Bell Helicopter Textron (Canada)

Due to the growing requirements to the fleet in terms of increasing the efficiency of solving assigned tasks, taking into account the ever-increasing operational situation, increased use of unmanned aerial vehicles is required, including small and medium-displacement ships. Thus, an important trend in the development of helicopter-type unmanned aerial vehicles (HT UAVs) is their adaptation to ship-based conditions. The key problem of adaptation is ensuring the take-off and landing on the ship’s landing pad (runway). This article discusses the influence of ship-based conditions, the most important of which is ship’s pitching, and requirements for performing takeoff and landing operations, including the need to adapt to forced landing systems, on the formation of the design of the landing gear of a HT UAV, and formulates the design specifications typical to the landing gear of a shore-based aircraft. At the same time, to study the dynamic and static compatibility of the HT UAV with the ship, deterministic or probabilistic characteristics of the ship’s pitching should be set in the form of pitching amplitudes and periods, pitching spectral densities, variances of displacements and velocities of the runway center, as well as displacements, velocities and accelerations in the runway center. Based on the specified parameters, the kinematics of the movement of the center of the runway and its spatially complex positions are calculated to solve the problem of dynamic compatibility of the VTOL UAV with the ship. Dynamic compatibility includes determining the stability and controllability of the HT UAV, unwinding and stopping the main rotor, take-off and landing, and transporting the HT UAV along the runway. The existing and prospective basic design schemes of the skid landing gear are divided into four main types and evaluated for compliance with the specifics of operation on the ship, special attention is paid to the possibility of adaptation to forced landing systems on deck. Based on the evaluation results, a design scheme of the landing gear for a promising HT parallelogram-lever type UAV with an external shock absorber is proposed. As a confirmation of the compliance of the proposed scheme with the formulated requirements, the results of the calculation of the dynamic landing gear model during landing and rolling, performed in the Simcenter Motion software package, are presented. The proposed scheme can be implemented for both HT UAVs and manned ship-based and shore-based helicopters.

Low job satisfaction amongst emergency physicians is a significant risk to career sustainability. Anecdotal evidence suggests that prehospital and retrieval medicine (PHARM) physicians experience relatively high job satisfaction. The objective of this qualitative study was to explore the research question: 'What influences job satisfaction and sustainability for emergency physicians who maintain dual roles in PHARM and the emergency department?' Eligible emergency physicians from Australia and New Zealand were interviewed in-depth about their experiences and perceptions of job satisfaction and sustainability. The research team applied experiential knowledge and an inductive analytic approach to construct a conceptual understanding of the physicians' job satisfaction from the data, including factors contributing to career sustainability. Our sample included 11 participants, six from Australia and five from New Zealand. We identified six key themes influencing job satisfaction: workload, job factors, personal factors, focus on well-being, culture and management and bureaucracy. These are explored in detail, along with ideas on career sustainability. The nature of emergency medicine work remains inherently satisfying for participants in this study but is influenced by the culture and current working conditions found in many emergency departments, particularly when these factors impact the standard of clinical care physicians feel they can provide. Our findings offer practical guidance on protective factors for job satisfaction and sustainability, including fractional appointments, diversity and flexibility of practice, continuous professional development and access to professional supervision or peer support. Preserving career longevity in emergency medicine requires the implementation of evidence-based, sustainable initiatives.

This paper summarizes a industry-academic collaborative project to evaluate Out-of-Autoclave (OOA) prepreg material and its behavior during processing of complex parts. This was done by manufacturing two crew door demonstrator parts; one made from traditional epoxy autoclave cure prepreg while the other was with OOA prepreg. The goal was to evaluate the main differences between manufacturing with OOA prepreg versus standard prepreg material. The results from this study showed the impact of using sharp radii and difficult corners for both processing methods. Ultimately, this project established the capability to manufacture a part with OOA material that was of similar quality to the part manufactured with the traditional epoxy prepreg material.

Creep is an important factor that contributes to the clamp load loss and tightness failure of bolted joints with and without gaskets over time. Retightening of the joint can be expensive and time consuming; therefore, it is an undesirable solution. Currently, most efforts are put towards reducing load losses directly by tightening to yield, improving material creep properties, or making joint less rigid. An alternative solution of current interest is the use of bolts in shape memory alloys (SMAs). However, very few experimental studies are available, which demonstrate the feasibility of these alloys. The objective of this study is to explore the benefit of shape memory and superelasticity behavior of an SMA stud to recover load losses due to creep and thermal exposure of a gasket in a bolted-joint assembly. This paper explores several venues to investigate and model the thermomechanical behavior of a bolted joint with a nickel–titanium SMA stud. A stiffness-based analytical model which incorporates the Likhachev model of SMA is used as a representation of an experimental bolted-joint assembly. Based on this model, the rigidity of the experimental setup is optimized to make the best use of the SMA properties of the stud. This analytical model is compared with a finite element model, which also implements the Likhachev's material law. Finally, an experimental test bench with a relatively low stiffness representative of standard flanges is used, with and without gaskets to demonstrate the ability of the SMA stud to recover load losses due to gasket creep.

