Hello!
Originally Posted by
zlakarma
And when one is climbing on pure jet, and do not touch the power levers, is N1 constant or falling or rising?
That's a somewhat theoretical question as one usually does not leave the thrust levers untouched during climb... (unless the aircraft has FADEC). Again I can talk for the one I fly (PW535 variant): When takeoff thrust is set the ITT will show a certain value. After takeoff during initial climb this value tends to be higher, so there is an initial rise. But I do not think that this is caused by the change in altitude alone, gaining forward speed does have an influence as well. The fuel control unit (FCU) is a very complex (and non-linear) mechanism which has several T and P sensors and constantly adjusts fuel flow to match the changing conditions. There will be certain regimes where a change in altitude will result in an ITT rise and others where it will not. Because one of my tasks as a pilot is to protect the aircraft and it's engines from damage I will manually override the FCU by moving the thrust levers in order to keep the ITT within a comfortable range. Sitting there and watching what it will do on it's own is not an option...
Another Citation which I once flew had JT15 engines. These had the tendency to increase N1 speed with altitude (thinning air) when the thrust levers were not touched. Well beyond 100%. Leaving them alone in order to investigate what the ITT might do would have meant blowing up the engines in a matter of minutes!