and maintenance personnel. For certification, a dedicated test sequence has been defined, according to the FAA special condition.

From the outset of the Silvercrest design process, Snecma has drawn on sister company Turbomeca's experience in helicopter engine design, notably a centrifugal compressor stage.