As the technology in rotor deicing matures, more programs are
willing to engage in the certification of their helicopters for
flight into icing conditions. The S-92A™ helicopter, AW139, V-22,
and EC225 aircraft have been certified/qualified recently and are
illustrative examples of such engagement. The state-of-the-art
configuration definition of rotor ice protection systems that have
been introduced into the western rotorcraft manufacturer's
production line has been limited to electro-thermal deicing
systems. System configurations may use either chordwise or spanwise
shedding schemes and could differ in design and operation.
Regardless of the selected design configuration, an analysis of the
required extent of protection coverage must be performed unless one
has access to data offering sufficient similitude in terms of
airfoil geometry and flight conditions. The analytical path may be
required to account for blade oscillation with continuously
changing angles of attack through the entire azimuth, and
continuously changing local velocities along the span of the
blades, with local variation in the associated heat transfer and
water drop collection efficiency.
While Lewice2D has been the code of choice for fixed-wing
aircraft, its potential flow solver is quite limited when it comes
to analyzing small-chord airfoils at high angles of attack and at
local velocities approaching the speed of sound. Therefore, a
method has been explored which utilizes a more applicable flow
solver combined with the drop trajectory solver from the Lewice3D
code. This combination has been selected as the best option in
terms of accuracy and run time. Because of its availability and
level of familiarization within Bell Helicopter, the FENSAP flow
solver by Newmerical Technologies Inc. (NTI) was selected.
This paper presents the findings from the process used in
establishing the coverage extent on a representative and readily
available 206 helicopter tail rotor blade model. The model is to be
tested in the NASA Glenn Research Center Icing Research Tunnel in
support of the "High Fidelity Icing Analysis and Validation
for Rotors" project which is funded by Vertical Lift
Consortium (VLC) members Bell Helicopter, The Boeing Company, and
Sikorsky Aircraft Corporation. Georgia Institute of Technology and
NASA are active participants in the collaborative research effort,
which is partially funded by the National Rotorcraft Technology
Center (NRTC).