Light Combat Aircraft (LCA) named as Tejas is a single engine, tail-less, delta wing, supersonic fighter aircraft which is designed to be aerodynamically unstable in its longitudinal axis. In order to stabilize the airframe and achieve the desired performance over the entire flight envelope it incorporates a quad redundant full authority fly-by-wire (FBW) flight control system (FCS). The control laws in addition to guaranteeing stability optimize the aircraft performance and pilot handling qualities for various combinations of external store configurations. LCA has flown more than 4500 flights including trainer and naval variants. LCA (Tejas) has been inducted into IAF squadron. This talk narrates flight control law development cycle including parameter identification to update aero-database in order to expand flight envelope. In this talk fundamentals of control law design for an unstable fighter aircraft will be discussed and the mathematical challenges in order to achieve certain performance goals will be presented.
Dr Vijay Patel is currently Group Director (Flight Control Laws- LCA
Airforce) and is member of the National Control Law Team since 1995. The
National Control Law Team was setup for the Light Combat Aircraft (LCA)
by Dr. A. P. J. Abdul Kalam. Dr. Patel has been involved and also
responsible for the design, development and testing of flight control
system of LCA (later named as Tejas). His major contributions include the
successful design and development of flight control algorithms, design of
structural notch filters, verification of the flight control system
performance in the iron bird and on aircraft and responsible for piloted
handling qualities assessment at real time simulator and related detailed
flight test data analysis. He was also responsible for estimation of
aerodynamic coefficients from flight test data using nonlinear parameter
estimation techniques which enabled flight validation of the aerodynamic
data thereby allowing the aircraft to expand its flight envelope to lower
speeds and higher angles of attack. He played a major role in developing
boundary limiting features in flight control laws which in turn enabled to
expand the flight envelope safely, more rapidly without compromising
safety. Dr Patel is responsible for development of LCA flight control
laws features for carefree maneuvering.
Dr Patel has shared his flight control design, development and testing experience with other national projects such as ISRO’s RLV, Auotopilot of HAL’s Advanced Light Helicopter (ALH), ADE’s various UAV project and played major role in the technical reviews related to control systems of these project.
Dr. Patel obtained his PhD in the area of robust control from IIT Kharagpur in 1995 and did his post doctoral research at Virginia Tech, USA (2006-2007) in the areas of L1 adaptive flight control, coordinated path following for unmanned aerial vehicles (UAVs) and adaptive flight control design for unmanned combat aerial vehicles (UCAVs). During post doctoral fellowship period in 2006-2007, Dr. Patel got an opportunity to work with NASA (Hampton, USA) and Boeing sponsored projects which were futuristic aircraft and its flight control design problems. Dr. Patel has published 80 technical papers in peer reviewed international journals and conferences. He has also solved three open problems in mathematical control literature. He is recipient of INSA “Young Scientist Award (2001)”, INAE “Young Engineer Award (2004)”, DRDO Scientist of the year (2013) Award” and other awards from ISCA, NAL, DRDO.