About gust load factor, which statement is true?

• A. Only statement 1 is correct
• B. Only statement 2 is correct
• C. Neither statement is correct
• D. Both statements are correct

Answer: (D)

Gust load factor represents how much the lift during a gust exceeds the aircraft’s weight. When a vertical gust hits the airplane, it temporarily increases the angle of attack, causing lift to rise. The lift change from a small gust can be analyzed by noting that the gust creates an angle-of-attack change delta alpha roughly proportional to the gust speed times the gust duration, divided by the flight speed: delta alpha ≈ w t / V. Lift scales with dynamic pressure q = ½ρV^2 and with the lift-curve slope dC_L/dα, so the lift change during the gust is proportional to delta L ≈ (dC_L/dα) q S delta alpha. Substituting q and delta alpha gives delta L ≈ (dC_L/dα) (½ρ S) V (w t). That shows the increase in lift is proportional to the flight speed V for fixed gust strength and duration. Since the gust load factor is L divided by weight, higher flight speed makes a larger gust-induced load factor for the same gust.

So, statements describing that gust load factor increases with gust strength and that it increases with airspeed are both true, which is why the correct choice indicates both statements are correct.