Airworthiness Requirements Research Articles

Research on mission characteristics-based evaluation model of flight test workload

As a product of modern industrial cutting-edge technology, a large civil aircraft needs to undergo rigorous flight test before entering the aviation market, which fully ensures the safety of aircraft and its system. This makes the aircraft meet the airworthiness standards and requirements. The flight test of civil aircraft is a complex system project, which the top-level planning throughout the flight test period has an important influence on progress control and flight test efficiency of a new type aircraft. The core content of the top-level plan is the evaluation of flight test workload with consideration of test aircraft quantity. This paper proposes a flight test workload analysis and evaluation model based on the types of test missions through the analysis of the characteristics of civil aircraft flight test mission, which provides a feasible method for quantitative evaluation of flight test workload.

Effect of Bird Yaw/Pitch Angles on Soft Impact Damage of a Fan Assembly

This paper presents a numerical investigation of bird attitude angles affecting the soft-impact damage of a full fan assembly. Firstly, considering the geometry of a mallard, a real bird model is established by the Smoothed Particle Hydrodynamics (SPH) method and calibrated with available test data. Then, complying with airworthiness requirements, simulations of a full-bladed fan assembly subjected to a real bird were conducted to determine the critical ingestion parameters (CIP). Furthermore, a real bird with different attitude angles aimed at a full fan assembly was simulated. Results show that attitude angles of the bird produce a significant impact on the effect of the bird strike on rotating blades and would increase the possibility of blade failures, especially for the yaw angle of -45° and the pitch angle of −60°. It is invaluable for commercial airlines and engine manufactures to provide safe flight and landing by adopting the real bird model with critical yaw and pitch angles in the design for resistance to bird ingestion.

On the Preliminary Structural Design Strategy of the Wing of the Next-Generation Civil Tiltrotor Technology Demonstrator

The T-WING project is a Clean Sky 2 research project aimed at designing, manufacturing, qualifying and flight-testing the new wing of the Next-Generation Civil Tiltrotor Technology Demonstrator (NGCTR-TD), as part of the Fast Rotorcraft Innovative Aircraft Demonstrator Platforms (FRC IADP) activities. Requirements, design strategy, methodology and main steps followed to achieve the composite wing preliminary design are presented. The main driving requirements have been expressed in terms of dynamic requirements (e.g., limitations on natural frequencies), aeroelastic requirements, i.e., compliance with European Aviation Safety Agency (EASA) CS-25 and CS-29 Airworthiness Requirements), structural requirements (e.g., target wing structural mass), functional requirements (e.g., fuel tanks, accessibility, assembly and integration, etc.) and wing preliminary loads. Based on the above-mentioned requirements, the first design loop is performed by targeting an optimal wing structure able to withstand preliminary design loads, and simultaneously with stiffness and inertia distributions leading to a configuration free from flutter within the flight envelope. The outcome from the first design loop is then used to refine the model and compute more reliable flight loads and repeat aeroelastic analysis, returning further requirements to be fulfilled in terms of wing stiffness and inertia distributions. The process is iterated till the fulfillment of all the project requirements.

Flightcrew Light Alerting Design with Dark Cockpit Philosophy

An effective and reasonable flightcrew light alerting design in civil aircraft flight deck based on dark cockpit philosophy has been proposed. Considering the human factor engineering and airworthiness requirement, the paper analyses flight deck alerting system and defect of bright cockpit philosophy, then the state-of-art light alerting design using dark cockpit philosophy is given. According to operation scenarios and architectures of different aircraft systems, three type of the new design is presented. This approach consists of general light alerting part, standby system light alerting part and special light alerting part. The proposed design ensures that the flight crew not only obtain the aircraft system status intuitively, but also decrease their workload during the whole flight phase.

