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As per subject, what is the lifespan of a jet engine? Do they have a fixed hours which they can be used and regardless of the state have to be exchanged or are they serviced and maintained until they are deemed not good for use?

If they do have a lifespan, I suppose also that different types of airliner engines and models will have different lifespans.

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In general, the engine life is measured in terms of two things:

  • Flight hours
  • Flight cycles

A takeoff and a landing counts as a flight cycle.

The most important concept in engine life is the Time Between Overhaul(TBO), which is basically the manufacturer recommended time period after which the engine is stripped down,checked thoroughly and required parts replaced. After overhaul, the engine is usually cleared till the next TBO.

An overhauled engine is theoretically as good as a new one and comes with the same life (TBO) and warranty, if applicable. Airline engines (for example the Rolls Royce Trent series) usually have TBOs of over 15000 hours. The record for maximum time for an engine on wing (i.e. use in aircraft before removal for overhaul) is well over 40,000 hours.

The life of an engine is given by the manufacturer and are different for different engines. However, the engine life depends on a number of parameters and is usually different for various engine components.

  • The rotating components have life limits which are less than the engine and are replaced periodically, mostly during the TBO.
  • For example, the turbine blades are replaced after a set number of turbine cycles and/or after a set number of hours, which are lesser than the others.
  • In addition, most rotating components (compressors, turbines) are periodically subjected to checks, and are replaced if found damaged.
  • In case of abnormal operations, some parts are required to be replaced. For example, if one engine is required to give excessive thrust (for example in case of One Engine Inoperative), the engine is subjected to thorough checks similar to TBO.

Airline engines are usually serviced (Overhauled at TBOs) and maintained till they are deemed not good to use or not economical to (service/repair and) operate anymore.

Most of the engine manufacturers employ condition based health monitoring programs, which helps them to plan when to service and repair the engine. As a result, the engine life varies based on its condition.

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  • $\begingroup$ What about hours it just spends on the wing without flying? If airplane is parked somewhere for ten years whats has to be done with the engines? $\endgroup$ – Andrius Sep 7 '15 at 20:03
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    $\begingroup$ There are a few other things in the abnormal category that can shorten the life of a turbine engine (e.g. "hot starts"), and the "hot section" components usually have their own timelines for inspection or replacement (which may coincide with the compressors and such for convenience, but don't have to - particularly if the hot section's inspection comes up sooner from abnormal ops) $\endgroup$ – voretaq7 Sep 8 '15 at 5:13
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    $\begingroup$ Any info on this 40,000 hour engine? That sounds interesting. $\endgroup$ – FreeMan Sep 8 '15 at 18:27
  • $\begingroup$ @FreeMan It was a Rolls Royce RB211-535E4 on a Boeing 757 $\endgroup$ – aeroalias Oct 2 '15 at 6:00
  • $\begingroup$ Cool, thanks! Sounds like it's a regular thing for the RB211, not one particular engine that set a record. $\endgroup$ – FreeMan Oct 2 '15 at 12:50

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