Aircraft Certification Research Articles

Measuring drone noise for environmental reviews

In the United States, federal actions are covered by the National Environmental Policy Act which requires a review process to assess a proposed action's potential impact on the environment. One of the environmental impact categories that must be considered is noise. In order to assess the noise generated during a drone's typical operations, noise measurements of each portion of the drone's flight profile are needed. Because measurements required for type certification of aircraft are focused on source noise, they might not be sufficient to determine the noise resulting from a drone's entire operation from takeoff to landing. This paper discusses a range of feasible noise measurement approaches for assessing a drone operation's noise characteristics along with their associated fidelity. The paper presents a suggested practical measurement protocol that a drone manufacturer or operator could perform.

Noise-robust modal parameter identification and damage assessment for aero-structures

PurposeGround vibration testing is critical for aircraft design and certification. Fast relaxed vector fitting (FRVF) and Loewner framework (LF), recently extended to modal parameter extraction in mechanical systems to address the computational challenges of time and frequency domain techniques, are applied for damage detection on aeronautically relevant structures.Design/methodology/approachFRVF and LF are applied to numerical datasets to assess noise robustness and performance for damage detection. Computational efficiency is also evaluated. In addition, they are applied to a novel damage detection benchmark of a high aspect ratio wing, comparing their performance with the state-of-the-art method N4SID.FindingsFRVF and LF detect structural changes effectively; LF exhibits better noise robustness, while FRVF is more computationally efficient.Practical implicationsLF is recommended for noisy measurements.Originality/valueTo the best of the authors’ knowledge, this is the first study in which the LF and FRVF are applied for the extraction of the modal parameters in aeronautically relevant structures. In addition, a novel damage detection benchmark of a high-aspect-ratio wing is introduced.

Special Issue “Gust Influences on Aerospace”

An important prerequisite for the design, assessment, and certification of aircraft, their propulsion systems, and associated control systems is a quantitative specification of the environment in which the aircraft are intended to operate [...]

Civil aircraft negative acceleration airworthiness regulation differences analysis and certification

Civil aircraft negative acceleration airworthiness regulation differences analysis and certification

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.

Aircraft Takeoff and Landing Weight Estimation from Surveillance Data

Aircraft weight estimation is a common problem facing researchers working with aircraft surveillance data. Although knowledge of an aircraft’s weight and thrust is required for many types of analyses, such as those evaluating aircraft acoustic noise, fuel burn, and emissions, these parameters are typically not available from surveillance sources. Instead, researchers generally only have access to basic aircraft states: lateral position, groundspeed, and altitude. Therefore, methods for estimating the weight of aircraft from these basic states become necessary in cases where aircraft performance is a key component of the analysis. This paper introduces two weight estimation models: one for the estimation of aircraft takeoff weight from departure data, and another for the estimation of aircraft landing weight from arrival data. The models are mathematically simple but grounded in knowledge of aircraft certification, airline operations, and aircraft flight management system logic. The landing weight estimation model proposed is shown to have a mean absolute error equivalent to 2.66% of maximum takeoff weight and a standard deviation of 3.35% of maximum takeoff weight when validated using onboard data recordings from 240 Airbus A320 flights. Similarly, the proposed takeoff weight estimation model is shown to have a mean absolute error of 2.83% of the maximum takeoff weight and a standard deviation of 3.55% of the maximum takeoff weight when applied to the same validation dataset.

Aircraft Categorization Approach Using Machine Learning to Analyze Aircraft Behavior

The establishment of aircraft categories is a classification technique employed in a variety of aviation disciplines, including design and development, certification, ongoing airworthiness, air traffic management, surveillance, and safety analysis. Traditional approaches rely on manual feature engineering, which can be labor-intensive and ineffective for capturing complex patterns. In this paper, an approach to aircraft categorization using unsupervised machine learning clustering is proposed. The aim of the proposed approach is to be simple in order to be useful and understandable across disciplinary domains; to be scalable to large volumes of air traffic data; and to be adaptable to changes to account for the evolving technological and operational nature of the airspace environment. The application is based on an adapted version of the k-means algorithm that can group aircraft into clusters based on 3D position over time. The approach is validated using real-world, publicly available ADS-B air traffic data, and the results are compared to traditional categorization methods from the field of aircraft certification. The results showed that the model could be used to 1) identify and group aircraft sharing the same flight phase, 2) categorize aircraft with a similar general heading or direction, and 3) distinguish between local regional aircraft operations and longer flight operations. It was also shown that, depending on the use case, the model could be extended to identify more granular behaviors by increasing the K value used to create the model. Overall, the findings demonstrate that leveraging machine learning techniques for aircraft categorization provides an effective, automated, and scalable solution applicable to a wide range of current applications.

