Originally Posted by boofhead
I don't remember if the assumed temp takeoff thrust calculation took climb thrust into account.
On the 737 it doesn't, sometimes when using max. assumed temperature and full climb thrust, the thrust will actually increase at thrust "reduction" altitude, since max. climb thrust is higher than maximum assumed TO thrust.
Originally Posted by boofhead
It takes longer to get to the point where the change is made to climb thrust, say 1500 feet. So the engine is getting a lower temp application but for a longer period. Which is worse? The higher temp or the lower temp for a longer period?
Engineers say that it's the high temperature that hurts the engine, not the prolonged application of lower temperature. That's why the maximum continuous thrust is actually defined by for a margin lower EGT than takeoff thrust. For example, you can use maximum takeoff thrust for 5 minutes and then reduce thrust just a bit to bring the EGT down for about 40°C (of course, manufacturer-specific technique has to be observed) and you can run the engine at that setting until you're out of fuel.
Originally Posted by boofhead
And that always gets me back to the argument about flap. Using Flap 10, say in a B744 instead of flap 20, gets the airplane off the ground and up to the point at which climb thrust can be set in a shorter time. This would lead to less engine wear, but most airlines will not even consider it.
I wouldn't know about heavy metal, but on the 737 we almost always takeoff with minimum possible flap (5) and on top of that we sometimes have to use Boeing's dirty little V2 tricks (improved climb) to even get out. Other setting (15) is only when field-limited. Boeing even suggests taking off with higher-than-neccesary flap setting to increase tail clearance during rotation, but I don't think many companies do that.