Effect of Trail Aircraft Size on Sweet Spot Location for a Conventional Aircraft Pair in Formation

This paper studies the optimum fuel-saving locations for a pair of different-sized conventional aircraft flying in formation. The optimum location is studied based on methods previously defined by the authors, a static and a dynamic study. The static sweet spot, is the relative location of the trail aircraft where the lift-to-drag ratio is the highest and the dynamic sweet spot is the relative location with the least thrust required for the trail. It was seen that for a smaller conventional trailing aircraft, the static and dynamic sweet spots coincide but for a larger conventional trail, the two sweet spots differ. This is in agreement with prior work done by the authors using different-sized unconventional deltawing trailing aircraft. The results of this study lead to the conclusion that the relative sizes of the aircraft in the formation are the main factor on whether or not the location of highest lift-to-drag matches the location with the least required thrust for the trail aircraft.