Researches

Overview

The research group is dedicated to solving engineering science problems throughout the entire

aircraft lifecycle, spanning from demonstration and design to production, operation, and

maintenance. The core of our engineering research focuses closely on real-world aircraft usage

scenarios, ensuring that all research results are feasible for implementation and can generate

significant engineering benefits in the short to medium term. Regarding scientific problems, 

we aim to reveal the essence of phenomena and explore internal mechanisms. By constructing

corresponding theoretical models, we develop widely applicable scientific methods to effectively

guide practical applications in the field of aviation.

I. Aircraft Conceptual Design

(1) Aerodynamic Analysis Software Development

VLM513 is a software suite for aircraft aerodynamic and stability/control analysis based on the 

Vortex Lattice Method (VLM). Developed in MATLAB, the entire source code is released here as 

open-source. The primary development work was completed during my doctoral studies, and 

the software is currently updated on an irregular basis. While VLM513 initially referenced Tomas 

Melin's "Tornado" in its early stages, years of continuous development and refinement have 

resulted in over 90% of the current code being distinct from the original Tornado. Key 

improvements over Tornado include:

① Enhanced computational speed. Improved data structures have increased the calculation speed 

when solving for multiple states;

② More convenient input interfaces. Calculation targets can be defined via text files or imported 

from CATIA;

③ Improved numerical stability. The processing logic for calculating downwash at points near vortex 

lines was modified to enhance stability. Additionally, the aerodynamic calculation method for control 

surface deflection was revised to ensure continuous aerodynamic changes from neutral to a specific 

deflection angle;

④ Increased calculation accuracy in specific cases. Placing vortex lattices on the mean camber surface 

rather than the chordal plane has improved accuracy when dealing with high-camber airfoils. The 

inclusion of side-edge vortex analysis has significantly improved aerodynamic calculation accuracy 

when the aircraft is in a sideslip;

⑤ Added stability and control analysis functions. The software can calculate stability and control 

derivatives and conduct longitudinal/lateral-directional modal characteristic analysis by integrating 

inertia information from the input files.

This software can be used for learning aerodynamics courses as well as for aircraft conceptual design 

and optimization. The main interface is in English; for ease of use and learning, critical parts of the code 

include Chinese comments. Every algorithm has its scope and limitations; users must analyze the 

correctness of the results based on their own knowledge. The developer assumes no responsibility for 

any consequences arising from the use of the software.

Learning Tip: The Vortex Lattice Method is an aerodynamic algorithm based on solving linearized 

potential flow equations. Since potential flow does not account for viscosity, it cannot analyze 

viscosity-related effects, such as skin friction drag or flow separation. Because induced drag is 

generated by the deflection of the lift direction under the influence of downwash, it can be solved 

via VLM. The zero-lift drag in VLM is solved using the equivalent skin friction method introduced in 

Raymer's Aircraft Design: A Conceptual Approach, which is an engineering approximation method.

Verification Case for Solver Accuracy (Validated against NASA TM 4640 data)

Publications

[1] SONG Lei, YANG Hua, XIE Jingfeng, et al. Predicting Stability Derivatives of Flying Wing Aircraft Based 

on Improved Vortex Lattice Method [J]. Journal of Nanjing University of Aeronautics & Astronautics, 2014, 

46(3): 457-462.

[2] SONG Lei. Conceptual Design Optimization of Flying-wing Aircraft [D]. Beijing: Beihang University, 2017.

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(2) Parametric Representation Methods for Aircraft Airfoils

In the aircraft design process, aerodynamic optimization is a task that spans from conceptual to 

detailed design. Airfoil parameterization is the foundation for completing aerodynamic optimization; 

on one hand, it determines the coverage of the design optimization search range relative to the actual 

design space, and on the other hand, it significantly impacts the nonlinearity and continuity of the 

optimization problem at the mathematical level. A key goal of airfoil parameterization is to 

mathematically represent the airfoil curve as accurately as possible using fewer parameters.

