The majority of fixed-wing micro air vehicles with wingspans between 6 inches and 30 inches have significantly more wing flexibility than is common with larger aircraft. Such flexibility is introduced because pilot comments indicate that gust sensitivity is noticeably reduced as stiffness is decreased. This paper investigates the longitudinal gust sensitivity for a representative aircraft across a range of stiffness values. In particular, the flight dynamics are analyzed in the frequency domain to intepret the effects in terms of phugoid and short-period modes. Both modes are uniformly less sensitive to horizontal gusts but their sensitivity is somewhat more complicated when considering vertical gusts. The sensitivity of the phugoid mode decreases as stiffness decreases; however, the sensitivity of the short-period mode actually increases as stiffness decreases. The variations in modal damping and mode shapes due to aeroelastic effects are quantified and used to correlate with gust sensitivity. Also, a basic LQR controller is introduced to demonstrate that gust rejection remains feasible in response to both horizontal and vertical disturbances.
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