Typical Civil Aircraft Research Articles

Longitudinal SCAS design and simulation for civil aircraft simulator

Abstract In this paper, the principle and benefits of stability and control augmentation system (SCAS) are introduced. Four schemes of the longitudinal SCAS for civil aircraft in normal mode are analyzed and compared. One of them, i.e., C * response type, is selected. Its architecture is determined. Then, based on a typical civil aircraft, the flight control law of the longitudinal SCAS is designed. A simulation model of the longitudinal SCAS is established through MATLAB software. Finally, the simulation and verification of the longitudinal SCAS model is carried out. The simulation results show that the designed longitudinal SCAS is feasible and can be applied to engineering practice. Compared with either normal load or pitch rate command response type, with proportional and integral feedback for mixed control signals of pitch rate and normal load, C * not only improves the short period characteristics but also effectively separates phugoid and short period frequencies, thus achieving high control accuracy.

Directional control law functional analysis and design for civil aircraft simulator

Abstract Functional analyses of directional flight control law for a typical civil aircraft are conducted, including directional maneuver, rudder limiter, coordinated turn, Yaw Damper, Thrust Asymmetrical Compensation, Gust Alleviation, manual rudder trim, etc. Through inputs of doublet, step input, and sweeping frequency, open loop control characteristics are analyzed based on a linearized state-space matrix. Simulink block architecture of a closed-loop directional control law is constructed, aiming to fulfill flight control functions, including pedal-to-rudder control, Yaw Damper, coordinated turn, and gain-tuned rudder limiter. Simulations for the previously designed closed-loop directional control law are performed to verify the characteristics of directional handling qualities in the aspect of the Yaw Damper, directional static and dynamic stability, maneuverability, and sweeping frequency.

High-speed multi-camera videogrammetric measurement of full-field 3D motion and deformation in full-scale crash testing of typical civil aircraft

Crashworthiness has been and will continue to be the main concern in aircraft design. Crash tests are essential approaches to investigate the crashworthiness of civil aircraft. Videogrammetric methods have been employed in crash tests to overcome the disadvantages of laborious, time-consuming measurement data collection using contact sensors. However, previous methods using a single pair of cameras still face challenges in large-scale applications due to the inherent contradiction between measurement range and accuracy. In this paper, a videogrammetric method using four high-speed cameras is proposed to measure the full-field three-dimensional (3D) dynamic deformation for evaluating the impact response characteristics of the full-scale crash test aircraft. Increasing the number of high-speed cameras not only can enhance the resolution and then measurement accuracy of object, but also expands the measurement range significantly. To ensure the performance of digital image correlation (DIC) used for large-scale measurement range, a speckle pattern optimization design and fabrication method is presented to generate the random speckle with uniform spraying size and density. A global calibration method based on the high-precision total station is proposed to unify the data of different stereovision subsystems. The implementation of the proposed method is illustrated through a 6.0 m/s full-scale crash test using a civil aircraft approximately 24 m in length. The impact velocity, full-field displacement and strain of the fuselage structure are measured. The results show that the test data are complete and reliable. After the vertical crash at 5.71 m/s, the lower structure of the cabin floor is seriously deformed, and the upper structure of the fuselage in the central wing area is obviously deformed due to the inertia effect of the wing. The stiffness difference of the different fuselage segments results in significant differences in dynamic response. The higher the stiffness is, the smaller the deformation. This work may provide some valuable technical insights that could support the crashworthy design, verification, and certification of civil aircraft.

Tolerance analysis of slat gear rotary actuator in civil aircraft

Abstract The slat gear rotary actuator of civil aircraft needs to meet the requirements of small space and large transmission ratio. The planetary gear system based on triple teeth is a common actuator design, and the design structure is complex, so its tolerance control is also strict. In order to meet the design requirements of its internal structure, this paper presents a deviation analysis method for the internal structure design of a typical civil aircraft slat gear rotary actuator. The results of preliminary tolerance distribution and improved tolerance distribution are analyzed using the Jacobi-based assembly deviation model. By comparing the standard deviation of the analysis results, the validity of this deviation analysis method is verified, which proves that this method can be used to analyze the internal structure deviation of the rotary actuator of slat gear in civil aircraft.

