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The purpose of this paper is to analyze the electric propulsion use in civil aviation and propose a framework for certification of electric propulsion subsystems. Although electric propulsion architectures are discussed as key technology for the future of aviation, the industry standards as well as regulations fail to cover the application in full extent, specifically for commercial large airplanes. This paper proposes an approach for the analyses of reliability and certification of the new-generation propulsion system by pointing out the “common structure” among the possible architectures.

The research process used in this paper consists of following steps: the challenges of the hybrid-electric propulsion is listed, the architectures of the hybrid-electric applications in the literature are identified, the differences of the hybrid architectures from the present applications by means of application and standardization are discovered, the architectures are analyzed and the two main subsystems are defined – the present combustion system and the common unit, which is a similar structure used in all-electric aircraft. For this purpose, the standards used for design basis and certification of the present propulsion system and their relationship with the subsystems of the architectures have been analyzed. The procedure for the reliability assessment of the system is given, a framework for the safety assessment and the certification of the propulsion systems is proposed to make it easier and without sacrificing the already accumulated experience. This study shows that by using the common unit, the present certification framework can be used, by focusing on the reliability of the common unit and its integration with the rest of the architecture.

A specific definition of common unit is proposed, to point out the difference in certification efforts of hybrid-electric propulsion architectures. Yet, there is no data available for propulsion-level airborne battery and electrical systems to assess the reliability. Thus, dividing the propulsion system into two main systems and providing a model for certification of the common unit sub-system would be beneficial for easy deployment of the hybrid architectures both for design and for certification. In this paper, it is proposed that by using this common unit, the present certification framework can be used as it is, by focusing on the reliability of the common unit and its integration with the rest of the architecture.

The aircraft certification regulations act in two ways: they provide a starting point for new design projects, and they are a basis for certification of the final system. This study aims to draw focus on certification issues on the new-generation hybrid-electric propulsion systems. With the introduction of hybrid-electric propulsion for large aircraft, the present standards (CS-25, CS-E, CS-P, CS-Battery and CS-APU) create an obstacle for further progress as their borders get into each other. Instead of developing a new set of standard(s), this paper proposes a new approach by dividing the propulsion system into two subsystems.

This research proposes a definition of “common unit” for simplification of the hybrid-electric propulsion architectures for large civil aircraft. The common unit consists of both battery and electrical components and their reliability shall be considered for hybrid-electric propulsion.

The purpose of this paper is to define reliability requirements to be imposed on electric engines to assure similar or higher value of mean time between failures (MTBF) for mixed piston-electric propulsion configurations when compared to classic and unconventional piston engine configurations.

Reliability estimation was done using mathematical model of safety of light aircraft commercial operations. The model was developed on the basis of Federal Aviation Administration and National Transport Safety Board data. The analysis was conducted for numerous piston and electric configurations. It allowed comparison of selected solutions and definition of relation between electric engine MTBF and MTBF calculated for entire mixed piston-electric propulsion system.

It was found that, from reliability point of view, mixed piston-electric engine propulsion is attractive alternative for classic single- and twin-piston configuration. It would allow to at least doubling of MTBF for propulsion without increase of operational cost.

Rationale behind exploiting electric propulsion in aviation is provided. Relation between electric engine reliability and entire propulsion reliability was identified and defined. Minimum requirements concerning MTBF value for electric engine application in aviation was assessed. Conclusions from this study can be used for definition of requirements for new aircraft and by the regulatory authorities.

Originality consists in use of real accident statistics included in mathematical model of safety for assessment of MTBF for various classic and novel piston and piston-electric engine configurations of light aircraft. Output from the study can be exploited by the industry.

This paper aims to present the main results achieved in the frame of the TIVANO national-funded project which may anticipate, in a stepped approach, the evolution and the design of the enabling technologies needed for a hybrid/electric medium altitude long endurance (MALE) unmanned aerial vehicle (UAV) to perform persistent intelligence surveillance reconnaissance (ISR) military operations.

