On April 1, 2001, a Globe GC1B (registration N78321) was involved in an aviation accident near Cherry Point, NC. Investigators recorded the probable cause as: Fatigue cracking of the propeller hub assembly, which reduced its load carrying capacity until it could no longer withstand the centrifugal load, leading to propeller blade separation. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A Globe GC1B aircraft in formation lost a propeller blade in flight due to fatigue cracking in the propeller hub, leading to separation of the blade and subsequent loss of the hub assembly.
Accident Description
A Globe GC1B aircraft experienced a propeller blade separation while maneuvering in the number two position of a formation of three airplanes. The initial separation involved one propeller blade detaching from the propeller hub assembly. Subsequently, the second propeller blade together with the hub assembly separated from the engine crankshaft.
Examination Findings
Examination of the recovered propeller hub fracture surfaces revealed evidence of fatigue cracking. The fatigue fracture propagated until it intersected the outer surface of the hub.
Manufacturer's Analysis
According to McCauley Propeller, the fatigue cracking reduced the load-bearing capacity of the propeller hub. Eventually, the remaining cross section became insufficient to support the centrifugal load exerted by the propeller, resulting in the separation of the blade and hub.
Probable cause
Fatigue cracking of the propeller hub assembly, which reduced its load carrying capacity until it could no longer withstand the centrifugal load, leading to propeller blade separation.