Recent NASA Wake Surfing Flight Research

2019

Wake vortex encounter reports as well as simulations show a significantly higher encounter risk in ground proximity. This is caused by the special behavior of wake vortices in ground effect. Nevertheless, hazardous wake encounters with adverse consequences are rarely reported in reality. In order to gain more insight in the mechanisms of wake encounters close to ground a realistic flow field around an aircraft of the HEAVY category is initialized using a high fidelity Reynolds-averaged Navier–Stokes solution. The further development of the vortical wake during final approach until touchdown is investigated by large-eddy-simulation until final decay. The resulting flow fields are used for a hazard analysis of wake encounters close to the ground. Encounter simulations are performed with a simulation model of the DLR research aircraft A320 ATRA with autopilot engaged. Different wind conditions and vortex ages are considered as well as the effect of a so-called plate line. Recent studie...

AIAA and SAE, 1998 World Aviation Conference, 1998

A series of flight tests over the ocean of a four engine turboprop airplane in the cruise configuration have provided a data set for improved understanding of wake vortex physics and atmospheric interaction. An integrated database has been compiled for wake-characterization and validation of wake-vortex computational models. This paper describes the wake-vortex flight tests, the data processing, the database development and access, and results obtained from preliminary wake-characterization analysis using the data sets. * *

An essential part of operational clearance of a new aircraft is to certify that it is safe to fly even when wake vortices generated by another aircraft are encountered. For certification, it must be demonstrated that the aircraft can safely cross the wake at a certain separation distance. When the wake is encountered, airdata sensors that measure the directional of airflowin terms of Angle of Attack (AOA / Alpha), Angle of Side Slip (AOSS / Beta / SSA) and pressures (Total and Static Pressure) show large fluctuations. The ADS measurements are used for feedback to the fly-by-wire control laws.These large and rapid fluctuations in the ADS signals affects the commands generated by the fly-by-wire control laws and in turn results in generating high loads on the aircraft. Therefore, before actual flight tests it is necessary to predict the behaviour of Air Data System (ADS) onencountering wake. Appropriate wake encounter protection features should be incorporated in the ADS algorithms. T...

Lecture Notes in Computer Science, 2011

A flying aircraft disturbs the local atmosphere through which it flies creating a turbulent vortex at each wing tip known as a wake vortex. These vortices can persist for several minutes and endanger other aircraft traversing that turbulent airspace; large vortices are essentially invisible horizontal tornadoes and are a grave threat to smaller aircraft, especially during landing and take off. Accidents related to wake turbulence have resulted in both loss of life and aircraft destruction in the United States and around the world. Currently no cockpit instrumentation exists that tracks wake vortices and enables a pilot to sense and avoid wake turbulence in real-time. This paper presents a prototype of a novel, flight tested instrument that tracks wake vortices and presents this information to a pilot in real time using a synthetic virtual world augmented with wake turbulence information.

Progress in Aerospace Sciences, 2002

This paper discusses the problem of wake vortices shed by commercial aircraft. It presents a consolidated European view on the current status of knowledge of the nature and characteristics of aircraft wakes and of technical and operational procedures of minimizing and predicting the vortex strength and avoiding wake encounters. Methodological aspects of data evaluation and interpretation, like the description of wake ages, the characterization of wake vortices, and the proper evaluation of wake data from measurement and simulation, are addressed in the first part. In the second part an inventory of our knowledge is given on vortex characterization and control, prediction and monitoring of vortex decay, vortex detection and warning, vortex encounter models, and wake-vortex safety assessment. Each section is concluded by a list of questions and required actions which may help to guide further research activities. The primary objective of the joint international efforts in wake-vortex research is to avoid potentially hazardous wake encounters for aircraft. Shortened aircraft separations under appropriate meteorological conditions, whilst keeping or even increasing the safety level, is the ultimate goal. Reduced time delays on the tactical side and increased airport capacities on the strategic side will be the benefits of these ambitious ventures for the air transportation industry and services.

This article discusses the alternative methods for the quality assessment of ship wakes. Available methods are classified in two groups: heuristic methods and analytical methods. Within the context of the heuristic methods the wake quality criteria adopted by BSRA are presented and underlying reasoning is expressed. The methods based on flow kinematics, flow geometry and turbulent boundary layer approximation are the subjects of the analytical methods. It is shown that although these methods have a considerable potential for representing the flow quality, with the current wake survey t echni ques, analytic al meth ods cannot be applied adequately due to the lack of sufficient data. 34

Journal of Aircraft

Wake vortex encounter reports as well as simulations show a significantly higher encounter risk in ground proximity. This is caused by the special behavior of wake vortices in ground effect. Nevertheless, hazardous wake encounters with adverse consequences are rarely reported in reality. In order to gain more insight in the mechanisms of wake

Noise, vibration, air quality and other environmental parameters in an aircraft cabin affects comfort, well-being, performance etc of the flight and cabin crew, as well as passengers. The various physical, psychophysical and intrinsic factors (like health status) are linked to overall "output" parameters representing e.g. crews' health and performance. The mutual interaction of all factors must be investigated in order to establish a "human response model" which allows to quantify the impact of measures to improve the cabin environment. Experiments to reveal input-output relations are difficult to perform in real flights and are therefore conducted in simulated flight conditions using virtual reality. A selection of noise and vibration, of temperature and of humidity levels are investigated with respect to numerous "output" parameters determined by psychophysical methodology, by questionnaires and by physiological measurements. The experiments are p...

