Define load factor and explain how it affects the flight envelope.

• A. Load factor is lift divided by weight; higher load factors reduce safe airspeeds and increase stall risk.
• B. Load factor is weight divided by lift.
• C. Load factor is altitude divided by speed.
• D. Load factor is wing loading times speed.

Answer: (A)

Load factor is the ratio of lift to weight, a unitless measure of how many times the aircraft’s weight is being supported during a maneuver. In straight, level flight the load factor is 1, but during turns, pull-ups, or other maneuvers the aircraft must produce more lift to provide the needed centripetal force. Because lift is produced by airspeed and wing capacity, increasing the load factor means the airplane must fly faster to avoid stalling. The stall speed rises with higher load factors (approximately with the square root of the load factor), so the low-speed boundary of the flight envelope moves up as you demand more maneuvering.

This relationship tightens the envelope: you have less margin at low speeds since stalling becomes easier, and you are limited at the high end by structural and operation limits (the maximum safe load factor). So higher load factors shrink the safe operating region by raising stall speed and by imposing structural limits on how aggressively you can maneuver.