What effect does an increase in outside air temperature have on the true airspeed of an aircraft at constant power?

An increase in outside air temperature at constant power leads to an increase in true airspeed. This phenomenon is rooted in the relationship between air density and temperature. As the temperature of the air rises, the density of the air decreases, which means that the aircraft is encountering "thinner" air.

In simple terms, for a given engine power setting, an aircraft will generate the same amount of thrust but will experience less drag because the air is less dense. The less dense air imposes less resistance, allowing the aircraft to accelerate to higher true airspeeds. This effect is particularly significant at higher altitudes where temperature variations can have a more pronounced impact on air density and aircraft performance.

As a result, as the outside air temperature rises and the aircraft operates in less dense air, true airspeed increases when power remains constant.