Mechanical Engineering - Compressors, Gas Dynamics and Gas Turbines - Discussion

With the increase in altitude, the density of air decreases. The reduced density means a lower number of air molecules entering the core engine. For the fuel/air mixture to maintain its stoichiometric ratio, the required number of fuel molecules must decrease to cater for the decreased number of air molecules. This results in a lower amount of fuel required at higher altitudes.

Moreover, lower air density at high altitudes also increases flight efficiency by decreasing the skin-friction drag produced by the interaction of air molecules with the surface of the aircraft.

What is altitude in jet engine?

Adding to Nitin Ashraf, the jet engines are designed to operate at higher Mach values like Mach no.2, which is achieved without disturbance at higher altitudes only. So the efficiencies are higher at higher altitudes.

Well said. Thanks to all of your explanation.

At higher altitudes, temp and pressure reduce so S. F.C reduces so it is efficient at higher altitudes.

At higher altitude less air density as well as resistance.

Thanks @Nitin Ashraf.

They work better at high altitude firstly because the air is cooler. Cool air expands more when heated than warm air. . The second reason is the low density of the air. Low density causes low drag and therefore the aircraft flies much faster at high altitude than on low altitude when it is given the same thrust.

Thanks @Nitin Ashraf.