"In aviation, a sesquiplane is a variation on the biplane concept, where one wing (usually the lower) is significantly smaller than the other either in span, chord or both. The name means \"one-and-a-half wings.\" The arrangement reduces interference drag between the wings while retaining some of the biplane's structural advantage. The 1920s Pander E is an example of an aircraft with a lower wing of exactly half the span and nearly one quarter (23%) of the area of the upper one."@en . . .