Browse Topic: Certification
This paper outlines observations from an FAA-sponsored research project that examined aviation Fly-By-Wire (FBW) accidents. The goal was to identify risk areas that will help guide a focus for FAA certification testing. Part of this study specifically focused on current powered-lift tiltrotors, identifying six general categories of causal factors for accidents, which will be discussed in detail regarding how they influenced flight control designs. The results of this survey, along with extrapolation to current designs, will be discussed and will illustrate why manufacturers are moving toward state-based flight control designs. In a state-based flight control scheme, the pilot does not have direct control over aircraft attitudes and motor tilt angles. Instead, the pilot requests a speed and or flight path with inceptor input, and the commanded attitudes and motor tilts are scheduled by the flight control computer. Additionally, recent lessons learned from electric Vertical Takeoff and
Full-scale static test (FSST) is a key test program for the certification of new helicopter airframe. The strength and deformation requirements in airframe certification are substantiated by full-scale tests of the airframe structures. It provides experimental evidence that the structure is able to support limit loads without detrimental permanent deformation and carry ultimate loads for at least three seconds. In design stage, the total number of flight and ground limit load conditions is around 500. In FSST, the number of test load cases should be remarkably reduced. However, the selected load scenarios should cover all of the critical design load scenarios. In this paper, test load generation procedures in FSST of a light utility helicopter is explained. The comparison of design load envelope and static test load envelopes are provided.
Ever-increasing modeling and simulation capabilities and the desire to use simulations in support of system qualification, regulatory compliance, and other critical decision-making roles, raises the bar on the need for rigorous V&V of all aspects of the models used to create the simulation data. US Department of Defense Directives and Instructions, and emerging regulatory and industry standards on Modeling and Simulation in a Digital Engineering context require rigorous M&S Verification, Validation, and Accreditation (M&S VV&A). These specifications aim to create trusted and credible simulation data that can be used in critical decision-making roles on complex systems. Implementing a well-defined, structured, model-based and standards-based M&S VV&A Process early in the program lifecycle facilitates collaboration and documented buy-in on M&S VV&A for program with customers and/or regulatory agencies. This collaboration increases acceptance throughout the program and product lifecycles
Aircraft Certification is a mature and complex bureaucracy that has successfully ensured a very high degree of safety of aircraft design, construction, operation and maintenance. Outside of a very few doing the work, there is a general lack of knowledge of certification details. For novel technologies such as electric power, and innovative configurations such as multi-rotors, the rules are far less mature and still emerging and so also poorly understood. Within the Advanced Air Mobility (AAM) initiative, many new aircraft developments are underway using novel configurations, and the public announcements of regulatory progress toward FAA or EASA Type Certification capitalize on this ignorance by being vague or even misleading. Honeywell conceived the Regulatory Readiness Level (RRL) indicator as an objective measure of certification status to serve the AAM industry and ecosystem, with applicability across aviation. The released RRL Version 1 now enables credible, objective assessment of
In the last years, new rotorcraft configurations have increased the attention among industries, through which the tiltrotor one due to its capability of combining both rotorcraft and aircraft advantages. However, there are situations where the vertical take-off mode could be enhanced in hard environmental and flight conditions. Therefore, to address this challenge, this work aims to develop a methodology to characterize a roll take-off model for a general tiltrotor configuration in such situations. By combining the integration of the equation of motion and geometrical assumptions, the runway distance is determined for an acceptable range of nacelle tilting angles. The process is developed by meeting the requirements defined by the regulations, combining the aircraft certification standards (CS23 and CS25) with the available tiltrotor certification basis from the FAA project #TC3419RC-R. Following the Nominal application, a sensitivity analysis is carried out, which studies the main
In this paper, we describe an innovative V&V approach using the SCADE product, enabling significant reduction of effort while preserving compliance with DO-178C/DO-331. This new approach relies on a unique capability: automatic generation of Low-Level Tests. Details about savings will be provided to show how we can reduce costs, speed up certifications, and bring products to the market faster. We will conclude by summarizing the actual benefits and describing ongoing work to bring other savings in the future.
