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ABSTRACT The desire to use additively manufactured (AM) parts to ensure the availability of military aircraft, and to build limited‐life unmanned aerial vehicles (drones), coupled with the United States Air Force (USAF) approach to the airworthiness certification of AM parts has focused attention on durability analysis/assessment, and hence on the growth of small cracks in AM parts. Previous studies have shown that laser powder fusion built (LPBF) Scalmalloy® has: i) A yield stress and an ultimate strength that are greater than that of AA2024‐T3 and comparable to that of AA7075‐T6; ii) A resistance to crack growth that is better than that of AA7075‐T6 and comparable to that of AA2024‐T3. However, since the ability to predict the durability of a part is essential for its airworthiness certification, the present paper illustrates how to perform a linear elastic fracture mechanics (LEFM)‐based durability assessment of Boeing Space, Intelligence and Weapon System (BSIWS) LPBF Scalmalloy®. The durability study includes specimens with both machined surfaces and surfaces left in the as‐built condition. As a result, it would appear that BISWS AM LPBF Scalmalloy® is an ideal candidate for building limited‐life AM replacement parts for fixed and rotary wing aircraft and drones. [ABSTRACT FROM AUTHOR]

This paper aims to investigate phenomena that are related to SLD conditions in aircraft icing including gravity, non-spherical droplets, droplet breakup and droplet splash using an in-house computational tool. The in-house computational tool involves four modules for the computation of the flow field, droplet trajectories, convective heat transfer coefficients and ice growth rates. Droplet trajectories are computed using the Lagrangian approach, while ice growth rates are calculated using the Extended Messinger Model. In order to extend the capabilities of the computational tool to include SLD-related phenomena, empirical models that represent SLD physics are implemented. An extensive study has been performed using MS317 and NACA0012 airfoils, that aims to bring out the relative importance of the SLD-related phenomena, particularly on water catch rates and ice formation. The results of the study pointed to some important new conclusions that may shed further light on SLD physics. For example, multiple droplet breakup has been observed under certain conditions and droplet breakup emerged as a more important effect than previously reported. It was also seen that droplet splash influences both the energy balance and the mass balance in the icing process, which has been shown to have an important effect on the final ice shape, especially for very large droplets. [ABSTRACT FROM AUTHOR]

Despite children being vulnerable aircraft passengers, children's safety on aircraft does not attract enough public attention as it does in the automotive industry. Current regulations about Child Restraint Systems (CRSs) used on aircraft differ in various countries. This study introduces the potential injuries, injury mechanisms, and injury criteria for children on an aircraft. The protective effects of different CRSs are summarised. Among the four types of CRSs, automotive child seats are the most practical CRSs used on an aeroplane today. The airworthiness regulations and operation regulations of CRSs are also presented. The lack of injury criteria for the neck and abdomen in current regulations should be addressed. Finally, the social effects of mandatory regulations of using CRSs on an aircraft are discussed, and advice on the future improvement of children's safety in aircraft is provided. [ABSTRACT FROM AUTHOR]

The regulatory framework of Remotely Piloted Aircraft Systems (RPASs) has recently experienced an extraordinary evolution. This article seeks to improve the integration of certification considerations in RPAS conceptual design approaches so as to enhance the safety, certifiability and competitiveness of their resulting designs. The first part of the research conducts a two-stage analysis of contemporary regulations related to an RPAS's initial airworthiness. In the first stage, the broad international regulation paradigm is evaluated attending to a set of criteria that are tightly related to both airworthiness and design considerations. The second stage keeps the most promising documents from a design–integration standpoint, which are assessed according to their applicability considering both design and operational aspects. The results of this analysis provide insights regarding the main issues in airworthiness design criteria extraction and integration in design methodologies. To aid the designer in surmounting these challenges, a flexible procedure named DECEX is developed. Considering the documents and findings from the survey, and attending to the scope of the design methodology being developed, it aids in establishing a complete regulatory document corpus and in comparing and extracting the applicable airworthiness design criteria. Two case studies for different RPAS types are conducted to demonstrate its application. [ABSTRACT FROM AUTHOR]

