THE SMOOTH APPROACH

As the aircraft nears its final destination, the flight attendant announces it is time to return tray tables and chairs to their upright positions. Passengers are filled with the anticipation of either reaching their destination or returning home. Activity on the flight deck increases as the crew begins the initial descent to safely return the aircraft to earth.

Approach and landing is by far the most critical phase of the flight. To assure the highest safety standards, approach procedures must be accomplished with great precision. Checklists are completed and double-checked by flight crew members. The aircraft is handed off from the enroute to the approach radar air traffic controllers, who will direct the airliner to the runway while keeping all aircraft a safe distance apart.

The long, rigid body of the airliner acts like a teeter-totter combined with a roller coaster. As in a teeter-totter, the aircraft moves about the center of gravity when the pitch attitude is changed, while changes in flight path create effects similar to those experienced at the top and bottom of hills on a roller coaster ride. When a roller coaster reaches the bottom of an incline, the riders feel heavy as they are pushed down into their seats. This sensation is caused by the upward acceleration of 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.