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the coaster. The reverse occurs at the top of the hill, where riders experience a light,
floating sensation. Although roller coasters and teeter-totters are great fun, the flight
crew is careful to keep passengers from experiencing these sensations.
The teeter-totter effect is minimized by using flight controls called spoilers and
by making flight path changes extremely gently. By reducing the throttles and
actuating the spoilers to reduce the lift of the wings, the aircraft can begin descending
without the nose being pitched downward. As the air pressure outside the aircraft
increases with decreasing altitude, the cabin pressurization must be slowly and
continuously adjusted.
As the aircraft slows from cruise to approach speed, the wing flaps and slats
are activated to minimize the need to change the pitch attitude. When the aircraft
reaches the final approach fix and begins the final descent, the landing gear is
extended. The additional drag from the landing gear is used to assist in this descent.
`The most complex maneuver is the landing flair. Passing the runway
threshold, the throttles are closed and the nose is raised to the proper touchdown
attitude. This pitch change must be timed precisely so that the rate of descent at main
gear touchdown is kept to a minimum. The pilot must also compensate for any cross
winds. The landing gear struts act as shock absorbers, softening the touchdown. After
touchdown the spoilers deploy, increasing the downward force on the landing gear
and maximizing braking effectiveness. Assisting in this braking are the thrust
reversers. Devices on the jet engines engage, allowing the thrust to be directed
forward, thus slowing the aircraft.
The smoothness with which all of these changes are accomplished is a tribute
to the aircraft's design and the abilities of the flight crew. Amazingly enough, this
landing can even be accomplished automatically if weather conditions do not permit
the pilot to land safely using visual flight rules. Flight attendants sometimes have to
awaken passengers when the plane reaches the gate. That is indeed a compliment to
the pilot's expertise.
18.4. EXERCISES
1. Ответьте на вопросы.
1.
What are passengers filled with when the aircraft nears its final destination?
2.
Why does the activity on the flight deck increase?
3.
What are approach and landing?
4.
How must approach procedures be accomplished?
5.
What are the functions of the radar air traffic controller?
6.
Why does the long, rigid body of the airliner act like a teeter-totter combined
with a roller coaster?
7.
Why is the crew is careful during the flight?
8.
What are spoilers designed for?
9.
Why must the cabin pressurization be slowly and continuously adjusted?
10.When is the landing gear extended?
