Airliner engines - rotation
 

I have often wondered how engineers working on multi engined airliners stagger the engine life so that all the powerplants dont have to be changed at the same time.

For example on a BA 747 due routine snags mean the 4 engines are, through the process of time, all at different hours after they have been changed or do the engineers have to plan in engine changes during down time to stagger out the hours.

Im sure I have read somewhere a BA 747 held some form of record for a RB211 which had spent a long time hanging on a wing

I heard once that modern Heavy Transport turbines no longer had TBO's but rather operated on condition. I was told that a premature removal was based on vibration signatures, SOAP samples, and perfomance.

Is this not the case?

Cheers,
FA

That's Engine Condition Monitoring FA. A lot of parts such as compressor and even some turbine blades can be reworked using plasma spray techniques, nevertheless, many parts - turbine and compressor parts in particular - still have finite lives measured in operating cycles and are scrapped when their life limit is reached.

And yes, we do often stagger engines so that they fall due for work at alternate 'C' Check inputs. Not every operator can afford to have loads of spare engines lying around waiting for a pylon to hang onto. It makes managing the lease return conditions quite a complicated task though... :(

An operator with a new fleet will generally remove/replace an occasional part-time engine ("convenience" or "time-stagger" removal) for two reasons:

1) So not all fleet engines come due for a shop visit all at once, and

2) Refresher training for the engine swap crews.

I schedule engine changes on multi engine turbine Aircraft by using the PAD whereby I pull one engine 100 hours prior to TBO One at TBO and one 100 hours into an extension allowed by the manufacturer, it works well for 3 engine aircraft ! TMAB

themoonsaballoon, does your local aviation authority allow you to use an extension for this purpose?
FA