Dynamic Mechanics of Rigid Helicopter Systems During Ditching

Aircraft and helicopter often fly above open waters and thus have to observe regulations to ensure safe water landing under emergency conditions. This practice is also referred to as ditching - one of several types of slamming problems that are under review by the current regulations of the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA). Ditching is related to the controlled landing on water, with distinctive features such as hydrodynamic slamming loads, complex hydromechanics at tremendous forward speeds, as well as the interaction of multiphase fluid dynamics (air, water, and vapor). This paper presents the knowledge on system mechanics during helicopter ditching. The discussion begins with the fundamental kinetics of the rigid body, and then delves into dynamic relations to describe the effect of forces on motions. In the end, the paper discusses several relevant theories to further contribute to the understanding of the problem of impact

Investigation of Numerical Hydrodynamic Performance of Deformable Hydrofoil (Applied on Blade Propeller)

The hydrofoil is a hydro-lifting surface that significantly contributes to marine transportation such as a boat, ship, and submarine for its movement and maneuverability. The existing hydrofoils are in fixed-shaped National Advisory Committee for Aeronautics (NACA) profiles, depending merely on the variation of Angle of Attack (AOA) such as rudder, hydroplane, and propeller blade. This research is concerned with the deformable hydrofoil that aims at modifying its NACA profile rather than its AOA. However, there is still a lack of knowledge about designing an appropriate deformable hydrofoil. Therefore, a numerical investigation of hydrodynamic characteristics for selected hydrofoils was conducted. After undergoing the 2D numerical analysis (potential flow method) at specific conditions, several NACA profiles were chosen based on the performance of NACA profiles. NACA 0017 was selected as the initial shape for this research before it deformed to the optimized NACA profiles, NACA 6417, 8417, and 9517. The 3D CFD simulations using the finite volume method to obtain hydrodynamic characteristics at 0 deg AOA with a constant flow rate. The mesh sensitivity and convergence study are carried out to get consistent, validated, and reliable results. The final CFD modeled for propeller VP 1304 for open water test numerically. The results found that the performance of symmetry hydrofoil NACA 0017 at maximum AOA is not the highest compared to the other deformed NACA profiles at 0 deg AOA. The numerical open water test showed that the error obtained on K.T., K.Q., and efficiency is less than 8% compared to the experimental results. It shows that the results were in good agreement, and the numerical CFD setting can be used for different deformed profiles in the future

The effect of emergency floatation system (EFS) on helicopter stability during ditching

In recent times, there has been a notable increase in economic activities in the world’s oceans. This growth in oceanic economic activity is attributed to various natural resources, such as fish, minerals, and energy reserves, which promise significant economic gains. In many cases, helicopters have proven valuable for efficient and flexible transportation due to their ability to navigate challenging terrain and reach remote locations. They are often used for various transportation tasks, including emergency medical services, search and rescue operations, offshore oil rig transportation, and corporate travel. Flying across the ocean poses a significant risk due to the absence of a landing platform throughout the journey. In an emergency, there may not be a safe place to land, potentially endangering the lives of those on board. Additionally, aircraft must be equipped with advanced technology and safety features to mitigate potential risks and ensure a successful journey across the vast expanse of the ocean. The aviation authority’s studies on using Emergency Floatation Systems (EFS) have highlighted the need for improvements to prevent fatalities resulting from helicopter ditching. Despite implementing the Emergency Floatation System (EFS) in helicopters, several reports indicate that fatalities still occur, often related to the helicopter’s stability during ditching. This suggests that while safety measures have been put in place, there may be a need for further improvements in helicopter design and safety protocols to minimize the risk of accidents and fatalities. This research utilizes simulation techniques to measure the stability performance of helicopters during water ditching quantitatively. This study aims to optimize the configuration of EFS to prevent capsizing, with a particular focus on the role of weather conditions in contributing to EFS failures. Through careful analysis and consideration of this crucial factor, the research aims to identify and implement strategies to enhance EFS operations’ safety and stability, ultimately improving overall performance and reducing the risk of catastrophic incidents

Measuring severity of downtime influence factors to naval ship operational availability: a Delphi study

Rapid development in shipbuilding and ship repair calls for “cradle to grave” approach in ship maintenance to maximize growth. Organisations typically struggle to balance ideal maintenance philosophies against ongoing cost reductions whilst maintaining high availability of vessels. Due to limited research on Downtime Influence Factors (DIFs) on ships, improvement efforts could not be allocated precisely in tackling issues involving combined “human and equipment” aspects impacting ship availability. The purpose of this study is to generate RMN ship maintenance DIFs and their severity measures via a Delphi approach. The research pinpointed to 15 Severe DIFs as the key problem areas for prioritization of efforts in improving RMN ship availability