A380 LGW

[JETPORT]

Any comments on rudder use ?

Emirates A380 at Gatwick Airport - YouTube (http://www.youtube.com/watch?v=HcN1NV1HEFI&feature=youtu.be)

[B737-800W]

Its Airbus!!!

[John Farley]

JETPORT

With any aircraft after touchdown and before the nose wheel is on the ground the rudder is used by the pilot to keep the aircraft pointing down the runway. The amount and type of rudder use will depend primarily on the surface wind conditions which can act to disturb the aircraft. Once the nosewheel is on the ground nose wheeel steering may be available on many types and becomes an alternative to the use of rudder. Best practice means that after lowering the nose pilots are likely to continue to use the rudder until the ground speed is low.

Why do you ask?

[John Farley]

B737-800W

I presume you mean it is an Airbus.

If so your aircraft recognition is coming along.

But do you know which Airbus I wonder?

[JETPORT]

Thanks John but I was surprised at the amount of rudder inputs on the approach as the rudder seems to be pedalling a lot , overcontrolling left to right
I thought after the tail fell off American Airlines A300 that the rudder wasn't supposed to be moved like that?

[aeromech3]

On most Jets I have worked it is called rudder fine steering; activated once the nosewheel oleo is slightly compressed, the rudder bar inputs are interconnected to the nosewheel steering system, with a limited degree of authority ( a few degrees only). Once the aircraft speed has decayed sufficiently, the steering tiller is used for the courser inputs to maneuver off the runway.
At low air speed the rudder authority would not be limited as air loads are low and similarly effectiveness reduced, hence large movements. Interesting to watch!

[John Farley]

JETPORT

Ah, I see were you are coming from.

All aircraft are stressed to allow full rudder to be applied up to the so called manoeuvring speed. What is not catered for is then reversing the rudder to full the other way and back again. If the rudder is oscillated in that way in time with the way the nose starts to swing you can build up huge amounts of sideslip which could well have the fin off. It is just like a modest force applied to your kid's swing at just the right moment can build up the swing motion and if this is done a few times the kid will love the result without you ever applying the push needed to get such a big swing going using one monster shove.

On the vid it is not easy to see exactly what rudder motion is used before touchdown. To me it all looks like bursts of right rudder and back to central with no continous right/left/right/left oscillation and certainly no obvious oscillation of the nose side to side. In other words the rudder has been used intermittently to the right to counter the pilot sensing the nose starting to go left due to gusts.

[FlightPathOBN]

https://www.youtube.com/watch?v=WWeLJHaXd8M

[WhyByFlier]

If you youtube A380 crosswind landing you'll see the emirates pilots inputs are quite normal.

[misd-agin]

John Farley - All aircraft are stressed to allow full rudder to be applied up to the so called manoeuvring speed.

That is a light airplane statement and not application to passenger jetliners. AA 587 investigation addresses this.

[misd-agin]

If you youtube A380 crosswind landing you'll see the emirates pilots inputs are quite normal.

If you read Boeing AFM they discuss applying rudder as necessary when transitioning to a cross control for crosswind landings.

The video shows about 10 rudder inputs in the 17 seconds from 0:12 to touchdown at 0:29.

This is called 'walking the rudder' (left, right, left, right) and is poor technique and completely unnecessary.

[donpizmeov]

The FBW system is moving the rudder for gust suppression. No pilot input required. Because the 380 has a relatively low Vref the rudder movements appear large to be effective.

The Don

[Oakape]

Thanks Don, finally someone who knows what they are talking about!

If you guys find the rudder movements fascinating, you will love what the ailerons do! Plenty of youtube videos for you to check out.

As B737-800W says, it's an Airbus!

[BOAC]

As Don and oak post, the 380's computer generated control movements have caused much comment (and puzzled amusement). I suspect that 10 rapid rudder deflections/reversals in 17 seconds on an aircraft of that inertia will do nothing except use hydraulic power.

[Lord Spandex Masher]

Much like the over controlling, high input, stick wagglers.

[Capn Bloggs]

As Basil said to the nurse... "My god you're ugly!". :E

[Molokai]

Never flown on an A380 and not casting any aspersions, but what's with the slight bounce and skip on touchdown? My B727 instructor used to give me the " Gibbs's head slap on Tony Denozo " everytime I did that many suns ago. Is this a A380 tendency? Just curious, just asking.

[Capn Bloggs]

but what's with the slight bounce and skip on touchdown?
Overflared it.

[misd-agin]

777 rudder has gust suppression. If the movement was from gust suppression we'd see in on 777 landings also.

And if it was gust suppression it would happen on takeoff.

Even the KEF crosswing landings, in 40-50 kt crosswinds, or the Brest crosswind test videos, didn't have as much rudder inputs either for takoff or landing. (google 'A380 crosswind test flights')