The development of turbulence criteria to provide early guidance for the design of vertiports is presented in this paper. For any aircraft, winds, in particular crosswinds and gusty winds, are top of mind for all pilots engaging in take-off and landing maneuvers. It is anticipated that the same will be true for VTOL and eVTOLs landing on vertiports, in particular as new vertiports are built closer and closer to urban centres. First, a review of the current design criteria for vertiports around the world related to wind is presented, highlighting the commonality between the guidance and the gaps in their content. Second, the controllability criteria that VTOL and eVTOLs will likely need to meet in the pursuit of an airworthiness certification are reviewed and their pertinence with regards to vertiport design are discussed. Third, the characters of the wind and their impact on eVTOL flights at or near take-off and landing infrastructure is explored. Finally, a set of turbulence criteria
This paper describes the methodology, involving testing and simulation activities, to assess malfunction conditions of complex systems installed on fly-by-wire vehicles, including the evaluation of their effects. This paper provides also a description about how the system malfunction tests are designed, driven by input requirements and systems capability and behavior. With respect to prior publications, this paper includes some practical test examples, based on systems monitoring, logics and alerting functions. The case study described here comes from a portion of multiple laboratory certification tests done for AW609 Tiltrotor, focused on Avionics System malfunctions. These tests and simulations are a valuable Means of Compliance with respect to applicable airworthiness rules, and a suitable means to verify the design safety requirements. Three relevant examples are presented, grouped by input requirement and safety conditions. The effect of such malfunctions is evaluated, with
Sikorsky has successfully planned and executed several significant aircraft structural certification programs for military aircraft in the past few decades. These certifications included the CH-53K® with NAVAIR, the HH-60W with the Air Force and the Raider X® Competitive Prototype Aircraft with the Army. The methodologies for these certifications addressed the different requirements of each of these branches of the military as well as satisfying emerging techniques for structural life management ("Sikorsky Airframe Full Spectrum Customer/Supplier Collaboration", Reference 1). Safe Life Crack Initiation, Flaw Tolerant (Enhanced) Safe Life Crack Initiation and Fail Safe Life Limit Crack Propagation analysis had been rigorously pursued and demonstrated in these programs. This paper takes a retrospective look at what turns out to be many similarities in these methodologies that previously have been the subject of significant debate in the industry. The combined knowledge of these
The paper deals with the status of development and qualification/certification of electromechanical actuation for Helicopters and VTOL applications with the focus on aspects relevant to the Fault-Tolerance. In particular a linear Electromechanical Actuator (EMA) architecture is presented, derived from a fault tolerant ballscrew-based differential (speed-summing arrangement) actuation system patented by UMBRAGROUP S.p.A. The focus is on safety-critical and high reliability/availability requirements for electromechanical actuation certification. The main characteristic is the use of two independent mechanical actuation channels in the same envelope driven by independent Motor Control Electronics (MCEs). At the state of the art, the presented fault-tolerant architecture is under development in flight-critical swashplate application for eVTOL platform and under feasibility study in flight-critical swashplate application for CS27 platform.
To this point in aviation history, a typical aircraft type certification program has focused on the constituent systems that make up the aircraft, decomposing them further and further down until reaching their elemental parts and how they interact. This approach has traditionally treated the actual communication technology as only an interface, with technology and implementation based on a decision between multiple stakeholders via an ICD and high-level requirements. This has been necessary to ensure the accurate and on-time delivery of safety-critical data between nodes. When using legacy point-to-point or bus-based data communication technologies like ARINC 429 or MIL-STD-1553, this approach has worked well enough as these technologies are relatively straightforward and proven technologies. However, as onboard bandwidth needs for safety-critical data increase, these legacy technologies are increasingly no longer capable of meeting the needs of system integrators. Ubiquitous, high
Ground vibration testing (GVT) is an important phase of the development, or the structural modification of an aircraft program. The modes of vibration and their associated parameters extracted from the GVT are used to modify the structural model of the aircraft to make more reliable dynamics predictions to satisfy certification authorities. Due to the high cost and the extensive preparations for such tests, a new method of vibration testing called taxi vibration testing (TVT) rooted in operational modal analysis (OMA) was recently proposed and investigated by the German Institute for Aerospace Research (DLR) as alternative to conventional GVT. In this investigation, a computational framework based on fully coupled flexible multibody dynamics for TVT is presented to further investigate the applicability of the TVT to flexible airframes. The time domain decomposition (TDD) method for OMA was used to postprocess the response of the airframe during a TVT. The framework was then used to
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The aerospace ecosystem is a complex system of systems comprising of many stakeholders in exchanging technical, design, development, certification, operational, and maintenance data across the different lifecycle stages of an aircraft from concept, engineering, manufacturing, operations, and maintenance to its disposal. Many standards have been developed to standardize and improve the effectiveness, efficiency, and security of the data transfer processes in the aerospace ecosystem. There are still challenges in data transfer due to the lack of standards in certain areas and lack of awareness and implementation of some standards. G-31 standards committee of SAE International has conducted a study on the available digital data standards in aircraft asset life cycle to understand the current and future landscapes of the needed digital data standards and identify gaps. This technical paper presents the study conducted by the G-31 technical committee. This paper reviews the data being
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