Tail Design for Improved Stability and Control of a Short Take Off and Landing Aircraft at High Angles of Attack

Abstract

Short takeoff and landing (STOL) aircraft are an important part of life in Alaska. These aircraft allow pilots to land in places that would otherwise be considered too small for a standard aircraft. Part of being a STOL capable aircraft requires slow speed flight at high angles of attack. Many of the true STOL aircraft in Alaska are modified commercially available aircraft that were never designed for these high angles of attack. This paper will propose and analyze a set of modifications to an already modified Piper Cub to improve the tail authority at these higher angles of attack. These modifications include changing the cross-sectional geometry of the horizontal stabilizer, increasing the area of the tail, and increasing the length of the wing leading edge slats to improve flow quality. CFD was performed on both the original and modified designs in a variety of flight configurations to evaluate the stability and control of the aircraft system at a free stream velocity of 30mph. Analysis of the CFD found that the elevator authority increases by 12.3% and the maximum achievable angle of attack increases by approximately 5.5 degrees.