Coupled flight dynamics and CFD - demonstration for helicopters in shipborne environment

The development of high-performance computing and computational fluid dynamics methods have evolved to the point where it is possible to simulate complete helicopter configurations with good accuracy. Computational fluid dynamics methods have also been applied to problems such as rotor/fuselage and main/tail rotor interactions, performance studies in hover and forward flight, rotor design, and so on. The GOAHEAD project is a good example of a coordinated effort to validate computational fluid dynamics for complex helicopter configurations. Nevertheless, current efforts are limited to steady flight and focus mainly on expanding the edges of the flight envelope. The present work tackles the problem of simulating manoeuvring flight in a computational fluid dynamics environment by integrating a moving grid method and the helicopter flight mechanics solver with computational fluid dynamics. After a discussion of previous works carried out on the subject and a description of the methods used, validation of the computational fluid dynamics for ship airwake flow and rotorcraft flight at low advance ratio are presented. Finally, the results obtained for manoeuvring flight cases are presented and discussed

The Queen Elizabeth Class Aircraft Carriers: Airwake Modelling and Validation for ASTOVL Flight Simulation

This paper outlines progress towards the development of a high-fidelity piloted flight simulation environment for the UK’s Queen Elizabeth Class (QEC) aircraft carriers which are currently under construction. It is intended that flight simulation will be used to de-risk the clearance of the F-35B Lightning-II to the ship, helping to identify potential wind-speeds/directions requiring high pilot workload or control margin limitations prior to First of Class Flight Trials. Simulated helicopter launch & recovery trials are also planned for the future. The paper details the work that has been undertaken at the University of Liverpool to support this activity, and which draws upon Liverpool’s considerable research experience into simulated launch and recovery of maritime helicopters to single-spot combat ships. Predicting the unsteady air flow over and around the QEC is essential for the simulation environment; the very large and complex flow field has been modelled using Computational Fluid Dynamics (CFD) and will be incorporated into the flight simulators at the University of Liverpool and BAE Systems Warton for use in future piloted simulation trials. The challenges faced when developing airwake models for such a large ship are presented together with details of the experimental setup being prepared to validate the CFD predictions. Finally, the paper describes experimental results produced to date for CFD validation purposes and looks ahead to the piloted simulation trials of aircraft launch and recovery operations to the carrier

The Development and Use of A Piloted Flight Simulation Environment for Rotary-Wing Operation to the Queen Elizabeth Class Aircraft Carriers

Flight simulation is being used to inform the First of Class Flight Trials for the UK’s new Queen Elizabeth Class (QEC) aircraft carriers. The carriers will operate with the Lockheed Martin F-35B Lightning II fighter aircraft, i.e. the Advanced Short Take-Off and Vertical Landing variant of the F-35. The rotary wing assets that are expected to operate with QEC include Merlin, Wildcat, Chinook and Apache helicopters. An F-35B flight simulator has been developed and is operated by BAE Systems at Warton Aerodrome. The University of Liverpool is supporting this project by using Computational Fluid Dynamics (CFD) to provide the unsteady air flow field that is required in a realistic flight simulation environment. This paper is concerned with a research project that is being conducted using the University’s research simulator, HELIFLIGHT-R, to create a simulation environment for helicopter operations to the QEC. The paper briefly describes how CFD has been used to model the unsteady airflow over the 280m long aircraft carrier and how this is used to create a realistic flight simulation environment. Results are presented from an initial simulation trial in which test pilots have used the HELIFLIGHT-R simulator to conduct simulated helicopter landings to two landing spots on the carrier, one in a disturbed air flow and the other in clean air. As expected, the landing to the spot in disturbed air flow requires a greater pilot workload, shows greater deviation in its positional accuracy and requires more control activity. This initial trial is the first of a planned series of simulated helicopter deck landings for different wind angles and magnitudes

