Validation Fire Inspection Frequency

Trent 900: European Aviation Safety Agency (EASA) relaxed earlier ...

Three months before a superjumbo jet engine blew apart and forced an emergency landing, European safety regulators had relaxed their inspection order for the same section of the engine implicated in the dangerous mishap. In January, the European Aviation Safety Agency required airlines to inspect for wear on the shaft that holds one of the Rolls-Royce Trent 900 engine’s turbine discs. The more wear they found, the sooner future inspections would be required. In August, after Rolls-Royce had inspected several engines, EASA revised its directive. Previously, airlines had to calculate how worn out the part was based on the worst spot. Under the revised directive they calculate the average wear over the entire part. And previously they had to assume the part was wearing out at a worst-case rate. The new rule allows them to calculate the wear rate on each engine. That meant less frequent inspections, which the revised directive said were “sufficient to prevent unacceptable wear.”

The implication here is that the airlines (or Rolls Royce) were finding the inspection regime onerous and EASA responded by rationalising the change to base the frequency of future inspections on “average” wear rather than the “worst case wear” observed. Inspections of course require skilled resources, cost money and increase the down-time of aircraft. It becomes essentially an issue of operational cost. EASA – like all regulators – has to walk the tightrope balancing between public safety interests and the airlines’ need to keep costs reasonable.

Business Week The European directives warned of the potential for “in-flight shut down, oil migration and oil fire.” The U.S. Federal Aviation Administration went further in adopting a version of the European directive in September, warning of an “uncontained failure of the engine, and damage to the airplane.” Some of the parts inside jet engines rotate faster than the speed of sound. Engines are designed so that even if part of one shatters, pieces of metal aren’t sent rocketing away from the engine. An “uncontained engine failure” with shrapnel-like engine pieces that can damage other parts of the plane is both rare and extremely dangerous.

The different communications strategies used by the players involved have varied greatly. Rolls Royce have said remarkably little and even their latest statement was baked into a Trading Report for investors. In such a report the objective is to reassure the audience so that share price holds up and doesn’t crash. The conclusions – in consequence – have to be tailored to these objectives.  In this case the focus was on showing that while there will be some costs, profits for the year will not be hit too hard. Investors – and not passengers – were clearly the audience for this Rolls Royce communication and that is of some concern.