Mike Jones, Ph.D

The Open-Loop Onset Point (OLOP) criterion has, for many years, been successfully used as a method to predict quasi-non-linear pilot-induced oscillations (PIOs) for fixed-wing aircraft. Only limited research has been conducted using the criterion for prediction of PIOs occurring in rotorcraft. This paper details a study to extend the application of OLOP to rotorcraft, using the combination of control inputs appropriate for the task and a suitable pilot model. Results are compared between pilot… Show more

The Open-Loop Onset Point (OLOP) criterion has, for many years, been successfully used as a method to predict quasi-non-linear pilot-induced oscillations (PIOs) for fixed-wing aircraft. Only limited research has been conducted using the criterion for prediction of PIOs occurring in rotorcraft. This paper details a study to extend the application of OLOP to rotorcraft, using the combination of control inputs appropriate for the task and a suitable pilot model. Results are compared between pilot subjective opinion and OLOP predictions, from tests performed in a ground-based simulation facility. Using ‘task-specific’ application of OLOP, results obtained in the investigation are encouraging, whereby the objective predictions reflect subjective pilot assessment. From results obtained, a modified boundary is presented. Show less

The use of active inceptor systems allows for control of the aircraft even following mechanical failures within the control inceptor. For the specific case of isometric failure, whereby the inceptor "freezes" in position, a virtual force-displacement model is used to continue to provide control input. Testing on DLR's experimental helicopter (active control technology/flying helicopter simulator) has shown the potential to encounter pilot-induced oscillation (PIO) tendencies when flying using… Show more

The use of active inceptor systems allows for control of the aircraft even following mechanical failures within the control inceptor. For the specific case of isometric failure, whereby the inceptor "freezes" in position, a virtual force-displacement model is used to continue to provide control input. Testing on DLR's experimental helicopter (active control technology/flying helicopter simulator) has shown the potential to encounter pilot-induced oscillation (PIO) tendencies when flying using this mode. This paper presents results from a simulation campaign undertaken to determine whether PIOs could be exposed through this use of control and/or the resultant severity. The results show that isometric failure caused severe PIOs. Unacceptable failure characteristics were reported by all four pilots. PIO incipience was predicted through the use of offline tools. It is recommended that specific PIO investigations be undertaken during the evaluation of active inceptor failure modes. Show less

The state of the of art in flight control systems geared toward dual-pilot helicopters is the use of active inceptor systems to replace the traditional mechanical linkage between pilot and copilot inceptors. This work investigates the introduction of priority functions, which act to actively decouple inceptors in one control station. This approach has the potential to assist pilots to take over control in low-level flight and aid to mitigate loss-of-control accidents that occur in such… Show more

The state of the of art in flight control systems geared toward dual-pilot helicopters is the use of active inceptor systems to replace the traditional mechanical linkage between pilot and copilot inceptors. This work investigates the introduction of priority functions, which act to actively decouple inceptors in one control station. This approach has the potential to assist pilots to take over control in low-level flight and aid to mitigate loss-of-control accidents that occur in such conditions. Takeover control maneuvers are tested in a dual-pilot helicopter simulation environment to evaluate two inceptor decoupling methods, namely a priority pushbutton (manual) and a priority force threshold (automatic). Results indicate that the takeover maneuvers were successfully performed in low-level flight without over control (inaccurate control inputs) when using both priority functions. The priority functions led to a workload reduction when compared to a benchmark configuration without inceptor decoupling. Positive ratings in usefulness and satisfaction scales indicate pilot acceptance of the priority functions tested. Show less

The use of active inceptor systems allows for control of the aircraft even during mechanical failures within the control inceptor. For the specific case of isometric failure, whereby the inceptor ‘freezes’ in position, a virtual force displacement model is used to continue to provide control input. Testing on DLR’s experimental helicopter (ACT/FHS) has shown the potential to encounter pilot-induced oscillation (PIO) tendencies when flying using this mode. This paper presents results from a… Show more

