Narrative:

On mar/xa/01, a cessna caravan, equipped with a mccauley 3gfr34c703 propeller departed ZZZ at XA47 on a routine scheduled flight. Upon takeoff, the pilot noticed an unusual vibration from the propeller. The pilot declared an emergency and safely returned the aircraft without further incident. Upon inspection, it was discovered that one counterwt had separated from its corresponding blade causing damage to the spinner and blade. The propeller and spinner were exchanged and the flight was continued. Inspection of the counterwt bolt revealed that the bolt had 'stripped' out of the blade. This bolt was compared to a typical bolt that would otherwise connect the counterwt to the blade. These bolts were found to be identical in all respects except in length, which deviated by 3/8 inch. This is the alleged cause of the failure. The propeller is currently at the manufacturer for evaluation. This can be avoided in the future by proper part identify. Employing a color marking to differentiate between bolts should also be implemented. Callback conversation with reporter revealed the following information: the reporter stated the bolt that was installed in a blade counterwt and was found to be too short by .375 inches. The reporter said it was an approved bolt by the manufacturer of the propeller, but not in this type propeller. The reporter stated the problem was caused by improper part identify.

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Original NASA ASRS Text

Title: A CESSNA CARAVAN IMMEDIATELY AFTER TKOF DECLARED AN EMER AND DIVERTED DUE TO PROP VIBRATION CAUSED BY INCORRECT COUNTERWT BOLT INSTALLATION.

Narrative: ON MAR/XA/01, A CESSNA CARAVAN, EQUIPPED WITH A MCCAULEY 3GFR34C703 PROP DEPARTED ZZZ AT XA47 ON A ROUTINE SCHEDULED FLT. UPON TKOF, THE PLT NOTICED AN UNUSUAL VIBRATION FROM THE PROP. THE PLT DECLARED AN EMER AND SAFELY RETURNED THE ACFT WITHOUT FURTHER INCIDENT. UPON INSPECTION, IT WAS DISCOVERED THAT ONE COUNTERWT HAD SEPARATED FROM ITS CORRESPONDING BLADE CAUSING DAMAGE TO THE SPINNER AND BLADE. THE PROP AND SPINNER WERE EXCHANGED AND THE FLT WAS CONTINUED. INSPECTION OF THE COUNTERWT BOLT REVEALED THAT THE BOLT HAD 'STRIPPED' OUT OF THE BLADE. THIS BOLT WAS COMPARED TO A TYPICAL BOLT THAT WOULD OTHERWISE CONNECT THE COUNTERWT TO THE BLADE. THESE BOLTS WERE FOUND TO BE IDENTICAL IN ALL RESPECTS EXCEPT IN LENGTH, WHICH DEVIATED BY 3/8 INCH. THIS IS THE ALLEGED CAUSE OF THE FAILURE. THE PROP IS CURRENTLY AT THE MANUFACTURER FOR EVALUATION. THIS CAN BE AVOIDED IN THE FUTURE BY PROPER PART IDENT. EMPLOYING A COLOR MARKING TO DIFFERENTIATE BTWN BOLTS SHOULD ALSO BE IMPLEMENTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE BOLT THAT WAS INSTALLED IN A BLADE COUNTERWT AND WAS FOUND TO BE TOO SHORT BY .375 INCHES. THE RPTR SAID IT WAS AN APPROVED BOLT BY THE MANUFACTURER OF THE PROP, BUT NOT IN THIS TYPE PROP. THE RPTR STATED THE PROB WAS CAUSED BY IMPROPER PART IDENT.

Data retrieved from NASA's ASRS site as of July 2007 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.