158
N. Chari et al.
Table 12.1 Comparison of fixed, rotary and flapping wings
Parameters
Fixed wings
Rotary wings
Flapping wings
Aerodynamic forces
developed
Vertical lift opposing
drag and no thrust
Lift, drag and thrust
Lift, drag and thrust
Fulcrum at the wing
base
Wing rigidly fixed at
the base
Hinged to central rotor
hub; free to tilt up and
down and turn about
the longitudinal span
wise axis
Elastic hinge and
movable; possibly in
X, Y, and Z directions
Propeller or jet
(optional)
Usually separate
propellers are present
No separate propellers
No separate propellers
Acoustic level
Relatively high
Very high as in
helicopters
Variable; depends on
wingbeat frequency
Wing tip velocity
Constant
Constant
Variable, linear and
rotating
Aeroelastic effects
Present
Present and more
critical
Present and more
critical
Wing motion
Wing rigidly attached,
moves along with the
body
Circular (rotary) and
with up and down
oscillations
Oscillating and
twisting type of
motion
Wingtip traces
Practically straight line Circular superimposed
with up and down
oscillatory motion
Elliptical or figure of
‘8’ depending on
frequency
Stalling angle (onset) 15 to 20°
15 to 20°
Up to 70° or more
Landing/Take off
Long run way is
required
VTOL (Vertical
Takeoff and Landing);
no runway required
Need some runway
(STOL or V/STOL)
for MAVs
Rotary tail fan
Absent
Required to counter
rotor torque
Absent
Manoeuvrability
Limited
Torque of the moving
rotor is relatively high.
Hence limited
Relatively high
Translatory motion
Forward, long and
small distance flight
Forward and
backward, VTOL
Forward and
occasionally backward
Source Adopted and modified from Chari [1]
inspiration and provide many useful clues in the design of small man-made aerial
vehicles by incorporating flapping and flexible wings. The microaerial vehicles and
unmanned aerial vehicles (MAVs and UAVs) share many common characters with the
biological fliers. Presently there is an increased demand for the deployment of MAVs
for surveillance applications, paramilitary activities, civilian applications, military
and environmental missions for spying and surveillance. This is equally true for both
the advanced and developing countries. The design and production of successful
MAVs is still in experimental stages. There is also a serious problem of takeoff and