HERTSBORO, AL, USA
N8677G
CESSNA A188B
DURING AERIAL APPLICATION ONE PROPELLER BLADE SEPARATED FROM THE ACFT. THE ACFT COLLIDED WITH A TREE DURING THE FORCED LANDING ROLL. EXAM OF THE PROPELLER REVEALED THAT A FATIGUE FRACTURE ORIGINATED AT A SCORE MARK IN THE HUB THREADS OF THE BLADE. DEPOSITS WERE FOUND IN THE FRACTURE ENRICHED BY CARBON & OXYGEN. GRAPHITE, THE LUBRICANT USED IN THE PROPELLER ASSEMBLY, IS CARBON BASED. TESTING SHOWED THAT THE BLADE'S HARDNESS & TENSILE STRENGTH WAS BELOW MFG SPECIFICATIONS. THE SAFETY BOARD BELIEVES THAT THE FRACTURE WAS OPENED UP DURING THE LAST PROPELLER OVERHAUL, ABOUT 583 OPERATING HOURS PRIOR TO THE ACCIDENT. ALSO, OIL REQUIRED IN THE HUB TO ALLOW EARLY DETECTION OF BLADE CRACKS WAS ABSENT.
FATIGUE FAILURE OF THE PROPELLER BLADE WHICH RESULTED FROM IMPROPER OVERHAUL PROCEDURES, AND THE ABSENCE OF OIL IN THE PROPELLER HUB WHICH WOULD ALLOW THE DETECTION OF BLADE CRACKS.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
