Entity

Time filter

Source Type

NLR
Amsterdam-Zuidoost, Netherlands

Arntzen M.,NLR | Simons D.G.,Technical University of Delft
Applied Acoustics | Year: 2014

Traditionally aircraft flyover noise is assessed by displaying contours of noise metrics. These models can be used to study noise mitigation measures but they lack the possibility to play-back the audible sound as predicted by their calculations. To that end, noise synthesis is an option that allows to experience differences due to noise abatement procedures or new aircraft designs. A noise synthesis technique for aircraft noise is demonstrated by predicting the noise at a noise monitoring location near an airport. By comparing the synthesized results to a recorded measurement, an indication on the capability of this technique has been acquired. Differences between the synthesized and measured sound remain. A large part of that difference is believed to be caused by the inherent uncertainty when using predictive empirical source noise models. It is shown that differences between departure routes can be captured, thereby illustrating the potential of this method to listen to different take-off procedures. Future improvements in source noise prediction and the inclusion of the effects of turbulence on propagation will further aid to the realism of synthesized aircraft noise. © 2013 Elsevier Ltd. All rights reserved. Source


Roelen A.L.C.,NLR | Lin P.H.,Technical University of Delft | Hale A.R.,Technical University of Delft
Safety Science | Year: 2011

Event analysis is needed to learn and improve safety. In air transport, 'occurrences' are routinely reported by pilots and air traffic controllers, and in-flight data analysis systems automatically monitor aircraft system behaviour and capture parameter threshold exceedances. The safety analyst of a large airline has to analyse dozens of occurrences each day. To understand why events happened the analyst has to go beyond the given information and make causal inferences. The analyst is able to do this for causal factors closely related in time and space to the event itself by applying individual knowledge and expertise. But typically the result of the analysis is ad hoc reaction to each individual event. Systematic analysis is needed to find areas of improvement for factors that are further removed from the event (latent factors). New tools are needed to help the analyst in this respect. There is a need for models that represent possible causal event sequence scenarios that include technical, human, and organisational factors. Building such models is a huge task, and requires the combination of detailed knowledge of all aspects of the system, processing huge amounts of data, a substantial mathematical background and the ability to capture this all in a user friendly software tool to be used by the safety analysts. Experience in Causal Modelling of Air Transportation System (CATS) in the Netherlands and similar projects in FAA and Eurocontrol in aviation shows that this is indeed a formidable task, but it has to be done to further improve safety. © 2010 Elsevier Ltd. Source


Speijker L.,NLR | van de Leijgraaf R.,CAA
SAE International Journal of Aerospace | Year: 2011

Although Unmanned Aircraft Systems (UAS) have now for some time been used in segregated airspace where separation from other air traffic can be assured, potential users have interests to deploy UAS in non segregated airspace. Recent technological and operational improvements give reason to believe that UAS safety and performance capabilities are maturing. But the skies can only really open up to UAS when there is an agreed upon UAS safety policy with commonly accepted UAS Safety Risk Management (SRM) processes enabling to show that the risks related to UAS operations in all the different airspace classes can be adequately controlled. The overall objective is to develop a UAS SRM framework, supporting regulators and applicants through provision of detailed guidelines for each SRM step to be conducted, including 1) system description, 2) hazard identification, 3) risk analysis, 4) risk assessment, 5) risk treatment. The purpose is that all potential risks of the newly proposed UAS operations are controlled so that the existing safety level does not decrease (i.e. provides the baseline from which safety requirements for new proposed UAS operations are derived). A survey of UAS activities provides an initial view on the risks and hazards to be considered, the needs and role of potential SRM users, the scope of the aviation system to be considered, the risks to be regulated, selection of suitable risk metrics, and the setting of an acceptable level of safety. It is motivated that the main safety risks that need to be addressed to ensure that UAS can be introduced in non segregated airspace without degrading safety are risks to other airspace users and third party risk (to objects on the ground). It will be necessary to show that these risks do not increase as compared to the current aviation system with manned aircraft only. This paper focuses on the provision of guidelines for steps 2 to 4 of a UAS SRM process, covering both types of risks. The process for third party risk is based on a method that combines an accident probability model with an accident location model and an accident consequence model. This method enables evaluation of both individual risk and societal risk, and provides insight into probability and consequences of collision of a UAS with the ground. A method that addresses potential conflict scenarios (e.g. level busts, aircraft levelling of at the wrong flight level, flight track deviations due to operational errors) is proposed as basis for analysis of the risk of UAS to other airspace users. It is explained how the results may be used to build a Safety Case for UAS operations in non segregated airspace. Recommendations for application and validation of the proposed SRM process are also provided. © 2011 SAE International. Source


Arntzen M.,NLR
INTER-NOISE 2015 - 44th International Congress and Exposition on Noise Control Engineering | Year: 2015

The general aviation airport of Lelystad (the Netherlands) will be transformed into a commercially operated regional airport. Regional aircraft are expected to fly passengers to their holiday destinations. This means that several communities will be affected by new aircraft noise. Besides noise contours, there was a strong desire to inform the public regarding the actual sound that aircraft would generate in their communities. To that end, auralizations of aircraft noise were created to inform communities on the expected sound in their environment. NLR's Virtual Community Noise Simulator allows combining auralization with visualization. Short videos of each individual scenario were made and presented to disseminate the information. Each video comprised locally recorded background noise and aircraft noise that was tailored to represent the projected future flight paths near each location. The resulting videos (32 in total) were presented at six consultation evenings to inform the general public. Besides a plenary presentation, the videos were also presented in smaller rooms in combination with a loudspeaker system and a recording device to replay the videos at a calibrated level. This setup proved to be very valuable and provided the additional information desired by the public in a comprehensive manner. © 2015 by ASME. Source


Pavel M.D.,Technical University of Delft | Jump M.,University of Liverpool | Dang-Vu B.,ONERA | Masarati P.,Polytechnic of Milan | And 9 more authors.
Progress in Aerospace Sciences | Year: 2013

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. © 2013 Elsevier Ltd. Source

Discover hidden collaborations