Different architectures of hybrid-propulsion system are analyzed pointing out their operating modes to select the more suitable architecture for the reference aircraft. The selected architecture is further analyzed together with its electric power plant branch focusing on electric system architecture and the selected electric machine. A final comparison between the hybrid and standard propulsion is given at aircraft level.

The use of hybrid propulsion may lead to a reduction of the total aircraft mass and an increase in safety level. However, this result comes together with a reduced performance in climb phase.

This study can be used as a reference for similar studies and it provides a detailed description of propulsion operating modes, power management, electric system and machine architecture.

This study presents a novel application of hybrid propulsion focusing on a three tons class MALE UAV for ISR missions. It provides new operating modes of the propulsion system and a detailed electric architecture of its powertrain branch and machine. Some considerations on noise emissions and infra-red traceability of this propulsion, at aircraft level.

This paper aims to review national aeronautics and space administration (NASA’s) broad investments in electrified aircraft propulsion (EAP). NASA investments are guided by an assessment of potential market impacts, technical key performance parameters, and technology readiness attained through a combination of studies, enabling fundamental research and flight research.

The impact of EAP varies by market and NASA is considering three markets as follows: national/international, on-demand mobility and short-haul regional air transport. Technical advances in key areas have been made that indicate EAP is a viable technology. Flight research is underway to demonstrate integrated solutions and inform standards and certification processes.

A key finding is that sufficient technical advances in key areas have been made, which indicate EAP is a viable technology for aircraft. Significant progress has been made to reduce EAP adoption barriers and further work is needed to transition the technology to a commercial product and improve the technology, so it is applicable to large transonic aircraft.

Significant progress has been made to reduce EAP adoption barriers and further work is needed to transition the technology to a commercial product and improve the technology, so it is applicable to large transonic aircraft.

This paper will review the activities of the hybrid gas-electric subproject of the Advanced Air Transport Technology Project, the Revolutionary Vertical Lift Technology Project and the X-57 Flight Demonstration Project, and discuss the potential EAP benefits for commercial and military applications. This paper focuses on the vehicle-related activities, however, there are related NASA activities in air space management and vehicle autonomy activities, as well as a breakthrough technology project called the Convergent Aeronautics Solutions Project. The target audience is people interested in EAP.

The purpose of this article is to provide an outline of the challenges of thermal management for more-electric, hybrid-electric and all-electric aircraft, and to notionally discuss potential solutions.

A code algorithm was developed to facilitate architecture-level analysis of the coupled relationship between the propulsion system, the thermal management system, and the takeoff gross weight of aircraft with advanced propulsion systems.

A variety of coupled relationships between the propulsion and thermal management systems are identified, and their impact on the conceptual design choices for electric aircraft are discussed qualitatively.

This conceptual article merely illuminates some driving factors associated with thermal management. The software is still in its adolescence and is experiencing ongoing development.

Thermal regulation in electric aircraft is shown to be a topic that should be addressed in tandem with propulsion system architecture definition and component selection. High-power electronics are expected to emit an immense amount of heat, and the common avenues of heat dissipation could substantially impact the aircraft’s weight, drag and performance. Conversely, strategic management of this waste heat could support subsystems or even produce additional thrust.

This paper aims to direct the attention of researchers and designers in the field of hybrid- or all-electric aircraft design toward the challenges and potential benefits of thermal management.

This paper describes a novel conceptual design software and discusses its logic flow and implications.

This paper aims to create a terminal area operations (TAO) analysis software that can accurately appreciate the nuances of hybrid electric distributed propulsion (HEDP), including unique failure modes and powered-lift effects.

The program was written in Visual Basic with a user interface in Microsoft Excel. It integrates newly defined force components over time using a fourth order Runge-Kutta scheme.

Powered-lift, HEDP failure modes and electrical component thermal limitations play significant roles on the performance of aircraft during TAO. Thoughtful design may yield better efficiency; however, care must be given to address negative implications. Reliability and performance can be improved during component failure scenarios.

