Research Article
Parameter Estimation of Short-period Low Order Equivalent System for Fighter Aircraft Under Extreme Flight Conditions
Sayogyo Rahman Doko*
,
Rianto Adhy Sasongko
Issue:
Volume 12, Issue 1, June 2026
Pages:
1-11
Received:
29 July 2025
Accepted:
5 January 2026
Published:
30 January 2026
Abstract: This paper presents the estimation of Low Order Equivalent System (LOES) parameters for the longitudinal short-period mode of a fighter aircraft, using high-fidelity nonlinear simulation data of the F-16. The complex flight dynamics of such aircraft, effectively a High Order System (HOS) due to the presence of flight controls and component dynamics, require simplified equivalent systems for evaluating flying qualities against military standards. This study focuses on estimating LOES short period parameters using nonlinear flight simulation data under extreme flight conditions defined by high angles of attack up to 30 degrees. LOES parameters were identified through a hybrid approach combining time-domain regression and frequency-domain parameter estimation using a Maximum Likelihood Estimation (MLE) algorithm, resulting accurate identifications characterized by low standard deviations. Model validation confirms that LOES output closely matches HOS nonlinear data using inputs in the time domain, with a coefficient of determination R2 metric above 77% and fit error below 0.2. Additionally, the LOES model effectively represents nonlinear system responses in the frequency domain, yielding relatively low MIL cost and maintaining mismatch errors within the Maximum Unnoticeable Added Dynamics (MUAD) boundary.
Abstract: This paper presents the estimation of Low Order Equivalent System (LOES) parameters for the longitudinal short-period mode of a fighter aircraft, using high-fidelity nonlinear simulation data of the F-16. The complex flight dynamics of such aircraft, effectively a High Order System (HOS) due to the presence of flight controls and component dynamics...
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Methodology Article
Development of Algorithms and Computer Codes for the Aerodynamic Configurational Design
Satish Chander Gupta*
Issue:
Volume 12, Issue 1, June 2026
Pages:
12-27
Received:
5 May 2026
Accepted:
16 May 2026
Published:
12 June 2026
DOI:
10.11648/j.ajae.20261201.12
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Abstract: Several algorithms and computer codes are developed for the configurational aerodynamic design. Mathematical background, physics involved and their applications are brought out. These range from subsonic to supersonic, including transonic Mach number. Vortex lattice method is applied for handling subsonic and supersonic flow conditions under the linearised flow regime. Finite difference methodology is applied for transonic flow nonlinearities. Matrix of optimization is formed through principles of calculus of variations. The codes developed provide capabilities for inverse design for given loading, aerodynamic drag reduction, high lift to drag designs, generation of morphed profiles, wing optimization in the presence of canard, control surfaces sizing, design of reflex camber wings, and effect of ground proximity on flare manoeuvre, Analysis and Design is made over larger domain of flow field. Details on Camber morphing of wings are elaborated. Camber-morphing aerofoils aim to achieve their camber changes in a smooth way to potentially reduce the drag penalty. Morphing is possible by applying optimisation while restraining variation in camber in certain portions of the wing. A matrix for morphing is developed and scheme so developed is applied herein. Morphing as a concept is also applied to optimise wing for minimum induced drag in the presence of canard, where the slopes of canard camber are made to remain invariant to changes. As the aircraft comes close to ground during landing, runway interferes with aircraft flow field. Some aspects of interference effects of solid boundary wall are established. The influence of wall boundaries on the wing is estimated. Wing is placed at different heights above a horizontal solid surface plane, and an equal opposite vortex system is placed at depth equal to height below this surface. Codes developed find a useful application for design of aircraft for several aspects.
Abstract: Several algorithms and computer codes are developed for the configurational aerodynamic design. Mathematical background, physics involved and their applications are brought out. These range from subsonic to supersonic, including transonic Mach number. Vortex lattice method is applied for handling subsonic and supersonic flow conditions under the li...
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