Good vibrations

Numerical models for smoother helicopter rides

Helicopter-maker AgustaWestland developed new blades for its EH101 Helicopters, also known as Merlins, to increase both helicopter speed and lifting capability. However, engineers found that the new blades, which featured an accentuated “twist”, generated large vibratory forces.

Part of the issue was that standard modelling techniques treated blades like simple one-dimensional structures. AgustaWestland approached Professor Paul Weaver and colleagues at the University of Bristol’s Advanced Composites Centre for Innovation and Science (ACCIS), known for their advanced numerical modelling techniques.
AgustaWestland funded an EPSRC CASE student who, along with Weaver, developed a new blade model based on some fundamental concepts of structural engineering. When incorporated into new blades, this method reduced the vibratory control loads.

The Principal Rotor Engineer from AgustaWestland reported that "the design, which uses unbalanced anisotropic angle plies at a specific fibre orientation, gives performance enhancement by coupling bending and torsion within the blade to reduce the loads experienced by the rotor control system. Eighty-five of these blades, each with a typical value of £100k, have been purchased by the UK MoD as part of an Urgent Operational Requirement in order to enhance the range and capability of the EH101 aircraft in Theatre".

Read the good vibrations case study.

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