Helicopter Manufacturers Research Articles

Challenges of Machine Learning for eVTOL Reliability and Safety

The increasing number of requests for type certification received by the European Union Safety Agency on Vertical Takeoff and Landing (VTOL) aircraft attests to the expansion of frontiers in Urban Air Mobility (UAM). In addition, it has revealed the interest of traditional airplane and helicopter manufacturers in this new technology, all the while highlighting the emergence of new players developing their respective versions of electric-powered VTOLs (eVTOL). The perspective of eVTOLs going into service in the coming years for the transport of passengers raises new safety concerns. Indeed, it is necessary to ensure the reliability and safety aspects of those aircraft systems that will be flying under new operational missions, differing from current fixed wing (airplanes) and rotorcraft (helicopters) aircraft. At the same time, the evolution of aircraft systems monitoring technology is making it possible to acquire increasing amounts of data. The high complexity of new systems, combined with the huge amount of data provided, can make the decision-making process more difficult for pilots. Machine learning makes it possible to evaluate this data and improve reliability and safety.
 Even as the number of aeronautical accidents has decreased over the last years, 60–80% of those accidents are the result of human failure. In the initial implementation and operation stages of eVTOLs, machine learning (ML) can support pilots by using aircraft data to predict system failures and contribute to improve reliability and safety. Then, at an advanced stage of eVTOL operation, ML may help reduce human interaction with the aircraft, paving the way toward fully autonomous aircraft. The association of ML with technologies such as Digital Twins and 6G networks has the potential to enable safe and reliable autonomous flight. However, the introduction of eVTOLs will also increase air traffic in highly populated areas and thus needs to be studied to support the incorporation of the future autonomous aircraft. This paper addresses the main challenges for the incorporation of ML in the upcoming eVTOL fleet and its potential contribution to aircraft systems reliability and safety. It also explores the need for the use of ML techniques in a more autonomous air traffic management systems the face of increased air traffic.

Model of sound and vibration discomfort in helicopter cabins

Noise and vibrations are major sources of discomfort in helicopter cabins and helicopter manufacturers are seeking to estimate passenger discomfort based on noise and vibration measurements. To this end, series of perceptive experiments have been conducted to link subjective assessments of discomfort to objective measurements. Firstly, it has been shown that noise discomfort is governed by perceived intensity and an acoustic comfort equation has been established based on a sound loudness metric. A second series of tests is presented in this document and aims to estimate the global discomfort due to simultaneous noise and vibrations. Discomfort indicators specific to noise and vibrations were used to create a global discomfort equation. This equation shows a similar contribution to the global discomfort from the two sources but demonstrates an interaction term which disadvantages comfort if one of the sources is dominant.

Aerodynamic Interactions on Airbus Helicopters' Compound Helicopter RACER in Hover

In recent years, helicopter manufacturers have developed an increasing number of nonconventional configurations in order to extend flight envelopes of helicopters towards higher cruise speed. Airbus Helicopters' approach is the compound helicopter RACER, which is equipped with a boxwing and lateral pusher rotors. As the combination of these components with the main rotor induces a variety of mutual interactions, influencing their individual aerodynamic performance depending on the flight conditions, the understanding of these interactions is vital for the evaluation of the overall system. For this reason, the respective mutual influence of main rotor, wings, and lateral rotors is analyzed in this paper for hover. With the help of high-fidelity coupled aerodynamic simulations for the full RACER (Rapid And Cost-Efficient Rotorcraft) configuration as well as for setups omitting individual components, first- and second-order interactions of these components are isolated and analyzed for their effect on the helicopter's aerodynamic performance.

Correction system of the main rotor angular speed for helicopters of little weight categories

Currently, there are many types of 1-2 seats helicopters in the world, which transport the people or small cargos. Most often, aircraft use internal combustion engines that have not an electronic control system. Several small helicopter manufacturers try to use an automatic system of correction of engine rotational speed in such situation. The article is devoted to the analysis of such systems and the possibility of increasing their efficiency. The article discusses the experience of experimental studies of the system, which partially corrects the throttle control process from the pilot. The tests on the ultralight helicopter R-30 shows the device that uses the principle of a sliding control push rod, partially correcting the engine throttle, can be most effective in terms of both control and reliability. 20-30% of the possible movement of the control system by the pilot may be enough for automatic control.

