The Waltz of The Ailerons

Waltz of the the Ailerons or "Vales Des Ailerons"

Introduction

Before I begin this article we have to go back to the very basics. Back to one of the first topics covered during your theoretical training (or one of the first topics that will be covered during your training for all the yet to be aviators out there). 

This topic is "Loads Applied to Aircraft Structures". The two main Loads that are relevant to today's topic are Bending and Torsion.

Since this is a topic that you're reading on your free time, I will not bother you with endless lines of text describing aircraft loads. Instead, here's a picture that will do a better job at explaining the loads than my rambling.

Aircraft Loads

What is the "Waltz of The Ailerons"

The Waltz of The Ailerons, nicknamed Vales Des Ailerons (VDA) by Airbus engineers, is a function developed by Airbus specifically for the A380. It has to be noted that a similar function is available on the A350 but due to only having 2 ailerons per wing, the effects isn't as visually attractive as that on the A380.

As you can see in the video, the VDA seems like a completely random movement of the A380's 3 ailerons ("Outer", "Center", and "Inner" Ailerons). But with Airbus nothing is ever random!

The main purpose of the VDA is to reduce torsional and bending loads on the wing and also reduce undesirable lateral oscillations. This reduction in oscillations translates to better passenger comfort especially during manoeuvre-heavy phases of the flight.

The VDA is controlled by the primary flight computer (called "PRIM" on the A380 & A350). The VDA happens automatically and without any additional input from the pilots.

The VDA occurs during roll inputs and during cruise as part of the Load Alleviation Function. 

"The aim of the Load Alleviation Function (LAF) is to reduce the fatigue and the static loads on the wing." -
A380 Flight Crew Operating Manual (FCOM).

 

Airbus explains this in more details in an issue of their Safety First magazine (article found HERE). Since someone else did the work and explained the details, I won't act like an expert on the subject by copying and pasting their work, instead I will leave you with a couple of videos of this beautiful Aileron Waltz!