The successful introduction of the civil tilt rotor
into the national airspace system relies heavily on its
community acceptance. In particular, a tilt rotor with
reduced noise emissions is critical. Various
approaches are being considered to address this
problem. One such approach, the application of
remotely adjustable on-blade control elements to
rotor blades, is receiving considerable attention. This
research effort is an attempt to better define the on-blade
requirements and ultimately to identify a
feasible design implementation.
The objective of this effort, performed by Continuum
Dynamics, Inc. under an SBIR (Small Business
Innovation Research) Phase I contract, was to determine
a mix of on-blade control-surface deflection or
in-flight twist change to produce significant payload
and range enhancement and blade vortex interaction
(BVI) noise reduction for a representative civil tilt
rotor. In addition, they were to establish preliminary
designs for adjusting blade twist in a rotating environment
using smart structures.
Through the combination of a comprehensive
analysis and noise prediction code, BVI noise was
predicted for various levels of tilt-rotor blade washout
(see figure 1). These results demonstrate that if an
washout, the BVI noise level in front of the tilt-rotor
hub can be reduced by as much as 6 decibels. A
noise-reduction strategy combining both on-blade
deployment and nacelle tilt could reduce BVI noise
levels by as much as 12 decibels. These noise
reductions are consistent with NASA's 10- and
20-year goals and, if realized, could significantly
accelerate the acceptance of tilt rotors into our
national airspace system. In conjunction with this
analytical work, various concepts were identified and
considered as means to implement the necessary
blade twist changes.
Point of Contact: T. Norman
(650) 604-6653
tnorman@mail.arc.nasa.gov
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