Design and static testing of wing structure of a composite four-seater electric aircraft

Abstract Because of its light weight, high strength, designable, composite materials are more and more widely used in the field of aerospace, especially in the field of general aviation. In this paper, the structural design and analysis of the composite wing (include wing beam, rib, skin, leading edge and trailing edge) of a four-seater electric aircraft were carried out. The finite element numerical analysis model of the composite wing was established, and the deformation and strain distribution of the composite wing under the limited load required by airworthiness regulations were calculated. Finally, the static test of the whole composite wing was carried out to verify the accuracy of the finite element results. The finite element analysis and testing results showed that the structural design of the composite wing of the electric aircraft meets the structural strength requirements specified in the airworthiness standard (part 23 of China civil aviation regulations: air-worthiness requirements for normal, practical, special effects and commuting aircraft: CCAR 23-R3)

Complex composite technology investigation: simulations and experimental results

The paper deals with discussion of research activities within ITEMB (InTEgrated Full Composite Main landing gear Bay Concept) framework, an EU Clean Sky 2 program coordinated by Airbus. The driving motivation for the investigation on such a technology was found in the opportunity to design a main landing gear bay in a full composite configuration: rational approaches have been implemented in an efficient testing stage providing the necessary database for the static qualification of the conceived design. Advanced and innovative solutions for a “more integrated” system were duly analysed and experimentally validated thus proving the overall device compliance with industrial standards and applicable airworthiness requirements.

The Effect of Post-Processing on the Mechanical Behavior of Ti6Al4V Manufactured by Electron Beam Powder Bed Fusion for General Aviation Primary Structural Applications

In this work a mechanical characterization of Ti6Al4V processed by electron beam powder bed fusion additive manufacturing was carried out to investigate the viability of this technology for the manufacturing of flyable parts for general aviation aircraft. Tests were performed on different manufacturing conditions in order to investigate the effect of post processing as machining on the mechanical behavior. The study provides useful information to airframe designers and manufacturing specialists that work with this technology. The investigation confirms the low process variability and provides data to be used in the design loop of general aviation primary structural elements. The test results show a high level of repeatability indicating that the process is well controlled and reliable enough to match the airworthiness requirements. In addition, the so-called “as-built specimens”, i.e., specimens produced by the electron beam melting machine without any major post-processing, have lower mechanical performances than specimens subjected to a machining phase after the electron beam melting process. Specific primary structural elements will be designed and flight cleared, resulting from the findings presented herein.

Gust Load Alleviation of Flexible Composite Wing

Gust load due to atmospheric turbulence is mandatory to be considered in aircraft analysis as part of airworthiness requirement. This safety related issue becomes more relevant recently in relation to the global warming that induces more frequent and extreme atmospheric disturbances encountered during air transportation. A direct application of gust load on the wing structural analysis, however, is not recommended since it will result in a significant weight increase due to the overdesign of the wing structure. At this point, the gust load alleviation plays an important role to effectively utilize the wing structural flexibility without ignoring the safety issue. In the present work, a method to alleviate the wing gust load is proposed by considering different configurations of the wing planform, wing sweep angle, wing dihedral angle and composite material layers. The objective of the study is to minimize the wing root bending moment due to the gust. The gust load analysis of the Kim-Hwang’s wing model will be used and the results are compared to the literature for the validation purpose. A finite element approach is used to simulate the wing structure in combination with the doublet lattice method to model the wing aerodynamics. It is found that the wing dihedral angle plays insignificant changes to the wing root bending moment due to the gust load. The wing sweep angle, however, gives significant changes to the wing root bending moment. For the present configuration, the optimum swept back configuration with a 45° sweep angle and optimum composite lay-up showed an average decrease of the bending moment by 12% for frequency range of 0 to 100 Hz.