Determining the criticality of ice shapes is a necessary condition for verifying compliance with icing airworthiness regulations. However, the clear, concise, and applicable criterion based on the geometric characteristics of ice shapes has not been clearly given out by current advisory circulars. To address this problem, this paper summarizes aerodynamic performance items and recommended ice shapes the latest version of CCAR-25 and corresponding advisory circulars for a variety of flight phases, including takeoff, holding, en route, DTO, etc., instead of the single phase of holding in the previous research. Based on the geometric classification of the ice shapes, the dominant parameters of various ice shapes are clarified by the correlation between the geometric parameters and aerodynamic effects. The geometric parameters to determine the criticality of specific ice shapes are defined as the roughness height and range for the roughness ice and the total projection height in the direction of lift for the horn ice. On this basis, the detailed determination criterion of critical ice shape geometries corresponding to different flight phases and aircraft components is formulated, which will provide an operational selection methodology for determining the geometries of critical ice shapes at the airworthiness certification stage. [ABSTRACT FROM AUTHOR]

The consequences of new airspace entrants, such as novel aircraft concepts with innovative propulsion systems, on air traffic management operations need to be carefully identified. This paper aims to assess the impact of future aircraft with different performance envelopes on the European air traffic network from a flow-based perspective. The underlying approach assumes that all certification-related questions concerning airworthiness have been resolved and do not take into account any economic factors related to airline operations. For example, for an innovative propulsion system, a short range all-electric aircraft is considered in this study. Aircraft trajectory calculations are based on the dataset of base of aircraft data (BADA), which are developed and maintained by EUROCONTROL. The new design concept is integrated into BADA as well, resulting in a new set of coefficients for the all-electric aircraft. In addition to the adjusted parameters which affect airborne performances, ground-related aspects are also taken into account. This includes assumptions on operational procedures, charging capacities and adaptions in infrastructure. Investigations are carried out at the trajectory level as well as at the airport and the entire network. [ABSTRACT FROM AUTHOR]

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Hail absorption test of aeroengine is one of the important components of airworthiness certification. The accurate test data are closely related to the density and mechanical properties of the artificial hail used in airworthiness tests. Through experimental research, this study explores the impact of distilled water, carbonated water and deionized water on the density and mechanical properties of artificial hail. The study addresses the significant differences between the density and mechanical properties of artificial hail and natural hail in existing studies. Based on this, a new method for preparing airworthiness test hail is proposed. The results indicate that artificial hail samples with distilled water as the hail core and carbonated water as the hail shell have densities ranging from 0.87 cm3 to 0.89 cm3. Furthermore, the estimated average maximum compressive strength of samples is 6.538 MPa, with some samples as low as 3.681 MPa. The mechanical properties of this artificial hail are more similar to those of natural hail. This method can more realistically simulate natural hail environments and can be used for the fine design of airworthiness certification criteria. [ABSTRACT FROM AUTHOR]

Purpose: To ensure the safety of aircraft fuel tanks, the FAA issued an airworthiness clause (25.981(b)) suggesting that the risk of combustion and explosion be reduced by installing a Flammability Reduction Means or an Ignition Mitigation Means. The airflow distribution method has a significant effect on the inerting performance. Therefore, this study aims to determine an optimum airflow distribution method of the inerting system. Design/methodology/approach: This paper establishes the calculation model of the oxygen concentration in the ullage of a multi-bay fuel tank, calculates the oxygen concentration in the ullage of an aircraft tank in single-flow and dual-flow modes under series and parallel ventilation methods and analyses the inerting performance of the tank under different airflow distribution methods. Findings: The results show that: (1) the bleed flow rate required to achieve whole process inerting of multi-bay fuel tank in dual-flow mode is lower than that in single-flow mode; (2) under the parallel ventilation method, the decrease of oxygen concentration and the uniformity of each bay are better than that in the series ventilation method; (3) dual-flow mode staged ventilation method can be used to achieve the whole process inerting of the tanks under the minimum engine bleed consumption. Originality/value: The novelty of this paper is to analyze and optimize the airflow distribution method of the inerting system under the whole flight envelope to minimize the engine bleed consumption. [ABSTRACT FROM AUTHOR]

