AA 777 Severe Engine Damage EZE
 

Good work, uneventful RTF.

This was a Trent engine, not the previously problematic P&W.


https://avherald.com/h?article=5003630c

https://www.youtube.com/watch?v=8aGps5S9QLI

Isn't this what we do? Increase the time between inspections and overhauls until something breaks? We once X-rayed entire fuselages and wings looking for fatigue. But that's expensive and usually they don't fail catastrophicly so we stopped.

No, that's not at all "what we do."

No, we didn't x-ray entire fuselages or wings.

No, we don't keep extending intervals until something breaks.

This is all wild imagination, and ignorance.

Airframe times and engine and component times are adjusted by history and discovery, and intervals may increase or decrease; when intervals are expanded, the increase in cycles, operational time, or calendar limits is done incrementally, with inspections. There is no program which increases intervals on the basis of running it until it breaks.

Your sky-is-falling comment is made on the basis of what justification, in light of the failure on this engine? Which interval was increased until it broke? Or are you simply speaking out of your ass?

I didn't think I was being chicken little. I may have oversimplified the process but indeed what we do is incrementally increase intervals based on successful inspections. Since MTBF is fundamentally a statistical measure the longer that window becomes the more likely an outlier sneaks through.

This crew did a fine job and their experience and training saved the day. Time will reveal what happened with the engine but my money is on some type of age/cycle related fatigue. If that is the case what will happen? Via an AD or some other method the inspection interval for the component that failed will be decreased.

Again you don't know that. You're speculating. When a failure occurs, often it may be an unusual event, such as a manufacturing defect, and may require a one-time inspection with no change in interval. It may turn out to be a crack that was part of an existing program and may not require additional inspections in the fleet, or type.

Increasing inspection intervals does not equate to mean time between failures, particularly if the interval is not related to a failure mode. Your commentary assumes that all intervals are associated with failures, or expectation of a failure. Many inspection intervals are checks for function, tolerance checks, etc; they may have to do with wear limits, serviceability, pre-programmed intervals associated with a life-limited component, or any number of other rationale. Increasing the interval between inspections or service assigned to an airframe, engine, component, or appliance does not mean a greater possibility of a failure, even an "outlier." If we leave a pencil on a shelf that's due to be inspected yearly, and don't touch that pencil but find that it can be inspected every two years of sitting on the shelf, we haven't moved any closer to a failure.

Specifically, mean time between failures (MTBF) is NOT the same as inspection interval, service interval, overhaul interval, or any other interval. Some components have no MTBF. Some simply have life limits. Some work on life extension because initial numbers have proven conservative and inspections are unwarranted. If a component exists which does not have a failure, for which an inspection interval is gradually increased over a given period by virtue of ongoing inspections and gathered data. so long as that item does not have a failure, it does not have a mean time between failures; as no failure interval has been established.

When service difficulty reports and other reporting media establish evidence of a crack or wear or other problems, and these problems have commonality, there may be cause for the establishment of one-time inspections, repetitive inspections, component changes or upgrades or replacement, or modifications such as coatings, changes in material, reinforcements, or other actions. Manufacturer service bulletins are often issued, as well as mandatory regulatory actions such as airworthiness directives. These, in turn, may be one-time actions, or may serve to change intervals, establish new inspections, or other actions such as operational limitations.

The suggestion that increasing an inspection interval equates to a greater chance of component failure is a fallacy.

Failures are considered when designing life cycles, as in the P&W failures. Everyone I know in the industry understands that.
As usual, you are just being needlessly argumentative and pendantic.

Quite the opposite. I'm being truthful and correct, which is exactly NOT what the poster (not you) did, to whom I responded. READ.

You go ahead and show that increasing inspection intervals increases failures.

Then again, neither you, nor the other guy, know that such speculation and pure guesswork had any part of the incident in discussion.

It's hardly pedantic to note that the posters comments, literally all of them, were false, and to explain why (unless you simply don't understand).

Inspection intervals and life limits are not designed with failure in mind. They are designed to preclude failure. You understand the difference, or need that also be explained to you?