Interplane

Interplane refers to the space and the linked structural elements between two parallel planes in a multwing aircraft, most commonly a biplane or triplane. The term covers the interplane gap, which is the distance between the upper and lower wing planes, as well as the components that connect and brace them, such as interplane struts and interplane bracing wires.

In traditional biplane design, the interplane arrangement provides essential structural support while allowing the wings to be spaced apart. The interplane gap and the associated bracing influence aerodynamic interference between the wings, overall lift distribution, and the weight of the wing-wiring and struts. Designers balance the gap to reduce interference drag and to manage structural loads without excessive weight or complexity.

Historically, interplane concepts were central to early aviation, when many aircraft used two or more wings to achieve sufficient lift with the materials available. The popularity of interplane designs diminished as monoplanes with higher stiffness-to-weight ratios became feasible, but the terms interplane gap and interplane struts remain part of the vocabulary of biplane and triplane examples, as well as in restoration, modeling, and some modern light aircraft that employ tandem or stacked wing concepts.

Beyond aviation, interplane is sometimes used more generally in technical contexts to describe anything positioned between two planes or layers, such as components in layered systems or assemblies. The term originates from the Latin inter- meaning between and plane, and it is primarily encountered in aeronautical and mechanical engineering discourse.