The use of active inceptor systems allows for control of the aircraft even during mechanical failures within the control inceptor. For the specific case of isometric failure, whereby the inceptor ‘freezes’ in position, a virtual force displacement model is used to continue to provide control input. Testing on DLR’s experimental helicopter (ACT/FHS) has shown the potential to encounter pilot-induced oscillation (PIO) tendencies when flying using this mode. This paper presents results from a simulation campaign undertaken to determine whether PIOs could be exposed through this use of control and/or the resultant severity. The results show that control limiters cause severe PIOs during the isometric failure. Unacceptable failure characteristics were found for six different vehicle configurations and PIOs were exposed by all four pilots. PIO incipience was predicted through the use of offline tools. In future, it is recommended that specific PIO investigations are undertaken during the evaluation of active inceptor failure modes. Show less

When tuning motion platforms, subjective opinion is usually regarded as sufficient for
most applications, as it should provide verification that no false cueing occurs. However,
often systems are not configured to fully utilize the available motion for the desired purpose.
This paper presents a new method to objectively tune simulation motion platforms. Enhanced usage of the available platform motion space is shown through an example of its application to a specific mission task. The… Show more

When tuning motion platforms, subjective opinion is usually regarded as sufficient for
most applications, as it should provide verification that no false cueing occurs. However,
often systems are not configured to fully utilize the available motion for the desired purpose.
This paper presents a new method to objectively tune simulation motion platforms. Enhanced usage of the available platform motion space is shown through an example of its application to a specific mission task. The difference in motion filter settings for two simulator platform geometries is shown. This displays the suitability of the platforms for completion of the two-axis lateral reposition task. Show less

DOI: 10.1007/s13272-017-0256-1

Achieving good motion cueing in rotorcraft flight simulation is a long-standing challenge in the simulation community. The current reliance upon subjective opinion leads to a wide range of motion configurations, which almost certainly do not offer the optimal level of vestibular cueing. Furthermore, without the understanding of the optimal motion settings, objective criteria are difficult to apply. This paper presents a new method designed to optimise and… Show more

DOI: 10.1007/s13272-017-0256-1

Achieving good motion cueing in rotorcraft flight simulation is a long-standing challenge in the simulation community. The current reliance upon subjective opinion leads to a wide range of motion configurations, which almost certainly do not offer the optimal level of vestibular cueing. Furthermore, without the understanding of the optimal motion settings, objective criteria are difficult to apply. This paper presents a new method designed to optimise and evaluate the respo nse of any motion plat-
form, based upon the input to the system and the given motion system constraints. The method is utilised to tune the motion platform of the air vehicle simulator. Results show promise for the use of the optimisation, as good fidelity is shown through pilot subjective comments and ratings.
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Effectiveness of flight simulation platforms is often determined through the use of standardised methods and tools. Simulation guidelines specify effectiveness in terms of system configuration and performance. This is not the case for motion systems, which are regularly tuned using only pilot subjective opinion. This paper reports results from application of a number of tuning tools to studies using rotorcraft flight simulation, demonstrating how the effectiveness of current simulation motion… Show more

Effectiveness of flight simulation platforms is often determined through the use of standardised methods and tools. Simulation guidelines specify effectiveness in terms of system configuration and performance. This is not the case for motion systems, which are regularly tuned using only pilot subjective opinion. This paper reports results from application of a number of tuning tools to studies using rotorcraft flight simulation, demonstrating how the effectiveness of current simulation motion platforms can be enhanced. The effectiveness of the method is shown through the use of a case study, which includes analysis of a typical mission task that would be undertaken in a current training simulator. Show less

DOI: 10.1007/s13272-017-0246-3

Offshore helicopter operations are frequently conducted in both turbulent and degraded visual environments (DVE). This investigation assesses the combined influence of turbulence and DVEs on pilot workload to identify first limits for safe operations. Flight tests using a simulation model of the research helicopter ACT/FHS (active control technology/flying helicopter simulator) flight mechanics model were conducted in the air vehicle simulator (AVES) at DLR… Show more

DOI: 10.1007/s13272-017-0246-3

Offshore helicopter operations are frequently conducted in both turbulent and degraded visual environments (DVE). This investigation assesses the combined influence of turbulence and DVEs on pilot workload to identify first limits for safe operations. Flight tests using a simulation model of the research helicopter ACT/FHS (active control technology/flying helicopter simulator) flight mechanics model were conducted in the air vehicle simulator (AVES) at DLR Braunschweig. Tests were
completed using four pilots, and results show the effects on pilot workload, task performance and control input activity. It was found that DVE and turbulence increase the workload and reduce task performance, but each in a different manner. Furthermore, the impact on control activity and
pilot-induced oscillation tendencies are shown to have dependency upon the environmental conditions.


