Empennage Sizing: The Tail Lever Arm as a Percentage of Fuselage Length Determined from Statistics

This project gives an overview of a selection of geometrical parameters with respect to the tail volume coefficient. A statistic on the basis of 30 aircraft, which differ in their dimensions, was made. One target was to create a graphical method for finding the tail levers arms, both for the horizontal, and the vertical tail. The average tail lever arm for the horizontal tail of all 30 aircraft altogether is 46.2% of their fuselages. The average tail lever arm for the vertical tail of all 30 aircraft altogether is 41.8% of their fuselages. When considering two different configurations, the first configuration (A) is one in which the aircraft have their engines at-tached to the wing and the second configuration (B) is the one in which aircraft have their en-gines attached to the fuselage. The percentages alter to 47% and 44.7% for configuration A and 44.6% and 36.1% for configuration B. With these values and some other geometrical da-ta, it is, among other things, possible, to calculate the corresponding tail volume coefficients. In order to find the length of an aircraft’s tail lever arm, three-view drawings with proper scale were analyzed graphically. The literature work of this project includes the finding of exact data for a small selection of aircraft, which also were investigated, in order to validate the values found with the graphical procedure. The deviation of the two is about 1% on average. Overall, a relation between the fuselage length of an aircraft and its tail lever arms could be noticed. The longer the aircraft’s fuselage gets, the smaller the percentage increase of the tail lever arms are. Furthermore, tail volume coefficients were calculated and discussed with the help of the graphically determined values.