What was found
LEFT MLG INBD DOOR CAME OPEN AFTER TAKEOFF, REPORTED BY CONTROL TOWER. LANDING MADE WITHOUT INCIDENT. FND GEAR RETRACT IDLER BELLCRANK BROKEN 2 INCHES FROM END OF ARM THAT RUNS GEAR DOOR EXTEND/RETRACT LINKAGE. BELLCRANK SHOWS EVIDENCE OF HAVING BEEN CRACKED ONE-THIRD OF ITS THICKNESS FOR SOME TIME, MONTHS PERHAPS. THE RT BELLCRANK ON ACFT CRACKED AND LATER BROKE IN SIMILAR FASHION ABOUT 1 YEAR PRIOR. SUSPECT PRIOR IMPROPER RIGGING AND TOO MUCH GEAR DOOR TENSION WHEN GEAR DOWN. SUGGEST CLOSE INSPECTION AS THIS BELLCRANK IS IN SUCH A LOCATION THAT IT IS DIFFICULT TO INSPECT THOROUGHLY. SUGGEST CLOSE ADHERANCE TO CESSNA RIGGING PROCEDURES. CRACK BEGAN AT TOP.