A CESSNA 206 SUPER SKYWAGON (STATIONAIR) PILOT REPORTS TO MAINT OF INOPERABLE PROP CONTROL. MAINT FOUND PROP CONTROL ROD HAD UNSCREWED ITSELF FROM ITS OWN ROD END.

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RECEIVED PHONE CALL FROM DISPATCH SAYING PLT RPTED INOPERABLE PROP CTL IN ZZZ HE THOUGHT CABLE HAD BROKE. LOADED UP TOOLS PARTS AND HELPER. ARRIVED IN ZZZ; REMOVED COWLING. DISCOVERED PROP CTL ROD HAD UNSCREWED ITSELF FROM ITS ROD END. INSPECTED THREADS IN ROD END AND CONTROL ROD; NO DAMAGE FOUND. ASSEMBLED ROD END; RIGGED AND SAFETIED. PLT LOST PROP CTL AUTH AND RETURNED TO DEP ARPT; CONTACTED DISPATCH. WOULD LIKELY SAY THAT PREVIOUS MECH WORKING ON PROP CTL SYS FAILED TO TIGHTEN JAM NUT ON THE ROD END. HOWEVER; UNKNOWN WHY ROD END ACTUALLY SEPARATED FROM CTL ROD AS THE CTL CABLE DOES NOT SPIN IN ITS HOUSING; UNABLE TO FIGURE OUT HOW IT CAME UNSCREWED. PROCS ARE IN PLACE TO PREVENT THIS OCCURRENCE; UNKNOWN AT THIS TIME WHY PROCS FAILED. PERHAPS RII SHOULD INCLUDE A CHKLIST FOR CTL CABLES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THAT HE; OTHER MECHANICS AND INSPECTORS; STILL CANNOT EXPLAIN HOW THE PROP CONTROL ROD COULD HAVE UNSCREWED ITSELF FROM ITS OWN ROD END. NO DAMAGE WAS FOUND ON ANY OF THE THREADS OF THE VERNIER ROD/CABLE. THE ROD DISCONNECTED IN THE ENGINE COMPARTMENT AT THE PROP GOVERNOR. HIS COMPANY HAS DEVELOPED A BETTER CHECKLIST PROCEDURE AND NOW INCLUDES TWO INSPECTORS; INSTEAD OF JUST ONE; TO XCHK AND VERIFY THAT ENGINE AND FLIGHT CONTROLS ARE PROPERLY CONNECTED AND SECURE.