Tilt rotors are a new breed of subsonic aircraft
developed for both military and civil aviation. The
current production of the military V-22 Osprey and
the launch decision of the BA-609 civil tilt rotor will
certainly enhance the U.S. military and economic
competitive status in the international aviation arena.
In addition, civil tilt rotors have the potential to
increase air transportation throughput in congested
airports by off-loading busy runways. To support the
U.S. civil tilt-rotor development, NASA created the
Short Haul Civil Tiltrotor project (SHCT) from the
Aviation Systems Capacity program.
The SHCT program addresses critical enabling
technologies for civil tilt rotors that include low-noise
tilt rotors. NASA Ames and Langley Research Centers,
the U.S. Army Aeroflightdynamics Directorate, and
the U.S. rotorcraft industry, have jointly developed an
aeroacoustic research program aimed at accomplishing
the SHCT goals. One of the major milestones of
the program is to validate aeroacoustic analyses for
low-noise tilt-rotor designs. The primary objective of
the Tilt-Rotor Aeroacoustic Model (TRAM) project is
to provide a comprehensive database for code
validation.
The TRAM is a quarter-scale V-22 model with
two configurations: an isolated rotor configuration
and a full-span, dual-rotor aircraft configuration. The
TRAM isolated rotor was tested in the Duits-Nederlandse
Wind Tunnel in the spring of 1998. The
Full-Span TRAM (FS TRAM), shown in the figure, was
installed and will be tested in the NASA Ames 40- by
80-Foot Wind Tunnel to provide aeroacoustic data
for the complete aircraft configuration.
The FS TRAM is a highly complex aircraft model
designed to accommodate many aspects of tilt-rotor
research. The model has two rotor balances, one per
rotor, and a fuselage balance. The pressure-instrumented
blades provide high-frequency air-load
measurements, and wing-mounted pressure tabs
provide data about rotor-wing interaction effects. In
addition, both wings and blades are instrumented
with strain gauges for safety-of-flight monitoring and
structural load measurements. The data generated
from the FS TRAM wind tunnel test will be a unique
and valuable asset in the development of aeroacoustic
analyses for advanced tilt-rotor designs.
In addition to the intensive hardware and instrumentation
build-up, significant progress has been
made on the FS TRAM, including the complete
checkout of two new electromagnetic motors, the left
rotor drive system, and the new control system. A
700-channel slip ring was completely wired, and the
new rotor hubs were installed. Furthermore, modifications
made to the existing microphone traverse
system will allow measurements of the acoustic
directivity of both rotors. Significant preparations are
under way to install a particle image velocimetry
system for detailed flow measurements and a laser
light sheet system for flow visualization of the rotor
wakes.
Point of Contact: M. McCluer
(650) 604-0010
mmccluer@mail.arc.nasa.gov
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