For many years there has been a keen focus on pilot workload and its associated assessment methods, and it remains a highly relevant aspect of flight testing. This paper provides a synopsis of a novel workload rating scale and index, the Comeau-Duggan Pilot Workload Index, designed to bridge the gaps in existing subjective workload metrics – such as casual factor identification – that are present in the most widely used rating scales in flight tests. The conceptualization and development of this index represent a multi-year, dual-national research effort that builds on the foundational concepts and core principles underlying widely accepted workload rating scales used in Human Factors and Handling Qualities engineering. The Pilot Workload Index provides a structured and rigorous methodology for ascertaining and distinguishing factors that have contributed to the pilot workload of a given flying task, evaluating their impact using a systematic suffix-flowchart framework. The Pilot Workload Index was developed and assessed in piloted flight simulation trials conducted by University of Liverpool and in real-world flight trials conducted by the National Research Centre Canada for Ship-Helicopter Operating Limit and Roll-Step Mission Task Element assessments. Other scales were used during these trials (Bedford Workload Rating scale, NASA Task Load Index and Deck Interface Pilot Effort Scale, as appropriate) to compare results with the new rating scale. This paper presents a subset of the detailed Pilot Workload Index data recorded during flight simulation trials. It also explores the insights that can be derived from the data, highlighting the benefits of the Pilot Workload Index in workload assessments in flight tests.

This Chapter identifies the three Applicable Certification Rules (ACRs) selected to ‘examine’ the fidelity of the Flight Simulator and Flight Simulation Model through modelling and simulation. The structured method for the subjective as-sessment of simulator fidelity is introduced using pilot rating scales and question-naires for the ACRs assessed in Chapters 12–14. Key observations, conclusions and recommendations for each of the Case Studies are summarised.

Pilot workload assessment has been a keen area of research for many years and has key applicability in flight testing. This paper outlines the development of a novel workload rating scale and index, the Comeau-Duggan Pilot Workload Index, which bridges gaps, such as causal factor identification, between some of the most widely used rating scales in flight test. The conceptualization and evolution of this index has been a multi-year and multi-nation research effort that has built upon the foundation and fundamental principles that underpin current widely accepted workload rating scales used in Human Factors and Handling Qualities engineering. The pilot workload index facilitates a rigorous and robust methodology for identifying the factors contributing to a given flying task, quantifying their impact through a structured suffix flowchart approach. It can provide, for example, a quantifiable link between pilot workload and the operational use of the aircraft, and therefore could inform aircraft and system design, as well as tactics and procedural development. It was developed through flight trials conducted at the National Research Council of Canada and flight simulator trials conducted at the University of Liverpool.

Modern combat ships are often powered by gas turbine engines that discharge large volumes of hot exhaust gas, which can be deflected by winds from ahead toward the flight deck at the stern of the ship. While it is well documented that the turbulent airflow shed from the superstructure will adversely affect a helicopter when flying close to a ship, little consideration has been given to the exhaust plume, which can affect both the helicopter’s main rotor and engine. The oil and gas industry has long recognized that the safety of a helicopter operating to an offshore platform is affected not only by turbulent airflow but also by elevated air temperatures due to gas turbine exhaust; this has led to recommended limits for air temperature fluctuations over the platform helideck. To gain a better understanding of how the exhaust flow from a ship’s engine mixes with the airflow over the superstructure and interacts with a helicopter hovering close to the landing deck, a steady-state Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) analysis has been conducted. The coupled ship–helicopter CFD analysis shows how quickly the hot gases cool and how they are drawn into the main and tail rotors and the engine intakes.

The NATO Generic Destroyer (NATO-GD) is a conceptual generic combat ship, for which the geometry is freely available, and that has been developed to enable and encourage collaborative international research into the helicopter-ship dynamic interface (HSDI), i.e., the modeling and simulation of helicopter launch and recovery to ships. The purpose of this paper is to provide the HSDI research community with a baseline Ship-Helicopter Operating Limits (SHOL) diagram for a generic helicopter landing to the NATO-GD. The generic helicopter is based on the open-source GenHel flight dynamics model, which is also available within the commercially available aircraft simulation software, FLIGHTLAB. The SHOL was established by an experienced test pilot in a full-motion helicopter flight simulator. By making the generic SHOL diagram available, and in providing detail about how it was established, the intention is that it can be used as a reference point for future HSDI modeling and simulation research.

This Chapter addresses the question as to how the RCbS Process, as an element of virtual engineering, might be resourced. It is recognised that building a capability able to fully embrace virtual engineering in certification will take time and dedicated resources. The emphasis here on ‘dedicated’ is part of a recommendation, to ensure that capabilities are ‘grown’ without the constraints and pressures of current programmes.

