Search Results (83)

In response to the complexity and uncertainty in assessing the safety and economic impacts of the Changed Product Rule (CPR) in civil aviation products’ airworthiness certification, this paper constructs a comprehensive evaluation model based on a cost–benefit analysis framework. In previous research, studies on aircraft modification costs have consistently been conducted from the perspective of design organizations, focusing on modeling and optimizing the one-time engineering costs of the modifications themselves or remaining confined to the level of safety performance without addressing the calculation of economic value. The model proposed in this paper considers the entire aircraft service lifecycle and uniformly quantifies potential impacts into monetary terms for comparison. The model encompasses safety improvements, cost estimation, and discounted cash flow analysis, aiming to provide decision-makers with quantitative tools for determining the applicability of the “impracticality exception” standard. This ensures that modifications to aviation products balance safety with economic viability. Through case studies involving fuel tank access panel design changes and Auxiliary Power Unit (APU) inlet duct fire protection requirements, the effectiveness and practicality of the model are validated, offering an empirical foundation for future policy formulation and industry regulation. Nevertheless, the parameters in the model depend on historical data, and appropriate parameters must be carefully selected. Although the model has taken into account the entire lifecycle of the aircraft, it is still based on static assumptions and fails to consider the impact of the rapid development of the aviation industry over time. Ongoing model refinement, international data collection, and integration of non-economic factors remain key directions for future research. Full article

This work addresses the critical need for documentation and validation of structural flight loads for Medium-Altitude Long-Endurance (MALE) Unmanned Aerial Systems (UAS). Despite the increasing prevalence of these aircraft, the industrial and research landscape still exhibits a significant data gap regarding loads under extreme operating conditions, particularly for unconventional geometric configurations. This study presents a rigorous and comprehensive load analysis for the certification of a fixed-wing MALE UAS, which is distinguished by its unique V-Tail configuration, characteristic of platforms such as the Elbit Hermes series. The entire investigation was conducted in strict adherence to the requirements of the NATO airworthiness standard STANAG 4671, aiming to precisely define the aerodynamic behavior and structural integrity of the airframe under an exhaustive set of critical flight conditions. The implemented methodology relies on the use of high-fidelity Computational Fluid Dynamics (CFD) data, derived from RANS simulations to create a complete aerodynamic database. This advanced approach is crucial for the accurate modeling of forces and moments, especially those generated by the coupled control surfaces, known as the ruddervators of the V-Tail. The results obtained include the precise derivation of the operational envelope, which defines the maximum load factors for both maneuver and atmospheric gust conditions. A detailed analysis of balancing and specific loads on the control surfaces was performed, leading to the definition of structural load distributions essential for subsequent stress analysis. Notably, the analysis identified the Unchecked Pitch-Up maneuver performed at the maximum load factor as the dimensioning design condition, particularly for the empennage structure. This work not only provides fundamental data for demonstrating compliance with applicable airworthiness criteria but also establishes a robust and repeatable methodology for the evaluation of flight loads in structurally complex UAS configurations. Full article

Electric aircraft powered by lithium batteries (LIBs) have seen rapid development in recent years, making research into their thermal runaway (TR) characteristics crucial for ensuring flight safety. This study focused on the individual battery cells of a specific electric aircraft power battery system, conducting TR experiments under both the aircraft’s service ceiling temperature (−8.5 ± 2 °C) and ground ambient temperature (30 ± 2 °C). The experiments analyzed changes in battery temperature, voltage, and mass during TR. Experimental results indicate that the peak TR temperatures reached 589.6 °C and 654 °C under the two environments, respectively, with maximum heating rates of 8.6 °C/s and 16.9 °C/s. At ambient ground temperatures, battery voltage drops more rapidly, with the voltage of a 100% SOC battery decreasing over just 10 s. Peak mass loss during TR reached 265.48 g and 247.52 g, respectively. Combining TR temperature data with the Semenov thermal runaway model, the minimum ambient temperature causing TR in this electric aircraft power battery under sustained external heating was determined to be approximately 39 °C. Finally, a multi-level protection strategy covering the “airframe–battery compartment–cabin” was established. The findings from this research can serve as a reference for subsequent safety design of this aircraft type and the formulation of relevant airworthiness standards. Full article

