Method and apparatus for controlling thrust in a gas turbine engine

DETAILED DESCRIPTION We claim: 1.
Apparatus for controlling thrust of a gas turbine engine of the type having a compressor, a combustor and a turbine with means for producing signals proportional to engine inlet temperature, engine inlet pressure and comproessor physical rotational speed, a fuel controller, and a power lever adapted to be set to different angles to select a different desired engine thrust at each power lever angle, wherein the improvement comprises means for providing a demand compressor physical speed signal adjusted by engine inlet pressure and temperature wherein said means for providing a demand compressor physical speed signal comprises means for producing a first demand compressor corrected speed signal as a function of the selected power lever angle, said last recited signal being further proportional to compressor physical speed divided by .
theta.
.
sup.
n , wherein n is that exponent which provides flat-rated thrust independent of engine inlet temperature for those inlet temperatures which are below a preselected flat-rating inlet temperature, means for comparing said compressor physical speed signal and said demand compressor physical speed signal to develop an error signal, said error signal being coupled to said fuel controller in order to maintain said desired thrust at each selected power lever angle.
2.
The apparatus as recited in claim 1 wherein said means for providing a demand compressor physical speed signal comprises means for producing a demand compressor corrected speed signal as a function of power lever angle, means for providing a predetermined inlet pressure lapse rate signal which provides a predetermined thrust rating schedule which varies with altitude, and means for biasing said demand compressor corrected speed signal with said lapse rate signal.
3.
The apparatus as recited in claim 1 wherein said means for providing a demand compressor physical speed signal further comprises means for biasing the first demand compressor corrected speed at a predetermined lapse rate as a function of engine inlet pressure to produce a flat-rated demand corrected speed signal which increases with altitude