A Role for Virtual Engineering in Engineering Skills Development

The paper will address how the Problem-Based-Learning (PBL) approach developed at Liverpool for undergraduate and graduate students has been extended to the continued professional development (CPD) of practising engineers. As the complexity of engineering systems grows, engineers increasingly need to be able to use a range of tools to undertake synthesis and analysis, address affordability goals, and reduce risk as they work in the various phases of the engineering life-cycle. To assist engineers operate successfully within this product life-cycle, there have been significant developments in modelling and simulation tools. Integrating these tools in a Virtual Engineering (VE) environment allows engineers to examine potentially conflicting requirements within the different phases of the life-cycle, to develop a co-ordinated approach to requirements capture and product design through to identifying costly problems that might occur later in the development and operations phases. Technical skills development to use these tools is critical in this process. This paper presents the experiences, learning outcomes and lessons gleaned in the development and implementation of bespoke rotorcraft engineering training programmes at The University of Liverpool. The programmes were designed using a Problem Based Learning (PBL) framework where knowledge and skills are gained through solving problems. Four cases studies are presented in the paper, demonstrating how this PBL/VE approach has been used effectively in training programmes. Consideration is given to the future use of VE tools, together with some challenges for their successful application

Virtual Engineering in Skills Acquisition and Development in the Career of the Rotorcraft Engineer

As the complexity of engineering systems grows, engineers increasingly need to be able to use a range of tools in order to reduce the costs, and associated risks, as they work in the various phases of the engineering life-cycle. In order to help engineers operate successfully within this product lifecycle, there have been significant developments in modelling simulation tools. Integrating these tools in a Virtual Engineering (VE) environment allows engineers to examine the potentially conflicting requirements of the different phases of the life-cycle, to develop a co-ordinated approach to requirements capture and product design through to identifying potential costly problems that could occur later in the development and operations phases. Technical skills development to use these tools is key to this process. This paper presents the experiences, learning outcomes and lessons learned in the development and implementation of bespoke rotorcraft engineering training programmes. The programmes were designed using a Problem Based Learning (PBL) framework where knowledge and skills are gained through solving problems. Four cases studies are presented in the paper, demonstrating how this PBL/VE approach can be used in the training programmes. Consideration of the future use of VE tools is provided together with future challenges for their successful application

Initial progress in developing a predictive simulation tool to inform helicopter ship operations

The study presented in this paper is part of the project underway at the University of Liverpool (UoL) to develop a high-fidelity simulation tool that has a predictive capability to inform and support Ship Helicopter Operating Limit (SHOL) trials. The paper reports preliminary progress in developing a desktop based predictive simulation tool that uses a pilot modelling technique to represent the integrated Helicopter Ship Dynamic Interface (HSDI) simulation environment. The approach consists of: a pursuit pilot model, linearized vehicle dynamics, full standard deck landing task, ship motion and equivalent ship airwake turbulence. The tool was initially tested by performing a simplified land-based task for validation purposes. It was then used in HSDI simulations of an SH-60B helicopter operating to a generic single-spot naval frigate. Time and frequency domain comparisons have been made between the predictive tool and piloted simulation flight trials conducted in UoL's Heliflight-R full-motion simulator. It was found that the performance of the predictive tool in maintaining sufficient clearance between the aircraft and the ship whilst rejecting airwake disturbances is well within the desired task performance boundaries. These preliminary investigations show that the tool is capable of representing the dynamics of a pilot in the HSDI environment

Simulation study of helicopter ship landing procedures incoporating measured flow data

The aim of this article is to investigate the use of inverse simulation to help identify those regions of a ship's flight deck which provide the safest locations for landing a rotorcraft in various atmospheric conditions. This requires appropriate information on the wind loading conditions around a ship deck and superstructure, and for the current work, these data were obtained from wind tunnel tests of a ship model representative of a typical helicopter carrier/assault ship. A series of wind tunnel tests were carried out on the model in the University of Glasgow's 2.65 × 2.04 m wind tunnel and three-axis measurements of wind speed were made at various locations on the ship deck. Measurements were made at four locations on the flight deck at three different heights. The choice of these locations was made on the basis of preliminary flow visualization tests which highlighted the areas where the most severe wind effects were most likely to occur. In addition, for the case where the wind was from 30 to starboard, measurements were made at three further locations to assess the extent of the wake of the superstructure. The generated wind profiles can then be imposed on the inverse simulation, allowing study of the vehicle and pilot response during a typical landing manoeuvre in these conditions. The power of the inverse simulation for this application is demonstrated by a series of simulations performed using configurational data representing two aircraft types, a Westland Lynx and a transport helicopter flying an approach and landing manoeuvre with the worst atmospheric conditions applied. It is shown from the results that attempting to land in the area aft of the superstructure in a 30° crosswind might lead to problems for the transport configuration due to upgusts in this area. Attempting to perform the landing manoeuvre in an aggressive manner is also shown to lead to diminished control margin in higher winds