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No standard guidelines currently exist for tuning rotorcraft flight simulation motion platforms. This often leads to systems that are poorly utilized. This paper presents results from a study to determine the influence of parameter variations in two rotorcraft research simulators. Investigations were conducted using three Mission Task Elements (MTEs), and both subjective and objective analysis is used to determine the suitability of motion settings. Motion settings are compared with recommended… Show more

No standard guidelines currently exist for tuning rotorcraft flight simulation motion platforms. This often leads to systems that are poorly utilized. This paper presents results from a study to determine the influence of parameter variations in two rotorcraft research simulators. Investigations were conducted using three Mission Task Elements (MTEs), and both subjective and objective analysis is used to determine the suitability of motion settings. Motion settings are compared with recommended Objective Motion Cueing Test (OMCT) boundaries for fixed-wing aircraft. Results show differences in the fidelity of motion settings, and recommendations specifically for rotorcraft simulation are presented. Show less

When tuning motion platforms, subjective opinion is usually regarded as sufficient for most applications, as it provides verification that no false cueing, and subsequently no negative training occurs. However, often systems are far from optimal for their specific purpose. This paper presents a new method to objectively tune simulation motion platforms. Enhancement of motion utilization is shown through both theoretical appraisal of motion usage and through subjective pilot assessments. The… Show more

When tuning motion platforms, subjective opinion is usually regarded as sufficient for most applications, as it provides verification that no false cueing, and subsequently no negative training occurs. However, often systems are far from optimal for their specific purpose. This paper presents a new method to objectively tune simulation motion platforms. Enhancement of motion utilization is shown through both theoretical appraisal of motion usage and through subjective pilot assessments. The function used to tune the motion parameters is presented, and shows promise for a standard process for the continuous, and application based tuning, of future rotorcraft motion platforms. Show less

Virtual engineering tools are currently not extensively employed during the certification and commissioning of rotorcraft flight simulator motion platforms. Subjective opinion is regarded as sufficient for most applications, as it provides verification that the motion platform does not cause false cueing, and subsequently no negative training. However, the result are systems that are far from optimal for their specific purpose. This paper presents a new method to objectively tune simulation… Show more

Virtual engineering tools are currently not extensively employed during the certification and commissioning of rotorcraft flight simulator motion platforms. Subjective opinion is regarded as sufficient for most applications, as it provides verification that the motion platform does not cause false cueing, and subsequently no negative training. However, the result are systems that are far from optimal for their specific purpose. This paper presents a new method to objectively tune simulation motion platforms, using new virtual engineering tools. Enhancement of motion utilisation is shown through assessments conducted with rotorcraft pilots. The results show promise for the use of the method as a standard process for the continuous, and application based tuning, of future rotorcraft motion platforms. Show less

Offshore-Helicopter-Operations are frequently conducted in both turbulent and degraded visual environ-ments (DVE). This investigation assesses the combined influence of turbulence and DVEs on pilot workload in order to gain an understanding and identify first limits. DLR AVES (Air Vehicle Simulator) was used with the ACT/FHS (Active Control Technology/ Flying Helicopter Simulator)) flight mechanics model and was flown by three test pilots and one operational pilot. The paper shows the effects… Show more

Offshore-Helicopter-Operations are frequently conducted in both turbulent and degraded visual environ-ments (DVE). This investigation assesses the combined influence of turbulence and DVEs on pilot workload in order to gain an understanding and identify first limits. DLR AVES (Air Vehicle Simulator) was used with the ACT/FHS (Active Control Technology/ Flying Helicopter Simulator)) flight mechanics model and was flown by three test pilots and one operational pilot. The paper shows the effects on pilot workload, task performance and control input activity. It was found that DVE and turbulence are increasing the workload and reducing the task performance but each in a different manner. As well, the impact on control activity and pilot induced oscillations is changed through both environmental conditions. Show less