A serialized civil aircraft R&D cost estimation model considering commonality based on BP algorithm

The common design of serial civil aircraft, an important strategy of modern civil aircraft research and develop-ment, minimizes the whole life cycle cost of civil aircraft through asset reuse and resource sharing. However, the existing estimating model for the R&D cost of civil aircraft ignores the effects of common design, so the value estimated by estimating derivative models is significantly inconsistent with the actual one. To solve this problem, a novel assessment method for civil aircraft commonality indicators is developed based on fuzzy set in the present study, exploiting the attributes and structural parameters of the aircraft to be assessed as input to determine the degree of membership that pertains to the commonality sub-interval as the commonality indicator. Then the BP (Back Propagation) neural network algorithm is adopted to establish the relationship between the common index and the decrease rate of the R&D cost of derivative models. The model employs over a dozen typical civil aircraft models (e.g., Boeing, Airbus, and Bombardier) as the sample data for network learning training to build a mature neural network model for estimating the R&D cost of novel derivative models. As revealed from the comparative analysis on the calculated results of the samples, the estimated results of the model given the effects of commonality in the present study exhibit higher estimation accuracy and value for future work.

A Review of The Development of Civil Aircraft Family

The development of product family has become a major trend in industrial product research and development, which can meet the needs of market segments, shorten research and development time, reduce research and development costs, and quickly increase market share. The development of civil aircraft family is one of the important characteristics of modern civil aircraft design, which can bring significant economic benefits for aircraft life cycle. In order to meet the needs of the market and realize cost reduction and efficiency increase, the development of civil aircraft family has become the main direction of the development of modern civil aircraft, which has attracted widespread attention, and the major aircraft manufacturers have formed their own series of civil aircraft. Focusing on the development of civil aircraft family, this paper reviews the development of product family, the design of civil aircraft family and the development status of typical civil aircraft family in the field of civil aircraft. Then the challenges and future research directions of civil aircraft family are summarized and discussed.

DVB‐T based passive radar for simultaneous counter‐drone operations and civil air traffic surveillance

The effectiveness of DVB-T based passive radar (PR) in counter drones operations is investigated in this study aiming at monitoring airport terminal areas. In particular, the authors demonstrate that such sensors could be effectively employed to provide simultaneous short-range surveillance against drones and long-range monitoring of aircraft from civil air traffic. To this purpose, several experimental tests have been performed with the DVB-T based AULOS® passive sensor developed by Leonardo S.p.A. using very small RCS drones as cooperative targets along with conventional air traffic as targets of opportunity. An appropriate signal processing architecture is proposed for the two search tasks to be accomplished simultaneously. This is extensively applied against the collected datasets, based on the algorithmic solutions devised by the research group at Sapienza University. The reported results clearly prove the capability of a DVB-T based PR of simultaneously detecting and localising drones flying around the airport area as well as the typical civil aircraft at longer distances.

Multi-Echelon Inventory Allocation of Civil Aircraft Spare Parts Considering Maintenance Ratio

A multi-echelon inventory allocation technique with maintenance ratio for civil aircraft spare parts was proposed in this paper. Multi-echelon inventory allocation model was established, which integrates maintenance rate into METRIC (Multi-echelon technique for recoverable item control) model, and then marginal analysis method was applied to solve this model and accomplish multi-echelon inventory allocation of spare parts. Firstly, the theory of multi-echelon inventory allocation model with maintenance ratio was elaborated, and the mathematical model was established with the fleet availability as the optimization objective, the cost and the safeguard probability as the constraints. Secondly, the procedure of solving multi-echelon inventory allocation model considering the influence of maintenance ratio is discussed based on the marginal analysis method. Thirdly, landing gear LRU (Line repairable units) of a typical civil aircraft were selected as the research object, multi-echelon inventory allocation was investigated by considering maintenance ratio. The analysis results show that the minimum safeguard cost and fleet availability are respectively 2759833 dollars and 0.9806, and the number of LRU of multi echelon inventory allocation are obtained under the condition of satisfying the constrained optimization. The feasibility and effectiveness of the developed method are verified by comparing the traditional analysis method. This paper provides guidance for the accurate allocation of multi echelon inventory optimization for maintenance resources on the premise of reasonable cost reduction.

