Flight Simulation Facility Research Articles

Helicopter augmented control laws for ship deck landing: HACLAS ONERA/DLR Joint Team

Different types of control laws are implemented, tested and compared for maritime operations particularly ship deck landing maneuvers at the flight simulation facilities at both DLR (German Aerospace Center) and ONERA (The French Aerospace Lab). At DLR, “classical” cyclic and collective stick flight controls were used during the piloted simulator trials while active side-sticks were operated at ONERA. A joint maritime scenario for ship deck landing in the simulation environments of both institutes is presented. Test methodologies and assessment techniques to evaluate the ship deck landings are harmonized based on different criteria such as quantitative measures and handling qualities (HQ) ratings to analyze the developed control laws. Simulation results based on pilot studies for an EC135 in the DLR simulator and an EC225 at ONERA are presented.

High-Speed Rotorcraft Pitch Axis Response Type Investigation

This paper presents a systematic investigation of high-speed rotorcraft pitch-axis response types, command models, and handling qualities specifications. The investigation was done using two future vertical lift-relevant rotorcraft configurations—a lift offset coaxial helicopter with a pusher propeller and a tiltrotor. Five response types were investigated, consisting of a pitch rate-command/attitude-hold response type typically used for rotorcraft, a pitch rate-command/attitude-hold response type using a higher-order command model based on the conventional airplane pitch rate transfer function, a normal acceleration command/angle-of-attack hold response type, a flight path rate command/flight path hold response type, and a "blended" flight path rate command response type which varies the command model bandwidth based on stick input size. Designs of varying levels of pitch attitude bandwidth, flight path bandwidth, control anticipation parameter, and pitch attitude dropback were evaluated in a piloted simulation experiment conducted at the Penn State Flight Simulator facility using two high-speed mission task elements. The results of the piloted simulation suggest that both the pitch attitude bandwidth and the pitch attitude dropback requirements must be met for Level 1 handling qualities. A set of recommended specifications and associated updated level boundaries is provided in the Appendix.

XTAL VR System Use in a Novel AAM Research Cockpit

The Flight Simulation Facilities (FSF) at the National Aeronautics and Space Administration's (NASA) Langley Research Center (LaRC) provide high-fidelity, man-in-the-loop (MITL) and hardware-in-the-loop (HITL) simulation services to a number of research customers including NASA, academia, aviation industry partners, and other government agencies such as the Federal Aviation Administration (FAA) and the National Transportation Safety Board (NTSB). The Simulation Development and Analysis Branch (SDAB) management has determined that future research related to the emerging Advanced Air Mobility (AAM) sector will require a new type of simulator with a vastly different cockpit layout and field of view requirements for the out-the-window visual systems than any of the current cockpits. This new simulator might also benefit from integrated head-mounted displays (HMD). For these reasons, SDAB has decided to design and build a new cockpit that will meet the future AAM electric Vertical Take-Off and Landing (eVTOL) simulator needs. In this paper, the authors discuss the novel use of state-of-the-art head worn devices (HWD) to present augmented reality (AR) and virtual reality (VR) environments to researchers to improve the quality of the cockpit design and reduce the time-to-market and cost to obtain the new cockpit.

Acceptance testing and commissioning of a flight simulator for rotorcraft simulation fidelity research

The rotorcraft industry faces a number of challenges today regarding the replacement of ageing airframes, an expansion in the operational roles of helicopters and a requirement to improve safety whilst reducing the environmental impact of rotorcraft operations. The quantification of simulation fidelity underpins the confidence required for the expanding use of modelling and simulation to develop solutions to these challenges in a timely and cost-efficient manner. Current simulator certification standards do not provide a fully quantitative method for assessing simulation fidelity, especially in a research environment. This article details the commissioning and acceptance process of the new research flight simulation facility at the University of Liverpool, HELIFLIGHT-R, and its subsequent use in a research project ‘Lifting Standards: A Novel Approach to the Development of Fidelity Criteria for Rotorcraft Flight Simulators’ aimed at developing new predicted and perceptual measures of simulator fidelity. Some initial results from both piloted simulation and flight tests using the Bell 412 Advanced Systems Research Aircraft are reported within the context of the rotorcraft simulation fidelity project.

