An investigation into the cause of the unacceptably high incidence of fatigue failure of blades in the engine cooling fan fitted to Sioux helicopters led to a search for resonant frequencies of the fan blades. Tests on a stationary fan and in a rotating rig showed resonant vibration at various fan speeds; in particular, high stresses were generated by a second shaft order resonance close to the normal operating speed. A modification to overcome the problem was proposed, consisting of a stainless steel shroud fitted over the blade tips. Tests showed that this modification reduced stresses to a negligible level, and the mechanical soundness of the scheme was confirmed by an endurance run followed by an overspeed test. The modified fan was fitted to a helicopter and measurements comparing its cooling performance with a standard fan showed only small differences.
Vibration investigation of helicopter engine cooling fan
Schwingungsuntersuchung am Kuehlgeblaese fuer einen Hubschraubermotor
US Government Research Reports ; Mar ; 1-19
1977
19 Seiten
Report
English
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|EVALUATION OF HELICOPTER TURBINE ENGINE LINEAR VIBRATION ENVIRONMENT
SAE Technical Papers | 2021
EVALUATION OF HELICOPTER TURBINE ENGINE LINEAR VIBRATION ENVIRONMENT
SAE Technical Papers | 1976