What is a planform in aviation?

The term "planform" in aviation refers specifically to the shape of the wing as viewed from above. This perspective is crucial in aerodynamics, as it influences the lift, drag, and overall performance characteristics of the aircraft. The planform shape can be rectangular, elliptical, delta, or tapered, each providing distinct aerodynamic benefits. Understanding the planform is essential for analyzing how an aircraft will perform in flight, including stability and maneuverability.

In contrast, the other options cover different aspects of aircraft design. The shape of the wing viewed from the side pertains to the wing's profile or airfoil, which affects how air flows over it, but that's not what "planform" denotes. The overall design of the aircraft fuselage relates to the main body of the aircraft and is separate from wing design. Lastly, the configuration of the airplane's landing gear concerns how the aircraft is supported on the ground rather than its flight characteristics or wing shape. Thus, the correct definition of planform aligns with the shape of the wing when observed from a top-down view.