What was found
THE SPINNER ASSY FAILED IN FLIGHT ON A 2.2 HR FLIGHT LEG. APPROXIMATELY 1.5 HRS INTO THE FLIGHT A SMALL SHUDDER WAS FELT AND ALL INDICATION CHECKED NORMAL. THE AC COMPLETED THE FLIGHT AND IT WAS NOTED THAT 4" X 4" SECTION OF THE SPINNER BROKE OFF. THE COWLING HAD TWO SCRAP MARKS AND NO OTHER DAMAGE WAS NOTED. MFG SL-61-286 WAS ACCOMPLISHED 7.31 HRS PRIOR TO FAILURE. OWNER REPORTS SPINNER WAS CHECKED ON PREFLIGHT APPROXIMATELY 1.5 HRS PRIOR TO FAILURE. SPINNER TT 21.64 HRS. PROBABLE CAUSE: SPINNER DOME IS TOO LARGE FOR A SPINNER WITHOUT A FORWARD BULKHEAD FOR SUPPORT. (K)