Helicopter handling qualities: a study in pilot control compensation

The research reported in this paper is aimed at the development of a metric to quantify and predict the extent of pilot control compensation required to fly a wide range of mission task elements. To do this, the utility of a range of time- and frequency-domain measures to examine pilot control activity whilst flying hover/low-speed and forward flight tasks are explored. The tasks were performed by two test pilots using both the National Research Council (Canada)’s Bell 412 Advanced Systems Research Aircraft and the University of Liverpool’s HELIFLIGHT-R simulator. Handling qualities ratings were awarded for each of the tasks and compared with a newly developed weighted adaptive control compensation metric based on discrete pilot inputs, showing good correlation. Moreover, in combination with a time-varying frequency-domain exposure, the proposed metric is shown to be useful for understanding the relationship between the pilot’s subjective assessment, measured control activity and task performance. By collating the results from the subjective and objective metrics for a range of different mission task elements, compensation boundaries are proposed to predict and verify the subjective assessments from the Cooper-Harper Handling Qualities Rating scale.Engineering and Physical Sciences Research Council (EP/P031277/1 and EP/P030009/1

Rotorcraft Flight Simulation to support Aircraft Certification: A Review of the State of the Art with an Eye to Future Applications

This paper presents the approach for Rotorcraft Certification by Simulation proposed within the RoCS project. In particular, the aspects of model validation and credibility assessment through the usage of uncertainty quantification techniques are reviewed, and some lesson learned are presented. It is shown that the increase of effort required to thoroughly evaluate the capability of the simulation model is often counterbalanced by the advantages of the insight that can be obtained and possibly exploited also for design purposes. It is shown that the numerical approaches, and in some cases even the tools required to perform the necessary uncertainty analyses are publicly available and can be directly employed. This paper is one of a set presented at the 49th European Rotorcraft Forum discussing results from the EU Clean Sky 2 project, Rotorcraft Certification by Simulation (RoCS)

Case Studies to Illustrate the Rotorcraft Certification by Simulation Process; CS27/29 Dynamic Stability Requirements

This paper is one of a set presented at the 49th European Rotorcraft Forum displaying results from the EU Clean Sky 2 project, Rotorcraft Certification by Simulation (RoCS). The process developed by the RoCS team provides guidance on the requirements for the use of simulation in certification and features four case studies that illustrate aspects of the process applied using flight simulation models and flight test data provided by Leonardo Helicopters. This paper presents the case study on Dynamic Stability, for the relevant certification paragraphs in the EASA Certification Specifications CS-27 and CS-29. The Dynamic Stability paragraphs from the Specifications are described and results from simulation model fidelity assessment, and updating compared with test data, are presented for a reference flight condition. The credibility of extrapolations of the flight simulation model results to conditions at higher altitude, different airspeeds and vertical rates of climb are then discussed. Preliminary results from piloted simulation trials, with a new flight test manoeuvre, are included to illustrate flight simulator fidelity assessment methods and to explore the veracity of the stability margins set by the Certification Specifications

Validation of helicopter mathematical models

The validation of theoretical flight-mechanics models for helicopters is of considerable practical importance for the design of new rotorcraft. Conventional validation methods have involved comparisons of the responses of simulated and real helicopters to a simple input, such as a step or a pulse. The use of sufficiently small inputs allows the development and validation of linear models which can be used by the control system designer to endow the helicopter with acceptable stability characteristics and handling qualities over a limited operating envelope. For non-linear models, more suited to the investigation of large and rapid manoeuvres, one approach to model validation is to use linearisation about a range of trim conditions and apply system identification and parameter identification techniques. Additionally, it is possible to transform the problem to the frequency domain in order to eliminate subsystems from the validation process. The large amplitudes of typical nap-of-the-earth manoeuvres demand a new approach to validation. Inverse simulation has demonstrated its value in this context

Case study III: SA-330 PUMA

SA-330 Puma helicopter test data provided by the Royal Aerospace Establishment were analysed using a number of different identification techniques by six of the participating organisations in AGARD Flight Mechanics Panel Working Group WG-18. This section of the Report presents results of the six-degree-of-freedom identification, which are discussed in terms of the conventional rigid body modes of motion