Vacuum and Hover Tests of a Dihedral-Anhedral Tip Composite Rotor

This paper presents test data from vacuum and hover tests of a 2.8-ft-radius dihedral-anhedral tip composite rotor. The paper describes the blades, their fabrication, properties, instrumentation, the test conditions, and the data acquired. The blades were Mach-scaled to a generic but representative modern rotor. Vacuum chamber tests measured rotating frequencies and strains. Hover tests measured performance, blade loads, pitch-link loads, and strains under steady and cyclic loading conditions. Three-dimensional finite element structural models were developed to ensure completeness and consistency of property definition. The three-dimensional analysis was also used for a preliminary assessment of the test data. The test data revealed that the dihedral-anhedral tip influences the torsional and higher frequencies of a rotor blade significantly. The oscillatory blade loads show patterns consistent with the vertical center-of-gravity offset introduced by the tip. The surface strains reveal interesting higher-harmonic patterns of loading particularly near the dihedral junction.