A380 outboard aileron segmenting

[Reluctant737]

Hi everyone,

I've just been shown a video on Youtube taken by a passenger on the A380. I noticed that shortly before landing, the outboard aileron appears to segment into four pieces (give or take) and perform a little mexican wave just before touchdown!

Now I fly 737NGs in the day job, but never came across this or heard about it before!

If anybody knows what I'm referring to, could they possibly enlighten me as to what purpose this technique holds, apart from looking cool?

If not, may I direct you to the video in question - have a look from 4:04 onwards.

YouTube - Worst! Landing of A380 Tokyo(NRT)-Singapore

Cheers, Ad

p.s. ignore the name of the video, I know

[Fargoo]

http://www.pprune.org/questions/3276...behaviour.html

[FlightDetent]

In (Airbus type) FBW you do not control the individual surfaces. You ask for a attitude, and FBW makes sure it is delivered. If you ask for no change, you get no change even if that requires some hard aerodynamic work. The sequence of using individual aileron control panels for the 380 is down to design. Properly drawn.

FD (the un-real)

[ARINC]

You are indeed seeing Load Alleviation Function Law (Damping) available from PRIMS only. The segmentation in the diagram represents the different type of actuation. There are only 3 ailerons per side. IN, MID and OUT

[Spanner Turner]

You are indeed seeing Load Alleviation Function Law (Damping)

Mr Airbus would disagree, below from the training notes:


A380 TECHNICAL TRAINING MANUAL

PRIMARY F/CTL: FLY BY WIRE DESC. (3)
Auxiliary Functions (continued)
Load Alleviation Function
The aim of the Load Alleviation Function (LAF) is to alleviate the
fatigue and static loads on the wings by reduction of the wing bending
moment.
The LAF is composed of:
- the passive turbulence alleviation and,
- the active turbulence alleviation.
The passive turbulence alleviation alleviates the static loads in
turbulence and during maneuvers. The activation is based on the
vertical load factor given by normal law. The computed orders are
sent to the ailerons and spoilers 6 to 8.
The pitch compensation linked to the deflections is sent to the inner
elevators.
The active turbulence alleviation alleviates the fatigue and static loads.
The activation is based on the measurement of the vertical load factor
on the wings given by the accelerometer units installed on the pylons.
The computed orders are superimposed (added) to the computed orders
of the passive turbulence alleviation. They are sent to the ailerons.
Compensation orders are sent to the inner elevators.
The LAF is activated above a given speed and, vertical acceleration
thresholds but are inhibited when slats and flaps are in full
configuration.


In the video the flaps are at full config.

[TwinJock]

Interesting video!

Two things come to mind. The first is that the A380 has the same distinctive flap whine when extending or retracting flaps. Saw many a nervous passenger when the "siren" started.

Secondly, Singapore Airlines must have the most pathetic background music playing during the approach - sounds like a sound track from a porn movie!!

[ARINC]

The LAF is activated above a given speed and, vertical acceleration
thresholds but are inhibited when slats and flaps are in full
configuration.

Correct and a little silly of me not to read to the end !

[Basil]

Tonight on BBC2 and repeated Monday 16Feb, lightweight little piece using the A380 as a vehicle for explaining winglets, composites, rapid inflation (of sliderafts), and basic suspension springs/dampers presented by Richard Hammond of Top Gear.
He does a very good demonstration of how NOT to jump and sit on the slide.
He should have spoken to a CC SEP instructor or, if precluded by his serious injuries sustained in the high speed flip about a year ago, have let someone else demonstrate the correct technique for exiting in an emergency.
Very unfortunate example of negative training which could cost lives.

[raffele]

I watched the Hamster's Engineering Connections too and thought that when he jumped out of the mock up.

It was a good programme, but I felt it was a bit "Schools"ish really - sorta thing you'd show primary school kids. Well worth watching though.

But back to the actual discussion...

[Obi Offiah]

Here is an excerpt on the A380 from Flight International:

"At speeds above 240kt indicated the outermost aileron is locked out, the remaining two more than sufficient to attain desired roll rates. Each aileron is commanded independently and, due to structural aeroelasticity, may be out of step with its wing mates – deflecting up, for example, while the wing itself is rolling up. All of this is transparent to the pilot, with the system providing control in the roll axis that is precise and predictable."

Also checkout the following link: IFAC-PapersOnLine: A380 roll kinematics design

Its interesting to note that on the ground and with the flaps raised the spoilers open slightly.

I hope this helps
Obi