This paper demonstrates the training, optimisation, and predictive capabilities of Machine Learning (ML) for helicopter-ship certification. The work focuses on the development of a Linear Discriminant Analysis (LDA) model, trained specifically on pilot control activity data recorded during the hover phase of a recovery to a ship, to determine an operational boundary driven by pilot workload. The certification process currently relies heavily on embarked trials and the subjective workload assessment of test pilots. Modelling and Simulation (M&S), however, offers a potentially more efficient approach to addressing the high costs, resource-intensive nature, and inherent dangers associated with traditional clearance methods. By providing a relatively large amount of data for analysis, this approach creates an opportunity to bridge the gap between subjective and objective measures, enabling the prediction of workload limitations. An LDA model was trained using cross-validation on pilot control activity data and optimised through the inclusion of a penalty factor to reduce overfitting. Throughout the training process, the model demonstrated good performance, effectively distinguishing between high and low workload conditions based on pilot control activity data. When tested on unseen data, the model accurately predicted the Ship-Helicopter Operating Limit (SHOL) boundary for most cases. These results support the application of ML in the helicopter-ship certification process and demonstrate the model's ability to identify correlations within high-dimensional datasets, offering a more data-driven and objective approach to determining workload and clearance boundaries.

This paper expands on a previous exploratory investigation into the safety implications of helicopter operations at hospital landing sites. The paper analyses the interaction between rotor downwash, the turbulent wake shed from nearby buildings and the effect of varying windspeed and aircraft position. A RANS CFD method has been used to compute the mean airflow in the vicinity of a hospital helipad with a helicopter, representative of a Bell 412, hovering at three different positions around the site. The main rotor of the aircraft was modelled using a Virtual Blade Model, enabling a coupled solution between the airflow around nearby structures and the helicopter. The study examines the resulting airflow patterns and velocity magnitudes around the site for two incoming windspeeds and three varying aircraft positions. Results presented are focussed on areas where the rotor downwash is present and likely to impact pedestrians. The findings show that windspeed can affect how the downwash from the rotor is distributed through the local environment and highlights that, in certain areas, calculated air velocities are found to be at levels considered hazardous to pedestrians.

Turbulent ship airwakes can present a major challenge for a pilot landing a helicopter to the ship. A recent study has proposed modifications to the hangar of a simple ship, the SFS2, to improve the air flow over the deck. To assess the effect of the proposed hangar modification on the helicopter and pilot, the unsteady air flow over the modified ship has been computed using time-accurate CFD, and then integrated with a full-motion flight simulator for a pilot to conduct deck landings to the original and modified ship geometries in wind speeds from 30 kt to 50 kt. The effectiveness of the proposed modification was assessed through pilot workload ratings for the landing task, and by recording pilot control inputs and helicopter states. The study has shown that there are some benefits from the hangar modifications. In the headwind the helicopter was deemed to be at the safe limit at 50 kt when operating to the original SFS2, while the limit was not reached in the 50 kt wind for the modified ship. In an oblique wind, the safe wind speed limit was found to be 40 kt for the original ship and 50 kt for the modified version. Although the improvements are not substantial, they do represent a positive outcome.

This paper reports on the initial implementation of Machine Learning (ML) for predicting the workload experienced by a pilot when performing a recovery to a naval ship. Pilots classify their workload for each landing by providing a subjective rating, which is used to determine the ship-helicopter operating limit (SHOL). Different workload metrics have been trialed to bridge the gap between pilot subjective ratings and objective flight data. With hundreds of different helicopter, ship and airwake parameters available to examine, ML provides an approach to understanding the complex interactions between these variables. This paper looks at the initial results obtained by applying ML techniques to train a classification algorithm with pilot control input data. Preliminary results showed 77.14% accuracy when training a Linear Discriminant algorithm to predict pilot workload from cyclic, collective, and pedal input data.

This paper describes a detailed study into the aerodynamic loading of a 150 m long conceptual combat ship known as the NATO Generic Destroyer. Results are presented from a wind tunnel experiment in which the drag and side forces, and the roll and yaw moments, were measured around the 360 degrees degrees azimuth using a 0.75 m long model of the ship. Surface pressures were also measured between 0 degrees degrees and 180 degrees, degrees , using 252 pressure taps distributed over the surface of the ship. The measured loads and surface pressures are shown to agree reasonably well, for most wind directions, with those predicted by a steady RANS CFD method. An unexpected result was found in the drag measurements, whereby the force was found to be towards the stern for wind directions up to 120 degrees, degrees , i.e., with a wind component towards the bow. The reason for this apparent anomaly was explained by considering the flow field and the surface pressures acting on the ship for wind angles between 90 degrees degrees and 135 degrees. degrees . The primary purpose of the paper is to make available a set of high-quality aerodynamic load measurements for a well-defined ship geometry, which is freely accessible, thereby providing a test case for CFD validation.

High-fidelity rotorcraft flight simulation relies on the availability of a quality flight model that further demands a good level of understanding of the complexities arising from aerodynamic couplings and interference effects. This paper explores rotorcraft flight dynamics in the low-speed regime where such complexities abound and presents a new heuristic approach in the time domain to aid identification of nonlinear dynamics and fidelity assessment. The approach identifies flight model parameters "additively," based on their contribution to the local dynamic response of the system, in contrast with conventional approaches where parameter values are identified to minimize errors over a whole maneuver. In these early investigations, identified low-order, rigid-body, linear models show good comparison with flight-test data. The approach is extended to explore nonlinearities attributed to the so-called maneuver wake distortion and wake skew effects emerging in larger maneuvers. The results show a good correlation for the proposed nonlinear model structure, demonstrated by its capability to capture the time response and variations of the stability and control derivatives with response magnitude.

