The oil and gas industry relies heavily on helicopters for transporting personnel and cargo to and from offshore installations and support vessels. A growing number of offshore helicopter operations are to moving helidecks, which include large vessels such as FPSOs, drill ships, and semi-submersibles, as well as smaller service vessels. Landing a helicopter on a moving helideck presents additional challenges to those faced on fixed helidecks, not only at the point of touchdown but also for the entire period the helicopter remains on the helideck.The UK Civil Aviation Authority (CAA), on behalf of the joint CAA/industry Helicopter Safety Research Management Committee has led a comprehensive programme of research over a number of years, aimed at improving the operational safety of helicopters landing on moving helidecks. The work focused on the aspect of the stability of helicopters once landed on a moving helideck, this being the main source of in-service incidents and accidents as evidenced in the Mandatory Occurrence Reports. The project culminated in the development of a new standard for Helideck Monitoring Systems (HMS), which was published by the Helideck Certification Agency in April 2018 with an implementation compliance date of 31 March 2021. Operations to moving helidecks not equipped with HMS meeting the new standard will be restricted to stable deck conditions from this date. The research underpinning the new standard is presented in two papers.This paper (Part A), presents the analytical approach that has been developed to model the Reserve of Stability (ROS) for all modes of failure of a helicopter on a moving offshore helideck.The analytical model covers all modes of on-deck failure (roll-over and sliding), for any nose wheel tricycle undercarriage helicopter. The mathematical expressions that have been derived are remarkably simple, physically intuitive, and make the relative contribution of all the destabilising factors easy to understand and assess. These analytical expressions can be used to calculate the ROS of any helicopter in real time, as well as for calculating an envelope of safe operating limits.This approach has many advantages compared to conventional ‘black box’ modelling methods. The main advantage is that it simplifies the modelling of the destabilising effect of helideck motion and allows the most salient parameters governing on-deck ROS to be defined, namely the Measure of Motion Severity, the instantaneous wind speed as the Measure of Wind Severity, and the wind direction relative to the helicopter (Relative Wind Direction).The main rotor lift generated during the time the helicopter remains on-deck (at Minimum Pitch on Ground, MPOG) has been one of the most important unknowns that this research programme has sought to address. An empirical model for estimating the lift at MPOG has been developed, based on experimental and field data. Practical methods for quantifying fuselage wind drag and the vertical position of the centre of gravity were also developed, which allow different helicopter types to be assessed without recourse to helicopter Original Equipment Manufacturer (OEM) proprietary information or models. Finally, a comparison and evaluation of the model against dedicated field trial measurements is presented, together with a discussion of the modelling strengths and weaknesses, and recommendations for further work.

中文翻译：

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CAA 研究计划 - 将直升机运营转移到海上直升机平台

石油和天然气行业严重依赖直升机在海上设施和支援船之间运送人员和货物。越来越多的海上直升机作业涉及移动直升机甲板，其中包括大型船舶，如 FPSO、钻井船和半潜式船舶，以及较小的服务船。将直升机降落在移动的直升机甲板上对那些在固定直升机甲板上面临的挑战提出了额外的挑战，不仅在着陆点，而且在直升机停留在直升机甲板上的整个期间。英国民航局 (CAA)，代表CAA/工业直升机安全研究管理委员会多年来一直领导一项综合研究计划，旨在提高直升机降落在移动直升机甲板上的操作安全性。这项工作的重点是直升机降落在移动直升机甲板上的稳定性方面，这是强制性事故报告中证明的在役事故和事故的主要来源。该项目最终制定了直升机甲板监控系统 (HMS) 的新标准，该标准由直升机甲板认证机构于 2018 年 4 月发布，实施日期为 2021 年 3 月 31 日。未配备 HMS 的移动直升机甲板符合新标准从该日期起，标准将仅限于稳定的甲板条件。支持新标准的研究在两篇论文中进行了介绍。本文（A 部分）介绍了已开发的分析方法，该分析方法用于模拟直升机在移动的海上直升机甲板上的所有故障模式的稳定性储备 (ROS)。分析模型涵盖所有前轮三轮起落架直升机的所有甲板故障模式（翻车和滑动）。所推导出的数学表达式非常简单，物理上直观，并且使所有不稳定因素的相对贡献易于理解和评估。这些解析表达式可用于实时计算任何直升机的 ROS，以及计算安全操作限制的包络线。与传统的“黑匣子”建模方法相比，这种方法具有许多优点。主要优点是它简化了直升机甲板运动不稳定效应的建模，并允许定义控制甲板上 ROS 的最显着参数，即运动严重性测量，瞬时风速作为风严重性测量，和相对于直升机的风向（相对风向）。在直升机停留在甲板上期间产生的主旋翼升力（在地面最小俯仰角，MPOG）一直是该研究计划最重要的未知数之一试图解决。基于实验和现场数据，已经开发了一个用于估算 MPOG 升力的经验模型。还开发了量化机身风阻和重心垂直位置的实用方法，允许在不求助于直升机原始设备制造商 (OEM) 专有信息或模型的情况下评估不同的直升机类型。最后，介绍了模型与专门的现场试验测量的比较和评估，以及对建模优势和劣势的讨论，