Evaluation of the Mechanical Behavior of a Biocomposite Material in a Fuselage Section Numerical Drop Test

AbstractThe ever‐increasing need for eco‐compatibility in all sectors of industry is pushing scientific research to look for the so‐called environmentally friendly materials characterized by minimal environmental impact during the manufacturing process and high recyclability. In the aeronautical sector composites are well established for primary and secondary structures, but alternative biocompatible solutions are found out even if great efforts are being required to improve their properties. In this work, the mechanical behavior of a biocomposite material is tested by implementing it in an existing numerical model of a fuselage section subject to a vertical drop test. Deformations and failures of biocomposite parts are evaluated providing indications on their possible compliance with crashworthiness and airworthiness requirements.

Development of the Minimum Equipment List: Current Practice and the Need for Standardisation

As part of the airworthiness requirements, an aircraft cannot be dispatched with an inoperative equipment or system unless this is allowed by the Minimum Equipment List (MEL) under any applicable conditions. Commonly, the MEL mirrors the Master MEL (MMEL), which is developed by the manufacturer and approved by the regulator. However, the increasing complexity of aircraft systems and the diversity of operational requirements, environmental conditions, fleet configuration, etc. necessitates a tailored approach to developing the MEL. While it is the responsibility of every aircraft operator to ensure the airworthiness of their aircraft, regulators are also required to publish guidelines to help operators develop their MELs. Currently, there is no approved standard to develop a MEL, and this poses a challenge to both aviation regulators and aircraft operators. This paper reviews current MEL literature, standards and processes as well as MEL related accidents/incidents to offer an overview of the present state of the MEL development and use and reinstate the need for a systematic approach. Furthermore, this paper exposes the paucity of MEL related literature and the ambiguity in MEL regulations. In addition, it was found that inadequate training and guidance on the development and use of MEL as well as lack of prior experience in airworthiness topics can lead to mismanagement and misapplication of the MEL. Considering the challenges outlined above, this study proposes the combination of system engineering and socio-technical system approaches for the development of a MEL.

Model-Based Safety Analysis for the Fly-by-Wire System by Using Monte Carlo Simulation

Safety analysis is one of the important means to show compliance with airworthiness requirements. The traditional safety analysis methods are significantly dependent on analysts’ skills and experiences. A model-based safety analysis approach is proposed for typical fly-by-wire (FBW) systems based on the system development model built via Simulink, by which the response of system performances can be simulated. The safety requirements of the FBW system are defined by presenting the thresholds of system performance metrics, and the effects of failure conditions on aircraft safety are determined according to the system response simulation by injecting failures or failure combinations into the Simulink model. The Monte Carlo simulation method is used to calculate the probability of unsafe conditions, whose effects are determined by the system response simulation with fault injections. Finally, a case study is used to illustrate the effectiveness and advantages of our proposed approach.

Research on Civil Aircraft Emergency Evacuation Time for Ditching

Emergency evacuation for ditching is an important airworthiness requirement for civil aircraft to ensure safety. However, to demonstrate the emergency evacuation for ditching of a real aircraft is a time-consuming and laborious test with significant safety risks. Based on the analysis of airworthiness clauses, this paper proposes a method for calculating and analysing the emergency evacuation time for ditching. Taking a certain type of aircraft as an example, a typical case is selected for calculation and analysis, and the evacuation time under this typical case is obtained, which provides data support for the airworthiness emergency evacuation airworthiness compliance.

Experimental Study on the Attitude of Civil Aircraft Ditching with High Horizontal Tail Configuration

The airplane must meet the airworthiness requirements if certification with ditching provisions is requested. The probable behavior of the airplane ditching must be investigated by model tests or by comparison with airplanes of similar configuration. In this paper, aircraft with high horizontal tail configuration is considered as a research object, then the attitudes of civil aircraft in ditching is studied through a scaled model verification experiment. On this basis, this paper researches the effects of different parameters after ditching into the water, such as initial pitch angle, flap slat configuration and sinking speed. The research results in this paper can help to determine the ditching attitudes and parameters and thus develop strategies for ditching.