The Handling Qualities (HQs) of a helicopter can be adversely affected through the presence of an externally slung load. Helicopter stability margins may be reduced, due to the additional dynamics of the load system, which can subsequently increase pilot workload, and reduce the operational envelope. An Automatic Load Damping System (ALDS) has been designed and has been
successfully tested in flight. This system, alongside slung load scenarios, has been implemented within a piloted… Show more

The Handling Qualities (HQs) of a helicopter can be adversely affected through the presence of an externally slung load. Helicopter stability margins may be reduced, due to the additional dynamics of the load system, which can subsequently increase pilot workload, and reduce the operational envelope. An Automatic Load Damping System (ALDS) has been designed and has been
successfully tested in flight. This system, alongside slung load scenarios, has been implemented within a piloted simulation in DLR’s Air Vehicle Simulator. In this article, the results from a simulated test campaign to observe the influence of the stabilization system on the vehicle HQs are
presented. The system is assessed using three Mission Task Elements, modified for hoist operations. Results show that a conflict between pilot control and commanded inputs
from the ALDS can cause unstable slung load oscillations and degradation in HQs in hover. However, it is shown that when the stabilization system is used only when required,
both the HQs of the helicopter are conserved, and load oscillations are reduced. The results in this paper are intended to motivate future flight tests using DLR’s Active Control Technology/Flying Helicopter Simulator. Show less

Achieving good motion cueing in rotorcraft flight simulation is a long standing challenge in the simulation community. The current reliance upon subjective opinion leads to a wide range of motion configurations, which almost certainly do not offer the optimal level of vestibular cueing. Furthermore, without the understanding of the optimal motion settings, objective criteria are difficult to apply. This paper presents a new tool designed to optimize and evaluate the response of any motion… Show more

Achieving good motion cueing in rotorcraft flight simulation is a long standing challenge in the simulation community. The current reliance upon subjective opinion leads to a wide range of motion configurations, which almost certainly do not offer the optimal level of vestibular cueing. Furthermore, without the understanding of the optimal motion settings, objective criteria are difficult to apply. This paper presents a new tool designed to optimize and evaluate the response of any motion platform, based upon the input to the system and the given motion system constraints. This
tool is utilized in order to tune the motion platform of the Air Vehicle Simulator (AVES). Results show promise for the use of the optimization, as good fidelity is shown through pilot subjective comments and ratings. Show less

This work provides novel methods to quantify both the propensity of pilot-vehicle systems to RPCs, and the severity of these interactions. Methods have been designed with simplicity of use in mind, whereby they can be applied to vehicles of different configuration, are applicable to a wide range of Rotorcraft Pilot Couplings, and are easily understandable for prospective users. It is believed that research contained within can contribute to the realisation of European Commission… Show more

This work provides novel methods to quantify both the propensity of pilot-vehicle systems to RPCs, and the severity of these interactions. Methods have been designed with simplicity of use in mind, whereby they can be applied to vehicles of different configuration, are applicable to a wide range of Rotorcraft Pilot Couplings, and are easily understandable for prospective users. It is believed that research contained within can contribute to the realisation of European Commission 2020 objectives, by helping to reduce the average accident rate of global aircraft operators. Show less

The involuntary interaction of a pilot with an aircraft can be described as pilot-assisted oscillations. Such phenomena are usually only addressed late in the design process when they manifest themselves during ground/flight testing. Methods to be able to predict such phenomena as early as possible are therefore useful. This work describes a technique to predict the adverse aeroservoelastic rotorcraft–pilot couplings, specifically between a rotorcraft’s roll motion and the resultant involuntary… Show more