Development of a Promising Area of Diversification in Helicopter Industry

Many countries have main pipeline systems that deliver hydrocarbon deposits from fields to their places of consumption and for export. Pipelines during operation require constant maintenance, industrial safety monitoring, repair, and protection. An accident there entails significant loss of product, additional financial costs, tangible environmental damage, and, in some cases, loss of life. To prevent it, it is necessary to use various types of monitoring, including aerospace. In addition to existing control methods, unmanned aerial vehicles (UAV) of a helicopter type with a long flight range can become a modern high-tech tool for solving problems of monitoring main pipelines. For a helicopter manufacturing enterprise, this is a new perspective area in diversifying its production and commercial activities.

Coupled and Trimmed Aerodynamic and Aeroacoustic Simulations for Airbus Helicopters' Compound Helicopter RACER

In recent years, various helicopter manufacturers increasingly have been focusing on the development of new high-speed rotorcraft configurations, one of them being the compound helicopter RACER (rapid and cost-efficient rotorcraft) of Airbus Helicopters (AH). However, these new configurations encounter new aeromechanic challenges, in terms of aerodynamic interactions, flight mechanics stability, rotor dynamics, or aeroacoustic noise emission, to name only a few. To support AH at the minimization of risk of RACER's first flight, the Institute of Aerodynamics and Gas Dynamics provides high-fidelity coupled and trimmed aerodynamic and aeroacoustic simulations of the complete helicopter by the application of a multidisciplinary tool chain. In its first part, the work focuses on the description of this advanced tool chain and on important features for the analysis of this new configuration. In the second part, exemplary simulation results for a hover and a high-speed cruise flight condition are shown, and the main aerodynamic interactions between the different components are identified. As expected for this configuration, numerous interactions are found for both flight cases, e.g., main rotor–propeller interaction in hover or main rotor–wing interaction in high-speed flight. Finally, aeroacoustic results are shown for hover with a close look at the propellers' contribution.

Aerodynamic Interactions on Airbus Helicopters' Compound Helicopter RACER in Cruise Flight

With the pursuit of extending the flight envelopes of helicopters toward higher cruise speed, helicopter manufacturers increasingly have come up with nonconventional configurations in recent years. Among these, Airbus Helicopters' RACER (Rapid And Cost-Efficient Rotorcraft) is a compound helicopter equipped with a boxwing and lateral pusher rotors. In combination with the main rotor, these additional components determine the aerodynamic characteristics of the helicopter. Thereby, depending on the flight conditions, their individual performance is influenced by a variety of interactions. As the understanding of these interactions is vital for the evaluation of the overall system, the respective mutual influence of main rotor, wings, and lateral rotors is analyzed in this paper for cruise flight. For this reason, high-fidelity coupled aerodynamic simulations are conducted not only for the full RACER configuration but also for reduced setups omitting individual components to isolate the effect of these components on the helicopter's aerodynamic performance.

Mechanism for Adjustment of the Companies Innovative Activity Control Indicators to Their Strategic Development Goals

Innovative activity is an important factor for the development of companies, which to a large extent determines their competitive positions in the global market of goods and services. During the research, a hypothesis was put forward stating that the current company management mechanisms do not fully realize innovation development potential to achieve strategic outcomes. On the basis of the activity analysis of the largest Russian companies, it was estimated that innovation development indicators are not always aimed at achieving strategic outcomes. The identified problem hinders development of companies in the current context. For this reason, in order to solve it, the mechanism for the adjustment of innovative development indicators to the company strategic guidelines has been worked out. Its design was based on the groundwork of the demand to necessarily provide increasing payoff from innovative activity. To implement it, a certain procedure was suggested for maintaining the ratio between individual indicators of the company innovative activity efficiency and its strategic development indicators, reflected in the devised dynamical model. The proposals we suggested on forming the mechanism for control indicators adjustment were brought to the level of methodological support of investigated process. Experimental approbation of the devised approach was done from the perspective of functionality of the leading companies in the world market of civilian and military helicopters, including Textron (Bell Helicopters), Airbus (Helicopters), Leonardo, Sikorsky, Boeing, and Russian Helicopters. The possibility of practical application of the devised mechanism for indicators adjustment was demonstrated with regard to handling of applied problems of developing the helicopter manufacturing company Russian Helicopters, aimed at improving its competitiveness in the world market. Results of the conducted research, first, broaden scientific perceptions of the innovation impact on the achievement of strategic outcomes of the companies activity; second, contain methodological support for devising and further functioning of the mechanism for adjustment of innovative activity indicators to achieve the company strategic development benchmarks at the account of secured increasing payoff from innovative activity; third, represent practical interest from the point of handling applied problems of national companies development in various branches and fields, first of all those from developing countries, and so can be used by them when working out strategic and program documents for improving competitiveness in the global economic space.