Double–double (DD) laminates approach enables the design of mass‐minimized composite structures with number and orientation of plies tailored on the acting loads. Thus, the investigation of the crashworthiness capabilities is crucial in assessing the airworthiness of DD designed structures. In this work, two composite fuselage barrel configurations with conventional and DD designed frames have been compared to study their crashworthiness performance during an impact event. Numerical results highlight that configurations with DD optimized frames exhibit performance in terms of crashworthiness and passive safety for passengers comparable to the one with conventional designed frames while reducing the structure's total mass by up to 13%. [ABSTRACT FROM AUTHOR]

Featured Application: The paper demonstrates key structural characteristics of a novel aluminum alloy conceived for AM-based components in the aviation frame. The recent advances achieved in additive manufacturing (AM) technology demonstrate the potential to realize customized metal components, ensuring weight reduction opportunities. These benefits make AM attractive for high-cost aerospace applications, especially where high geometric complexity is required. In the context of an EU research scenario, the H2020 MANUELA (Additive Manufacturing Using Metal Pilot Line) project promotes the development of new technologies for design optimization by enabling the application of novel materials in AM. This paper illustrates recent advances in a new aluminum alloy (Al-HS1) with high strength emphasizing all of the characterization steps at the coupon level. This material has been employed in the re-engineering of a conventional hydraulic manifold using a powder bed fusion-laser beam (PBF-LB) process. Both the simulations and structural tests allowed for proving its compliance and technological maturity with industrial standards and applicable airworthiness requirements. [ABSTRACT FROM AUTHOR]

With the significant expansion of civil aviation, particularly in the low-altitude economy, there is a significant gap between the escalating demand for airworthiness certification of novel aircraft designs, such as electric vertical take-off and landing (eVTOL) vehicles, and the inefficiency of the current safety assessment process. This gap is partially attributed to safety assessors' limited exposure to these innovative aircraft models in the safety assessment process, necessitating extensive efforts in identifying precedents and their handling strategies. Complicating matters further, pertinent case studies are scattered across diverse, unstandardized digital formats, obliging assessors to navigate voluminous electronic records while concurrently establishing links among fragmented information scattered across multiple files. This study introduces an advanced information integration methodology, comprising a multi-level path-based architecture and a self-updating algorithm. The proposed method not only furnishes safety assessors with pertinent knowledge featuring explicative interconnectedness automatically, but also dynamically enriches this knowledge corpus through operational usage. Additionally, we devise a suite of evaluative criteria to validate the capacity of our method in processing and consolidating relevant safety datasets. Experimental analyses affirm the efficacy of our proposed approach in streamlining and refreshing safety assessment data. The automation of the retrieval of analogous cases, which relieves the reliance on expert knowledge, enhances the efficiency of the overall safety appraisal procedure. Consequently, this research contributes a solution to enhancing the velocity and accuracy of aircraft certification processes. [ABSTRACT FROM AUTHOR]

