ETOPS Statistics Bely the Facts
Two 777 Engine diversions in 1 day

It's being reported that UA 777 flying FRA-IAD diverted to KEF [Keflavik] (PW powered) and a CO 777 NRT-HOU [Narita to Houston] (GE powered) diverted into Midway. At a rough count that makes 4 engine-related diversions, all while over water in 6-8 weeks [1 GE90 into Dublin + 1 GE90 into Fortaleeza, Brazil]

Are we seeing something here that with the benefit of hindsight may prove to be significant, equipment ages, and not always at the rate the manufacturer expects.

Personally I have always thought that the 2 engine failure statistics are misunderstood, even if it is predicted only

 once in 10 million flight hours

1) It is predicted to happen sometime
2) That statistic doesn't discount 3 tomorrow and no more for 100 years!

Added to this there is something I like to refer to as Shuttle Mathematics. Back in 1980 it was predicted that the shuttle system would fail once in 10,000 launches (or something like that) after Challenger that figure was reduced to 1 in less than 100, ie you would lose another one before completion of the ISS. I think the actual stats now show a 2 in 107.

What this tells us is that stats are just numbers built on assumptions and that in real life experience can sometimes prove them to be worthless - especially when there is pressure for the "right result" from on high.

Getting to the point, I doubt that 2 of the above diversions were in ETOPS sectors so they will not even find their way into the IFE stats, further distorting the real world reliability stats. I will also throw the Trent 800 (un)contained failure at MEL [Melbourne] into this category.

Who's keeping score? how are these stats arrived at? is there any independent non-regulatory input. Are the regulators too close to the Airlines?


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