The involuntary interaction of a pilot with an aircraft can be described as pilot-assisted oscillations. Such phenomena are usually only addressed late in the design process when they manifest themselves during ground/flight testing. Methods to be able to predict such phenomena as early as possible are therefore useful. This work describes a technique to predict the adverse aeroservoelastic rotorcraft–pilot couplings, specifically between a rotorcraft’s roll motion and the resultant involuntary pilot lateral cyclic motion. By coupling linear vehicle aeroservoelastic models and experimentally identified pilot biodynamic models, pilot-assisted oscillations and no-pilot-assisted oscillation conditions have been numerically predicted for a soft-in-plane hingeless helicopter with a lightly damped regressive lead–lag mode that strongly interacts with the roll mode at a frequency within the biodynamic band of the pilots. These predictions have then been verified using real-time flight-simulation experiments. The absence of any similar adverse couplings experienced while using only rigid-body models in the flight simulator verified that the observed phenomena were indeed aeroelastic in nature. The excellent agreement between the numerical predictions and the observed experimental results indicates that the techniques developed in this paper can be used to highlight the proneness of new or existing designs to pilot-assisted oscillations. Show less

The Handling Qualities (HQs) of a helicopter can be adversely affected through the presence of an externally slung load. Helicopter stability margins may be reduced, due to the additional dynamics of the load system, which can subsequently increase pilot workload, and reduce the operational envelope. An automatic slung load stabilisation system has been designed and has been successfully tested in flight. This system, alongside slung load scenarios, has been implemented within DLRs Air Vehicle… Show more

The Handling Qualities (HQs) of a helicopter can be adversely affected through the presence of an externally slung load. Helicopter stability margins may be reduced, due to the additional dynamics of the load system, which can subsequently increase pilot workload, and reduce the operational envelope. An automatic slung load stabilisation system has been designed and has been successfully tested in flight. This system, alongside slung load scenarios, has been implemented within DLRs Air Vehicle Simulator (AVES). In this paper, the results from a simulated test campaign to observe the influence of the stabilisation system on the vehicle HQs are presented. The system is assessed using three Mission Task Elements (MTEs), designed for externally slung load operations. Results show that the conflict between pilot and stabilisation can cause degradation in HQs. However, it is shown that when the stabilisation system is used only “when required”, both the HQs of the helicopter are conserved, and load oscillations are reduced. The results in this paper are intended to motivate future flights tests using DLR’s Active Control Technology / Flying Helicopter Simulator (ACT/FHS). Show less

Unmasking aircraft pilot couplings (APCs) prior to vehicle entry into service have been a long standing challenge in the aerospace industry. APCs, often only exposed through unpredictable or very specific circumstances, have arisen throughout the history of manned powered flight and have required stopgap “fixes” to ensure system safety once a problem has been identified. This paper describes two newly created novel tools, one objective and one subjective, to detect and analyze APCs. The Phase… Show more

Unmasking aircraft pilot couplings (APCs) prior to vehicle entry into service have been a long standing challenge in the aerospace industry. APCs, often only exposed through unpredictable or very specific circumstances, have arisen throughout the history of manned powered flight and have required stopgap “fixes” to ensure system safety once a problem has been identified. This paper describes two newly created novel tools, one objective and one subjective, to detect and analyze APCs. The Phase Aggression Criterion is the objective assessment method and, in the advanced form described in this paper, is capable of APC detection in near real time. The innovative Adverse Pilot Coupling Scale is a subjective assessment method for APCs experienced during completion of closed-loop tasks. Results from the application of both of these tools are presented as well as the very good correlation between them. Furthermore, the application of the tools to simulated flight-test data has shown how existing handling qualities mission task element courses and their associated performance tolerances can be inadequate when used to unmask the proneness of a pilot–vehicle system to APC. Show less

Unmasking Adverse Pilot Couplings (APC) prior to vehicle entry into service has been a long standing challenge in the Aerospace Industry. APCs, often only exposed through unpredictable or very specific circumstances, have arisen throughout the history of manned powered flight, and have required short-term ‘fixes’ to ensure system safety. This paper case studies the use of newly created objective and subjective tools for the appraisal of APCs, which have been specifically designed for use during… Show more

Unmasking Adverse Pilot Couplings (APC) prior to vehicle entry into service has been a long standing challenge in the Aerospace Industry. APCs, often only exposed through unpredictable or very specific circumstances, have arisen throughout the history of manned powered flight, and have required short-term ‘fixes’ to ensure system safety. This paper case studies the use of newly created objective and subjective tools for the appraisal of APCs, which have been specifically designed for use during in-flight evaluation. The Phase Aggression Criterion (PAC) is an objective
assessment method and is capable of detection during real-time observations. The Adverse Pilot Coupling (APC) scale is a subjective method for the assessment of APCs experienced during completion of closed-loop tasks. Results from the application of both of these tools are presented as well as the correlation between them. The results support the use of both of the tools to improve the understanding of APCs experienced during flight. Furthermore, the application of the tools helps to show the influence of task performance tolerances on the incipience of pilot-vehicle systems to APCs. Show less