In the stage of aircraft development and airworthiness verification, it is necessary to master the influence of lithium-ion battery (LIB) thermal runaway (TR) propagation. In this paper, the battery TR propagation behavior under different trigger positions and modes is studied experimentally, and the calculation and comparison are carried out from the parameters of real-time temperature, voltage, propagation speed, total energy released, and solid ejecta. When the two adjacent cells at the top corner, side, and center of the module are overheated, TR occurs at about 1000 s for the triggered cells, while the whole-overheating trigger mode takes a longer time. The latter's transmission speed is extremely fast, spreading 2.67 cells per second on average. The heat generated by the solid ejecta of the whole-overheating trigger mode is 82,437 J, which is more destructive. The voltage of the triggered cell fluctuates abnormally in a precursor manner when the internal active substances in the cell undergo a self-generated thermal reaction. This work can provide a reference for the safety and economical design of system installations and the correct setting of airworthiness verification Method of Compliance (MoC) experiments to verify whether the aircraft can bear and contain the adverse effects caused by LIB TR. [ABSTRACT FROM AUTHOR]

In order to scientifically sort out the differences in airworthiness management of military and civilian aircraft and improve the airworthiness safety of military and civilian aircraft, the input-process-output ( IPO) model in system engineering theory was innovatively applied, and airworthiness management was regarded as a management process in system engineering. A airworthiness management process IPO model based on system engineering theory was established. A differential analysis of military and civilian aircraft airworthiness management was conducted using the five elements of input, output, enable, control, and activity in the airworthiness management process IPO model. The similarity between military and civilian aircraft airworthiness management lies in the fact that both are comprehensive and full process control management aimed at ensuring the safety of aircraft engines. The differences lie in the level of management and enforcement in terms of security objectives, management institutions, standards/ regulatory systems, tailorability of standards/ regulations, deployment and division of labor, and regulatory methods. The specific differences between military aircraft airworthiness management and civil aircraft airworthiness management were analyzed, which provides reference opinions for the subsequent development of military and civil aircraft airworthiness management. [ABSTRACT FROM AUTHOR]

Purpose: The lightweight design of aircraft seats can significantly improve fuel efficiency and reduce greenhouse gas emissions. Metal additive manufacturing (MAM) can produce lightweight topology-optimized designs with improved performance, but limited build volume restricts the printing of large components. The purpose of this paper is to design a lightweight aircraft seat leg structure using topology optimization (TO) and MAM with build volume restrictions, while satisfying structural airworthiness certification requirements. Design/methodology/approach: TO was used to determine a lightweight conceptual design for the seat leg structure. The conceptual design was decomposed to meet the machine build volume, a detailed CAD assembly was designed and print orientation was selected for each component. Static and dynamic verification was performed, the design was updated to meet the structural requirements and a prototype was manufactured. Findings: The final topology-optimized seat leg structure was decomposed into three parts, yielding a 57% reduction in the number of parts compared to a reference design. In addition, the design achieved an 8.5% mass reduction while satisfying structural requirements for airworthiness certification. Originality/value: To the best of the authors' knowledge, this study is the first paper to design an aircraft seat leg structure manufactured with MAM using a rigorous TO approach. The resultant design reduces mass and part count compared to a reference design and is verified with respect to real-world aircraft certification requirements. [ABSTRACT FROM AUTHOR]

The European Union Aviation Safety Agency (EASA) continues to promulgate Safety Management Systems (SMS) across aviation organizations when it recently issued SMS requirements for EASA certificated Part 145 maintenance, repair and overhaul (MRO) organizations and Part 21 Design & Manufacturing (D&M) organizations. Currently, the FAA has no such rule in place for these U.S. based organizations, which may challenge those doing business in countries where EASA policies apply. Given that most of the United States' D&M and MRO population is made up of smaller organizations, it is likely a U.S. SMS regulation will require justification of the associated costs and benefits. This study explored the potential benefits SMS may provide these organizations by exploring the overall scope and nature of safety controls implemented through Airworthiness Directives (AD), which may help safety practitioners better understand how SMS in D&M organizations may reduce the number of AD related corrective actions. Researchers analyzed a sample of 189 ADs issued over a ten-year period and found that approximately 55% of the sampled ADs were the result of a new risk control, and approximately 45% were the result of a revised risk control. In these cases, the risk controls were not sufficient, and the AD action was necessary to ensure an acceptable level of safety. More effective risk controls have the potential to significantly reduce the number of ADs the industry must address. Every AD involves unplanned costs, often at multiple levels, and other variables that must be managed and implemented as part of the aircraft maintenance and manufacturing process. SMS may further improve the industry's safety performance by reducing the number of corrective actions and their associated costs. [ABSTRACT FROM AUTHOR]