Advances in motor technology and the application of distributed electric propulsion systems have greatly promoted the development of electric vertical take-off and landing aircraft. As a critical safety component of eVTOL aircraft, the motor system design must satisfy both performance requirements and stringent airworthiness standards. This paper studies the lift–thrust unit drive motor system of an eVTOL aircraft and proposes an architecture that utilizes analytical redundancy to enhance system-level reliability. This paper focuses on threshold optimization in analytical redundancy systems. Through simulations and reliability analyses, the performance of the analytical redundancy system is quantified, with false alarm and missed detection probabilities evaluated, fault detection thresholds optimized, and overall system reliability enhanced analytical redundancy systems is improved. Simulation and calculation results demonstrate that the proposed fault detection method can effectively meet the requirements for rapid detection and achieve optimal reliability at the given optimal threshold. Full article

This work addresses the challenges of airline planning, which requires the integration of flight scheduling, aircraft availability, and maintenance to ensure both airworthiness and profitability. Current solutions, often developed by human experts, are susceptible to bias and may yield suboptimal results due to the inherent complexity of the problem. Furthermore, existing state-of-the-art approaches often inadequately address critical factors, such as maintenance, variable flight numbers, discrete time slots, and potential flight repetition. This paper presents a novel approach to aircraft routing optimization using a model that incorporates critical constraints, including path connectivity, flight duration, maintenance requirements, turnaround times, and closed routes. The proposed solution employs a simulated annealing algorithm enhanced with specialized perturbation operators and constraint-handling techniques. The main contributions are twofold: the development of an optimization model tailored to small airlines and the design of operators capable of efficiently solving large-scale, realistic scenarios. The method is validated using established benchmarks from the literature and a real case study from a Mexican commercial airline, demonstrating its ability to generate feasible and competitive routing configurations. Full article

Civil aviation airworthiness regulations are the fundamental basis for the design and operational safety of aircraft. Their provisions exhibit a high degree of specialization, cross-disciplinary complexity, and hierarchical structure. Moreover, the regulations are frequently updated, posing unique challenges for automated question-answering systems. While large language models (LLMs) have demonstrated remarkable capabilities in dialog and reasoning; however, they still face challenges such as difficulties in knowledge updating and a scarcity of high-quality domain-specific datasets when tackling knowledge-intensive tasks in the field of civil aviation regulations. This study introduces a retrieval-augmented generation (RAG) approach that integrates retrieval modules with generative models to enable more efficient knowledge acquisition and updating, encompassing data processing and retrieval-based reasoning. The data processing stage comprises document conversion, information extraction, and document parsing modules. Additionally, a high-quality airworthiness regulation QA dataset was specifically constructed, covering multiple-choice, true/false, and fill-in-the-blank questions, with a total of 4688 entries. The retrieval-based reasoning stage employs vector search and re-ranking strategies, combined with prompt optimization, to enhance the model’s reasoning capabilities in specific airworthiness certification regulation comprehension tasks. A series of experiments demonstrate the effectiveness of the retrieval-augmented generation approach in this domain, significantly improving answer accuracy and retrieval hit rates. Full article

In this paper, we propose and prove an innovative radar antenna concept suitable for collision avoidance (CA) systems installed onboard small, unmanned aircraft (UA). The proposed architecture provides 360° monopulse coverage around the host platform, enabling the detection and accurate position estimation of airborne, non-cooperative intruders using lightweight, low-profile antennas. These antennas can be manufactured using low-cost 3D printing techniques and are easily integrated into the UA airframe without compromising airworthiness. We present a Detect and Avoid (DAA) concept of operations (ConOps) aligned with the SESAR U-space ConOps, Edition 4. In this ConOps, the Remain Well Clear (RWC) and CA functions are treated separately: RWC is the responsibility of ground-based U-space services, while CA is implemented as an airborne safety net using onboard equipment. Based on this framework, we derive operation-centric design requirements and propose an antenna architecture based on a fixed circular array of sector waveguides. This solution overcomes key limitations of existing radar antennas for UAS CA systems by providing a wider field of view, higher power handling, and reduced mechanical complexity and cost. We prove the proposed concept through a combination of simulations and measurements conducted in an anechoic chamber using a 24 GHz prototype. Full article

