Narrative:

VFR under the control of denver approach control for practice instrument approachs at apa. While cruising at approximately 8000 ft MSL (2 inch manifold pressure and 2450 RPM), we heard a loud 'thump'. Immediately suspecting a bird strike (of about the size of a crow or hawk), we checked engine instruments, inspected the aircraft visually from inside the cockpit and checked flight control effectiveness. We observed no deviations from normal at that time. We continued the instrument training flight, making 2 ILS approachs to runway 35R at apa. The first ILS approach terminated in a missed approach and the second ILS approach terminated in a full stop landing. Our landing at apa was successful without incident. After we taxied off runway 35R, the engine quit, probably because the power was brought back too much. We were not able to restart the engine while it was hot. The battery was not particularly well charged. I exited the aircraft, obtained a tow bar and fastened it to the nose landing gear. At that time I noticed that the spinner had partially disintegrated, leaving only 4 or so inches of spinner loosely attached only at its very center since the outer portion had torn off and disappeared. One of the propeller blades had 2 nicks in it -- apparently caused by it striking the portion of the spinner that had separated from the aircraft. Further inspection of the aircraft revealed no other damage and no remnants of bird parts such as blood or feathers. I concluded that 'thump' noise heard was the sound of the spinner disintegrating and/or its separated part being struck by the propeller blade. We parked the aircraft at apa to be subsequently inspected (and repaired) by qualified aircraft maintenance personnel. We ceased flight operations with the aircraft at that time. When the aircraft was preflted, a small crack was noticed in the spinner near one of the attachment screws. We did not realize the potential for damage that a crack of that size posed, the aircraft's owner rptedly knew of the crack's existence and did not believe that it was any problem. When hearing the 'thump' while in flight, we mistakenly believed that it was caused by a bird strike that caused no damage to the aircraft. Even though no additional damage and no injuries resulted from the incident, in retrospect I believe that it would have been more prudent for us to have landed the aircraft at apa immediately after completing the first instrument approach, rather than performing a missed approach and doing the second instrument approach as well. We were quite fortunate that the nicks in the propeller blade did not cause its catastrophic failure with a resulting tearing of the aircraft engine from its mounts and a crash of the aircraft.

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Original NASA ASRS Text

Title: PROP SPINNER SHATTERED IN FLT. CONTINUED TRAINING.

Narrative: VFR UNDER THE CTL OF DENVER APCH CTL FOR PRACTICE INSTRUMENT APCHS AT APA. WHILE CRUISING AT APPROX 8000 FT MSL (2 INCH MANIFOLD PRESSURE AND 2450 RPM), WE HEARD A LOUD 'THUMP'. IMMEDIATELY SUSPECTING A BIRD STRIKE (OF ABOUT THE SIZE OF A CROW OR HAWK), WE CHKED ENG INSTRUMENTS, INSPECTED THE ACFT VISUALLY FROM INSIDE THE COCKPIT AND CHKED FLT CTL EFFECTIVENESS. WE OBSERVED NO DEVS FROM NORMAL AT THAT TIME. WE CONTINUED THE INSTRUMENT TRAINING FLT, MAKING 2 ILS APCHS TO RWY 35R AT APA. THE FIRST ILS APCH TERMINATED IN A MISSED APCH AND THE SECOND ILS APCH TERMINATED IN A FULL STOP LNDG. OUR LNDG AT APA WAS SUCCESSFUL WITHOUT INCIDENT. AFTER WE TAXIED OFF RWY 35R, THE ENG QUIT, PROBABLY BECAUSE THE PWR WAS BROUGHT BACK TOO MUCH. WE WERE NOT ABLE TO RESTART THE ENG WHILE IT WAS HOT. THE BATTERY WAS NOT PARTICULARLY WELL CHARGED. I EXITED THE ACFT, OBTAINED A TOW BAR AND FASTENED IT TO THE NOSE LNDG GEAR. AT THAT TIME I NOTICED THAT THE SPINNER HAD PARTIALLY DISINTEGRATED, LEAVING ONLY 4 OR SO INCHES OF SPINNER LOOSELY ATTACHED ONLY AT ITS VERY CENTER SINCE THE OUTER PORTION HAD TORN OFF AND DISAPPEARED. ONE OF THE PROP BLADES HAD 2 NICKS IN IT -- APPARENTLY CAUSED BY IT STRIKING THE PORTION OF THE SPINNER THAT HAD SEPARATED FROM THE ACFT. FURTHER INSPECTION OF THE ACFT REVEALED NO OTHER DAMAGE AND NO REMNANTS OF BIRD PARTS SUCH AS BLOOD OR FEATHERS. I CONCLUDED THAT 'THUMP' NOISE HEARD WAS THE SOUND OF THE SPINNER DISINTEGRATING AND/OR ITS SEPARATED PART BEING STRUCK BY THE PROP BLADE. WE PARKED THE ACFT AT APA TO BE SUBSEQUENTLY INSPECTED (AND REPAIRED) BY QUALIFIED ACFT MAINT PERSONNEL. WE CEASED FLT OPS WITH THE ACFT AT THAT TIME. WHEN THE ACFT WAS PREFLTED, A SMALL CRACK WAS NOTICED IN THE SPINNER NEAR ONE OF THE ATTACHMENT SCREWS. WE DID NOT REALIZE THE POTENTIAL FOR DAMAGE THAT A CRACK OF THAT SIZE POSED, THE ACFT'S OWNER RPTEDLY KNEW OF THE CRACK'S EXISTENCE AND DID NOT BELIEVE THAT IT WAS ANY PROBLEM. WHEN HEARING THE 'THUMP' WHILE IN FLT, WE MISTAKENLY BELIEVED THAT IT WAS CAUSED BY A BIRD STRIKE THAT CAUSED NO DAMAGE TO THE ACFT. EVEN THOUGH NO ADDITIONAL DAMAGE AND NO INJURIES RESULTED FROM THE INCIDENT, IN RETROSPECT I BELIEVE THAT IT WOULD HAVE BEEN MORE PRUDENT FOR US TO HAVE LANDED THE ACFT AT APA IMMEDIATELY AFTER COMPLETING THE FIRST INSTRUMENT APCH, RATHER THAN PERFORMING A MISSED APCH AND DOING THE SECOND INSTRUMENT APCH AS WELL. WE WERE QUITE FORTUNATE THAT THE NICKS IN THE PROP BLADE DID NOT CAUSE ITS CATASTROPHIC FAILURE WITH A RESULTING TEARING OF THE ACFT ENG FROM ITS MOUNTS AND A CRASH OF THE ACFT.

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.