What was found
AFTER TAKEOFF DOOR SEAL & CABIN DOOR ANNUNCIATOR ILLUMINATED, LOUD WIND NOISE FROM AROUND DOOR. ACCOMPLISHED AIR TURNBACK AND UPON LANDING THE MAIN ENTRANCE DOOR FELL OPEN. REPLACED AFT DOOR STRUT MOUNTING FRAMES IAW CESSNA 560XL B/P 6611267, BOTH DOOR CABLES IAW CESSNA 560 XL MM 52-10-03. PERFORMED CABIN LEAK RATE PRIMARY AND SECONDARY SEALS CHECKED GOOD IAW CESSNA 560 XL MM 21-30-00. VERIFIED DOOR OPERATION AND DOOR SEAL LEAK DOWN RATE GOOD IAW CESSNA 560 XL MM 52-10-04.