2015

This paper presents a severity metric supporting the characterization of the effect of a wake vortex encounter on a follower aircraft. The proposed metric is the Rolling Moment Coefficient computed using various simplified assumptions that lead to a simple and usable metric. The metric can indeed be computed using available aircraft data. The paper also presents the assessment of the metric based on the results of a wake vortex encounter flight test campaign performed by Airbus. The use of the proposed metric yields good agreement with the experimental data. Because it is simple, yet realistic compared to experimental data, the metric can be used in a relative safety analysis permitting a reduction of the wake turbulence separations compared to today’s ICAO standard, as was done in the framework of the RECAT-EU project. Keywords-Wake Turbulence; Wake Vortex Encounter; Rolling Moment; Severity Metric; Rolling Moment Coefficient; RECAT-EU

Comptes Rendus Physique, 2005

Wake turbulence is a major concern for busy airports since it limits capacity. Solutions for new aircraft staggering procedures are sought which relax the current separations but keep safety on a high level. Systems which advice air-traffic control on wakevortex behaviour under present and expected weather conditions will, hopefully, contribute to such a solution. Knowledge on transport and decay of wake vortices in the atmosphere is presented. Concepts and designs of wake-vortex advisory systems in Europe and the USA are outlined. European wake-vortex measurement and prediction campaigns are described where the components of such systems have been tested successfully. To cite this article: T.

Progress in Aerospace Sciences, 2011

The flow and flight physics of wake vortex systems has been intensively investigated concentrating on a large variety of aspects. This paper gives a brief overview on past and present wake vortex research activities such as early studies, integrated programs, model and flight tests, numerical investigations, fundamental physical aspects and alleviation strategies. Then, detailed results of the properties of the wake near field and extended near field are presented addressing typical length and time scales and especially turbulence quantities. Progressing from the near field to the far field wake instability mechanisms are explained along with their relevance for wake vortex decay. Characteristic quantities are given for the short and long wave instabilities associated with vortex merging and wakes consisting of two and four trailing vortices. A non-dimensional frequency parameter is introduced to classify the main instability types. Means for wake vortex alleviation are described aimed at influencing the wake vortex turbulence field or triggering and amplifying the inherent instabilities. The methods discussed include passive means such as the effects of spoilers, differential flap setting and four-vortex systems and active means using oscillating flaps or auxiliary devices.

Journal of …, 2009

Engineering Notes ENGINEERING NOTES are short manuscripts describing new developments or important results of a preliminary nature. These Notes should not exceed 2500 words (where a figure or table counts as 200 words). Following informal review by the Editors, they may be published within a few months of the date of receipt. Style requirements are the same as for regular contributions (see inside back cover).

Proceeding of the 33rd European Safety and Reliability Conference

A multidisciplinary team of academics, flight safety experts, pilots, flight simulation engineers and human factors specialists adapted the Boeing 737 Next Gen simulator Airfox UPRT at AMST, Ranshofen, Austria to be capable to 'inject' a variable wake vortex encounter (WVE) in cruise flight and measure the effect on a type-rated operating crew. As part of the EU SAFEMODE project (2019-2022), this was used to carry out a validation study for the use of new Air Traffic Control (ATC) cruise wake alerting procedures. Developed at DMU, the flight simulation model for the extended flight envelope allowed continuation of flight simulations in case of onset of high angles of attack and stall conditions following WVE. Along with facilitating the validation of new ATC procedures, the flight data also provided insights into pilot upset prevention and recovery training (UPRT) in the era of recurrent academic and flight training for upset prevention and recovery.

JISSA Conf., Paris, …, 2005

The ATC-Wake project is funded by the EC under the "Information Society Technology" Programme. Main objective is the development of an Air Traffic Control Wake Vortex Safety and Capacity Integrated Platform (IP). This IP is used to evaluate interoperability with existing ATC systems, to assess possible safety and capacity improvements, and to evaluate operational usability and acceptability for air traffic controllers. It constitutes an essential step for installation of an "integrated ATC decision support system" at airports, enabling air traffic controllers to safely apply new optimised weather based aircraft spacing. The system integrates four new wake-vortex related subsystems: a Separation Mode Planner component (based on a weather forecasting and nowcasting system), a Predictor component (based on the weather nowcasting system and on a wake vortex prediction system), a Detector component (based on weather and wake sensors), a Monitoring and Alerting component (which notifies the air traffic controllers in case of a discrepancy between prediction and detection information), as well as Human Machine Interfaces to the controllers. Used in combination with new wake vortex safety regulation, the ATC-Wake System will provide both tactical and strategic benefits, while maintaining the required level of safety. This paper focuses on the ATC-Wake Predictor, which predicts for individual aircraft the wake vortex behavior in the pre-defined arrival or departure area(s). Prediction is performed using probabilistic wake vortex prediction models fed by real-time meteorological data (most recent nowcast data as well as ground or down-linked airborne measurements) from the time the aircraft reaches a critical arrival area entry until it lands and from the take-off until it leaves the critical departure area. The prediction quality being directly related to input data quality (meteorological and radar data), a safety buffer is applied to satisfy accuracy requirements of Air Traffic Controllers and/or regulatory authorities. The prediction is updated in short intervals (6 seconds) and the information is provided to ATC through a HMI in the form of a Wake Vortex Vector. It is also vaulted/assessed by wake vortex measurements (performed by the Detector) .