Aerodynamics and flight mechanics analysis of Airbus Helicopters\u2019 compound helicopter RACER in hover under crosswind conditions

In recent years, various helicopter manufacturers have been focusing increasingly on the development of new high-speed rotorcraft configurations, one of them being the compound helicopter RACER of Airbus Helicopters (AH). However, these new configurations encounter new aeromechanic challenges, in terms of aerodynamic interactions, flight mechanics stability, rotor dynamics or aeroacoustic noise emission, to name only a few. In the following study, the behaviour of RACER in hover under the influence of crosswinds from eight different directions is investigated to support AH at the de-risking of RACER for this flight condition prior to the first flight. Therefore, a multidisciplinary, high-fidelity tool chain for coupled and trimmed aerodynamic simulations of the complete rotorcraft is applied. The presentation of the results is organized in three parts. In the first part, the flight mechanic behaviour is analysed and successful de-risking of ground clearance is shown. The second part focuses on the performance of the main rotor, the lateral rotors and the tail surfaces under wind conditions and shows that minimal power is required for headwind. In the last part, an analysis of the engines is performed, including a closer look at the inflow quality to the core engine and the convection of the hot exhaust gases.

Impact of icing weather conditions on the patients in helicopter emergency medical service: a prospective study from Northern Finland

BackgroundA high number of denied or cancelled HEMS missions are caused by poor weather conditions especially during winter season. Furthermore, many helicopter manufacturers have denied their helicopters to be operated in known icing conditions. Icing is a widely known phenomenon in aviation, but there is a lack of evidence about its influence on HEMS operations and patients.MethodsA prospective observational study of HEMS missions in Northern Finland was conducted over a 1-year period in 2017. A patient was included in the study when the use of helicopter was denied or cancelled due to icing weather conditions. Patients were categorised into two groups based on whether definitive treatment was delayed or not according to previously defined end-points.ResultsDuring the study period the Finnish northernmost HEMS unit received 1940 missions. A total of 391 missions (20%) could not be operated by helicopter because of poor weather conditions. In 142 of these missions (36%) icing was one of the limiting weather factors. The year-round incidence of icing was 7.3/100 missions. A total of 57 patients were included in the analysis. Icing weather conditions, resulting in denied helicopter flights, caused a delay in definitive treatment for 21 patients (37%). Definitive treatment was more often delayed in trauma and internal medicine patients than in neurological patients. Nevertheless, the patients whose definitive treatment was delayed were located closer to the hospital. The estimated time that would have been saved by helicopter transport was more than 60 min for 10 patients with delayed treatment.ConclusionsIn this study the incidence of icing weather conditions was substantial compared to all HEMS missions in year 2017. The delay in definitive treatment was accentuated among trauma and internal medicine patients. During the 1-year study period many patients whose definitive treatment was delayed would have had a notable (> 60 min) time saved by helicopter transport. A helicopter equipped with an adequate ice protection system for the weather conditions in Northern Finland would have shortened the delay in patients’ definitive treatment significantly.

Integration of human factors into the design process of helicopter maintainability

AbstractThe integration of human factors and ergonomics (HFE) in maintenance activities may improve the working conditions of maintenance operators by reducing errors and accidents. Maintainability takes into account HFE in the aeronautics industry to anticipate the design of the aircrafts, following the CPA regulation FAR/CS‐25.1309, for large transport category. For the helicopter field, there are no official recommendations but the rotorcraft industry tries to integrate HFE into its design phases of maintainability to increase flight safety. Without a standard framework, the aviation industries (plane and helicopter) develop their own way of working and requirements. Furthermore, previous studies highlight the lack of compromise between the design and HFE criteria in maintainability. The purpose of this paper is, therefore, to investigate how HFE is integrated within all steps of the design process in the maintainability department of helicopter manufacturers in France. The ergonomic skills and knowledge of stakeholders were studied and the associated tools to evaluate the HFE criteria were surveyed. We observed that maintainability stakeholders underutilize powerful simulation tools, which are sufficient for and efficient at performing HFE analysis. Additionally, it was reported that understanding of HFE information weakened over the course of the milestones of the design project progressed. Our conclusion details the need to provide a simple methodology or rather a relevant tool that helps maintainability stakeholders to integrate HFE in a homogenous way along all the design project milestones.

