Reading Performance Charts and Load Factor

A performance chart turns conditions into predicted numbers. To use a takeoff or landing chart you enter with pressure altitude and temperature, then track across for weight, wind, and obstacle height, interpolating between the printed lines rather than rounding to the nearest one. The chart assumes a well-maintained airplane flown at the book technique and speeds, so real-world results can be worse and a safety margin is wise. Load factor is a related idea in the air. It is the ratio of the load the wings carry to the airplane weight, measured in Gs. In a level turn it grows with bank angle — roughly 1.15 Gs at 30 degrees, 1.41 Gs at 45 degrees, and 2.0 Gs at 60 degrees. Because stall speed increases with the square root of load factor, that 60-degree turn raises the stall speed by about 40 percent, which is why an accelerated stall can surprise a pilot in a steep turn.