LA-2302 -- Propeller Fan Stresses and Vibrations

Propeller fan vibrations, so far, are traditionally approached in an empirical manner. Fans are many times not designed from a vibration viewpoint or even failure viewpoint at the drawing board, rather, these viewpoints are taken into account after the first prototype has been built and tested for aerodynamic performance. Principally, there is nothing wrong with this approach; it is time-honored and it works. However, once in a while rather baffling failures or noise generation effects occur. These present puzzling problems and, while they are eventually eliminated by experimental detective work and by trial and error procedures, are usually not understood in a manner that prevents reoccurrence.

The comments that follow do not by themselves constitute a design procedure. They are rather an attempt to discuss real and potential vibration effects in fans by means of simple, isolated mathematical models to provide additional information to that already collected in other papers (1).