Aerospace Science and Technology 9 (2005) 692–700 www.elsevier.com/locate/aescte Aircraft maneuverability improvement by direct lift control system application Andrzej Tomczyk Department of Avionics and Control, Rzeszów University of Technology, W. Pola 2, 35-959 Rzeszów, Poland Received 26 May 2004; received in revised form 23 June 2005; accepted 8 September 2005 Available online 13 October 2005 Abstract The handling qualities of an aircraft will be improved if the Direct Lift Control (DLC) system is applied. In this paper, an attempt has been made to evaluate the influence of DLC-type system parameters on the aircraft’s maneuverability and to determine the desired values of these parameters for the purpose of obtaining required values of the handling maneuverability criteria. Published papers which deal with direct lift control do not list requirements for evaluating handling qualities and maneuverability of aircraft equipped with DLC system. In this paper, three new criteria permitting the evaluation of results of employing DLC have been defined. Analysis of influence of DLC system parameters on selected known handling qualities criteria (for example CAP, C ∗ ), as well as new DLC efficiency coefficients, have been illustrated with a numeric example of A4D “Skyhawk” fighter aircraft and PZL M-18 “Dromader” agricultural airplane control system modification.  2005 Elsevier SAS. All rights reserved. Keywords: Handling qualities; Direct lift control; Flight control systems 1. Introduction Classic handling performance criteria allow for the evalua- tion of properties of aircraft equipped with typical flight control systems. New methods of aircraft control, like thrust vectoring, as well as aerodynamics configuration modification of aircraft, require employing other criteria for evaluating flying quali- ties. One of the groups of aircraft characterized by controlled configuration (Control Configured Vehicle – CCV) employs Di- rect Lift Control – DLC [9]. Employing such control changes both static properties of aircraft (in steady states) and its dy- namic properties (stability and controllability). The vertical acceleration change at aircraft’s center of grav- ity after stick displacement describes the longitudinal maneu- verability of plane. Aircraft response to elevator step input may be well characterized by the time-path of normal load E-mail address: atomczyk@prz.edu.pl (A. Tomczyk). Fig. 1. Aircraft’s response for a step pilot’s stick displacement: A – classic control system, B – direct lift control system. factor ∆n z . Example of the responses is shown in Fig. 1, where: ∆n z (t) = n z (t) − 1, n z (t) = P z m · g , ∆n z (t) = ∆P z m · g , (1) where: P z – lift force, ∆P z – lift increment, m – aircraft mass, g – gravity acceleration. In a classic longitudinal control system, the change of lift force is caused by a change of the angle of attack of the wing. This requires rotating the aircraft around its starboard axis. The 1270-9638/$ – see front matter  2005 Elsevier SAS. All rights reserved. doi:10.1016/j.ast.2005.09.004