Progress in the development of guidance strategies for the landing flare manoeuvre using tau‐based parameters

PurposeTo provide a progress report into research conducted to establish guidelines for the development of guidance vision aids.Design/methodology/approachThe first stage of the research is to establish a coherent engineering basis for the methods of (visual) motion perception and control to inform the design of pilot aids that will support flight in degraded visual conditions, particularly when close to the ground. The next stage will then be to construct and evaluate synthetic displays that recover the visual cues necessary to allow flight in degraded visual conditions for a range of manoeuvres using the flight simulation facilities at the University of Liverpool (UoL). The research is guided by tau (time to contact) theory from the field of ecological psychology.FindingsThe closure of spatial gaps for a number of aircraft manoeuvres are presented in the tau domain. Analysis of the landing flare manoeuvre suggest that both a constant rate of change of tau strategy and an intrinsic tau‐guidance strategy will yield benefits in terms of touchdown descent rate if presented as display symbology.Research limitations/implicationsResults are presented from trials where only one professional pilot was used. Results from a wider population of pilots need to be analysed to ensure that the observed trends are generic.Practical implicationsThe reported results are being used in the next phase of the research project to inform the design of a guidance vision‐aid for the flare manoeuvre. These displays will be tested in flight simulation trials.Originality/valueThe research takes a theory of motion perception and applies it to aircraft guidance display technology.

ON-BOARD STATISTICAL DETECTION AND CONTROL OF ANOMALOUS PILOT-AIRCRAFT INTERACTIONS

A statistical method for the on-board detection and control of oscillatory phenomena in pilot-aircraft systems is presented. Recursive identification is used to obtain a linear model of the system at every time instant. The estimated system parameters are monitored, and the system stability margins are continuously assessed. Oscillations due to stability loss are detected early using a composite statistical hypothesis test. Finally a simple stability augmentation system is designed to assist the pilot-aircraft system during the critical time intervals. The method is successfully tested with data from a detailed nonlinear aircraft model and a flight simulator facility.

SHEAR LAYER REFRACTION CORRECTIONS FOR OFF-AXIS SOURCES IN A JET FLOW

A set of equations is derived for converting acoustic measurements taken in a free-jet flight simulation facility, such as the U.K. Noise Test Facility at Pyestock or the French CEPRA-19 wind tunnel at Saclay, to equivalent farfield flight conditions. The equations are based on the high-frequency geometrical acoustics approximation, whose application in the present context was justified in early studies by Morfey and Tester in 1977 and by Amiet in 1978. However, the present work differs by allowing the source to be positioned off the jet centreline, anywhere within the flight stream. The flight stream jet is modelled as an axisymmetric parallel shear flow, with a shear layer thickness which is small compared with the jet diameter. The model also permits the microphone to be located anywhere outside the flow, arbitrarily close to the open jet. The consequences of off-axis source location are illustrated by numerical calculations.

Flight Simulation Facilities in Europe

Simulation is an established technique used in the man-machine systems area for training, evaluation of performance, and research. The principal task of flight simulation is the creation of a dynamic representation cf an aircraft’s behaviour while allowing one or more human operators - the pilots - to interact with the simulation. In this paper, we give an introduction into flight simulation, its possibilities and actual capabilities plus a summary on contemporary European flight simulation facilities.

The Effect of Roll-Stabilized Sensor Information on Pilot Performance

A study of the night vision sensor systems on helicopters was conducted at the flight simulation facilities at Sikorsky Aircraft. The study was concerned with determining possible pilot performance improvements with the sensor system being roll-stabilized with respect to the airframe as opposed to it being non-roll-stabilized. A six-pilot × two-sensor factorial experiment was designed and data were collected with respect to nine response variables. The results of the statistical analysis performed on the data were mixed in terms of the superiority of one sensor design over the other. The power collective input was significantly greater for the roll-stabilized design. However, the pilots also flew faster and made fewer errors, though the differences were not significant. One reason for such results might be that the pilots were less familiar with the roll-stabilized design, as it is a more recent technology.

Application of active noise control to model propeller noise

The potential of using “active noise control” to reduce cabin noise on the external fuselage surface of turboprop aircraft is demonstrated by conducting several laboratory experiments. The principle of active noise control is to reduce the noise radiated from a primary source by superimposing a signal from a secondary source, which is made identical in amplitude but opposite in phase to the primary sound signal. A computer-controlled algorithm was developed to implement this concept in a free field environment, in which the noise from the primary source (eventually the propeller) and the noise measured at several locations on a representative surface (eventually the fuselage) were used to create the input for the secondary source. In the first set of experiments, a single-channel system for delay and amplification of secondary source input was used. For single-frequency experiments, an average noise reduction of 8–14 dB was achieved on the surface in the frequency range of 200–1000 Hz. Next, the concept was applied to the propeller problem, where the sound signal contains many discrete tones at harmonics of the blade-passage frequency. For this purpose, a pre-recorded noise-time history of a 1 10 - scale model propeller was used to drive the primary source. An average noise reduction of about 15 dB was observed at the first two blade-passage frequencies, and 12 dB and 5 dB reductions were observed at the 3rd and 4th blade-passage frequencies, respectively. Finally, the active noise control concept was demonstrated by using a 1 10 th scale propeller and fuselage, installed in an anechoïc chamber with flight simulation facility. A substantial amount of noise reduction was achieved on the model fuselage surface. The noise reduction was further improved by using multi-channel system for delay and amplification for secondary source input. Noise reduction of 8–13 dB was achieved for the first four propeller noise tones at some areas on the model fuselage.

