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What is the actual numerical reliability statistics of the modern, large-aircraft, commercial turbofan engines available today?

e.g. How many running hours can we expect a failure after? Are there empirical or projected MTBF statistics?

How is credible MTBF established for a new engine model?

Is there a significant difference in the failure rate between engine models or manufacturers?

I was motivated to ask by this snippet on another answer on SE Aviation:

In the days of the 747 regulations required at least 3 engines if you ventured more than 60 mniutes of flying time away from a suitable diversion airport (in case the second one also failed). However as reliability of engines increased this got extended with ETOPS certificates.

How rapidly has engine reliability improved? Do we have a time trend of reliability numbers?

Why do modern airliners have only two engines?

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  • $\begingroup$ I'm certain this is a dupe, or at least addressed elsewhere, but my query-fu is failing me. $\endgroup$
    – FreeMan
    Commented Feb 8, 2016 at 17:02
  • $\begingroup$ I found a few rough figures here: pprune.org/engineers-technicians/… but more detail might need to be more model-specific... $\endgroup$
    – Andy
    Commented Feb 8, 2016 at 17:42

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What is the actual numerical reliability statistics of the modern, large-aircraft, commercial turbofan engines available today?

e.g. How many running hours can we expect a failure after? Are there empirical or projected MTBF statistics?

Buried in this GE press release is the comment that the GE90 has 'only one engine IFSD per one million engine flight-hours'.

This ICAO presentation has a lot more info, including these threshholds for ETOPS IFSD rates:

Propulsion system should achieve an in-flight shutdown (IFSD) rate of:

  • 0.05 / 1000 engine hours for EDTO 120 min
  • 0.02 / 1000 engine hours for EDTO 180 min
  • 0.01 / 1000 engine hours for EDTO beyond 180 min
  • Rate computed based on world fleet data, on a 12-month rolling average

This strongly implies that the reliability targets are empirical, not based on theoretical numbers.

Is there a significant difference in the failure rate between engine models or manufacturers?

Page 56 of the presentation above has some data, but IMHO not enough to draw any conclusions.

How rapidly has engine reliability improved? Do we have a time trend of reliability numbers?

All I can say is it's definitely improved massively, but I'm not sure where to find the info.

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  • $\begingroup$ Welcome to Aviation.SE this answer is more of a link-only answer. It would be better if you elaborated more on it. $\endgroup$
    – SMS von der Tann
    Commented Mar 26, 2016 at 15:22

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