THE SECRET OF TAKEOFF AND LANDING

THE SECRET OF TAKEOFF AND LANDING

The 6 or 7 minutes during takeoff or landing are the most critical times for any fl ight. Pilots must be trained hundreds, if not thousands, of times in each operation and have everything carefully calculated to make it a success. What are the little-known secrets behind takeoffs and landings?

Text by Yunshi Wu Translation by Leo Illustrations by Haolun Zhang

飛機起降的奧秘

在飛行過程中，起飛6分鐘和降落7分鐘是最敏感最關(guān)鍵的時段。飛機起降的每一個角度，都經(jīng)過飛行員千百次的計算和千百次的訓(xùn)練，每一個動作，背后都有鮮為人知的奧妙。

Lift it up

An aircraft uses the lift generated by its wings to become airborne while taxiing on the runway.

A relative speed between the airplane and air is produced as the airplane gains speed due to the thrust generated by its engines. Because of the streamlined shape of the wings, air travels slower under them and faster over them, creating a higher pressure under them and a lower pressure above them. This is how lift is generated.

At a certain point during takeoff, the pilot will pull back on the control stick to defl ect the elevators up. To reduce takeoff speed and shorten the takeoff roll, the pilot will lift the nose gear (so that the aircraft is in a two-point attitude) to increase the angle of attack and lift coeffi cient of the wings, when the aircraft reaches a certain speed. This must be done when the airplane reaches the right speed, or a tail strike may occur.

Landing

Aircraft landing involves more complicated manoeuvres than takeoff does as more changes occur at a faster pace during the process.

The basic idea of landing is to bring down the engine thrust, the aircraft speed and the speed of airfl ow over the wings. At landing, the engines idle; and the pilot must slow the forward speed and the rate of descent, while avoiding stalled engines, in order for the airplane to touch down at the approach end of the runway in time. In the process, fl aps and slats are often used to change the aircraft shape and the angle of descent.

Blind landing

“Blind landing” is a process in which a pilot is forced to land an airplane in cloudy or otherwise low-visibility conditions when the runway is not clear, relying on radio signals and high-intensity light arrays. Blind landing systems are needed to guide the plane to a safe landing. Two alternative systems are often available at mainstream airports to guide the aircraft down to 30 metres above the ground, where the pilot can see the runway.

升力起飛

飛機從地面滑跑到離地升空，憑借的是機翼產(chǎn)生的升力。

發(fā)動機帶來的推力給予飛機快速向前運動的速度，使飛機與空氣產(chǎn)生了相對運動。由于機翼的流線體設(shè)計，空氣流經(jīng)機翼上下速度不一，上下表面產(chǎn)生壓力差，從而產(chǎn)生了向上的升力。

起飛時，飛行員會有一個拉桿動作，以控制飛機尾部的水平升降舵。為減小離地速度，縮短滑跑距離，當(dāng)飛機速度增大到一定程度時需要抬前輪作兩點姿態(tài)滑跑，以增大迎角和升力系數(shù)。飛行員必須在正確的速度下抬前輪，速度過大或過小，都可能導(dǎo)致飛機擦尾。

著陸原理

飛機降落的操作更難于起飛，降落是飛機變化最多最快的階段。

飛機降落原理是減小發(fā)動機的推力，使飛機速度減小，從而減小空氣流經(jīng)機翼的速度。此時發(fā)動機處于慢車工作，飛行員必須控制飛機在一個緩慢的速度下，一邊向前飛行一邊下降，避免失速，爭取在跑道頭接地。其間要放襟翼和縫翼，改變飛機外形，調(diào)整下降角度。

特殊盲降

盲降是在低云、低能見度的儀表氣象條件下，飛行員無法辨清跑道時進行，使用無線電信號及高強度燈光陣列來引導(dǎo)飛機安全降落的著陸系統(tǒng)，也稱為“盲降系統(tǒng)”?，F(xiàn)在主流機場都有二類盲降系統(tǒng)，可以引導(dǎo)飛機下降到30米，飛行員見到跑道后再進行著陸。