1. It had three-bay wings without sweepback , wing folding. 2. The wings of both the monoplane and biplane versions featured prominent sweepback . 3. The wing is tapered in plan with less sweepback outboard. 4. Too much dihedral or sweepback generally causes Dutch roll. 5. There was then no flight experience with wings of this amount of sweepback . 6. Analysis work by Boeing engineer Vic Ganzer suggested an optimum sweepback angle of about 35 degrees. 7. The wings were sharply tapered with straight trailing edges, which introduced sweepback on the leading edge. 8. The trapezoidal wing has a 20-degree sweepback on the leading edge and a straight trailing edge. 9. The second version had a reduced sweepback to 32? allowing the wing and cockpit to be moved rearward. 10. Other changes to the wing included the removal of stagger from the design and the introduction of slight sweepback . 
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