Abstract
This paper analyses the causes of an incident in an aircraft propeller hub. The aluminum alloy propeller blade hub was detached from the plane bearing one of its two blades with the other one being jettisoned away. Stereoscopic examination of the fractured hub revealed that it was initially cracked by fatigue, with the crack initiating on the root of the third and fourth spirals and propagating form the inner to the outer. SEM analysis showed that the crack epicentres were created very close or/and on the spiral roots and were attributed to microcracks from corrosion pits and high stress concentration. Non Destructive Inspection was both used on the other side of the hub and the remaining three hubs of the plane and confirmed the presence of cracks similar to those which caused the fatigue failure of the fractured hub but at earliest stage of development.
Highlights
The propeller consists of several blades held in place by a central hub
Other components typically include the spinner, which creates aerodynamic streamlining over the propeller hub, the bulkhead, which allows the spinner to be attached to the rest of the propeller, the pitch change actuator, to transmit hydraulic energy to rotate the blades in the hub and a source of high pressure oil to supply hydraulic energy to the propeller actuator
Analysis is based on Visual Inspection, StereoMicroscopy, Metallography, Chemical Analysis, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS)
Summary
The propeller consists of several blades held in place by a central hub. The propeller hub holds the blades in place and is connected to the engine through a propeller drive shaft and a gearbox. It depends on the fact that when the material or part under test is magnetized, magnetic discontinuities that lie in a direction generally transverse to the direction of the magnetic field will cause a leakage field to be formed at and above the surface of the part. The presence of this leakage field, and the presence of the discontinuity, is detected by the use of finely divided ferromagnetic particles applied over the surface, with some of the particles being gathered and held by the leakage field. Analysis is based on Visual Inspection, StereoMicroscopy, Metallography, Chemical Analysis, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS)
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