What was found
AFTER T/O, HEARD A LOUD SOUND AS THE GEAR WAS RAISED. DURING THE AFTER T/O FLOW, FO(P.M.) POINTED OUT THE LEFT MAIN GEAR LT WAS SHOWING RED. THE CONFIG SYNOPTIC ALSO SHOWED RED FOR THE LEFT GEAR. FOLLOWED THE QRH AND BROUGHT THE GEAR DOWN - ALL GREEN. RAISING THE GEAR AGAIN PER QRH LEAD BACK TO ALL RED LTS FOR THE LEFT MAIN. CONSULTED MX OVER SATCOM AND ELECTED TO RETURN KIND ON APPROACH, AS A/C SLOWED TO 200K, GEAR UNSAFE LT EXTINGUISHED. CONTINUED APPROACH TO UNEVENTFUL LANDING. SHGN 01MAY21 13:59 IND U AFTER A/C RETURNED TO GATE, THE LEFT MAIN GEAR DOOR DROPPED, ONCE HYD PRESSURE WAS REMOVED. UPON PERFORMING THE GVI OF THE LEFT GEAR AREA, FOUND DOOR CRACKED AROUND THE ENTIRE PERIMETER OF WHERE THE DOOR FITTING (IPC 52-82-01-01, FIG 1, SHT 1, ITEM 456) ATTACHES TO THE DOOR. NEW LEFT MAIN LANDING GEAR DOOR IS NEEDED. L/H MLG DOOR, CPN 5213662, SHOWS IN STOCK AT IND BASE. FACT 02MAY21 16:18 IND CONTINUED INSTALLATION OF LEFT MAIN GEAR DOOR FROM 3. D. (4) THROUGH COMPLETION REF AMM 32-14-01-2. LEFT MAIN GEAR DOOR AND INDICATION CHECKS NORMAL, NO FAULTS NOTED.