Many accidents are occurred because pilots failed to understand the effects that varying conditions can have on aircraft performance.
In addition to those of W&B, others, such as density altitude, humidity, winds, runway gradient, and runway surface conditions, all can profoundly influence how an airplane performs.
Air density can effect airplane performance because it has a direct bearing on the power output of the engine, the efficiency of the propeller, and the lift generated by the wings.
When the air temperature increases, the density of air decreases and, as altitude increases, the density also decreases. From this combination of occurrences, then, comes the term “density altitude“.
Because it can get a little confusing, remember that a decrease in air density means a high-density altitude. Or said another way, it means that because the air is thinner than standard, the air at a given altitude has the characteristic of air at some higher altitude. The thinner air, in turn, adversely affects lift, engine power, fuel consumption, and overall engine efficiency. Conversely, an increase in air density means a lower-density altitude (the air is becoming thicker, heavier, more dense), and the aircraft lift as well as engine performance is more efficient. Saying it once again, it means that the altitude takes on the characteristics of a higher altitude because the density is lower, and thus the air is thinner.
(to be continued)