What was found
IN-FLIGHT, AFTER LANDING GEAR FAILED TO RETRACT PROPERLY, LANDING GEAR SELECTED DOWN AND FAILED TO EXTEND. NO LANDING GEAR EXTENSION OCCURRED UNTIL UPHOLSTERY WAS REMOVED AND LANDING GEAR CONTROL VALVE MANUALLY MOVED TO EXTEND LANDING GEAR. SAFE LANDING MADE. MAINTENANCE FOUND ROLL PIN SHEARED IN HANDLE MECHANISM. NO PARTS BREAK DOWN IN IPC. FACTORY PROVIDED PART NUMBER FOR PIN. SUGGEST TIME CHANGE OF THIS PART AND AFM SUPPLEMENT INSTRUCTING CREW HOW TO GAIN ACCESS AND MANUALLY MOVE LANDING GEAR CONTROL VALVE IN CASE OF HANDLE FAILURE. VERY DANGEROUS SITUATION.