Rigid body RPC involve adverse coupling phenomena dominated by helicopter lower frequency dynamics with pilot in the loop. Using as example the Bo-105 helicopter enhanced by a rate command attitude hold control system, the paper will demonstrate the applicability of bandwidth-phase delay and OLOP criteria to unmask Cat I PIO and respectively Cat II PIO. The paper will introduce a novel on-line prediction algorithm, the so- called PRE-PAC (phase aggression criterion) based on analysis of the… Show more

Rigid body RPC involve adverse coupling phenomena dominated by helicopter lower frequency dynamics with pilot in the loop. Using as example the Bo-105 helicopter enhanced by a rate command attitude hold control system, the paper will demonstrate the applicability of bandwidth-phase delay and OLOP criteria to unmask Cat I PIO and respectively Cat II PIO. The paper will introduce a novel on-line prediction algorithm, the so- called PRE-PAC (phase aggression criterion) based on analysis of the phase distortion between the pilot input and vehicle response. Special attention will be given to pilot modelling for RPC detection in the so-called boundary avoidance tracking (BAT) concept. Show less

Unmasking Aircraft and Rotorcraft Pilot Couplings (A/RPC) prior to vehicle entry into service has
been a long standing challenge in the aerospace industry. A/RPCs, often only exposed through unpredictable or very specific circumstances have arisen throughout the history of manned powered flight, and have required short-term ‘fixes’ to ensure system safety. One of the reasons for this occurrence is the lack of detailed practice regarding the prediction and detection of RPCs prior to… Show more

Unmasking Aircraft and Rotorcraft Pilot Couplings (A/RPC) prior to vehicle entry into service has
been a long standing challenge in the aerospace industry. A/RPCs, often only exposed through unpredictable or very specific circumstances have arisen throughout the history of manned powered flight, and have required short-term ‘fixes’ to ensure system safety. One of the reasons for this occurrence is the lack of detailed practice regarding the prediction and detection of RPCs prior to full-scale testing. Often in simulation, A/RPCs are only investigated once problems have been experienced during other qualification activities. This is a particular issue for the rotorcraft community, where system sophistication is ‘catching up’ with their fixed-wing counterparts. This paper shares results from real-time simulation campaigns conducted during the European Collaborative ARISTOTEL project. Results are included from tests, conducted in full motion simulators, specifically designed to unmask Rigid Body and Aeroelastic RPC tendencies. Results from this paper act as guidelines for exposing RPCs in real-time simulation campaigns. This includes the introduction of novel test procedures and analysis methods. Show less

One of the objectives of the European project ARISTOTEL (2010-2013) is to provide guidelines to designers and simulator programs to reveal RPC aspects of the vehicle to be designed. First, a methodology to assess the sensitivity of Handling Qualities (HQs) and RPCs to design parameters is presented: a design envelope is created around a baseline configuration while considering various parameter constraints and simulation models in state space representation are developed. Second, three PIO… Show more

One of the objectives of the European project ARISTOTEL (2010-2013) is to provide guidelines to designers and simulator programs to reveal RPC aspects of the vehicle to be designed. First, a methodology to assess the sensitivity of Handling Qualities (HQs) and RPCs to design parameters is presented: a design envelope is created around a baseline configuration while considering various parameter constraints and simulation models in state space representation are developed. Second, three PIO criteria are applied to predict the susceptibility to PIO of a set of configurations belonging to the design envelope. Assessment based on Bandwidth-Phase Delay (BPD) reveals that the lowest tip speed values and the lowest disc loading values have the best HQs. Category II PIO assessment based on Open Loop Onset Point (OLOP) shows that lowest actuator rate limits are obtained for the configurations with high tip speed values and high disc loading values. PIO prediction based on the newly developed Predictive Phase-Aggression Criterion (PRE-PAC) shows that results for models tested reflect those of the BPD criteria. Show less

