Steve - a couple thoughts...
First, gyroscopic effect on bearings is pretty real when you've got a moving airplane and the motion creates precession that adds load. Clearly, there is less in a power plant.
Next, airlines, engine manufacturers and airplane builders have come up with more detailed and precise calculations of required takeoff performance. So, thrust can be reduced much further than it used to be reduced. This benefits the airline economically with increased engine life.
So, consider the thrust reduction, and if the power isn't needed for second segment single engine climb (sea level, flat terrain, light weight airplane all reduce the power requirement for climb following a failure), then its simple F=MA where we've reduced F to the minimum needed. A got a lot smaller as a result.
We don't nurse bad engines. We replace them.
But turbines are happy steady state, and we operate them in stop/start, heat/cool cycles. So, whatever we can do to reduce the amount of time that they're at maximum stress, which is maximum wear, and maximum potential for failure, we do for economic reasons.
Take off with the potential for wind shear, or on a short runway, or where there is rising terrain, and we will use the full rated power available.
First, gyroscopic effect on bearings is pretty real when you've got a moving airplane and the motion creates precession that adds load. Clearly, there is less in a power plant.
Next, airlines, engine manufacturers and airplane builders have come up with more detailed and precise calculations of required takeoff performance. So, thrust can be reduced much further than it used to be reduced. This benefits the airline economically with increased engine life.
So, consider the thrust reduction, and if the power isn't needed for second segment single engine climb (sea level, flat terrain, light weight airplane all reduce the power requirement for climb following a failure), then its simple F=MA where we've reduced F to the minimum needed. A got a lot smaller as a result.
We don't nurse bad engines. We replace them.
But turbines are happy steady state, and we operate them in stop/start, heat/cool cycles. So, whatever we can do to reduce the amount of time that they're at maximum stress, which is maximum wear, and maximum potential for failure, we do for economic reasons.
Take off with the potential for wind shear, or on a short runway, or where there is rising terrain, and we will use the full rated power available.
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