Advanced concepts flight simulation facility

The cockpit environment is changing rapidly. New technology allows airborne computerised information, flight automation and data transfer with the ground. By 1995, not only will the pilot's task have changed, but also the tools for doing that task. To provide knowledge and direction for these changes, the National Aeronautics and Space Administration (NASA) and the Lockheed-Georgia Company have completed three identical Advanced Concepts Flight Simulation Facilities. Many advanced features have been incorporated into the simulators — e g, cathode ray tube (CRT) displays of flight and systems information operated via touch-screen or voice, print-outs of clearances, cockpit traffic displays, current databases containing navigational charts, weather and flight plan information, and fuel-efficient autopilot control from take-off to touchdown. More importantly, this cockpit is a versatile test bed for studying displays, controls, procedures and crew management in a full-mission context. The facility also has an air traffic control simulation, with radio and data communications, and an outside visual scene with variable weather conditions. These provide a veridical flight environment to evaluate accurately advanced concepts in flight stations.

An experimental study of transmission, reflection and scattering of sound in a free jet flight simulation facility and comparison with theory

When a free jet (or open jet) is used as a wind tunnel to simulate the effects of flight on model noise sources, it is necessary to calibrate out the effects of the free jet shear layer on the transmitted sound, since the shear layer is absent in the real flight case. In this paper, a theoretical calibration procedure for this purpose is first summarized; following this, the results of an experimental program, designed to test the validity of the various components of the calibration procedure, are described. The experiments are conducted by using a point sound source located at various axial positions within the free jet potential core. By using broadband excitation and cross-correlation methods, the angle changes associated with ray paths across the shear layer are first established. Measurements are then made simultaneously inside and outside the free jet along the proper ray paths to determine the amplitude changes across the shear layer. It is shown that both the angle and amplitude changes can be predicted accurately by theory. It is also found that internal reflection at the shear layer is significant only for large ray angles in the forward quadrant where total internal reflection occurs. Finally, the effects of sound absorption and scattering by the shear layer turbulence are also examined experimentally.

Air-to-air combat simulation

The Flight Simulation Facility at the Warton Division of British Aerospace provides support for the design and development of advanced military aircraft. In fulfilling this rôle, opportunities often arise for innovation in the required flight simulation equipment. The combat simulator which we will describe is a good example of such an opportunity.The practice of using flight simulators for research and development is well established, and the range of problems which are solved by this means is continually growing. Computers, which are at the heart of all simulators, are being improved at a remarkable rate, and improvements in other areas—electronic, hydraulic and mechanical, all contribute to more effective simulators. At the same time, the demand for simulation increases because the cost saving trade-off improves as the cost of flight testing to the ever-more-stringent design goals increases.

Noise measurements in a free jet flight simulation facility: Shear layer refraction and facility-to-flight corrections

The conversion of free jet facility data into equivalent flyover results is discussed. The essential problem is to “calibrate out” the acoustic influence of the outer free jet shear layer on the measurements, since this is absent in the flight case. Results are presented which illustrate the differences between current simplified models (vortex sheet and geometric acoustics), and a more complete model based on the Lilley equation. Finally, the use of geometric acoustics for facility-to-flight data conversion is discussed.

Sextant Sighting Performance for Space Navigation Using Simulated and Real Celestial Targets

the feasibility of using a hand-held sextant for taking navigation measurements from on board a manned spacecraft is being studied at Ames Research Center. It would be advantageous to use a reliable, light-weight, handheld instrument instead of a relatively complex, vehicle-mounted, automatic or semiautomatic device for taking such measurements if it provided sufficiently accurate angular measurements. The primary objective of the Ames research program is to determine the operational feasibility, scope of application, and accuracy of the manual measurement technique. A flight simulation facility has been used for examining navigator performance and the operational problems of the sighting task with hand-held sextants. Measurements of real star and lunar landmark angles are being obtained to evaluate the problems associated with absolute sighting accuracy. The accuracy typically considered necessary for space navigation is 10 arc seconds. A sighting experiment on board the Gemini spacecraft will be conducted to examine in a more realistic environment the feasibility and operational problems of using a hand-held navigation sighting instrument and to validate the results of ground-based investigations. The purpose of this paper is to describe some results of this program.