The paper presents the importance of electricity parameters in transient states for assessing the ability of an aircraft's power grid to self-regulate. It has been shown that the quality of electrical energy of an aircraft's power system is influenced by its operating time. Aging changes resulting from long-term operation of the power system cause deterioration of electrical energy parameters, which directly affects airworthiness and flying safety. Maintaining standard energy parameters in transient states is very important to ensure proper operation of the aircraft. The article describes the method of measuring the quality of electricity in transient states, and using the example of the DC power system of the Su 22 aircraft, the essence of its network diagnostics in transient states is presented. Also presented are sample results of research conducted by the authors regarding changes in electrical energy parameters in transient states of the Su 22 aircraft, obtained during its many years of operation. [ABSTRACT FROM AUTHOR]

This qualitative case study explores the reasons behind disconnects between United States Army (Army) aviation safety and cybersecurity groups' processes. The disconnects were defined as dissimilarities between Army aviation systems and inadvertent overlap of system implementation requirements. The disconnects cause an absence of explicit means to verify systems' reresiliency to cybersecurity attacks that increase the risk to flight safety and mission readiness. Literature review revealed the absence of explicit guidance and the increase of cybersecurity issues affecting interconnected aviation systems. This study sought to discover the reasons behind the disconnects and explore how the disconnects could be improved to increase resiliency to cybersecurity attacks and decrease the risk to flight safety and mission readiness. The researcher used the organizational discontinuity theory (ODT) as the framework for determining the reason behind the lack of explicit guidance. Additionally, the researcher conducted interviews with knowledgeable safety and cybersecurity professionals and conducted data source triangulation using the safety and cybersecurity groups' respective process documentation to justify key research findings and accomplish data analysis activities. Data analysis identified three themes: awareness, process critique, and logical and complementary improvement. This study concluded that one primary reason behind the disconnects between safety and cybersecurity groups' processes is that both processes are isolated in terms of execution across the systems' lifecycles. The isolation causes conflicting process requirements and inadvertent overlap where requirements could be improved if cross-functional group coordination occurred. This study also confirmed the necessity for leadership guidance to implement cross-functional group coordination and comprehensive processes to address the disconnects. [ABSTRACT FROM AUTHOR]

The stability of aircraft during taxiing is an important issue in the development of landing gear and airworthiness certification. Incidents and abnormal problems consistently arise due to landing gear shimmy. The integration of a model involving tricycle landing gear and aircraft structure is a major advancement in addressing shimmy oscillations. A formulated nonlinear mathematical modeling approach integrates airframe motions with landing gear modes, which provides deep insights into their coupling effect. It effectively determines the critical speed region and types of shimmy oscillations that can occur. An increase in landing gear shimmy intensifies lateral forces on landing gear components, which affects the yaw motion of the aircraft. The optimization of aircraft mass, the critical value of torsional damping, and their influence on directional stability are investigated. This work is useful in the conceptual design of landing gears and in avoiding the potential risks associated with shimmy oscillations to extend the lifespan of landing gears. [ABSTRACT FROM AUTHOR]

