Airliner landing ?

Question

When an airliner lands which is the primary funtion of the spoilers, to dump lift or airbraking or both.

Is that the reason why they are called spoilers?

Is the air braking effect just an added result of their position in the airflow.

Answer 1

They act like a wall... both, causing tons of drag on the airplane, as well as deflecting air upwards, you will see that they are slightly angled back... this air getting deflected upwards "pushes" the airplane into the ground which obviously, counteracts lift... and the slowing down of the airplane, also sheds lift...

In sort, it accomplishes both tasks...

Answer 2

Both. The intent is to decellerate quickly and in a controlled fashion. Having the spoilers deploy to full extension after touchdown provides aerodynamic braking shortening the landing run. It also decreases lift. However, this isn't to prevent the plane from possibly becoming airborne again. Dumping lift increases the weight on the wheels and therefore allows you to apply greater braking (without skidding) also shortening the landing roll.

Answer 3

Spoilers serve two functions on a heavy jet aircraft. In flight, they augment aileron flight control movement. They only move about 35 degrees and are moved by inputs from an aileron/spoiler mixer (DC9 in mind here). When the aircraft touches down on landing and the squat switch is made, the spoilers revert to what is called "ground spoilers". The spoilers now deploy to 60 degrees in order to dump lift and keep the aircraft pinned to the runway.

Answer 4

While landing, and I am making the assumption you mean "landing" (i.e. wheels touching the ground aircraft slowing down dramitically) rather than "approach" (wheels down and still desending to the ground), the "spoilers" are used for both. Some people call them spoilers some call them flaps but there main purpose it to help steer the aircraft along its axis'