Airport noise assessment and mitigation: A simple and flexible methodology

Airport noise assessment and mitigation have been recognized as major challenges in the current civil aviation context. This paper aims to provide a general, simple, and flexible methodology to approximate airport noise-influenced zones and quantify the social cost of noise pollution. The proposed methodology performs this assessment without the need for specific software, monitoring stations, and sophisticated data. Airport noise-influenced zones are estimated by relying on publicly available aircraft certification data, while the social cost of such estimation is computed by taking into account the distribution of residential units located within zones affected by noise. We present an application of this method to a group of Italian and Spanish airports, as well as possible beneficial policy interventions in terms of minimization of noise impact on the population living in the airport neighborhoods. In addition, possible mitigation policies are presented in the form of noise surcharges applied to different aircraft categories.

Jet noise of a low bypass turbofan with internal mixing and external plug

Jet noise generated by turbofan engines which are designed for supersonic aircraft operation is expected to remain a challenge for the aerospace industry. For civil supersonic transport, low bypass ratio engines with internal mixing and external plugs are currently seen as promising exhaust architecture to meet aircraft mission and certification requirements. Measurements of the noise from a representative low-bypass ratio long duct mixed flow with external plug exhaust configuration were made, along with corresponding steady-RANS and LES analyses. The measured data showed excess high frequency noise across a wide range of operating conditions as compared to an equivalent single stream jet, or an equivalent uniform jet with internal plug. The absolute levels of the excess noise were relatively insensitive to forward flight, and the excess noise was most dominant when the primary and secondary streams had large velocity and temperature mismatch just upstream of the internal mixer. Preliminary indications from the LES analysis also indicated that significant pressure fluctuations, at the same frequencies which are insensitive to forward flight, develop inside the nozzle as the internal shear layer from the mixer grows and gets accelerated by the external plug. Parametric study test measurements on the fan and core operating conditions were performed, providing support for the hypothesis that the excess noise is generated as the internal shear layer, starting inside the nozzle, gets accelerated by the plug and passes through the weak shock at the nozzle exit where the flow accelerates more and turns over the external plug.

Design of a metal additive manufactured aircraft seat leg using topology optimization and part decomposition

PurposeThe 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/approachTO 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.FindingsThe 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/valueTo 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.

Hopkinson bar impact force measurement for application to development of an artificial bird

A test method has been published for measuring forces from bird cadavers and artificial birds to demonstrate equivalency to support the use of artificial birds in aircraft certification testing. The test method involves a large diameter Hopkinson bar as the technique for measuring and comparing forces. The method involves the assumption that a force on one end of the bar results in a one-dimensional plane wave that travels down the bar. To avoid reflected waves from the end of the bar overlapping the input pulse, and due to practical limitations on the length of the bar, strain transducers are located relatively close to the impacted face of the bar, raising questions about the validity of the assumption of one-dimensional wave propagation. In addition, the large diameter of the bar can introduce dispersion effects in the propagated pulse. These must be assessed to determine the impact on the accuracy of impact force measurements and, if significant, dispersion correction techniques must be used. In this study analytical, experimental, and computational methods are used to analyze the wave propagation characteristics for impact forces expected from realistic bird impacts. While wave dispersion and effects of non-concentric impacts are present, the resulting errors are small relative to typical test-to-test variation observed in bird impact testing. For the response we expect to see in bird impacts up to velocities of approximately 300 m/s the large diameter Hopkinson bar test appears to be an acceptable method for measuring the impact forces and comparing the response of real and proposed artificial birds.

Paving the Way for the Electrified Future of Flight: Safety Criteria Development for Integrating Structural Batteries in Aircraft

AbstractWithin the global push towards environmental sustainability, the aviation industry is increasingly investigating electrification as a potential solution to reduce emissions and combat climate change. However, traditional battery integration faces significant drawbacks due to their limited energy and power densities, which negatively impact aircraft weight and performance. In this scenario, structural batteries are gaining interest, since they combine energy storage and load-bearing capabilities in multifunctional material structures, thus potentially eliminating barriers to the electrification of the air transport sector. While this novel technology holds immense potential, its integration raises new and unique airworthiness concerns. The present activity aims to support the development of aircraft certification requirements for structural batteries. Recognizing the dual nature of this technology, the proposed approach seeks to maintain or even enhance the current level of safety in both normal and emergency flight conditions.

