Airbus Rudders are Made of Reconstituted Dog Biscuits

[Graybeard]

Inflammatory title? That was the title of an email forwarded to me which has no text, but has 4 pix of an Airbus rudder that tore off. I might post the pix, but don't know how to upload them. The tail was blue, with a star under a cloud.

From the look of it, the rudder is only a skin with foam filler. Can anyone explain the design, construction and source of strength?

GB

[Computer George]

To show te pictures, go to a site like http://www.freeimagehosting.net/ Upload your pictures on that site and post a link in your post.

[Carnage Matey!]

Better they tear off than stay at full deflection and flip the aircraft on its back like the Boeing design. I believe Concorde rudders used to depart in flight at fairly regular intervals too.

[Eirefly]

Thats true, so many accidents have been caused on Boeings due to the rudder locking to the left or right.

[Anotherflapoperator]

Yes but thanks to FDA and BA's investigative chaps this is now a known and fixable issue, is it not? Fundementally, aren't Airbus aircraft designed so they don't need to be stronger than the flight envelope design, as the FBW will protect the airframe from abuse. Thus you can make the bits from paper and dog biscuits and usually get away with it.

Plus you benefit from a far lighter airframe, lower power from smaller, more economical engines and a cheaper and more efficient operation. The only lowers are Dog owners who have to pay more for their buscuits!

[Henry VIII]

Should be an old story, take a look here (http://www.pprune.org/forums/showthread.php?t=166083&highlight=airbus+varadero+tail).
HVIII

[Whitehatter]

Air Transat A310 if memory serves. It didn't tear off as such, just fell to bits. It's still an ongoing investigation but there seems to be a theory it was due to water contamination causing ice to form and expand where it shouldn't.

[DozyWannabe]

Either way, the airframe was more than capable of handling it.
No-one's denying it is an undesirable failure mode, but at least it remained capable of returning for a landing. I think the DHL A300 in Baghdad is the only instance of an airliner making a successful RTB after a missile strike too...

It's a not dissimilar material to that used to construct Formula 1 cars, and those things are designed to be relatively safe upon an impact at 200mph+

[Clandestino]

FBW will protect the airframe from abuse

Yes, but in pitch only. There's no FBW protection in yaw, as Airbus' designers couldn't concieve a situation where a simple rudder TLU wouldn't suffice to prevent the rudder/tailfin/airframe overstress. As a consequence of AA587 accident, we didn't get FBW protection in yaw, just warning in POH not to wag the rudder when airborne.

What was the rudder made of is of small rellevance as long as it: 1) passess the certification criteria 2) demonstrates in everyday use that it's up to its envisaged task. As long as 1&2 are satisfied, i don't mind them being made of dog biscuits or carboard or whatever.

[Dutch Gold]

If you have a club foot you shouldn't be flying

[World of Tweed]

From the depths of my seedy past in the Design Office..... the rudder like many of the control surfaces and fairings on AI and BOE aircraft are constructed from a honeycombe-aluminium/CFRP composite.

Essentially its a stiff lattice type material that is expanded into a honeycombe structure and shaped as dsesired. (on some components the honeycombe is made from Aluminium alloy) Then shrouded in either alloy or a fibre-glass/composite skin to finish the component.

Any "foam" interior you may have seen might be adhesive or more likley, a result of a repair carried out to the component previously. When any damage is found the usual repair involves cutting out the damaged skin and a portion of the honeycombe centre - then filling with an epox resin and foam combination finally applying a patch to the skin by curing (if composite).

This method of construction results in a higher weight to strength ratio compared to traditional construction and is successfully used on numerous civil aircraft types. One issue is they are prone to insideous Ice damage after relatively light impacts (from gravel or FOD) as water craftily tries to delaminate the composite from the inside..... although I'm pretty sure the same would be true of Dog biscuits!

Ultimately they contibute to fuel savings (less weight) and reduced maintenance (reduced corrosion risk) with no impact (that I'm aware of) to the actual aerodynamic/handling characteristics.