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Dec 3, 2010

Airbus A380 High Lift Devices

An interesting video about A380 hi-lift devices. Notice that when using full flaps the small aileron becomes so inefficient that additional large span spoilers are needed. It is also interesting that the actual aileron is splitted to several parts and they seem to work sequentially: when one part is fully used the next part assists. The LAF (Load Alleviation Function) system must play a role here also.

Spoilers are sometimes called "lift dumpers". Spoilers that can be used asymmetrically are called spoilerons and are able to affect an aircraft's roll. For readers not familar with aircraft controls here is more basic information about it.

The flaps and slats are operated by long shafts and gear boxes from single motors located in the center of the fuselage as seen in the following picture. This is the noise heard in the videos.

SFCC stands for Slats & Flaps Control Computers.

Here is how the splitted aileron works and why it works as it does:

"The 380 has 3 ailerons per wing, an outer, mid, and inner, the inner aileron has an electrical back so the aircraft could be controlled even in the event of a total hydraulic failure.

For takeoff landing the ailerons deflect down a little, that is called the "Aileron Droop Function" (ADF), the objective of the ADF is to increase the high lift function performed by the slats and flaps. All the ailerons droop downwards (3 each side), when the flaps are extended. Ailerons and spoilers execute the roll function. Spoilers are needed at slow speed since ailerons only would be too unefficient for the roll function.

The ailerons also have another function called, "Load Alleviation Function" (LAF), the objective of the LAF is to reduce structure fatigue and static loads on the wing during manoeuvres and turbulence.Spoilers 6 to 8 and all the ailerons are involved in the LAF.

The LAF unloads the stresses on the wing by momentaraly deploying the flight spoilers and deflects ALL ailerons upward. The function is so fast that it is hardly noticable. I do not think that it makes the turbulance feel any worse though. The function seems to work very well.

These functions (apart from the electrical backup) are common on other Airbus types."

Some additional Airbus flight control documents (pdf format):

A380 Flight Controls Overview

Airbus flight control system

Airbus A330/A340 Flight Control System

Airbus Digital Electrical Flight Control System

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