This paper presents the results of a flight simulator test campaign aimed at understanding the effect of high-frequency dynamics associated with helicopter aeroservoelasticity on the proneness to rotorcraft-pilot couplings and specifically to pilot-assisted oscillations. Linearised aeroservoelastic models representative of helicopters in hover and in forward flight have been flown in a full motion flight simulator by trained test pilots, performing selected mission task elements. The handling… Show more

This paper presents the results of a flight simulator test campaign aimed at understanding the effect of high-frequency dynamics associated with helicopter aeroservoelasticity on the proneness to rotorcraft-pilot couplings and specifically to pilot-assisted oscillations. Linearised aeroservoelastic models representative of helicopters in hover and in forward flight have been flown in a full motion flight simulator by trained test pilots, performing selected mission task elements. The handling qualities of the vehicles have been intentionally degraded by modifying the gearing ratios between the control inceptors and the flight controls and by introducing time delays representative of realistic fly-by-wire flight control systems. Clear evidence of pilot-induced oscillations has been found while performing the roll step manoeuvre, especially with the soft-inplane hingeless helicopter with a lightly damped main rotor first regressive lead-lag mode. Based on subjective pilot ratings and objective measures, the aeroservoelastic models require higher pilot workload than corresponding rigid-body models. The repeatable occurrence of an unstable pilot-assisted oscillation event with only one test pilot flying the aeroservoelastic model has been explained by the interaction of the pilot’s involuntary biodynamic feedthrough, identified by specific experiments, and the above mentioned regressive lead-lag mode. Show less

This paper presents a proposed new method for the prediction of rotorcraft pilot-induced oscillations (PIO), through the application of the previously developed phase-aggression criterion. The novel method attempts to define the susceptibility of the overall pilot-vehicle system, and attempts to avoid the limitations of previously developed methods. Importantly, the criterion attempts to identify the susceptibility of the complete PVS control input envelope. Entitled Predictive-PAC, the results… Show more

This paper presents a proposed new method for the prediction of rotorcraft pilot-induced oscillations (PIO), through the application of the previously developed phase-aggression criterion. The novel method attempts to define the susceptibility of the overall pilot-vehicle system, and attempts to avoid the limitations of previously developed methods. Importantly, the criterion attempts to identify the susceptibility of the complete PVS control input envelope. Entitled Predictive-PAC, the results obtained, for roll axis maneuvers only at this stage, have been shown to be comparable with those found using the bandwidth criterion to determine its applicability to simple rate command vehicle models. The primary goal of the introduction of this method is to allow a synchronous process to be developed for both prediction and detection of PIO. The results obtained suggest that the method is capable of predicting unfavorable pilot couplings, and can aid in both the design and evaluation process. Show less

Significant effort has been expended to develop criteria to predict the susceptibility of an air vehicle to so-called pilot-induced oscillations . Much of this work has been carried out for fixed-wing aircraft and it is only recently that their applicability to rotorcraft has started to be assessed. Real time pilot-induced oscillation identification methods provide an alternative means to at least warn the pilot that a pilot-induced oscillation is in progress so that preventative action can be… Show more

Significant effort has been expended to develop criteria to predict the susceptibility of an air vehicle to so-called pilot-induced oscillations . Much of this work has been carried out for fixed-wing aircraft and it is only recently that their applicability to rotorcraft has started to be assessed. Real time pilot-induced oscillation identification methods provide an alternative means to at least warn the pilot that a pilot-induced oscillation is in progress so that preventative action can be taken. Existing methods, however, have some limitations and have rarely been used for rotary-wing purposes. Specifically, the existing methods assessed in this paper do not provide an indication of the severity of the event and mask the underlying data that are being used to generate the warning. This paper proposes and presents a new method to identify pilot-induced oscillations, either in near real time or as a postprocessing aid for recorded flight-test data, that addresses both of these issues. The new method, entitled “phase-aggression criterion,” is compared with current methods. It is shown, for a specific set of test cases and a limited test pilot population, that not only can it provide more information about the pilot-induced oscillation but it can also provide an earlier warning of its onset. Show less

