Cracks appear in public understanding of metal fatigue
Updated with Airbus statement
Something of a case study in aviation media communications is taking shape, or rather, cracking up, in relation to ‘minor’ cracks found in the wings of some Airbus A380s, including the Qantas one that remains under repairs at Singapore’s Changi airport following its mid-air engine disintegration drama in November 2010.
This is a development that can be seized on for all sorts of agendas, well meaning or otherwise, and lends itself to anything from a screaming tabloid headline to a few paragraphs in News-in-Brief, even though it turns out to be a manufacturing issue that comes with no safety of flight implications.
It was a story that should be neither dismissed as irrelevant, nor seized upon to forbid the loathsome, ugly, un-American, despicable, French, flying machine ever taking off with another passenger’s life at risk again ever.
But as usual, both types of story will appear, if not in Australia, anywhere else that is having a slow news day.
The truth about airframe cracks and manufacturing anomalies, which is what this is about, is that in the case of every passenger airliner entry into service since the original ill-fated Comets, such issues, serious and non-serious, have always arisen.
There are thousands of service bulletins, and at the least, many hundreds of their more urgent counterpart, airworthiness directives, that have been issued and remain in continued effect in relation to structural cracks or material failures appearing in every engine/wing combination known to the jet age.
In relation to fatigue they reflect the reality that the wear and tear of pressurization cycles and landings will cause cracking in airframe and engine structures, including engine pylons, wheel gear, window frames, fuselage joins, and in the skin or surface of wings and the stringers that connect panels to the internal structure.
The trick is to catch the ones that might become serious, or were not predicted by the fatigue modelling and testing of an airliner type that is a part of its certification process.
When they are found they may require immediate rectification, through an airworthiness directive, which will usually become a part of a set of ADs devised to deal with a particular issue with more and more precision as inquiries progress, or the incorporation of a remedial process into those already set down for a regular service interval, which is preset to a certain number of cycles or hours, and which become more invasive and costly as a particular airframe ages.
In fact the whole regulatory process for dealing with structural cracks because of the early history of airliner design disasters, like that of the Comets, the Vickers Viscounts, the Vickers Vanguards, Lockheed turbo-prop Electras, and more recently, aged Boeing 737s and 747s, is as crushingly boring as watching grass growing. But it works.
Every jet every reader ever flies on will have developed crack issues or alerts of some nature, as well as a schedule for their oversight and if necessary, removal or repair, within at least a few years of service.
The Airbus statement says:
Airbus confirms that very small cracks were found on some non-critical wing rib-skin attachments on a limited number of A380 aircraft.
We have traced the origin to a material-related manufacturing issue and developed an inspection and repair procedure which will be done during routine, scheduled, maintenance checks.
This is not a safety issue. Aircraft performance is not affected. Any fix, if necessary, can be done during regular (4 year) maintenance.
Airbus has informed all A380 operators. The European Aviation Safety Authority (EASA) is fully aware of the issue and in line with the Airbus approach. Airbus emphasises that the safe operation of the A380 fleet is not affected.
The Qantas A380 incident near Singapore which led to the repair process which found evidence of this unrelated manufacturing anomaly, saw its wing pierced and seriously damaged in many places by a Rolls-Royce engine that had a fault the maker didn’t tell Qantas about while it set about rectifying it to its own schedule. The advanced load transfer capability of the A380 composite/alloy wing design kept it intact for nearly two hours. In earlier Airbuses, or Boeings, such damage might have led to rapid wing failure and a loss of control and a major air disaster.
This document, prepared for Airbus for A380 customers, deals with the actual damage suffered by the wing, and was exclusively published by Plane Talking last year soon after the incident and read by hundreds of thousands of people.
The first reports of the small cracks found in the wings were naturally associated with Singapore incident, but they are unrelated.
The Qantas A380 incident remains a testimony to an outstanding design, as well as exceptional professionalism by the pilots.