Question

Due to efficiency considerations related to its bow wake, the supersonic transport aircraft must maintain a cruising speed that is a constant ratio to the speed of sound (a constant Mach number). If the aircraft flies from warm air into colder air, should it increase or decrease its speed? Explain your answer.

Answer 1

It depends on its speed and altitude:

An aircraft flying at 10 km altitude will "feel" a temperature of ~-50 deg than the temperature of the sea (due to the variation of the air temperature with the altitude).

If it has Mach 7 speed, its temperature increases around 10 times the ambient temperature. It depends also on the composition of the body, the temperature range accepted by the alloy.

At Mach 1.2, the same altitude, the effects are equilibrated (cold atmosphere vs high speed) and the aircraft will "feel" almost the same temperature as at the sea level.