concept

Load factor

The lift a wing is producing divided by the animal's weight - the number usually spoken of as "g". In level flight the load factor is one. To turn, the wing must make more lift than the weight, because some of that lift is now bending the flight path rather than merely holding the body up: a sixty-degree bank already demands double. Load factor is what connects the geometry of a turn to what a body can survive - bone, membrane and blood vessels each have a ceiling, and that ceiling, not speed, sets the tightest turn an animal can actually live through.