Recurring cost has become a critical driver in the design of helicopter airframes, and although composite materials have become widely used in aircraft structures, the hand lay-up manufacturing process in many cases prevents these applications from being cost-effective. Automated manufacturing technologies promise not only reduced production costs but also higher quality, repeatable parts. The introduction of existing automated manufacturing techniques and technologies from industries such as the automotive sector into aerospace can be challenging due to the unique product characteristics as well as the stringent certification and quality control requirements of the industry. The aerospace industry is a low-volume, high value production environment where "hand-made" products are produced by highly experienced and qualified trades-people. Both metallic and composite components are subjected to precise manufacturing control and documentation requirements. The introduction of automated manufacturing technologies must be done in such a way as to respect these often demanding constraints. The introduction of automation to industrialized processes impacts not only the way parts are produced, but also the way they are designed. Successful composite design and manufacturing automation in the aerospace industry requires the engineering designer and analyst to become increasingly involved in the manufacturing of the product, as machine limitations and producibility become increasingly important drivers for design. This paper presents an overview of a development project intended to evaluate the effectiveness and benefits of the automated fibre placement technology through the design, prototype build and testing of a composite tailboom. The discussion centres on the "design for manufacturing" concept and provides a perspective on the project objectives, material and process selection and trade-offs, geometric and structural considerations, and component assembly and fastening.

A damage tolerance (DT) testing method is necessary to support DT design and certification and to simplify flight test monitoring of titanium yoke flexure components. A building block testing program was conducted. While the validity of the basic approach was confirmed by the testing results, a number of aspects have been revealed that are of primary importance to designing and certifying titanium yoke flexure components in particular, and any titanium rotorcraft component in general. In common practice, the through-crack data are used as material properties for crack growth analysis, although the majority of crack growth in rotorcraft components is observed to occur in part-through mode. The application of through-crack data to surface crack of a titanium part needs to be evaluated when taking the surface conditions into account. This is because the crack growth behavior of titanium components was found to be sensitive to microstructure changes and residual stresses that are induced during machining and surface treatment. Underestimating these factors and using through-crack data to predict the part-through crack growth can lead to an incorrect conclusion for a titanium component. Furthermore, unevenness of part-through crack growth between depth and surface growth needs to be considered differently for the basic material in terms of material form and heat treatment, and for the components with machined and shot-peened surfaces. This paper presents considerations supported by testing that lead to improvements in testing and analysis of rotorcraft titanium components and will allow for better use of this material for rotorcraft components.

<div class="htmlview paragraph">Design limits in aerospace are constantly being challenged forcing engineers to look for materials and material combinations that will provide the strength needed, yet meet the lightweight requirements demanded throughout the industry. These material combinations provide demanding and unique challenges to all involved in the development of robust, reliable assembly processes. As advancements are pushed forward in aircraft materials, advancements must also be made in the technologies/methodologies used to drill close tolerance holes in these complex materials. These advancements will be discussed in the following paper.</div> <div class="htmlview paragraph">Common stack-ups of aircraft materials include various combinations of graphite, aluminum, and titanium. Many problems arise when trying to drill the different combinations of these materials due to the extreme differences in physical properties. The primary factors considered in our studies were feed rates, cutter speed, and preferred cutter geometries for each material. In addition, the effects of forced air along with various coolants were studied and analyzed for possible application.</div>

Piezoelectric stacks can normally take significant compressive loads but cannot tolerate tension. Therefore, conventional piezoelectric stack actuators are mainly designed for the push-only actions and usually incorporate a compressive preload mechanism to protect the stack from experiencing tensile stresses. A common preload method is to include a mechanical spring in parallel with the stack, which may reduce the free stroke capability of the actuator and affect performance. In this research, a new bi-directional (can operate in both push and pull directions) actuator design is introduced, utilizing a pair of matching piezoelectric stack elements within the actuator housing. The stack elements are integrated in a mechanically opposing configuration and are electrically operated out of phase. To examine the performance advantages of the new concept, both analytical and experimental studies are conducted. The dual-stack actuator is compared with two internally preloaded single stacks integrated in a parallel configuration, thus both actuator systems are utilizing equivalent volumes of the piezoelectric material. The analysis indicates that the dual-stack actuator produces greater free stroke, output energy, and energy efficiency than the two parallel single-stack actuators. For experimental evaluations, a dual-stack actuator and an internally preloaded single-stack actuator are fabricated using the same materials, similar construction techniques, and the same piezoelectric stack elements. A testing procedure is formulated to determine the free stroke and blocked force of both the actuators. The experimental results verified the trends observed in the analytical predictions. That is, in addition to being bi-directional, the dual-stack arrangement can produce higher free stroke, blocked force, output energy, specific output energy, and energy efficiency, as compared to two preloaded, parallel-configured single-stack actuators. It is also concluded that by tailoring the dual-stack actuator, it will be 62% volume and weight of a conventional single-stack actuator that produces the same amount of blocked force and free strain.

In Part II of this two-part study, system simulations and experimental correlations of a Shape Memory Alloy (SMA) based vibration isolation device (briefly described in Part I) has been presented. This device consists of layers of preconstrained SMA tubes undergoing pseudoelastic transformations under transverse dynamical loading. In Part II, detailed description of the prototype vibration isolation device, its experimental setup, and actual experimental test results are presented. An extensive parametric study has been conducted on a nonlinear hysteretic dynamical system, representing this vibration isolation device utilizing a physically based simplified SMA model and a Preisach model (an empirical model based on system identification) developed in Part I. Both the physically based simplified SMA model and the modified Preisach model have been utilized to perform experimental correlations with the results obtained from actual testing of the device. Based on the investigations, it has been shown that variable damping and tunable isolation response are major benefits of SMA pseudoelasticity. Correlation of numerical simulations and experimental results has shown that large amplitude displacements causing phase transformations of SMA components present in such a device are necessary for effective reduction in the transmissibility of such dynamical systems. It has also been shown that SMA-based devices can overcome performance trade-offs inherent in typical softening spring-damper vibration isolation systems. In terms of numerically predicting the experimental results, it has been shown that the Preisach model gave relatively accurate results due to better modeling of the actual SMA tube behavior. However, for a generic parametric study, the physically based simplified SMA model has been found to be more useful as it is motivated from the constitutive response of SMAs and hence, could easily incorporate different changes in system conditions.