CRYSTAL RIVER, FL, USA
N157JM
MASON, JACK A. VELOCITY
DURING CRUISE FLT, APRX 17 INCHES OF ONE PROP BLADE SEPARATED. DURING THE EMERGENCY DESCENT FOR A FORCED LANDING, THE ACFT COLLIDED WITH TREES THEN THE WATER. EXAM OF THE PROP REVEALED THAT THE FWD HUB WHICH CONTACTS THE FWD MOUNTING FLANGE WAS BURNED. A PROP SPINNER WAS NOT INSTALLED. IT HAD BEEN REMOVED BEFORE THE PLT PURCHASED THE ACFT APRX 9 MONTHS EARLIER. THE PROP SPINNER BACKING PLATE WHICH IS .125 INCH THICK ATTACHES BETWEEN THE FWD MOUNTING FLANGE AND THE FWD HUB OF THE PROP. THE CORRECT PROCEDURE TO DETERMINE IF THE ATTACH BOLTS ARE THE CORRECT LENGTH IS TO INSTALL THEM THROUGH THE AFT MOUNTING FLANGE & THE PROPELLER BACKING PLATE (IF INSTALLED), THEN SCREW THEM INTO THE FWD MOUNTING FLANGE UNTIL THE BOLTS BOTTOM OUT. THE WIDTH BETWEEN THE TWO FLANGES (IF A PROP SPINNER IS NOT INSTALLED) SHOULD BE MEASURED, THEN THE WIDTH OF THE PROP HUB SHOULD BE MEASURED. THE WIDTH OF THE PROP HUB SHOULD BE GREATER THAN THE WIDTH BETWEEN THE FLANGES TO ALLOW FOR COMPRESSION OF THE HUB WHEN THE BOLTS ARE PROPERLY TORQUED.
FAILURE OF AN UNKNOWN INDIVIDUAL TO DETERMINE THAT THE PROPELLER WAS PROPERLY SECURED AFTER REMOVAL OF THE PROPELLER SPINNER, RESULTING IN SEPARATION OF ONE OF THE PROPELLER BLADES DURING CRUISE FLIGHT. CONTRIBUTING TO THE ACCIDENT WAS UNSUITABLE TERRAIN ENCOUNTERED DURING THE FORCED LANDING.
Source: NTSB Aviation Accident Database
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