Clifford Development and Stevens Aviation have expanded their Clifford Citation 550 and S550 engine conversion partnership. Stevens Aviation will install an optional Rockwell Collins three-display Pro Line 21 IDS that is certified in a dual AHRS (attitude-heading reference system)/turbulence radar configuration. Clifford Development has certified 35 improvements as part of the C550/S550 Williams engine installation STC, including an Ametek digital engine display, the Rockwell Collins three-display Pro Line 21 IDS System, heavy-duty Goodrich brakes and a dual Fadec system. The Williams FJ44-3A engines are thermodynamically rated at 3,000 pounds each (takeoff thrust is flat-rated to 2,820 pounds) versus the original engine’s 2,500-pound rating. According to Clifford, the modification reduces the typical Citation 550/S550’s basic operating weight by 200 pounds while decreasing the original one hour and 37 minute step climb profile to FL430 to 22 minutes. The modification also provides an 18-percent increase in maximum cruise speed and a 59-percent increase in NBAA IFR range with four passengers.