Limitations:
Now We all are discussing about the
limitation of helicopters. The means of limitation is the disadvantage of the
helicopter.
The main limitation of the helicopter is
its low speed. There are several reasons a helicopter cannot fly as fast as a
fixed-wing aircraft. When the helicopter is hovering, the outer tips of the
rotor travel at a speed determined by the length of the blade and the RPM. In a
moving helicopter, however, the speed o the blades relative to the air depends
on the speed of the helicopter as well as on their rotational velocity.
The airspeed of the advancing rotor blade
is much higher than that of the helicopter itself. It is possible for this blade
to exceed the speed of sound, and thus produce vastly increased drag and
vibration.
Because the advancing blade has higher
airspeed than the retreating blade and generates a dissymmetry of lift, rotor
blades are designed to “flap”-lift and twist in such a way that the advancing
blade flaps up and develops a smaller angle of attack.
Conversely, the retreating blade up and
develops a higher angle of attack. And generates more lift. At high speed, the
force on the rotors is such that they “flap” excessively and the retreating
blade can reach too high an angle and stall.
Helicopter also vibrate and unadjusted
helicopter can easily vibrate so much that it will shake itself apart. To reduce
vibration, all helicopters have rotor adjustments for height and weight. Blade height
is adjusted by changing the pitch of the blade. Weight is adjusted by adding
and removing weights on the rotor head and at the blade end caps.
if
you have any doubts
feel
free and comment here.