This program has and will support the investigation of novel propulsion system architectures and aero-propulsive relationships through accurate TAO performance prediction.

Powered-lift and HEDP architectures can be employed to improve takeoff and climb performance, both during nominal and component failure scenarios, however, reliance on powered-lift may result in faster approach speeds. High-lift and system failure behavior may also allow new approaches to design and sizing requirements.

This program is unique in both the public and private sectors in its broad capabilities for TAO analysis of aircraft with HEDP systems and powered-lift.

Recent advancements in electrified transportation have been necessitated by the need to reduce environmentally harmful emissions. Accordingly, several aviation organisations and governments have introduced stringent emission reduction targets for 2050. One of the most promising technologies proposed for achieving these targets is turboelectric distributed propulsion (TeDP). The objective of this study was to explore and identify key indicators for enhancing the applicability of TeDP in air transportation.

An enhancement valuation method was proposed to overcome the challenges associated with TeDP in terms of technological, economic and environmental impacts. The result indicators (RIs) were determined; the associated performance indicators (PIs) were analysed and the key RIs and PIs for TeDP were identified. Quantitative measurements were acquired from a simulated TeDP case study model to estimate the established key PIs.

It was determined that real-world TeDP efficiency could be enhanced by up to 8% by optimising the identified key PIs.

This study is the first to identify the key PIs of TeDP and to include a techno-economic environmental risk analysis (TERA) based on the identified key PIs. The findings could guide developers and researchers towards potential focus areas to realise the adoption of TeDP.

This paper aims to suggest a new thermonuclear space propulsion and electric generator for aerospace.

Methods of thermonuclear physics are used for research.

The paper applies, develops and researches mini‐sized Micro‐AB thermonuclear reactors for space propulsion and space power systems. These small engines directly convert the high‐speed charged particles produced in the thermonuclear reactor into vehicle thrust or vehicle electricity with maximum efficiency. The simplest AB‐thermonuclear propulsion offered allows spaceships to reach speeds of 20,000‐50,000 km/s (1/6 of light speed) for fuel ratio 0.1 and produces a huge amount of useful electric energy. The offered propulsion system permits flight to any planet of the solar system in a short time and to the nearest non‐Sun stars by E‐being or intellectual robots during a single human life period.

Technical limitations may be apparent.

The theory of this propulsion and electric generator is developed and possibilities researched.

The purpose of this study is to examine state-of-the-art in hybrid-electric propulsion system modeling and suggest new methodologies for sizing such advanced concepts. Many entities are involved in the modelling and design of hybrid electric aircraft; however, the highly multidisciplinary nature of the problem means that most tools focus heavily on one discipline and over simplify others to keep the analysis reasonable in scope. Correctly sizing a hybrid-electric system requires knowledge of aircraft and engine performance along with a working knowledge of electrical and energy storage systems. The difficulty is compounded by the multi-timescale dynamic nature of the problem. Furthermore, the choice of energy management in a hybrid electric system presents multiple degrees of freedom, which means the aircraft sizing problem now becomes not just a root-finding exercise, but also a constrained optimization problem.

The hybrid electric vehicle sizing problem can be sub-divided into three areas: modelling methods/fidelity, energy management and optimization technique. The literature is reviewed to find desirable characteristics and features of each area. Subsequently, a new process for sizing a new hybrid electric aircraft is proposed by synthesizing techniques from model predictive control and detailed conceptual design modelling. Elements from model predictive control and concurrent optimization are combined to formulate a new structure for the optimization of the sizing and energy management of future aircraft.

While the example optimization formulation provided is specific to a hybrid electric concept, the proposed structure is general enough to be adapted to any vehicle concept which contains multiple degrees of control freedom that can be optimized continuously throughout a mission.

The proposed technique is novel in its application of model predictive control to the conceptual design phase.