As the operational life of aircraft hardware increases, repetitions of phenomena previously explained as “isolated incidents” have been seen to occur. These problems are not necessarily application specific, nor material’s anomaly, nor design defect, nor operational abuse, nor any single cause, but, usually, an unfortunate combination of degradation in several of these factors, which becomes, statistically, more probable as the operational hours increase. Because they are rare, it can take years to collect enough clues to identify these links and synthesize the event.
When the problem involves an aging commercial aircraft turbine engine, that has passed from the designer to the manufacturer, and then to the airframer and the operator, through the hands of the maintainer, the repairer and the spare parts breakout supplier, the combinations of variables becomes too large to attack individually.
This paper characterizes a common sense approach to solving these problems. This approach favors a small team with a strong leader dedicated to that task. It is based on a theory that clues may be found in the history of the product and the industry, as well as in the exhibits and demographics of the incidents, and that a broad approach to fact finding, coupled with disciplined treatment of data, will allow the investigators to develop some intuitive sense of their problem, and facilitate linking of the pertinent facts.
This paper includes a hypothetical example, based on information in the public domain, of such a problem relating to an aging gas turbine engine. It is not meant to represent an actual case history, but is rather a combination of recognizable events, not uncommon, in either type or quantity, in the gas turbine industry, combined to illustrate this theory.