What was found
MAIN DOOR PRIMARY SEAL: DESCENDING THOUGHT 5000 FEET THERE IS A LOUD WHISTLE COMING FROM THE MAIN CABIN DOOR SEAL. // SIGNOFF// B.EGAN TO TROUBLESHOOTING THE MAIN ENTRY DOOR, INSPECTED THE DOOR SEALS FOUND THE AFT SECTION OF THE MAIN ENTRY CABIN DOOR SEAL RETAINER RING LOOSE , RESECURED THE RETAINER RING SEAL AS REQUIRED, POWER UP THE AIRCRAFT AND STARTED THE ENGINES AND PRESSURIZED AIR RAFT AND COMPLIED MAIN CABIN DOOR ENTRY DOOR SEAL LEAK CHECK IS GOOD .IAW CE-680A MM 52-10-35.