Originally Posted by
Jumpjim
Some light reading for you guys....
Stopkotte, Jack. “Minimizing Costs While Maintaining Performance Margins, Part 1 — Lowering Costs and Improving Reliability.” GE Aircraft Engines, September 2003. (If you can find a copy....)
"When less is more" - Aerosafety World magazine
Statistically, utilising the minimum Perf A compliant takeoff thrust makes you 5x less likely to have an engine failure, along with significant cost savings in engine wear...
That was quite an interesting reading. Thanks for pointing us to that article. It particularly explains what Derfred first said: engine life improves using flex/derate thus reducing likelihood to failure.
Personally, given the choice and all other things being equal, I'd take the longer runway. The aircraft is designed to fly safely out of the short or the long runway, but more concrete to get off the ground will always be more appealing to me, even if using flex. If the engine fails you still have more thrust to use (assuming you're using flex) even though the aircraft should meet OEI requirements just using flex. If you reject the takeoff, the performance calculations already have you covered; if you're not comfortable with the margin given by the highest flex, you can use one that's a bit more conservative. Plus, I reckon the couple of extra minutes of taxi will be far offset by the reduced wear using flex on the longer runway (even if the question was not considering economics)