Prioritization of product-service business model elements at aerospace industry using analytical hierarchy process

The paper aims to propose a business model framework under a product-service approach in the aerospace industry based on the main elements identified in the literature. Through a Multi Criteria Decision Method - the AHP (Analytical Hierarchy Process) - a set of elements was prioritized by nine specialists from the industry for establishing a fractional ownership business model in the civilian market of a Brazilian helicopter manufacturer. The results indicate ten elements for composing the business model framework, in which value proposition, customers and culture are part of it. The practical implication of this study indicates an opportunity to boost the integration of product and service in the aerospace industry, specially using AHP for business model construction. For future researches, others companies can be considered in the study. In addition to manufacturers, service firms or operators of helicopters can compose the specialists group. Besides, another Multi Criteria Decision Method can be applied aiming to do a comparative analysis of the results among the methods. The paper fulfills a gap about how business model is structured in a product-service integration context, especially in an industry originally considered as manufacturer.

ГЕОМЕТРИЧЕСКОЕ МОДЕЛИРОВАНИЕ ТЕХНИЧЕСКИХ ПОВЕРХНОСТЕЙ ИЗБРАННЫХ КЛАССОВ

In the work there is offered a generalized method
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 industry. It is approbated at lecturing subjects “Engineering
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 with specialties “Aircraft and Helicopter Manufacturing”,
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Epidemiology of helicopter accidents: Trends, rates, and covariates

The objective of this work is to provide a better understanding of helicopter accidents and to identify important areas for different stakeholders to focus their attention and resources for accident prevention. To this end, we undertook Record Linkage of two federal data sources: the FAA civil helicopter registration data and the NTSB accident data. First, the analysis of accident rates and trends shows little progress in accident prevention over the last decade. Second, we find that helicopter accident rates vary significantly by number of main rotor blades, with the four- and six-bladed helicopters having the safest track record. Third, we show that accident rates vary by engine types when controlling for the number of blades. For example, the combination of reciprocating engine and three-bladed (3B) helicopters is associated with one of the highest accident rates. We further examine differences in accident rates between single and twin-engine helicopters, controlling for engine type and number of blades. The worst-in-class in terms of rates are the 5B and 6B single-engine turboshaft helicopters, whereas the worst-offenders in terms of contributing to the total count of accidents are the single-engine 2B reciprocating and turboshaft helicopters. The 4B single-engine turboshaft occupy a safety sweet spot and have the lowest accident rates of all single-engine helicopters. We provide risk ratios for pairwise comparisons and 95% confidence intervals for all accident rates, and discuss possible confounders for these results. The issues here examined lend themselves to a rich set of technical and operational implications, and they deserve careful attention from helicopter operators, regulators, and manufacturers. Any serious effort to improve helicopter safety will entail action on multiple safety levers, including design, operational, and policy-related ones. These actions should be evidence-based and they require better helicopter accident investigations and better data.

The influence of energy attenuating aircraft seats on lumbar spine burst fractures: an incident reconstruction

Many injuries from helicopter crashes are due to large vertical loads transferred from the ground, through the aircraft and to the spine of seated occupants. Helicopter manufacturers aim to reduce these loadings through energy-attenuating seats. This report details the methodology used to reconstruct an incident and determine the loads experienced by the passengers, specifically a passenger who sat in the rear right seat of the helicopter and suffered a lumbar burst fracture. (a) analysing the injury; (b) analysing damage to the seat to estimate impact forces, and (c) analysing the mechanism of failure of the landing strut to calculate the impact angle and validate the impact forces at the seat. Once the range of force experienced by the passenger was estimated, the effect of the choice of seat was investigated to determine if this injury could have been avoided using seats commercially available at the time of helicopter manufacturing.

Control of the through-thickness temperature distribution in carbon composite aerospace parts during induction welding

The increasing content of thermoplastic composites in the aerospace industry requires the application of new joining technologies. Their main assembly advantage is rivetless joining, which needs to be examined in greater detail in order to compensate the higher costs of these materials. Induction welding is already used in aerospace industry and shows a high potential for the application in helicopter manufacturing. In order to implement this technology in serial production, the main requirement is to determine and control the process temperature distribution. A wide range of literature describing various approaches that characterize the aforementioned temperature distribution exists. Although all approaches validate their findings by temperature measurement on the surfaces of their parts, their results seem inconsistent due to different results. In this article, a new approach is presented and validated by interlaminar temperature measurement. Based on this new approach, for induction welding, effects that are not yet described are discussed. Hereby, cooling of the surface by air jets is investigated as a mean to influence the thermal effects of the induction welding process.

