An in depth literature survey has been carried out on the main rotor blade of helicopters is carried out, and the indigenous Black Hawk has been chosen for design, development and testing on a sub-scale level. The blade configuration details including the platform, taper, twist, root joint and profiles is studied. The scale is so chosen that the hardware is of respectable 2 to 4 meters, which can be realized within the financial and time constraints.

The various load cases have been analyzed, and critical load case arrived at. The blade is redesigned with skin/shell out of composite material ( E glass woven fabric reinforcement with room temperature setting epoxy matrix) primarily taking the structural loads, with a rigid poly urethane foam as the filler core, facilitating fabrication. Mechanical properties of the composite are evaluated from coupon level testing on symmetric, balanced and quasi-isotropic laminates, cured at room temperature. The preliminary designed is carried out by mechanics of solids approach of solids approach, and ply-offs are resorted to, thereby placing the material where required and not adding to the weight unnecessarily. Detailed drawings are prepared. Structural analysis is carried out to arrive at micro-strains, and locations of stress concentrations and un-acceptable of safety have been redesigned.

Root plug is made as a separate insert, consisting of metal and composite.

A pattern of the blade in two halves is made out of wood, and composite moulds are realized by doing a composite lay-up together with longitudinal and transverse wooden reinforcements, directly on the said wooden pattern. Taking into account the variations in the shell thickness at various locations, the configuration of the foam core is worked out, and the same is shaped by loft-template technique, for a best fit. The matrix wetted reinforcement fabrics are laid up in either mould, the pre-fabricated form core and the root plug are placed in one mould, and the other mould with the lay-up is closed over this, and bolted together. The assembly is left over night for cure. The blade is removed from the mould, next day excess flash is trimmed off.

The critical load case loads are lumped at 3 or 4 discrete locations and the blade is loaded in cantilever fashion, at those said stations by means of dead weights. The loading is done up to the proof level only. The tip deflections are noted. One strain gauge is bonded at the root portion of the skin/shell, and its reading is noted. The test data is reconciled with predictions.