520
P. Liu
Fig. 7.99 Comparison of the landing status of the eagle and B747
and at the same time, the wings are deployed with a rapid downward air
discharge, so that they can take off. Obviously, no matter whether the ground
run-up takeoff or bouncing takeoff, the bird has to exert great strength during
the takeoff process, which consumes a lot of energy. In comparison, when the
bird is gilding, the speed of the airflow around the wing is high, and the bird
is flying in the upward airflow as much as possible, so the effort is small. Some
people may think that if the high-lift device is not installed on the wing, that
is, the wing area of the aircraft in cruising is the same as that of taking off
and landing, which is equivalent to the speed of takeoff and landing is similar
to the speed of cruising. What will happen? At this time, if the aircraft takes
off and lands at the cruising speed, it not only greatly increases the length of
the runway, but also has extremely poor safety. When the aircraft is taking
off normally, due to the excessive ground speed, the aircraft taxies a large
distance on the ground runway. If the aircraft taxies to the lift-off speed, the