This paper describes the development of a realistic piloted simulation of helicopter recovery to an offshore platform, which has been used to assess the effect of turbulent air flow on a helicopter landing on a full-scale offshore platform. Time-accurate CFD was used to create the unsteady turbulent airwake generated by an offshore platform. The computed unsteady airwake velocities were integrated with a flight dynamics model representative of a Sikorsky SH-60B Seahawk helicopter in a six-degree-of-freedom motion flight simulator. A simulated flight trial was conducted in which a test pilot was instructed to perform a series of helideck landings to the platform for wind speeds of 20 to 50 kt and to give workload ratings for the difficulty of the task. The workload ratings, along with the corresponding pilot control activity and helicopter positional accuracy, are discussed in relation to the effect of the airwake on the helicopter and pilot workload. The results show that as the freestream wind speed increased, the vertical velocity fluctuations and pilot workload also increased. The paper demonstrates the potential for realistic piloted flight simulation to be used to support helicopter operations to offshore platforms.

This paper presents an analysis of the unsteady aerodynamic loading of a helicopter immersed in the airwake of a generic destroyer undergoing several ship motion types: static, sinusoidal pitching, regular 2-DOF, and realistic irregular 3-DOF ship motions. The study was a collaborative effort between the National Research Council Canada and the University of Liverpool, where each organization have applied their respective modeling approach (whether by simulation or experiment). It was shown that whilst there were only marginal differences in the mean helicopter loads for each motion type, the effects of ship motion are more apparent in the RMS loads, and the instantaneous load and air-velocity spectra. Dominant peaks in the thrust load spectra, as well as subsequent second and third harmonics, are shown at the ship motion frequency for sinusoidal pitching and regular 2-DOF ship motions, which have been attributed to the interaction between the turning rotor and the moving ship. This analysis provides a foundation for understanding the relationships between ship airwake and helicopter loading, and for extending that understanding to impacts on flight operations.

The aim of this paper is to provide guidance on the employment of flight simulation to demonstrate, either directly or indirectly, compliance with the flight-related requirements within the certification standards for small or large rotorcraft. Herein are presented the approaches that are suggested in the guidelines for rotorcraft certification by simulation developed by the RoCS project to tackle the topic of the credibility of simulation.

This paper describes an investigation of the air flow over the flight deck of a twin-island aircraft carrier with the ship's lifts in a raised and lowered position, and the subsequent effect on the helicopter and on pilot workload. Computational Fluid Dynamics was used to model the unsteady flow over the flight deck in a 40 kt wind approaching from 60°starboard. The turbulence intensity and velocity flow field produced over the flight deck for each lift configuration was analyzed and compared. The unsteady air flow computed for each lift position was combined with a flight dynamics model of a helicopter configured to represent a SH-60B Seahawk an integrated with a full-motion flight simulator. To analyze the effect of the two airwakes on the helicopter and on pilot workload, a series of simulated flight trials were conducted in which the pilot performed landings to the flight deck of the aircraft carrier. The results show that while the lift configuration does affect the air flow over the flight deck, the effect on pilot workload is dependent on the location on the flight deck the pilot is landing to.

Turbulent wind is known for potentially deteriorating rotorcraft performance and handling qualities when fulfilling their operation and duties. However, related research is rarely reported and could be possibly attributed to the absence of an effective analytical tool. This paper proposes a pilot model to explore the effect of turbulent wind on rotorcraft handling qualities. It consists of three components: a stabilization control component, a trajectory planning component, and a trajectory tracking component. A slalom task in the turbulent wind is used for the validation of this new pilot model. The simulation results have demonstrated that the new pilot model can not only plan and track a desired trajectory by determining a pilot's guidance strategy, but also predict handling qualities through modeling the effect of the vestibular system. The new pilot model predicts the effect of steady wind component on a pilot's maneuvering aggressiveness and yaw control performance for various ground speeds. It is also capable of predicting the handling qualities in turbulent wind due to increased turbulence intensity and reduced flight control authority.

The rotorcraft is a complex dynamical system that demands specialist modelling skills, and a high level of understanding of the aeromechanics arising from the main rotor wake and aerodynamic couplings. One such example is the difficulty predicting off-axis responses, particularly in hover and low-speed flight, associated with induced velocity variation through the rotor disk resulting from the rotor wake distortions. Various approaches have been developed to deal with this phenomenon but usually demand prerequisites of high levels of expertise and profound aerodynamic knowledge. This paper presents a new and practical approach to capturing this wake distortion through an augmented rotor inflow model. The proposed model is coupled with a nonlinear simulation using the FLIGHTLAB environment, and comparisons are made between the simulation results and flight test data from the National Research Council of Canada's Advanced System Research Aircraft in hover and low speed. Results show good predictability of the proposed nonlinear model structure, demonstrated by its capability to closely match the time responses to multi-step control inputs from flight test. The results reported are part of ongoing research at Liverpool and Cranfield University into rotorcraft simulation fidelity.