Failure Investigation of Counterweight Separation from Aircraft Propeller

Failure Investigation of Counterweight Separation from Aircraft Propeller The counterweight of a propeller in a turboprop aircraft was separated during an engine run-up inspection. If this separation occurs in-flight, it may result in an accident involving serious damage or injury. In this investigation, the failed counterweight clamping assembly was studied to determine the root cause of failure. Both experimental and computational investigations were performed to explore and confirm the effects of experimentally observed anomalies on potential clamping assembly failure. Dimensional measurement of the failed clamping thread area by X-ray CT scanning revealed significant deviation from requirements in the major diameter of the thread. Fractographic and microscopic examination along with chemical analysis confirmed that the clamping bolts were pulled out due to overload stripping failure of the internal threads. Detailed computational fracture modeling utilizing the XFEM crack simulation technique provided further insight proving that thread engagement length had a significant effect on the clamping assembly failure. Based on these observations, it was concluded that the main root cause of the stripping failure was the dimensional nonconformance of the internal thread from the requirements in standard 7/16-20UNF-3B that resulted in the loss of thread engagement length. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Failure Analysis and Prevention Springer Journals

Failure Investigation of Counterweight Separation from Aircraft Propeller

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Publisher
Springer US
Copyright
Copyright © 2018 by ASM International
Subject
Materials Science; Tribology, Corrosion and Coatings; Characterization and Evaluation of Materials; Classical Mechanics; Structural Mechanics; Quality Control, Reliability, Safety and Risk
ISSN
1547-7029
eISSN
1864-1245
D.O.I.
10.1007/s11668-018-0438-0
Publisher site
See Article on Publisher Site

Abstract

The counterweight of a propeller in a turboprop aircraft was separated during an engine run-up inspection. If this separation occurs in-flight, it may result in an accident involving serious damage or injury. In this investigation, the failed counterweight clamping assembly was studied to determine the root cause of failure. Both experimental and computational investigations were performed to explore and confirm the effects of experimentally observed anomalies on potential clamping assembly failure. Dimensional measurement of the failed clamping thread area by X-ray CT scanning revealed significant deviation from requirements in the major diameter of the thread. Fractographic and microscopic examination along with chemical analysis confirmed that the clamping bolts were pulled out due to overload stripping failure of the internal threads. Detailed computational fracture modeling utilizing the XFEM crack simulation technique provided further insight proving that thread engagement length had a significant effect on the clamping assembly failure. Based on these observations, it was concluded that the main root cause of the stripping failure was the dimensional nonconformance of the internal thread from the requirements in standard 7/16-20UNF-3B that resulted in the loss of thread engagement length.

Journal

Journal of Failure Analysis and PreventionSpringer Journals

Published: Mar 6, 2018

References

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