Bird Collision Prevention Systems in Passenger Aviation

The purpose of this article is to present the results of a preliminary analysis of modern methods for preventing collisions between birds and aircraft. The focus was in particular on methods that enable defining the level of threat in passenger aviation and existing solutions for eliminating these threats. The first section defines the level of the existing threat of collision with birds for civil aviation on the basis of collision statistics based on collision reports submitted by pilots. The second chapter describes normative documents on methods intended to reduce the risk of collisions with birds, such as aviation rules and regulations, passenger aircraft certification, bird detection and deterrence systems, procedures of flight crews and air traffic controllers, and the development of bird detection and deterrence methods. Based on the analysis of existing solutions, the third chapter proposes a block diagram of an on-board system reducing the risk of aircraft collisions with birds by determining the level of collision risk and transmitting information about the risk level to the flight crew in order to reduce the effect of surprise among pilots, improve the accuracy of the statistics and operational safety by carrying out a technical inspection of the aircraft after the collision. The final chapter contains conclusions.

Analysis of Personnel's Understanding of Safety Culture in the Implementation of Safety Management System at Yogyakarta International Airport

The global spread of industries towards the era of Industry 4.0, encompassing the integration of cyber technology and automation. Safety Management Systems (SMS) are employed at each airport differently due to their distinct characteristics. Airport security and order disruption are security issues. Cases such as apron breaches, trespassing, and negligence occur. Aviation accidents pose security issues stemming from SMS implementation, operational oversight, aircraft certification, and flight health factors. There are 8 accident categories and 22 serious incidents resulting in 5 fatalities.This research employs a qualitative approach with a descriptive method. To attain answers, the researcher designed a qualitative research design. Qualitative research aims to investigate, discover, describe, and explain the quality of social influences. Data analysis is conducted through data collection, reduction, display, and conclusion drawing. Validity is ensured using source triangulation. The research findings reveal that personnel safety culture at Yogyakarta International Airport aligns with SOP. Out of 165 criteria, the achievement rate is 92.7%, indicating a positive relationship between safety culture and safety management system (KP 622/2015). The effectiveness of safety management system implementation at the airport is 72%. Strategies like Avoidance, Reduction, and Segregation are used to mitigate risks. Although risks cannot be entirely avoided or eliminated, adherence to standard operating procedures (SOP) and risk mitigation through facilities and human resources help minimize these risks.

A wall-modelled large eddy simulation approach based on large scale parallel computing for post stall flow over an iced airfoil

Safety evaluation for ice accretion is one of the most important jobs for the airworthiness certification of commercial aircraft. Ice accretion would induce strong performance degradation of lifting surfaces by modifying the geometry of the leading edge and the state of boundary layers, and inducing premature flow separation. In this paper, a wall-modelled large eddy simulation (WMLES) approach combined with high performance computing is presented and evaluated for numerical simulation of post stall flow at Mach number 0.12 and Reynolds number 3.5 million over an iced airfoil with angle of attack 6 degrees for business jet, which is known as the GL305/944 airfoil with horn ice. Both RANS and an improved DDES (IDDES) based on SST model are also completed to validate the results. The results are compared with the experimental data in details that includes total forces, velocity profile, averaged velocity field, RMS of pulsating velocity, et al. It is concluded that the WMLES approach presented here can greatly improve the numerical accuracy for post stall flow with large separation; Basically, WMLES can relatively accurately predict the total forces, the pressure rooftop length and the pressure recovery, and the shear layer instability induced by the horn ice.The relative error of lift coefficient for WMLES is only 0.47%, which is far less than RANS with -26.7%.

A procedure for obtaining forecast turbulence parameters in the atmospheric boundary layer for acoustic propagation

Propagation through turbulence causes a mean reduction in loudness of sonic booms and in some cases can cause significant fluctuations in loudness about that mean. Understanding these effects is important for accurately planning loudness levels during upcoming community noise tests with the X-59 aircraft as well as mitigating the risk for excessive loudness due to turbulence. Current methods for modeling acoustic propagation through turbulence require several atmospheric parameters including the atmospheric boundary layer (ABL) height, friction velocity, mixed-layer velocity scale, surface-layer temperature scale, as well as ambient pressure, temperature, and humidity within the ABL. Accurate forecasts of these parameters are needed for X-59 flight planning and may also be useful for planning future supersonic aircraft certification flight tests. This presentation showcases one method for obtaining the forecast turbulence and ambient atmospheric parameters from freely available Climate Forecast System Version 2 data. Forecast parameters are compared to measurements to assess accuracy and utility.

