Originally Posted by
TangoAlphad
I think he meant surviving being forced to spin up by the action of landing.
Wether they are or are not providing power is irrelevant, the mechanisms still need to survive that wear and tear.
That was indeed my point.
And of course I'm not saying it's not do-able. I'm saying that the engineering and development effort with all the considerations required is highly unlikely to be cheap and easy.
It's not being closed minded, just realistic. Of course it is possible. But is it worth it? There are many risk vs reward considerations.
You can make an economic case for anything. My airline famously made an economic case for only using idle-reverse thrust on landing until it ran a perfectly serviceable Boeing 747 full of passengers off the end of a runway into a golf course. The aircraft was as near to a write-off as you can get, without actually being written off (the decision to repair raised eyebrows in some circles), then we spent the next 15 years using full reverse thrust on all landings.
How good do people reckon the economics were there?
You can make economic cases for instantaneous fuel savings for many things but you have to balance operational and engineering risks too, so it's just not that simple. Over my 30 year career I've not once ever seen a bean-counter who understands what "operational" or "engineering" actually means but I've seen quite a number of fuel-saving decisions reversed, reversed back again, then reversed back again, then reversed back again, etc. They sit at a desk (be surprised if they even have a window) and deal with numbers.
We had a scenario not long ago where one department in the airline made a decision to stop washing fuselages and compressors because it was expensive and it had no bearing on flight safety (true), and helped them meet their KPIs. It cost flight operations many millions of dollars in fuel penalties due to performance factor increases. Took something like 6 months
after the supporting data was gathered to get it reversed, but in the meantime multiple millions of dollars fluttered away, never to return. Amazing how tenaciously senior managers hang on to their KPIs.
The whole thing is an absurd game. But I just fly the things.