Abstract: A fan rotor assembly having decreased susceptibility to vibratory damage is disclosed. In one embodiment described the rotor assembly includes a plurality of principal fan blades 22 and a plurality of secondary fan blades 36 associated therewith. The secondary blades are coextensive with the principal fan blades over the inner portion of the principal blade span.

Abstract: Apparatus and methods for measuring deflection of rotating fan blades of a gas turbine engine is disclosed. The measurement of bending and torsional deformation in response to integral and to nonintegral vibration as well as to structural loading is developed. Optical measuring techniques including the projection of collimated light beams into the fan section of the engine are employed. A linear readout of angular deflection is displayed on a distant screen for amplification of the actual deflection. The plurality of beams provide a deflection profile covering the full surface of the blade.

Abstract: A rotor blade system which is adapted for long term reliable operation in a gas turbine engine is disclosed. Techniques for altering the natural frequency of the blade system to reduce the detrimental combined effects of external excitation and self-excitation are developed. One structure shown utilizes a shroud for the control of self-excitation in combination with a pin root to lower the fundamental first natural bending frequency of the blade system below the level of the 2E frequency at idle.

Abstract: A hollow composite compressor blade having two airfoil-shaped half sections formed of composite material bonded together, one or more span members of metal or composite material bonded and integral therewith and an appropriate root structure. The composite material being preferably silicon carbide coated boron filament with an aluminum matrix for the shell.