File:VIDEO - Operation of flaps, spoilers and ailerons on a landing Boeing 747-400 (Landing configuration) (6129413784).jpg

The wings of modern aircrafts do much more than just producing lift, usually serving as fuel tanks and in many cases carrying and transferring thrust from the engines too. In particular, the wings of large aircrafts are fairly complex and use movable surfaces to change their aerodynamic characteristics which must meet a diverse range of requirements throughout the operating envelop of the aircraft.

This video shows the operation of few of the movable surfaces of the wing in a Qantas Boeing 747-400 (landing configuration).

In the clip, the spoilers (the plates on top of the wings that are deployed upwards) and the triple-slotted trailing-edge flaps (the devices extended downwards on the trailing edge of the wing) can be seen in operation. At the start of the video, both the spoilers and the flaps are shown deployed. The spoilers are then lowered and finally the triple-slotted trailing-edge flaps are retracted.

[The following text was extracted from Wikipedia.org]

In aeronautics, a spoiler (sometimes called a lift dumper) is a device intended to reduce lift in an aircraft. The spoiler creates a carefully controlled stall over the portion of the wing behind it, greatly reducing the lift of that wing section. Spoilers differ from airbrakes in that airbrakes are designed to increase drag making little change to lift, while spoilers greatly reduce lift making only a moderate increase in drag.

Slats (not shown in the video) are aerodynamic surfaces on the leading edge of the wings of fixed-wing aircraft which, when deployed, allow the wing to operate at a higher angle of attack. A higher coefficient of lift is produced as a product of angle of attack and speed, so by deploying slats an aircraft can fly more slowly or take off and land in a shorter distance. They are usually used while landing or performing maneuvers which take the aircraft close to the stall, but are usually retracted in normal flight to minimize drag.

Flaps are hinged surfaces on the trailing edge of the wings of a fixed-wing aircraft. As flaps are extended, the stalling speed of the aircraft is reduced, which means that the aircraft can fly safely at lower speeds (especially during take off and landing). Flaps are also used on the leading edge of the wings of some high-speed jet aircraft, where they may be called Krueger flaps