Fixed and rotary wing pilots alike are familiar with potential instabilities or with annoying limit cycle oscillations that arise from the effort of controlling aircraft with high response actuation systems. Understanding, predicting and suppressing these inadvertent and sustained aircraft oscillations, known as aircraft (rotorcraft)-pilot couplings (A/RPCs) is a challenging problem for the designers. The goal of the present paper is to give an overview on the state-of-the-art in RPC problem… Show more

Fixed and rotary wing pilots alike are familiar with potential instabilities or with annoying limit cycle oscillations that arise from the effort of controlling aircraft with high response actuation systems. Understanding, predicting and suppressing these inadvertent and sustained aircraft oscillations, known as aircraft (rotorcraft)-pilot couplings (A/RPCs) is a challenging problem for the designers. The goal of the present paper is to give an overview on the state-of-the-art in RPC problem, underlining the future challenges in this field. It is shown that, exactly as in the case of fixed wing APCs, RPCs existed from the beginning of rotorcraft development and that the problem of eliminating them is not yet solved: the current rotorcraft modelling for RPC analysis is rather limited to the particular case analysed and there is a lack of quantitative pilot behavioural models to analyse RPCs. The paper underlines the importance of involuntary pilot control actions, generally attributed to biodynamic couplings in predicting RPCs in rotorcraft. It is also shown that recent experiences demonstrate that modern rotorcraft seem to embed tendencies predisposing the flight control system FCS system towards dangerous RPCs. As the level of automation is likely to increase in future designs, extending to smaller aircraft and to different kinds of operation, the consequences of the pilot ‘fighting’ the FCS system and inducing A/RPCs needs to be eradicated. In Europe, the ARISTOTEL project (2010–2013) has been launched with the aim of understanding and predicting modern aircraft's susceptibility to A/RPC. The present paper gives an overview of future challenges to be solved for RPC-free design and some new solutions herein. Show less

This paper describes the application of the newly developed Phase-Aggression Criterion to data obtained during a simulated flight test campaign, in order to assess its suitability to detect Rotorcraft Pilot Coupling events. Due to the increasing complexity of modern rotorcraft, both the frequency and severity of Rotorcraft Pilot Coupling events is envisaged to increase. This concern is also due to the lack of industry guidelines and standards when designing the 'future rotorcraft'. The… Show more

This paper describes the application of the newly developed Phase-Aggression Criterion to data obtained during a simulated flight test campaign, in order to assess its suitability to detect Rotorcraft Pilot Coupling events. Due to the increasing complexity of modern rotorcraft, both the frequency and severity of Rotorcraft Pilot Coupling events is envisaged to increase. This concern is also due to the lack of industry guidelines and standards when designing the 'future rotorcraft'. The Phase-Aggression Criterion is a detection tool for these events, capable of achieving a near real-time update of the vehicle's incipience to Rotorcraft Pilot Couplings. Boundaries used by the criteria serve to display severity of any detected 'events'. In this paper, the criterion has been applied to two Mission Task Elements, completed using four test pilots and two motion base simulators. The results presented illustrate good agreement between pilot subjective opinion, output test data and the Phase-Aggression boundary descriptors. Show less

This paper presents the initial results of an investigation to study the effect of motion, visual and force-feel settings on incipience to Rotorcraft Pilot Couplings of a basic heave-only rotorcraft model within a generic rotorcraft flight simulator. Currently, there are no guidelines outlining requirements for simulation facilities to either validate offline Rotorcraft Pilot Coupling predictions or define new ones. The results indicate that it is important that simulation facilities be… Show more

This paper presents the initial results of an investigation to study the effect of motion, visual and force-feel settings on incipience to Rotorcraft Pilot Couplings of a basic heave-only rotorcraft model within a generic rotorcraft flight simulator. Currently, there are no guidelines outlining requirements for simulation facilities to either validate offline Rotorcraft Pilot Coupling predictions or define new ones. The results indicate that it is important that simulation facilities be equipped with motion capabilities and correct force-feel characteristics. This is shown to be of greatest importance when assessing cases close to the boundaries of RPC incipience. The findings suggest that poor quality visual systems may be compensated for by the pilot through the use of any motion cueing available. Show less