All aircraft must meet controllability requirements to be certified for commercial use or adopted by the military. Many military aircraft also have additional maneuverability requirements. An aircraft's ability to meet these requirements is often limited by the amount of control authority available. Thus, it is essential for designers to evaluate the control authority of candidate concepts early in the conceptual design phase. Normally the designer considers numerous possible configurations before the stability and control group starts their analysis. An early evaluation by the designer, before detailed control system design starts, makes the design process much more efficient. In this report a methodology for rapid control power evaluation of conceptual and early preliminary design configurations against requirements at the critical flight conditions is established. First, the critical flight conditions to be considered using this methodology are discussed. Next, to examine a variety of aircraft configurations and accelerate the process of estimating stability and control derivatives, a FORTRAN program using the vortex-lattice method to estimate subsonic, low angle-of-attack aerodynamics is described. Then, a simple spreadsheet is used to combine the aerodynamic and geometric data to assess whether the design concept possesses adequate control power to satisfy the requirements at the critical flight conditions. This allows the designer to perform " what if " studies to decide how to change the design to satisfy the requirements. To trim configurations with three lifting surfaces or two lifting surfaces and thrust vectoring, a program implementing a recent NASA Langley method is provided. For further study, a bibliography relevant to control power issues is included.

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Control Authority Issues in Aircraft Conceptual Design: Critical Conditions, Estimation Methodology, Spreadsheet Assessment, Trim and Bibliography

On the feasibility of low-speed aircraft maneuvers involving extreme angles of attack

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Aerodynamic pitch-up of cranked arrow wings: estimation, trim, and configuration design

This paper discusses the influence of canard deflection angle on the aerodynamics characteristic of a Blended Wing Body (BWB) Baseline-II aircraft obtained from wind tunnel test. Canard is added as longitudinal control. All tests are carried out in UiTM Low Speed Wind Tunnel using 1/6 scaled model at around 0.1 Mach number at several canard angle. The result of the lift coefficient (C L ), the drag coefficient (C D ), and the pitching moment coefficient (C M ), are plotted and analyze to show the characteristics of the BWB with different canard deflection angles.

Aerodynamics characteristic of UiTM's BWB UAV Baseline-II at different canard deflection angles at low pitching angle

Applied Computational Aerodynamics - Case studies

Equivalent canard and tail control surfaces are compared on an advanced, carrier-based fighter/attack aircraft featuring variable wing sweep and vectorable, two-dimensional nozzles. Evaluations of stability and control characteristics, trimmed drag due to lift, minimum takeoff rotation speeds, and carrier approach speeds are presented. The results show that the canard configuration has substantially less supersonic trim drag and a lower carrier approach speed, which can yield appreciable takeoff weight savings, but the tail configuration exhibits better stability and control characteristics with less development risk.

Dario Rajkovic

Papers

Canard/tail comparison for an advanced variable-sweep-wing fighter

Canard/tail comparison for an advanced variable-sweep-wing fighter