Load Factor

Load factor is the ratio of the aerodynamic lift being generated by the wings to the total weight of the aircraft. In straight and level unaccelerated flight, load factor is 1g. In manoeuvres, load factor increases: in a 60° banked turn it is 2g; in an 80° bank it approaches 6g.

Load Factor and Stall Speed

Stall speed increases with the square root of the load factor. At 1.41g (approximately 45° bank), stall speed increases by 19%. At 2g (60° bank), stall speed increases by 41%. At 3g, stall speed is 73% higher. This is why stall characteristics in manoeuvring flight are very different from straight-and-level stalls, and why base-to-final turns are so dangerous.

Structural Limits

Aircraft are certified for specific load factor limits. Normal category: +3.8g / −1.52g. Utility: +4.4g / −1.76g. Aerobatic: +6.0g / −3.0g. Exceeding these limits — even momentarily in turbulence — can cause structural damage. Maneuvering speed V_A is the speed below which full deflection of one control surface will not overstress the airframe.

On the TC Written Exam

Load factor and its relationship to bank angle and stall speed are heavily tested. Know the load factor at standard bank angles (2g at 60°, ~6g at 80°) and the stall speed formula: V_S bank = V_S × √(load factor).

Related Terms

See also: Angle of Attack, Maneuvering Speed, Gross Weight.