This research group has proposed an Improved Geometric Parameter (IGP) airfoil parameterization 

method. By separately describing the camber and thickness distributions, this method achieves a 

parametric description of the airfoil using only 8 variables (comparison with other methods is shown 

in Table 2.1). The variables used in this method are easily linked to general airfoil description methods 

in aerodynamic research, making it easier to guide and analyze the airfoil optimization process using 

aerodynamic design experience. Furthermore, because this method decouples the description of 

camber and thickness, it is convenient for use in aerodynamic solvers based on potential flow theory 

(such as VLM). In this context, aerodynamic optimization can be focused solely on the camber curve, 

as thin airfoil theory suggests that the lift characteristics of a wing at small angles of attack are primarily 

determined by its camber. To verify this method, the research group performed fittings using airfoils 

from the Profili database; the fitting accuracy was excellent, as detailed in the published paper linked 

below.

Table 2.1  Comparison of each method's number of parameters.

Publications

[1] Xiaoqiang L, Jun H, Lei S, et al. An improved geometric parameter airfoil parameterization method 

[J]. Aerospace Science and Technology, 2018, 78: 241-247.

II. Flight Mechanics and Flight Testing

(1) Lateral-Directional Self-Stability Design for Flying Wing Aircraft

Due to the lack of vertical stabilizers, flying wing aircraft exhibit significantly lower directional stability 

than conventional aircraft. Currently, general engineering solutions to this problem include two 

categories: 1. Sideslip angle feedback via automatic control systems (e.g., B-2, X-47B); 2. Adding 

wingtip stabilizers (e.g., X-48B). In our research on flying wing aircraft design, our group has proposed 

a third method distinct from the previous two: lateral-directional self-stability design. This design 

targets the convergence characteristics of the primary lateral-directional modes and employs an 

inverse design of the dihedral distribution across the spanwise sections of the aircraft. By adjusting the 

values of lateral-directional stability derivatives, passive dynamic stability is achieved within the design 

speed range without relying on active control. Meanwhile, because dihedral adjustment does not affect 

the longitudinal aerodynamic coefficients when there is no sideslip, self-stability design does not 

significantly impact the aircraft's lift-to-drag performance.

This technology has been validated through tests on flight platforms of various sizes. During this 

process, new aerodynamic and stability/control issues for flying wing aircraft were discovered, and 

related research is continuously advancing.

Publications

[1] Song L, Yang H, Zhang Y, et al. Dihedral influence on lateral–directional dynamic stability on large 

aspect ratio tailless flying wing aircraft [J]. Chinese Journal of Aeronautics, 2014, 27(5): 1149-1155.

[2] SONG Lei, YANG Hua, YAN Xufeng, HUANG Jun. Lateral-directional Dynamic Stability Design Method 

for Flying Wing without Augmentation [J]. Systems Engineering and Electronics, 2015, 37(11): 2561-2565.

[3] Song L, Yang H, Xie J, et al. Method for Improving the Natural Lateral-Directional Stability of Flying 

Wings [J]. Journal of Aerospace Engineering, 2016, 29(5): 06016003.

[4] SONG Lei. Conceptual Design Optimization of Flying-wing Aircraft [D]. Beihang University, 2015.

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(2) Flight Test Research on Dutch Roll Mode Convergence under Zero 

Directional Static Stability

It is generally believed that directional static stability (weathercock stability) is a necessary condition 

for achieving Dutch roll mode convergence. This study designed an interesting set of experiments to 

verify that an aircraft can achieve lateral-directional Dutch roll dynamic stability even in the absence 

of directional static stability. First, the possibility of Dutch roll mode convergence without directional 

static stability was proven using purely mathematical methods. Subsequently, an RC glider was chosen 

as the research object. By reducing the vertical tail area and adding a vertical stabilizer forward of the 

center of gravity, the directional static stability was adjusted to zero while maintaining a constant 

side-force stability (Cy_beta). After numerical calculations proved that the aircraft could achieve Dutch 

roll convergence, actual flight tests were conducted. The flight test results confirmed the theoretical 

analysis but also revealed new changes in the aircraft's stability and control characteristics after 

modification. These results indicate that, on one hand, the method of emphasizing only directional 

static stability during Dutch roll mode analysis is incomplete, and on the other hand, the impact of 

directional static stability on other stability and control characteristics beyond the Dutch roll mode 

warrants further study.

