Disbond of my belief
After reading this thread focus mainly on rudder ratio and related control systems and human inputs, I am now forced to ask:
Are we going to now consider the events of 2005 when an A310 of Air Transat -
flight 961- routing from Cuba to Canada on March 6, 2005, lost its rudder in
flight and experienced Dutch Roll and some flight profile deviations- followed
by a successful landing back at its POD.
I am unaware that anyone blames the pilot flying it, for dubious rudder pedal
inputs - nor is any such suggestion extant. But I am aware that the rudder came
off, and upon subsequent inspection, two of the main fin fuselage- to -fin attachment points had reportedly been damaged and that the fin was left hanging on by less than its normal number of attachment points (3 each side, half alloy, half composite and glue....).
Stress fractures or fluid ingress damage near hinge points were framed as being
the rudder's issues- but few looked at the main empenage's issues....
I believe that this (subsequent to AA 557) incident may relevant in re-evaluating AA587 and Mr Molin’s actions.
Of note:
The Air Transat A310 rudder failed and departed the airframe – leaving only a
few below hinge sections remaining. The reasons for the failure are linked to our lack of
understanding and lack of monitoring knowledge and procedures for the ageing
composite airframe.
‘Tapping’ the fin – as is done on the ramp - and doing a quick ultrasound are not really going to reveal the true state of an ageing composite and the deep layers of its build, cure, bond, resin state and delamination, let alone decide if the current ‘acceptable’ standards for build and resin faults are safe.
There are known existing problems with the manufacture of large scale hot bonded aerospace structures. Several incidents of manufacturing bonding and curing errors took place- leading Airbus to repair/rebuild new build tail fins pre-delivery.
The significant issues are these;
(a) It is hard to inspect or quantify failures in curing (autoclave) and bonding during new build.
(b)Such failures are well known and well documented.
(c) Leading composite researchers have argued for years over the technique of creating a 'peel' during manufacture. Such chemical peel of the composite, can create a non suitable surface on the peeled item once removed - any structure that is then bonded to it can suffer from disbonding etc over time and effects thereof.
So, what are we doing to properly inspect the resin states, lamination, gel
coats, molecule attrition from oil based contaminants and the effects of water / fluid ingress and freezing expansion at high altitudes and low temperatures?
(As an aside -can anyone recall the anecdotes of water allegedly pouring out of Airbus rudders on the ramp after arrival from warmer climes via high level, circa -59 degrees cruise?)
Yet the key reveal of the Air Trasnt A310 event, was the alleged damage to the fin attachment points.
And what are we doing now, all these years later, to address the design and
structural issues that may or may not be apparent in the design of composite rudders and vertical stabs and their crucial attachment point design.
Does the Air Transat event, (and subsequent events with the Air Canada Airbus
fleet subject of a recent statement), have any relevance to the previous incidents?
What other large series production airframe has had such a fin attachment design
and build, and what other airframe suffers fin attachment damage after losing
its rudder and suffering Dutch Roll?
IE: Why did Concorde’s main fin not come off each time part of its composite
rudder failed and broke off in flight – with resulting very severe vibrational harmonics affecting the fin structure? And did you know that the first composite rudder (made by Ciba
Geigy) testing (that is rudder only) was on an RAF VC10 over two years in the early 1970s - a
wonderfully trouble free record over thousands of hours.
What structural differences exist between Airbus tail fin design and strengths
relevant to differing thrust options within each relevant per model type? Answer
? Is it: None?
Why are factory repairs to new cure composite structures allowed? AA587 had such
did it not. And how can adding a strut brace to a composite structure devoid of
a load path carrying chassis, not do anything but expectedly fail at its reinforcement point - that is always going to happen...
Why is the Airbus fin attached with an alloy fitting down one side and a direct
composite fitting down the other- whatever the design loads, whatever the fact
that the AA557 fin failed at beyond its design load, this type of design is
always going to concentrate stress in a small area and at differing resistance
rates - is it not?
Even ff we accept that Mr Molin was using the rudders as evidenced, why do some
blame him solely for that supposed single action - why do we not ask why he was
using the rudders as alleged- was it due just to his own construct, due to the
AA training programme, the rudder ratio issue - or did something happen that was not considered at the time but may, repeat may now be focused by subsequent events - contribute to his actions. Was there a rudder issue not cited then, but apparent now from more recent events? Was there a fin attachment issue? Was there an ageing composite
issue ?
I guess we will never know. But we do now know that the fin is not intended to handle a certain type of rudder action.
Let us remember that in the 1960s a BOAC 707 crashed over Mount Fuji after a
turbulence hit- and the fin failed beyond design limits- just as the AA 587 fin
failed beyond design limits.- so, no, I am not having a 'bash' at Airbus. But
what I am asking is this - does the record of the Airbus fin design, have
a hidden factor only told by the advent of the ageing composite airframe - or
our subsequent knowledge of how to design and build large composite fins- and
crucially, how to keep them attached?
How many more pictures of fins floating in the water - as in AA557, AF 447, and
the NZ 'unexpected turn' Perpignan test flight, will we see?
It has taken years, but are we now at a point where anecdote might indicate a
consistent pattern of evidence?
FYI: I am only asking. The opinions stated above are just that- they are not claims of actuality nor are they evidence. They are just obvious questions after a very long wait.
So shoot me down now why don't you? Someone will....
Meanwhile, what are YOU doing to research the issue of the ageing composite and the legacy of early composite design issues?
Air Transat Ref:
Report Number A05F0047. Transportation Safety Board of Canada(TSB). 2007-11-22.