Business Trends in the Civil Aircraft Industry

This paper tracks the growth and status of leading Aircraft manufacturers from North America, Europe, South America and Asia in the twentieth and early part of the twenty first century. Since the 1960s, high costs associated with passenger aircraft development and certification necessitates international partnerships for program risk sharing and apportionment of expenses. The number of joint ventures among aircraft manufacturers rose from 10 in 1969 to 50 by 1992. The paper also describes the way forward for India to adopt global best practices for starting a civil aircraft industry.

Global stability analysis of elastic aircraft in edge-of-the-envelope flow

Shock buffet on wings is a phenomenon caused by strong shock-wave/boundary-layer interaction resulting first in self-sustained flow unsteadiness and eventually in a detrimental structural response called buffeting. While it is an important aspect of wing design and aircraft certification, particularly for modern transonic air transport, not all of the underlying multidisciplinary physics is thoroughly understood. Building upon a single-discipline shock-buffet stability study, this work now investigates the impact of an elastic structure in these extreme flow conditions. Specifically, a triglobal stability analysis of a fluid–structure coupled system is presented, utilising the implicitly restarted Arnoldi method with a sparse iterative Krylov solver and novel preconditioner. Asymmetry resulting from a static aeroelastic simulation based on a finite-element model of the underlying geometry in a wind tunnel modifies the global modes of the earlier fluid-only symmetric full-span analysis. A flutter stability analysis at wind-tunnel flow conditions below shock-buffet onset finds no instability in the structural degrees-of-freedom, whereas in shock-buffet flow with globally unstable fluid modes additional marginally unstable structural (and fluid) modes emerge. The developed stability tool for coupled analysis is instrumental in identifying those physically relevant and strongly coupled modes where a standard pk-type (p being eigenvalue and k reduced frequency) flutter analysis fails. With the complementary computation of adjoint eigenmodes, the core of the instability is pinpointed to a relatively small wing area which may help to effect the control and delay of this detrimental transonic unsteadiness. We contribute to the question on how the presence of the elastic wing structure impacts on the otherwise pure aerodynamic three-dimensional shock-buffet dynamics.

A model-based safety analysis approach for airborne systems using state traversals

Safety analysis is an important task in both the development and certification of civil aircraft. The traditional safety analysis is significantly dependent on the skills and experiences of analysts. A model-based safety analysis approach is proposed for airborne systems based on the model built with Simulink. This study builds Simulink models of typical failure modes as well as the fault injection methods. The responses of system performances are monitored by traversing all failure combinations based on a state space reduction method. The system will be in an unsafe condition when the responses exceed their thresholds. The minimal cut sets of the system are obtained automatically by recording the failure combinations leading to the unsafe condition. Finally, a lateral-directional flight control system is taken as a practical example to illustrate the application and effectiveness of our proposed method. The result shows that our method has higher accuracy and the causes of the unsafe conditions can be determined by the automatic generation of the minimal cut sets. Additionally, the cumbersome work of building a traditional safety analysis model such as the fault tree, the Markov model, or the dependence diagram can be avoided.

A novel hybrid method for aerodynamic noise prediction of high-lift devices

Aerodynamic noise of High-Lift Devices (HLDs) is one of the main sources of airframe noise, and has immediate impacts on the airworthiness certification, environmental protection and security of commercial aircraft. In this study, a novel hybrid method is proposed for the aerodynamic noise prediction of HLD. A negative Spalart-Allmaras (S-A) turbulence model based Improved Delayed Detached Eddy Simulation (IDDES) method coupling with AFT-2017b transition model is developed, in order to elaborately simulate the complex flow field around the HLD and thus obtain the information of acoustic sources. A Farassat-Kirchhoff hybrid method is developed to filter the spurious noise sources caused by the vortex motions in solving the Ffowcs Williams-Hawkings (FW-H) equation with permeable integral surfaces, and accurately predict the far-field noise radiation of the HLD. The results of the 30P30N HLD indicate that, the computational Sound Pressure Levels (SPLs) obtained by the Farassat-Kirchhoff hybrid method conform well with the experimental ones in the spectrum for the given observation point, and are more accurate than those obtained by the Farassat 1A method. Based on the hybrid method, the acoustic directivity of the HLD of a commercial aircraft is obtained, and the variation of the SPLs in the spectrum with the deflection angle of the slat is analyzed.