Narrative:

Received phone call from dispatch saying pilot reported inoperable propeller control in ZZZ he thought cable had broke. Loaded up tools parts and helper. Arrived in ZZZ; removed cowling. Discovered propeller control 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. Pilot lost propeller control authority/authorized and returned to departure airport; contacted dispatch. Would likely say that previous mechanic working on propeller control system failed to tighten jam nut on the rod end. However; unknown why rod end actually separated from control rod as the control cable does not spin in its housing; unable to figure out how it came unscrewed. Procedures are in place to prevent this occurrence; unknown at this time why procedures failed. Perhaps rii should include a checklist for control cables. Callback conversation with reporter revealed the following information: reporter stated that he; other mechanics and inspectors; still cannot explain how the propeller 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 propeller 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.

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Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.