Electric aviation is the future development direction of aviation industry technology. Electric vertical take-off and landing aircraft(eVTOL) is an important carrier of electric aviation, whose technology research and development, processing and manufacturing, airworthiness certification and industrialization boom have been set off around the world. The electric propulsion technology has achieved rapid development as the key technology of eVTOL. Aiming at the demand for high torque density and high reliability of electric propulsion system, the paper analyzed the technical indexes of electric motor products of domestic and foreign benchmark enterprises. The key technologies such as motor integration, new electromagnetic topology, lightweight structure design, and high efficiency cooling is studied. It is pointed out that in order to pursue the high torque density and fault-tolerance performance, the integrated precise modeling of motor and controller, advanced materials and manufacturing technology are the development trend of the electric propulsion technology. The breakthrough of eVTOL electric propulsion technology can accelerate the commercial operation of civil eVTOL and promote the development of new quality productive forces. Full article

The development of advanced air mobility—an eco-friendly, next-generation transportation system—is underway and garners significant attention. Due to the novel propulsion concept of eVTOL (electric Vertical Take-Off and Landing) and its operation in low altitude, urban environment, regulations for commercialization have not yet been established. Consequently, related research on passenger safety in emergency landings is ongoing, and this study focuses on enhancing the crashworthiness of advanced air mobility. To ensure the crashworthiness of advanced air mobility, civil airworthiness standards were referenced to determine the appropriate test conditions, and a design criterion for developing an energy-absorbing structure was derived. In this study, lattice structures are considered for designing an energy-absorbing structure that satisfies the design criterion, and finite element analysis is conducted to predict the performance of lattice structures. Based on the predicted data, surrogate models are constructed using the Kriging method according to the type of lattice structure. To verify the data obtained from numerical models, representative structures are manufactured using EBM (Electron Beam Melting) technology, and compressive tests are conducted to obtain the force–displacement curves. The test data are compared with the numerical data, and it is confirmed that the test data show good agreement with the numerical data. After this confirmation, the constructed surrogate models are utilized to select a lattice-based energy-absorbing structure that satisfies the crashworthiness-related design criterion. Finally, a crash simulation of a vertical drop test is carried out using the selected lattice structure, and results indicate that the resulting acceleration due to the collision is below the human tolerance limit, thereby verifying the crashworthiness of the energy-absorbing structure. Full article

The growing use of quadrotor unmanned aerial vehicles (UAVs), especially in low-altitude airspace, has raised concerns about their susceptibility to high-intensity radiated fields (HIRFs). These electromagnetic interferences can significantly affect UAV performance and safety. Therefore, understanding the electromagnetic behavior of quadrotor UAVs in HIRF environments and establishing robust airworthiness standards is crucial. In this paper, a novel transfer function model specifically designed for small quadrotor UAVs in HIRF environments is studied, covering the frequency range from 100 MHz to 6 GHz. The model characterizes the relationship between internal electric field strength and frequency in response to external excitation conditions. A comprehensive simulation of the interference with UAVs in the HIRF environment is conducted, followed by test validation in an anechoic chamber. To assess the consistency between simulation and test results, the feature selection validation (FSV) method is employed. This paper also compares the UAV transfer function with that of a conventional aircraft, revealing the unique electromagnetic characteristics of quadrotor UAVs and offering insights into their vulnerability in HIRF environments. The findings provide valuable contributions to the development of UAV airworthiness certification standards and their safe operation in complex electromagnetic environments. Full article

Controlling the simulated smoke flow field is important in the airworthiness verification experiment for the smoke detection system in aircraft cargo compartments to accurately replicate actual fire smoke. In existing studies, the unsteady adjustment performance of the actuator to the simulated smoke flow field has not been comprehensively evaluated, and the model-based closed-loop flow control method encounters the unmodeled dynamics of the complex turbulent flow field. To solve the aforementioned problems, this study first uses the system identification method to obtain transfer function models for different actuation modes. Moreover, the transient adjustment capabilities of different actuation modes for the simulated smoke flow field are thoroughly evaluated. Then, an adaptive flow control law based on a radial basis function neural network is designed based on the selected actuating mode. Furthermore, closed-loop control experiments based on the adaptive control law are performed. The root locus of the transfer functions for two different actuation modes are compared, which reveals that adjusting the flow rate of simulated smoke exhibits a better stability margin than the actuation mode that regulates the upward momentum of simulated smoke. The experimental results in a full-scale mock-up of an aircraft cargo compartment demonstrate that the designed control law realizes dynamic tracking control with the unsteady concentration of actual fire smoke as the control target. Compared with that of PID control, the root mean square error of the control system is reduced by more than 40%. The simulated smoke under the closed-loop control obtains a light-transmission response equivalent to that of the actual fire smoke within a 5% error margin. The proposed closed-loop adaptive flow control method for simulated smoke approximates the unsteady process of actual fire smoke. It provides technical support for the replacement of actual fire smoke in the airworthiness verification experiment of smoke detection in aircraft cargo compartments. Full article