Crashworthiness Analysis and Evaluation of Fuselage Section with Sub-floor Composite Sinusoidal Specimens

Crashworthiness is one of the main concerns in civil aviation safety particularly with regard to the increasing ratio of carbon fiber reinforced plastic (CFRP) in aircraft primary structures. In order to generate dates for model validations, the mechanical properties of T700/3234 were obtained by material performance tests, and energy-absorbing results were gained by quasi-static crushing tests of composite sinusoidal specimens. The correctness of composite material model and single-layer finite element model of composite sinusoidal specimens were verified based on the simulation results and test results that were in good agreement. A typical civil aircraft fuselage section with composite sinusoidal specimens under cargo floor was suggested. The crashworthiness of finite element model of fuselage section was assessed by simulating the vertical drop test subjected to 7 m/s impact velocity, and the influences of different thickness of sub-floor composite sinusoidal specimens on crashworthiness of fuselage section were also analyzed. The simulation results show that the established finite element model can accurately simulate the crushing process of composite sinusoidal specimens; the failure process of fuselage section is more stable, and the safety of occupants can be effectively improved because of the smaller peak accelerations that was limited to human tolerance, a critical thickness of sub-floor composite sinusoidal specimens can restrict the magnitude of acceleration peaks, which has certain reference values for enhancing crashworthiness capabilities of fuselage section and improving the survivability of passengers.

Experimental and Numerical Methods for Transition and Drag Predictions of Laminar Airfoils

The friction component is responsible for more than 40% of typical civil aircraft drag. As a consequence, the issue of laminar flow has been of prime importance in aeronautics for many years now. This article is focused on Tollmien–Schlichting-induced transition and drag predictions of two-dimensional laminar airfoils obtained with experimental and numerical methods. In 2012, a test campaign in the ONERA-S2MA wind tunnel, including infrared acquisitions, pressure sensors, and wake analyses, allowed substantial data to be obtained on such airfoils in transonic conditions. To complete this study, two-dimensional fluid dynamics computations have been performed, either with a Reynolds-averaged Navier–Stokes solver using transition criteria or with a boundary-layer code combined with direct stability analysis. Furthermore, experimental (wake survey) and numerical (far-field theory) techniques allowing airfoil drag breakdown have been employed. Wind-tunnel and computational fluid dynamics transition predictions have been compared. Good agreement has been observed but the transition criteria may show some limitations in particular situations, such as long separation bubble development. The gains in lift and drag due to laminar flow have been quantified (natural vs triggered transition). Concerning drag reduction, the importance of the viscous pressure component has been highlighted. Finally, the effects of parameters such as angle of attack, Mach number, and Reynolds number on transition location and drag have been investigated.

Crashworthiness uncertainty analysis of typical civil aircraft based on Box–Behnken method

The crashworthiness is an important design factor of civil aircraft related with the safety of occupant during impact accident. It is a highly nonlinear transient dynamic problem and may be greatly influenced by the uncertainty factors. Crashworthiness uncertainty analysis is conducted to investigate the effects of initial conditions, structural dimensions and material properties. Simplified finite element model is built based on the geometrical model and basic physics phenomenon. Box–Behnken sampling and response surface methods are adopted to obtain gradient information. Results show that the proposed methods are effective for crashworthiness uncertainty analysis. Yield stress, frame thickness, impact velocity and angle have great influence on the failure behavior, and yield stress and frame thickness dominate the uncertainty of internal energy. Failure strain and tangent modulus have the smallest influence on the initial peak acceleration, and gradients of mean acceleration increase because the appearance of material plastic deformation and element failure.

Aircraft Wheel Design and Proving

Aircraft manufacturers now demand wheels which are not only light but also have a long life capability. A typical civil aircraft project such as the Boeing 757, requires a fully approved wheel with a demonstrated life of 50,000 roll miles which equates to approximately 10,000 landings.