Positioning of the Wing Relative to the Fuselage
Positioning of the wing relative to the fuselage is an iterative process dictated by the location of the aircraft CG at a desired position, expressed in terms of percentage of the wing MAC. The aircraft CG is kept close to the quarter-chord position of the wing MAC. Unfortunately, at this stage of design, the aircraft weight and CG are not accurately known.
A designer’s expertise is the way to estimate the wing position relative to the fuselage as a starting point. Experienced designers minimize the number of iterations that could occur with “wing-chasing,” explained in Section 4.11. The CG position varies with aircraft loading, fuel status, and military aircraft armament carried. Positioning of the wing should be such that the aircraft stability margin is not jeopardized by extremes of the operational CG position.
For newcomers to aircraft design, this offers an interesting exercise: Very quickly, a “feel” for locating the wing can be developed. A starting position for wing placement relative to the fuselage is approximately at the middle of the fuselage (somewhat farther behind for aft-mounted engines).