The safety of Jettisoned FDRS in the process of separation from an aircraft is a key factor in designing Jettisoned FDRs and enabling them to pass airworthiness certification and be widely used in civil aircraft. The separation process of Jettisoned FDR installed on NASA Common Research Model is studied by the simulation method based on anisotropic unstructured hybrid grid and overset grid technology coupled with the rigid body 6-DOF equation. First, the numerical simulation accuracy of software under same simulation method is verified by WPFS standard model. Then, according to the three main aerodynamic parameters, including incoming Mach number, angle of attack α and sideslip angle β, 10 conditions including standard condition are designed and the separation process of recorder is simulated numerically. The simulation obtained the movement of Jettisoned FDRs in 6 degrees of freedom relative to the body coordinate system in different operating conditions during the separation process and confirmed that Jettisoned FDRs can be safely separated under these operating conditions. Finally, combined with the standard operating condition, the impact of three parameters’ changes on recorder’s 6 degrees of freedom motion and the time required to complete separation are analyzed, and conditions to ensure the safe separation of Jettisoned FDRs are summarized according to the requirements of airworthiness terms. Full article

Besides the fact that civil and military aerospace are governed by the same physics and design fundamentals, differences exist between the initial and continued airworthiness criteria for these two aviation fields. Whereas civil aerospace is highly regulated by national and international organizations, the military is mainly governed by national regulations or, in multinational projects, by agreed-upon regulations. A trend exists towards the homogenization of rules in both fields; however, due to national security interests, these are generally agreed upon on a case-by-case basis. This review aims to provide an overview of the processes employed for initial and continued airworthiness of civil and military aviation, focusing on the similitudes and differences. Full article

This paper introduces the development history and process of low altitude economy, explains the characteristics and advantages of low altitude economy, and further discusses the development direction and trend of commercial low-altitude aircraft. By analyzing the current popular commercial aircraft avionics system design features and considering the current low-altitude economic application scenarios, the characteristics of commercial low-altitude aircraft avionics systems design are described. Then, through the analysis of the design of low-altitude aircraft avionics systems, this paper puts forward the additional airworthiness requirements of commercial aircraft avionics system designs in low-altitude operation environments and explains the problems that should be paid attention to in the low-altitude operation application scenario. Through the research application of the airworthiness requirements of commercial aircraft avionics system design in the low-altitude economy, this paper provides guidance for the future development of low-altitude aircraft avionics systems. Full article

Fan blade icing can affect efficiency and aerodynamic stability, and the shed ice may be sucked into the core of the engine, causing adverse effects or even damage to the compressor components. Ice accretion and shedding are among the key issues in engine design and tests. But they have not been clearly understood. In this work, ice shedding from rotating aero-engine fan blades during continuous icing is experimentally investigated under the relevant airworthiness requirements. The phenomena of icing and ice shedding under different ambient temperatures and engine speeds are recorded to obtain the ice-shedding time and the characteristic length of the residual ice. Force analysis is used to understand the corresponding behavior. The degree of ice-shedding balance $D_b$ is defined to explore the symmetry of ice shedding. The results show that the shedding time is significantly affected by the rotational speed, and the characteristic length will first shorten and then grow as the ambient temperature decreases. When the ice shedding is completed instantaneously, $D_b$ will show a violent shock. There is a critical ambient temperature, below which the ice accretion will worsen significantly as temperature decreases. For aero-engine fan blade icing tests during ground idle, the critical ambient temperature ranges from −${5 }^{\circ }$C to −${9 }^{\circ }$C. In order for the ice to shed faster, the engine speed has to reach a threshold. This study can shed light on the preliminary characteristics of ice shedding from rotating components and provide guidance and a data basis for the numerical simulation of fan blade icing and the design of an aero-engine. Full article