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The heading reversal of air-to-air missile is designed based on relaxed static stability and aerodynamic torque generated by static instability of air-to-air missile, and the kinematic sign is proposed. The slender body theory and the viscous crossflow theory are used to investigate the aerodynamic characteristics involved in the redirection of air-to-air missile. The slender body is assumed to be incapable of achieving the proposed kinematic sign of completing redirection, and it is necessary to increase control techniques such as aerodynamic rudder surface or direct force. The aerodynamic characteristics of a fin-body configuration are obtained for the angle of attack from 0° to 180°, and the trajectory and attitude of air-to-air missile during the process of heading reversal are calculated. The results show that the heading reversal is finished in 1.15 s, and the process of redirection is safe, quick and stable. Finally, some key technologies are discussed in the process of heading reversal.

The upset state is an unexpected flight state, which is characterized by an unintentional deviation from normal operating parameters. It is difficult for the pilot to recover the aircraft from the upset state accurately and quickly. In this paper, an upset recovery strategy and pilot assistance system (PAS) based on reinforcement learning is proposed. The man–machine closed-loop system was established and the upset state, such as a high angle of attack and large attitude angle, was induced. The upset recovery problem was transformed into a sequential decision problem, and the Markov decision model of upset recovery was established by taking the deflection change of the control surface as the action. The proximal policy optimization (PPO) algorithm was selected for the strategy training. The adaptive pilot model and the reinforcement learning method proposed in this paper were used to make the aircraft recover from the upset state. Based on the correspondence between the flight state, the recovery method, and the recovery result, the aircraft upset recovery safety envelopes were formed, and the four-level upset recovery PAS with alarm warning, coordinated control, and autonomous recovery modes was constructed. The results of the digital virtual flight simulation and ground flight test show that compared with a traditional single pilot, the aircraft upset recovery strategy, the upset recovery safety envelopes, and the PAS established in this study could reduce the handling burden of the pilot and improve the success rate and effect of upset recovery. This research has certain theoretical reference values for flight safety and pilot training.

The landing maneuver of aircraft is considered to be a feasible way to solve the problem of ultra short distance,precise landing of carrier based fixed wing aircraft. The existing researches mainly focus on aerodynamic modeling,nominal landing trajectory optimization and trajectory tracking control in the process of landing,but few on the overall analysis of the landing mission. Based on the dynamic model of aircraft longitudinal landing maneuver,the concept of landing trajectory reachable region is introduced,and the mathematical description of reachable region is given;On this basis,the Gauss pseudo-spectral method with both computational speed and accuracy is used to solve the reachable region problem,which is divided into three trajectory optimization problems. Firstly,the upper boundary of the terminal height of the perching trajectory is solved. Secondly,the nearest trajectory is solved when the terminal height is fixed. Finally,the farthest trajectory is solved when the terminal height is fixed.The simulation results show that:the model and solution method can quickly get the calculation results,the vertical landing trajectory of unpowered aircraft can reach the asymmetric region of narrow upper and wide lower,and the left and right boundary curves have good linearity.

Inspired by birds raising their feathers to control the separation flow, vortex flap has become an approach to control the separation flow over airfoils at high angles of attack.In this paper, the aerodynamic characteristics and physical mechanism of vortex flap controlling separation flow over airfoils under different Reynolds number are numerically studied.The results show that vortex flap is able to greatly improve the lift of airfoil at low Reynolds number under high angle of attack.Its physical mechanism is that the vortex flap makes the core position of main separation vortex closer to the airfoil comparing to the original airfoil, and the vorticity of the vortex center position is also greatly improved so that the low-pressure characteristics caused by the vortex core will affect the flow field on the upper airfoil surface.In addition, the pressure filed on the upper surface of the airfoil is divided by vortex flap into two parts:the low pressure aera in the front and the high pressure aera at the back.However, under high Reynolds number(corresponding to conventional aircraft Reynolds number), the effect of vortex flap on improving the aerodynamic characteristics of airfoil at high angle of attack is far less effective compared to the case of low Reynolds number.This explains why birds can improve lift characteristics through feather lifting, while vortex flap can only be used as drag plates in conventional aircraft.

This paper aims to investigate the side force on a cone–cylinder geometry at different angles of attack (α) by adopting experiments and computations. The cone–cylinder configuration had a length to diameter ratio (L/D) of 10, and a base diameter (D) of 25 mm. The nose shape had a fineness ratio of approximately 3. Results indicated that the side force increases with the increasing of the angle of attack. A circular ring was used to reduce the side force at different angles of attack. Using a smaller height ring (2% of local diameter) in the initial portion of the body did not reduce the side force significantly at lower angles of attack. However, a ring with larger height (5% of local diameter) placed at 2.5 times the diameter of the body from the tip reduced the side force at almost all the angles of attack.

The aerodynamic characteristics of a NACA0012 wing geometry at low Reynold’s numbers and angle of attack ranging from 0° to 90° are investigated using numerical simulations and the results are validated by wind tunnel experiments. Further experiments are conducted at low Reynold’s numbers of 1 × 105, 2 × 105 and 3 × 105. Findings of the study show a similar trend for the lift and drag coefficients at all the investigated Reynold’s numbers. The lift coefficient is linearly increased with angle of attack until it reaches its maximum value at 32° which is the stall angle. It is observed that further increment in angle of attack results in decrement of lift coefficient until it reaches its minimum value at 90° angle of attack. The drag force acting on the airfoil increases as the angle of attack is increased and increment in the drag force results in change of laminar flow to turbulent flow. As the turbulence gets higher the flow starts to separate from the airfoil surface due to eddies generated by turbulence. Hence, the lift force generated by the wing is reduced and drag force is increased simultaneously, which results in poor performance of the wing.

The purpose of this paper is to present the aerodynamic and flow characteristics of a slender body with a 30° swept wing configuration undergoing a limit cycle oscillation using a synchronous measurement and control technique of wing rock/particle image velocimetry/dynamic pressure associated with the time history of the wing rock motion. The experimental investigation was concentrated on 3 main areas: motion characteristics, static and dynamic surface pressures and static and dynamic particle image velocimetry. The tests’ results revealed that the lag in asymmetric twin vortices over the forebody switching from the left vortice pattern to the right one exhibits a hysteresis evolvement during the wing rock motion; the asymmetric triple vortices over the forebody interacted with the flowfield over wings appeared to induce the instability and damping moments. The main flow phenomena responsible for wing rock of wing body configuration were completely determined by the forebody vortices. These exhibit apparent dynamic hysteresis in vertical position, which further influences the wing flows, and the dynamic hysteresis of flows yields the damping moments sustaining the oscillations.

A flight test research program employing a remotely piloted vehicle (RPV) within high angle of attack range has commenced at the Faculty of Power and Aeronautical Engineering of Warsaw University of Technology, Poland. The initial flights of the scaled model of the “Bielik” aircraft were made with the aim to correlate RPV and full‐scale flight stall and departure and spin controllability considering the effects of dynamic scaling laws and Reynolds number. The remotely controlled research aircraft, which is powered by a turbine jet engine and equipped with a flight data recording system, proved to be good source of stability and control data at relatively low cost and without additional risk. The research remotely piloted vehicle and results of its initial flights are presented in this paper. First Published Online: 14 Oct 2010