Originally Posted by PT6driver

It's my understanding that this engine was derated from 1,600SHP to 1,200SHP (5 minute limitation) and then to 1,000SHP continuous.

How was this derating achieved? ITT limit? TQ limit? Both?

I ask because some of my coworkers run the engine well below it's maximum continuous ITT limit for climbs and cruise and I just don't understand the justification behind it other than, "we only have one so we'll take it easy" and, "this is the way "everyone" else runs it."

In the Series 9, Max. Continuous ITT is 760*C. We run it at 720*C.
In the NG, Max. Continuous is 820*C. We run it at 780*C.

It's also my understanding that Pratt & Whitney says you don't need to observe any specific TQ values in cruise so long as you stay under the Max. Continuous ITT. Pilatus provides a maximum TQ chart in cruise and have heard this is only a CYA move by Pilatus for liability reasons. I run the engine exactly as I've been taught but I just don't understand the "why" aspect of it all.

Why are we being taught to be easy on an engine that is already derated? I don't do well with "just run it this way." I need to understand the reasoning behind it.