Crossover cooling flow for multi-engine systems

1. A method of operating a multi-engine system in an aircraft, the method comprising:

operating the multi-engine system in an asymmetric cruise mode during a cruise phase of flight of the aircraft, wherein the asymmetric cruise mode comprises operating a first gas turbine engine at a first power rating and a second gas turbine engine at a second power rating, wherein the first power rating is higher than the second power rating and wherein the second gas turbine engine comprises a second engine central longitudinal axis, a second compressor and a second turbine, the second compressor and the second turbine each rotating about the second engine central longitudinal axis;

wherein in response to the multi-engine system operating in the asymmetric cruise mode, a portion of a total compressor flow of a first compressor of the first gas turbine engine is routed to a turbine component of the second turbine of the second gas turbine engine to cool the turbine component, the portion of the total compressor flow being routed through a crossover cooling network that extends from the first compressor of the first gas turbine engine to the turbine component of the second turbine of the second gas turbine engine.

2. The method of claim 1 , wherein in response to the multi-engine system operating in the asymmetric cruise mode, the second gas turbine engine is operated with a fuel flow rate that is lower than a self-sustaining idle fuel flow rate of the second gas turbine engine if the second gas turbine engine were operating without the portion of the total compressor flow of the first compressor of the first gas turbine engine being routed to the turbine component.

3. The method of claim 1 , wherein during operation of the multi-engine system in the asymmetric cruise mode, total power generation of the multi-engine system is the same as, but overall fuel consumption is lower than, if the multi-engine system were operating under a symmetric cruise mode.

4. The method of claim 1 , wherein the first compressor and a first turbine of the first gas turbine engine are each configured to rotate about a first engine central longitudinal axis of the first gas turbine engine.

5. The method of claim 1 , wherein the first gas turbine engine and the second gas turbine engine are identical.

6. The method of claim 1 , wherein the crossover cooling network is a first crossover cooling network, wherein the multi-engine system comprises a second crossover cooling network that extends from a second compressor of the second gas turbine engine to the first gas turbine engine.

7. The method of claim 6 , wherein in response to the multi-engine system operating in the asymmetric cruise mode: a first crossover airflow through the first crossover cooling network is between 5% and 20% of a first total compressor flow through the first compressor; and a second crossover airflow through the second crossover cooling network is 0% of a second total compressor flow through the second compressor.

8. The method of claim 6 , wherein in response to the multi-engine system operating in the asymmetric cruise mode: a first crossover airflow through the first crossover cooling network is 10% of a first total compressor flow through the first compressor; and a second crossover airflow through the second crossover cooling network is 0% of a second total compressor flow through the second compressor.

9. The method of claim 7 , wherein in response to the multi-engine system operating in the asymmetric cruise mode: the first total compressor flow is between 90% and 100% of a first compressor inlet corrected flow capacity of the first compressor; and the second total compressor flow is less than or equal to 40% of a second compressor inlet corrected flow capacity of the second compressor.