High-speed impact assessment for composite air inlet

PurposeThe purpose of this paper is to describe the approach for the design of a jet engine composite air inlet for a new generation of jet trainer aircraft from the perspective of airworthiness requirements regarding high-speed impact resistance.Design/methodology/approachValidated numerical simulation was applied to flat test panels. The final design was optimised and verified by validated numerical simulation and verified by testing on a full-scale demonstrator. High-speed camera measurement and non-destructive testing (NDT) results were used for the verification of the numerical models.FindingsThe test results of flat test panels confirmed the high durability of the composite structure during inclined high-speed impact with a near-real jet inlet load boundary condition.Research limitations/implicationsOwing to the sensitivity of the composite material on technology production, the results are limited by the material used and the production technology.Practical implicationsThe application of flat test panels for the verification and tuning of numerical models allows optimised final design of the air inlet and reduces the risk of structural non-compliance during verification tests.Originality/valueNumerical models were verified for simulation of the real composite structure based on high-speed camera results and NDT inspection after impact. The proposed numerical model was simplified for application in a real complex design and reduced calculation time.

Analysis of Airworthiness Requirements for Emergency Evacuation Demonstration Test of Transport Aircraft

Analysis of Airworthiness Requirements for Emergency Evacuation Demonstration Test of Transport Aircraft

Aeroelastic Assessments and Functional Hazard Analysis of a Regional Aircraft Equipped with Morphing Winglets

The application of morphing wing devices can bring several benefits in terms of aircraft performance, as the current literature shows. Within the scope of Clean Sky 2 AirGreen 2 European project, the authors provided a safety-driven design of an adaptive winglet, through the examination of potential hazards resulting from operational faults, such as actuation chain jamming or links structural fails. The main goal of this study was to verify whether the morphing winglet systems could comply with the standard civil flight safety regulations and airworthiness requirements (EASA CS25). Systems functions were firstly performed from a quality point of view at both aircraft and subsystem levels to detect potential design, crew and maintenance faults, as well as risks due to the external environment. The severity of the hazard effects was thus identified and then sorted in specific classes, representative of the maximum acceptable probability of occurrence for a single event, in association with safety design objectives. Fault trees were finally developed to assess the compliance of the system structures to the quantitative safety requirements deriving from the Fault and Hazard Analyses (FHAs). The same failure scenarios studied through FHAs have been simulated in flutter analyses performed to verify the aeroelastic effects due to the loss of the actuators or structural links at aircraft level. Obtained results were used to suggest a design solution to be implemented in the next loop of design of the morphing winglet.

Overview regarding the certification of a new military jet aircraft for school and training

The requirements for designing a new Romanian school and training military jet, IAR 99 NG, are in line with the EMAR - European Military Airworthiness Requirement. The Approval Regulation for the new school and training military jet is EMACC - European Military Airworthiness Certification Criteria. In addition to the basic regulation, the main categories of norms used for designing, manufacturing and testing are as follows: AIR, MIL, NA, EN and SR EN etc. For each system used on the new school and training military jet, Standard Defense 00-970 and NATO STANAG regulates the requirement to perform tests on a functional model. In order to be tested, each modeled system, must accurately reproduce the original system.

Gyroplane Rotor Hubs Strength Tests

Abstract In this article a review of rotor, hub constructions were presented. Discussed rotor’s hub is made of composite or aluminum alloys materials. Two types of rotor hub were presented (four-blades and two-blades teetering rotor hub), each of them are dedicated to gyroplanes. Typical gyroplane main rotors are characterized by simple design, especially in case of rotors for light gyroplanes. In the following part of the article the type of strength tests required by certification process were shown. The test programs based on legal aspects of admission to the flight tests taking into account legislation such as CS 27 (Subpart C – Strength Requirements), CAP 643 British Civil Airworthiness requirements Section T Light gyroplanes, ASTM F2972. Furthermore, this article discusses strength tests of gyroplane rotor hub such as measured parameters, methodology of measurement, types of sensors, course of test, test stands, and limit loads. The loads during “pull-up from level flight” manoeuvre are limit loads during tests. Required additional processes, like a verification the same parameters by two types of method were shown i.e. deformation of structure were tested by strain gauges and reverse engineering. Strength tests had to be made before flight test, based on results of them aircrafts are flight authorized. In conclusion, the results of tests were presented and fulfilment of legal assumptions and requirements were shown.

