Should Large Business Jets Have Four Under the Wing?

A preliminary design study is conducted of three very long range business jets. One has two engines mounted on the rear fuselage, like most existing business jets. The other two have two or four engines mounted under the wing.

The paper shows that the design takeoff weight of very long range business jets is extremely sensitive to three parameters: design range, design sfc and design L/D. Depending on the design range and wing loading, these airplanes are also critical in terms of available fuel volume.

The paper gives an analysis of the pros and cons of either configuration. A cost comparison in terms of DOC (Direct Operating Cost) is also given. When considering both cost and takeoff weight, the 2-engines-under-the-wing design is shown to come out on top.