Originally Posted by ross_M
Assumed temperatures seem quite a hack to indirectly fooling the engine into lower power.
It is not a hack.
Airbus, Boeing, etc, use defined methods and procedures. The process is incorporated into the management systems.
In using reduced thrust, you are using the engine performance that would be available from those engines in a higher ambient temperature (ie not as much oomph), to lift the mass that would be possible in the higher ambient conditions. However, you are still in your own ambient conditions.
Net result- overall wear rates on the engines are reduced.
And if in doubt. Don't select it.
Originally Posted by ross_M
Are there maufacturers that just allow the flight crew to enter a percent of rated / calculated power? Seems a bit safer as a philosophy.
Yes. In some machines. It is a derate. And a slightly different set of circumstances. On the B737NG, it was selectable. ie a 27K engine could be operated at 24K (I cannot remember the full figures)
On several aircraft I flew once, this allowed an intermix of rated engines. ie a 22K engine, with a 24K engine on the same airframe.
But this is not intended as a per-flight, selectable value. They are treated as separate procedures.
ps. open to correction of my poor explanation....