When tire burst debris impacts a wing fuel tank, the momentum and kinetic energy are transferred to the fluid and the surrounding structure, which increases the risk to the aircraft. In this paper, two types of hydrodynamic effects, defined as the pressure wave mode and the fluid displacement mode, were investigated in the process of tire burst debris impacting a wing tank, and an accurate numerical model was established. A fluid–solid interaction (FSI) model with the coupled Eulerian–Lagrangian (CEL) method is proposed to reproduce the hydrodynamic effects; the model fully considers the interaction between the tank and the fuel, and the accuracy of the numerical model was verified by experiments that met the airworthiness conditions. Analysis of the pressure wave propagation, fuel pressure, fuel displacement, and cavity evolution showed that the pressure wave first affects the structure, then the fluid gradually evolves a cavity near the impact point, and finally the fluid displacement significantly increases the impact on the structure. The numerical analysis method for simulating the hydrodynamic effects of tire burst debris impacting a wing tank is presented and was evaluated. It can provide a reference for airworthiness certification and structural design of aircraft. [ABSTRACT FROM AUTHOR]

The main task of operators is to maintain the airworthiness of aircraft by implementing the technologies outlined in the sets of documents attached to standard products. Engines, the main source of energy for flight, usually work in conjunction with many systems, each of which, in turn, is accompanied by instructions and manuals to ensure operability. In accordance with accepted practice, most of the disaggregated information is provided in text form. These forces you to remember the necessary data or constantly search for it in dozens of updated and replaced pages of the provided technologies, or create your own convenient techniques that allow you to conduct parametric analyzes and develop decisions on control actions to correct the technical condition. Using examples of power plants with turboprop engines, approaches to the development and application of step-bystep unified graphical generalizations of processes and control parameter values, combined with indications of characteristics setting elements, are proposed. For the full cycle of work, the article proposes the most convenient, applicable to different types of power plants, unified method for constructing compact representations of all information in a generalized form. Recommendations have been developed for monitoring, adjusting characteristics and making decisions on the prospects for further operation. The methods have been tested under operating conditions, having confirmed their convenience and effectiveness at different stages of operation, and can be recommended for inclusion in Flight Operations Manuals created by airlines in relation to the range of operating conditions of their aircraft fleet. [ABSTRACT FROM AUTHOR]

To achieve the commercialization of electric vertical takeoff and landing (eVTOL) aircrafts, which have recently garnered attention as the next-generation means of transportation, objective certification based on rigorous procedures is essential. With the advancement of structural analysis technology, aircraft airworthiness standards recommend a combination of testing and analytical methods to demonstrate structural integrity. In this study, we propose analytical techniques for demonstrating the structural integrity of components for eVTOL aircrafts in accordance with airworthiness standards. We evaluated the static structural integrity and fatigue safety of an electro-mechanical actuator. Multibody dynamics analysis was performed to calculate the loads for application in finite element analysis. Subsequently, static analysis and fatigue analysis based on finite element analysis were conducted to calculate the safety margin and fatigue life of all key components. Therefore, we have confirmed the feasibility of utilizing analytical methods for the structural integrity assessment of aircraft components. We propose the utilization of the technique introduced in this study as one of the approaches for demonstrating compliance with airworthiness standards for eVTOL aircrafts through the application of analytical methods. [ABSTRACT FROM AUTHOR]

Airworthiness certification requires proof of structure strength, which is performed generally through a building block approach. To achieve this, representative intermediate-scale experiments generated by test benches are, in general, needed, in addition to material characterization on a coupons scale and structure testing on a large scale. The VERTEX test bench can generate the combined loading of tension/compression-shear-pressure on structural elements and was modelled with Finite Elements to perform virtual testing, representative of its intermediate-scale specificity. The numerous bolted joints of the bench were modelled and their behavior was identified in previous tests, so the model could quantitatively estimate the transfer function of the bench, which is the relationship between the displacements imposed by the jacks and the resulting loads on a given sample. The VERTEX model was identified to represent load shapes and amplitudes based on a training set and was later confronted by a validation set of tests of tension and shear. A model with ideal boundary conditions was also developed for a comparison, but it failed to predict some load shape specificities and did not give any indication of the loading amplitude. Application cases of the developed model are shown to assess a range of virtual testing possibilities. [ABSTRACT FROM AUTHOR]

