Which of the following does not affect aircraft performance?

Relative wind does not affect aircraft performance in the same fundamental way that weight, altitude, and temperature do.

To understand this, it helps to define what relative wind is. It refers to the airflow that is produced by the motion of the aircraft through the air. While relative wind is crucial for understanding aerodynamic forces, such as lift and drag, it is a result of the aircraft's movement rather than a condition that alters the performance parameters.

On the other hand, weight impacts performance by influencing takeoff distance, climb rate, and fuel efficiency. As weight increases, the aircraft generally requires longer distance and more power to take off and climb.

Altitude plays a significant role, as operating at higher elevations can affect engine performance due to thinner air, thus impacting thrust and climb rates. Additionally, higher altitude typically results in lower air density, which can also influence aerodynamic performance.

Temperature affects aircraft performance primarily through its effect on air density. Warmer temperatures lead to lower density, which can reduce lift, engine performance, and overall aircraft efficiency.

In contrast, while relative wind is essential for performance analysis, it is like the effect of gravity; it is always present when the aircraft is in motion but does not create a change in performance parameters on its own.