The Perfectionists by Simon Winchester

Author:Simon Winchester
Language: eng
Format: epub
Publisher: HarperCollins
Published: 2018-04-01T04:00:00+00:00

The tube and the assembly around it had been manufactured in a Rolls-Royce plant, Hucknall Casings and Structures, sometime in the spring of 2009. In normal circumstances, it would have been trivially easy to machine the pipe for the filter fitting, and to do so to the exacting standards laid down by the designers of the engine. But for this particularly complicated part of this particular engine, it was decided to complete first the entirety of the hub assembly that separates the high-pressure from the intermediate-pressure areas of the engine—and then and only then, once the pipe had been fitted into place in this assembly, to drill out the tube to its design specifications. This proved to be exceptionally difficult, however, because now parts of the pipe could not be readily seen, as other parts of the fully assembled hub and newly made welds of its various pieces obscured the engineers’ clear sight of it.

These engineers did the best they could, but in the end, the tiny pipe that would eventually go into the turbine of the engine that would be suspended from the port side wing of the Qantas A380 was machined improperly: the drill bit that did the work was misaligned, with the result that along one small portion of its circumference, the tube was about half a millimeter too thin.

The assumption is that, during manufacture, the hub assembly somehow moved a tiny amount as it was being drilled, with the result that the drill bit moved fractionally closer to one wall of the pipe, reducing it to what would be dangerously vulnerable thinness. More dangerously still, the quality-control departments at Hucknall Casings, and the computer-driven machines that check the conformance of all critical parts of an aircraft, passed the tube as being satisfactory. The badly made part should have thrown up all manner of red flags. It should have been discarded—a high-pressure turbine blade, deemed to be an absolutely critical and safety-critical part of an engine, would have been tossed out and smashed for an error far less significant than the error in this tube.

Yet, for reasons that have much to do with what is euphemistically called the “culture” of that particular facility within Rolls-Royce’s immense engineering establishment, the stub pipe passed all its inspections. A potentially weakened engine component made its way all along the supply chain until it was placed into the engine, and there to await its inevitable breakage—and the equally inevitable destruction of the entire engine. It should have failed inspection, but it didn’t. It just failed in real life.

Metal fatigue is what did it. The aircraft had spent 8,500 hours aloft, and had performed 1,800 takeoff and landing cycles. It is these last that punish the mechanical parts of a plane: the landing gear, the flaps, the brakes, and the internal components of the jet engines. For, every time there is a truly fast or steep takeoff, or every time there is a hard landing, these parts are put under stress that

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