Examining the stability derivatives of a compound helicopter

ABSTRACTSome helicopter manufacturers are exploring the compound helicopter design as it could potentially satisfy the new emerging requirements placed on the next generation of rotorcraft. It is well understood that the main benefit of the compound helicopter is its ability to reach speeds that significantly surpass the conventional helicopter. However, it is possible that the introduction of compounding may lead to a vehicle with significantly different flight characteristics when compared to a conventional helicopter. One method to examine the flight dynamics of an aircraft is to create a linearised mathematical model of the aircraft and to investigate the stability derivatives of the vehicle. The aim of this paper is to examine the stability derivatives of a compound helicopter through a comparison with a conventional helicopter. By taking this approach, some stability, handling qualities and design issues associated with the compound helicopter can be identified. The paper features a conventional helicopter and a compound helicopter. The conventional helicopter is a standard design, featuring a main rotor and a tail-rotor. The compound helicopter configuration features both lift and thrust compounding. The wing offloads the main rotor at high speeds, whereas two propellers provide additional propulsive thrust as well as yaw control. The results highlight that the bare airframe compound helicopter would require a larger tailplane surface to ensure acceptable longitudinal handling qualities in forward flight. In addition, without increasing the size of the bare airframe compound helicopter’s vertical fin, the Dutch roll mode satisfies the ADS-33 level 1 handling qualities category for the majority of the flight envelope.

Test and Simulation of an Active Vibration Control System for Helicopter Applications

A significant source of vibration in helicopters is the main rotor system, and it is a technical challenge to reduce the vibration in order to ensure the comfort of crew and passengers. Several types of passive devices have been applied to conventional helicopters in order to reduce the vibration. In recent years, helicopter manufacturers have increasingly adopted active vibration control systems (AVCSs) due to their superior performance with lower weight compared with passive devices. AVCSs can also maintain their performance over aircraft configuration and flight condition changes. As part of the development of AVCS software for light civil helicopter (LCH) applications, a test bench is constructed and vibration control tests and simulations are performed in this study. The test bench, which represents the airframe, is excited using a pair of counter rotating force generators (CRFGs) and a multiple input single output (MISO) AVCS that consists of three accelerometer sensors and a pair of CRFGs; a filtered-x least mean square (LMS) algorithm is applied for the vibration reduction. First, the vibration control tests are performed with uniform sensor weights; then, the change in the control performance according to changes in the sensor weight is investigated and compared with the simulation results. It is found that the vibration control performance can be tuned through adjusting the weights of the three sensors, even if only one actuator is used.

Towards greener helicopters

Environment protection is now considered as a key point by the population and has become a political and economical stake as related in Kyoto protocol signature which defines objectives for greenhouse effect gases reduction. Based on greenhouse effect gases like carbon dioxide (CO2) and increasing temperature, European Union has implemented an Emission Trading System to give each country emission CO2 targets and a trade tool to share tons of CO2. The European Union has fixed specific objectives to aeronautic section via the Advisory Council for Aviation Research and innovation in Europe. Helicopter community is implementing qualitative tools called environmental metrics to measure the achieved progress. Environmental acoustic metrics have been defined based on noise levels and colors, related to ICAO limitation levels and in the frame of European research project Cleansky. Similarly, environmental metrics for CO2 emission have also been defined based on fuel consumption values and colors. The more the helicopter is environment friendly, the greener the metric. In anticipation of environmental requirements strengthening, some helicopter manufacturers have launched research studies on environmental technologies like Friendcopter project to develop low acoustic level flight procedures based on HELENA computations, or engine manufacturers have invested in technological research projects to improve engine performance and environment impact. In addition, the helicopter product full life cycle is globally considered under the international standard ISO 14001 for environment management as well as human health and environment protection in comparison to REACH European regulation. The reader of the article will certainly notice that the challenge is now: “Towards greener helicopters”.

Simulation of Flow around Isolated Helicopter Fuselage

Low fuselage drag has always been a key target of helicopter manufacturers. Therefore, this paper focuses on CFD predictions of the drag of several components of a typical helicopter fuselage. In the first section of the paper, validation of the obtained CFD predictions is carried out using wind tunnel measurements. The measurements were carried out at the Kazan National Research Technical University n.a. A. Tupolev. The second section of the paper is devoted to the analysis of drag contributions of several components of the ANSAT helicopter prototype fuselage using the RANS approach. For this purpose, several configurations of fuselages are considered with different levels of complexity including exhausts and skids. Depending on the complexity of the considered configuration and CFD mesh both the multi-block structured HMB solver and the unstructured commercial tool Fluent are used. Finally, the effect of an actuator disk on the predicted drag is addressed.