Abstract: A method of operating a gas turbine engine (20) comprising a variable geometry compressor (24), a variable geometry combustor (28), and a variable geometry turbine (30). The method comprises operating the variable geometry combustor (28) such that a corrected flow ?c through a combustion zone (46, 48) of the combustor (28) matches a predetermined value.

Abstract: A gas turbine engine (20) comprising a variable geometry engine compressor (24), a variable geometry engine turbine (30) coupled to the engine compressor (24) and a combustor (28). The combustor (28) has an inlet (34) arranged to receive air from a first engine compressor outlet (34), and an outlet arranged to deliver combustion products to the engine turbine (30); a combustor bypass passage (50) having an inlet (53) arranged to receive air from a second engine compressor outlet (53), and an outlet (54) in fluid communication with a main fluid flow path downstream of a combustion zone (46, 48) of the combustor (28), and upstream of a turbine inlet (31); wherein the combustor bypass passage (50) comprises a bypass control valve (52) configured to selectively modulate the ratio of air flowing to the combustor inlet (34) to air flowing through the bypass passage (50).

Abstract: A bleed air system for an aircraft has a gas turbine engine and operating method. The system includes an environmental control system (ECS) for providing cabin airflow to the aircraft, including operating modes such as first and second air cycle machine operating modes and heat exchanger operating modes. The ECS includes first, second and third bleed ports each configured to provide engine bleed air from gas turbine engine compressors to the ECS. The ECS includes a bleed air system sensor arrangement configured to sense one or more bleed air system conditions, an environmental control system controller that selects an environmental control system operating mode that provides required cabin air flow and temperature at an optimal specific fuel consumption of the gas turbine engine at the sensed system conditions, and a bleed port valve controller which determines an operating pressure required to operate the environmental control system in the selected mode.

Abstract: A method of operating an electrical power generation system on an aircraft. The method includes assessing a required electrical power of the aircraft, assessing whether a first and a second electrical power source are able to provide the required electrical power in combination, assessing a predetermined condition, determining an operating mode of the first and second electrical power sources to match the predetermined condition, and operating the first and second electrical power sources according to the determined operating mode.