- ENGINE - INLET NO.3 BEARING ASSEMBLY GEARBOX (72-61-00)- NEW BALL THRUST NO 3 BEARING RECOMMENDED WITH NITRIDE HARDENING. SERVICE BULLETIN MOS CS-FEB-2012 HRSI.1SC - ENG SB 72-0813 NO. I ENGINE - ENGINE - HIGH PRESSURE TURBINE ROTOR ASSEMBLY (72-52-00) - INTRODUCTION OF HPT BLADE INFORMATIONAL P