37-SL-21-078 REV. B 02-APR-2009 FORWARD DOOR HEAT SYSTEM FLEXIBLE DUCT KINKING. SERVICE LETTER MOS RECOMMENDED SI. 737-SL-21-079 EÆ COOLING IN PS PANEL - POTENTIAL WIRE CHAFING RECOMMENDED AGAINST HOSE CLAMP. SERVICE LETTER MOS I2-MAY-2009 SL 737-SL-21-080 AIR-CONDITIONING DUCT CLAMP ASSEMBLY TORQUE. SERVICE L