Publications

[1] Fu J, Huang J, Song L, Yang D. Experimental Study of Aircraft Achieving Dutch Roll Mode Stability 

without Weathercock Stability. International Journal of Aerospace Engineering. 2020;2020.

[2] Fu J, Huang J, Wang L B, et al.Oscillation mode flight data analysis based on FFT [J]. Aircraft 

Engineering and Aerospace Technology, 2018, 91(1): 157-162.

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(3) Sub-scale Flight Testing and Flight Data Measurement

Publications

[1] Hua Y, Lei S, Cheng L, et al. Study on powered-parafoil longitudinal flight performance with a fast 

estimation model [J]. Journal of Aircraft, 2013, 50(5): 1660-1668.

[2] YANG Hua, SONG Lei, WANG Wenjian, et al. Longitudinal Four-Degree-of-Freedom Dynamic 

Simulation of Powered Parafoil [J]. Journal of Beihang University, 2014 (11): 1615-1622.

[3] YANG Hua, SONG Lei, HUANG Jun. Research on Gliding Performance of Ram-Air Parafoil [J]. Flight 

Dynamics, 2014 (6): 510-513.

[4] Hua Y, Lei S, Weifang C. Research on parafoil stability using a rapid estimate model [J]. Chinese 

Journal of Aeronautics, 2017, 30(5): 1670-1680.

[1] Song L, Yang H, Yan X, et al. A study of instability in a miniature flying-wing aircraft in high-speed taxi 

[J]. Chinese Journal of Aeronautics, 2015, 28(3): 749-756.

[2] Fanxing Li, Gang Lin, Xiaoqiang Lu, and Lei Song. Enhancement of Insensitivity for Pitot-Static Probe 

by Static-Pressure Orifices Optimization [J]. IEEE Transactions on Instrumentation and Measurement 71 

(2022): 1-8.

[3] Li F, Song L, Xie J, et al.Preliminary Layout Design Method of Flush Airdata Sensing System [J]. 

IEEE Transactions on Aerospace and Electronic Systems, 2024, 60(6): 9221-9230.

Related Invention Patents

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(4) Flight Simulators for Aircraft Design Education

The team collectively developed the flight simulators for aircraft design education at the "Digital 

Collaborative Innovation Center for Aircraft" on the Shahe Campus, including one transport aircraft 

simulator and two fighter aircraft simulators. All simulators utilize a MATLAB/Simulink-driven 

underlying architecture for aerodynamic and flight dynamics solver development. The visual software 

is based on secondary development of popular modern flight simulation software, achieving 

bidirectional data communication with Simulink. Instruments were developed using rapid 

programming tools to allow students to modify them based on course learning and research needs.

In terms of hardware, the transport simulator employs a multi-monitor display solution to balance wide 

field-of-view with high-resolution requirements. The cockpit layout references modern fly-by-wire 

airliners, with most panels using touchscreen control to simulate various switch effects, while also 

facilitating rapid modifications to the cockpit interface. The fighter simulators utilize Mixed Reality (MR) 

headsets to integrate virtual external scenery with simulated internal cockpit views. The cockpit layout 

references modern 4th-generation fighters based on large-screen touch panels. Both types of simulators 

feature programmable active stick force control systems, which allow for easy force-feel programming 

to implement speed-dependent force gradients, as well as stick pusher and stick shaker effects.

The simulators are currently in use at the "New Generation Fully Digital Aircraft Science and Education 

Collaborative Innovation Center" located in Building 8, Room B119, Shahe Campus.

Promotional Video: https://www.bilibili.com/video/BV1wv4y1c7Qx

III. Stealth Technology

Publications

[1] Liu D, Huang J, Song L, et al. Influence of aircraft surface distribution on electromagnetic scattering 

characteristics [J].  Chinese Journal of Aeronautics, 2017, 30(2): 759-765.

[2] Yacong Wu, Jun Huang, and Lei Song. Influence of CAD modeling accuracy on target scattering 

characteristics [J]. Optik 203 (2020): 163975.