Display Luminance Management Algorithm in Aviation Cockpit

An effective and reasonable luminance control algorithm, with ambient and forward field of view illumination compensation, has been proposed. This paper analyses the airworthiness requirement and human eye characteristics in terms of visual sensitive and as the basis of luminance control research. This algorithm introduces the display luminance comparison method to maintain the luminance consistency among all the head-down displays. The relationship between display luminance and ambient light is realized by power function to approximate the eye logarithmic response. Based on Webber-Fechner law, the adaptive mismatch compensation is utilized for the eye adaptation for transitions from forward field of view luminance levels. Considering the compensation for the display aging and the individual preference, the log-linear manual adjustment could help the crew to achieve the comfortable visual effect.

On the matter of the terminology of aeronautical structures survivability

Aim. The paper examines the existing definitions of survivability and damage tolerance (operational survivability) of aeronautical structures. An attempt is made to unambiguously define the survivability of aeronautical structures that can subsequently be extended to an aircraft as a whole and other complex technical items. The primary goal of this paper is to clearly distinguish between dependability and survivability. In order to ensure efficient operation and flight safety, an aircraft must possess airworthiness, a comprehensive characteristic of an aircraft that is defined by the implemented design principles and solutions and that allows performing safe flights under expected conditions and under the established methods of operation. The expected operating conditions are described in the Aviation Regulations – Airworthiness Requirements. Despite the fact that compliance with the Airworthiness Requirements ensures a sufficiently high level of flight safety, the most vital structural components are designed in such a way as to remain operable even under extreme conditions beyond the expected operating conditions. But dependability cannot be responsible for operability outside the expected operating conditions. Conclusion suggests itself that under extreme conditions beyond the expected operating conditions operability is to be ensured by another property, i.e. survivability. Methods. This research was conducted using the logical and probabilistic approaches. The author examined literary sources primarily dedicated to the matters of dependability and survivability of aeronautical structures, as well as other complex technical items. In order to ensure an optimal understanding of the differences and correlation between the concepts of dependability and survivability, the probabilistic approach was used. Results. Upon the analysis of literary sources, survivability was defined as the property of an item to retain in time the capability to perform the required functions under extreme conditions beyond the expected operating conditions under the specified methods of maintenance, storage and transportation. Additionally, the paper proposes the definition of damage tolerance (operational survivability) as the property of an item to retain in time the capability to perform the required functions under extreme conditions beyond the expected operating conditions depending on the methods of maintenance, storage and transportation. The probabilistic approach to the delimitation of the concepts of dependability and survivability of aeronautical structures was examined using the known indicator of operating efficiency of a transport aircraft that is represented as the mathematical expectation of the efficiency indicator. An aircraft may be either in the expected operating conditions or in extreme conditions beyond the expected operating conditions. No third option exists. Then, the sum of the probabilities of an aircraft encountering such conditions must be equal to one. The probability of no-failure can be calculated by means of the probability of the contrary event, i.e. the probability of failure that can be represented as the product of the probability of an aircraft encountering certain operating conditions and the probability of failure in such conditions. For the case of extreme conditions beyond the expected conditions the well-known concepts of perishability and vulnerability with the author’s improvements can be used. Conclusions. A definition of survivability was obtained that is clearly different from the concepts of dependability and fail-safety. Additionally, the concept of damage tolerance (operational survivability) was proposed that was introduced similarly to the previously introduced concept of operational dependability.