D BY SL 737-SL-27-246 REV. A). SERVICE LETTER MOS SL 737-SL-27-246 REV. A POSSIBLE EXTERNAL LEAKAGE FROM AILERON/ELEVATOR POWER CONTROL UNIT (PCU) CRANK ASSEMBLY. RECOMMENDED SERVICE LETTER MOS 02-JUN-20I4 SL 737-SL-27-247 HORIZONTAL STABILIZER TRIM ACTUATOR- INPUT CAM ASSEMBLY- IMPROPERLY CARBURIZED. S