The advancement of electric vertical take-off and landing (eVTOL) aircraft has expanded the horizon of urban air mobility. However, the challenge of generating precise vertical take-off and landing (VTOL) trajectories that comply with airworthiness requirements remains. This paper presents an approach for optimizing VTOL trajectories considering six degrees of freedom (6DOF) dynamics and operational constraints. Multi-phase optimal control problems are formulated to address specific constraints in various flight stages. The incremental nonlinear dynamic inversion (INDI) controller is employed to execute the flight mission in each phase. Controlled flight simulations yield dynamically feasible trajectories that serve as initial guesses for generating sub-optimal trajectories within individual phases. A feasible and sub-optimal initial guess for the holistic multi-phase problem is established by concatenating these single-phase trajectories. Focusing on a tilt-wing eVTOL aircraft, this paper computes VTOL trajectories leveraging the proposed initial guess generation procedure. These trajectories account for complex flight dynamics, align with various operation constraints, and minimize electric energy consumption. [ABSTRACT FROM AUTHOR]

Sustainable aviation fuels (SAFs) are considered an important solution for reducing carbon emissions. Safety is the most important prerequisite for a new fuel to be used in an aero-engine. As a special component in aero-engines, fuel is required to comply with both airworthiness and technical standards. These two types of standard work together to guide SAF development. In this paper, the SAF safety issues related to aero-engines are first analyzed. Subsequently, SAF-related standard systems are analyzed in detail, and the different safety responsibilities of airworthiness authorities and industry associations are explained. Moreover, the relationships between airworthiness and technical standards are determined from the perspective of actual SAF certification. Furthermore, the revision of the standards is reviewed to summarize the historical evolution and outline the revision intention. Finally, the future SAF certification standards are discussed and prospected, including the blending ratio, property specifications, and testing equipment. According to the discussion, increased safety and fewer constraints are the principal objectives for the development of SAF standards. Analysis, review, and discussion of the SAF standards systems from an aero-engine safety perspective will contribute to the establishment of the next generation of standards to release the fuel potential and improve safety. [ABSTRACT FROM AUTHOR]

Bird striking engines are most likely to cause aircraft damage and accidents in bird strike accidents. In order to study the bird strike airworthiness performance of the first stage compressor rotor of the engine, bird strike tests are conducted on the engine rotor under working conditions. The bird strike test, in which the bird weight, velocity and rotate speed of engine blades are 1 000 g, 195 m/s, 8 525 r/min respectively, is made in a vacuum space. Based on the explicit collision dynamics analysis software PAM-CRASH, a corresponding blade bird strike numerical calculation model is established, and the rationality of the calculation model in this paper is verified by comparing it with experimental results. Also, the ability of engine blades against bird strike in different situations is researched. The results indicate that big bird strike leads to a worse situation compared with medium bird flock and small bird lock. Large deformation appears at the tip of the blades due to the impact at the tip part, while impact at the root and middle of the blades will cause a large concentrated stress around the root of blades, and lead to the fracture of the blade.

Determining the criticality of ice shapes is a necessary condition for verifying compliance with icing airworthiness regulations. However, the clear, concise, and applicable criterion based on the geometric characteristics of ice shapes has not been clearly given out by current advisory circulars. To address this problem, this paper summarizes aerodynamic performance items and recommended ice shapes the latest version of CCAR-25 and corresponding advisory circulars for a variety of flight phases, including takeoff, holding, en route, DTO, etc., instead of the single phase of holding in the previous research. Based on the geometric classification of the ice shapes, the dominant parameters of various ice shapes are clarified by the correlation between the geometric parameters and aerodynamic effects. The geometric parameters to determine the criticality of specific ice shapes are defined as the roughness height and range for the roughness ice and the total projection height in the direction of lift for the horn ice. On this basis, the detailed determination criterion of critical ice shape geometries corresponding to different flight phases and aircraft components is formulated, which will provide an operational selection methodology for determining the geometries of critical ice shapes at the airworthiness certification stage.