Method of operating a turbine engine having a bleed system

A method of operating a turbine engine having a high-pressure compressor including a high-pressure compressor flowpath and a plurality of stages of high-pressure compressor rotor blades and high-pressure compressor stator vanes, and a bleed system comprising a plurality of bleed flowpaths including a first bleed flowpath from one stage of the plurality of stages and a second bleed flowpath from another stage of the plurality of stages, the method comprising:

• directing compressed air through the high-pressure compressor flowpath;
• directing a first portion of the compressed air through the first bleed flowpath, the first portion of the compressed air having a first mass flow;
• directing a second portion of the compressed air through the second bleed flowpath, the second portion of the compressed air having a second mass flow;
• determining an altitude of the turbine engine;
• and
• changing the first mass flow of the first portion of the compressed air through the first bleed flowpath as the altitude of the turbine engine increases or decreases by modulating the first mass flow of the first portion of the compressed air through the first bleed flowpath to progressively change as the altitude changes.