| Resumo : |
The box wing aircraft is an unconventional design that is esteemed to present lower levels of induced drag when compared with conventional aircraft design. This configuration presents no horizontal tail and two wings swept in opposite directions in a diamond shape. The unconventional aerodynamic characteristics of the box wing lead to concerns about the feasibility of an aircraft with this configuration. One of the main concerns around any unconventional aircraft configuration is related to stability and control of the design. This dissertation presents an investigation of the flight qualities characteristics of a box wing aircraft in the preliminary design phase. The stability of a box wing aircraft is compared with a conventional aircraft with the same narrow body and wing area. The comparison intends to understand how the box wing configuration can affect flight qualities and controllability of an aircraft, using as reference an aircraft with known good flight characteristics. The stability investigation includes evaluating means for trimming the box wing aircraft, short-period oscillation, phugoid oscillation, maneuvering margin, among other studies. The analysis of results involves flight quality levels of the box wing aircraft, neutral point determination, and static margin analysis. Another important objective of the analysis is to evaluate limits for CG positioning in terms of control and longitudinal stability for the box wing to support evaluations of mass and balancing to be performed in future studies. Results obtained in this work confirm the feasibility of the design concerning controllability and longitudinal stability, showing that aircraft with box wings have similar flight mechanics characteristics to those of a conventional aircraft. Using elevators and flaps as options for trimming the box wing presented satisfactory results when compared with a conventional aircraft that has a horizontal stabilizer, however, more detailed aerodynamic modeling is necessary to evaluate all flight phases. Criteria for defining the CG range of an aircraft with this configuration are also presented, showing that a more rear CG position is required to maintain the same level of static margin that a conventional aircraft has. |