If an aircraft is flying at constant power and altitude and the outside air temperature decreases, what will happen to true airspeed?

When an aircraft is flying at a constant power setting and altitude, the relationship between temperature and true airspeed becomes important to understand. If the outside air temperature decreases, the air becomes denser, which affects the aircraft's performance.

As the temperature decreases, the density altitude also decreases, leading to increased air density. With the engine operating at constant power, the aircraft will maintain its indicated airspeed, but because the air is denser, the true airspeed will actually decrease. This phenomenon occurs because the aircraft is less efficient at producing lift in cooler, denser air at the same indicated airspeed.

Thus, in this scenario, if the temperature drops while maintaining constant power and altitude, the true airspeed will decrease due to the increase in air density, and correspondingly, true altitude will also decrease as a result of the denser atmosphere contributing to a lower density altitude. This aligns with the correct choice reflecting the relationship between temperature, air density, and aircraft performance characteristics.