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Anyone who has experienced turbulence in flight knows that it is usually not pleasant, and may wonder why this is so difficult to avoid. The book includes papers by various aviation turbulence researchers and provides background into the nature and causes of atmospheric turbulence that affect aircraft motion, and contains surveys of the latest techniques for remote and in situ sensing and forecasting of the turbulence phenomenon. It provides updates on the state-of-the-art research since earlier studies in the 1960s on clear-air turbulence, explains recent new understanding into turbulence generation by thunderstorms, and summarizes future challenges in turbulence prediction and avoidance.
A limited set of radar and aircraft data acquired during the 1981 and 1982 Joint Agency Turbulence Experiment are used to compare incoherent and coherent radar methods for atmospheric turbulence severity estimation. Time series of ground-based radar in-phase and quadrature signal return data are processed by Doppler (Fast fourier tranform) and incoherent (R-meter with and without noise correction) methods to determine Doppler spectrum variance. These variance data serve as input to a turbulence algorithm to derive estimates of turbulence severity. Theses estimates are then compared with in-situ aircraft measurements. Results show the order of preference for the radar methods is Dopple, R-meter with noise correction, and R-meter without noise correction. The Doppler, R-meter with noise correction, and R-meter without noise correction. The R-meter without noise correction method must be considered unreliable since it results in large overestimates of turbulence severity when the signal to noise ratio is less than about 12 dB. The R-meter with noise correction, and R-meter with noise correction method generally duplicates well the results derived from Doppler analysis and may be considered a reasonable alternative when Doppler capability is not available. Keywords: Incoherent radar; Doppler radar; R-meter; Turbulence severity; Eddy dissipation rate; Composite severity class.
The book is a concise guide dealing with the subject of air turbulence and its methods of detection with particular applications to aviation turbulence. It begins with a general description of turbulence and provides a background into the nature and causes of atmospheric turbulence that affect aircraft motion, giving updates on the state-of-the-art research on clear air turbulence (CAT). Important physical processes leading to the Kelvin-Helmholtz instability, a primary producer of CAT, are also explained. The several categories of CAT along with its impact on commercial aviation are also presented in a separate chapter, with particular emphasis on the structural damages to planes and injuries. The central theme of the book deals with both the earlier and the latest CAT detecting methods and techniques for remote and in situ sensing and forecasting. A concise presentation of new technologies for reducing aviation weather-related accidents is also offered. A chapter on the weather accident prevention project of the NASA aviation safety program is also included. Additionally, the book ends with a full description of the recent research activities on CAT and future challenges in turbulence detection, prediction and avoidance.
The purpose of this study was to investigate the detection and display of weather avoidance information to commercial airline, business aircraft, and general aviation aircraft cockpits from the perspective of the professional pilot. A flight campaign was conducted over a period of three years. Convective weather detection was attempted utilizing an experimental airborne weather radar installed on NASA's Airborne Research Integrated Experiments Systems (ARIES) Boeing 757. Additionally ground-based Next Generation Radar (NEXRAD) information and textual data was linked to the aircraft for correlation. It was determined after encountering several heavy turbulence events that radar detection and conventional displays alone were inadequate to provide the types of data needed by the professional flight crew in order to make informed decisions concerning weather avoidance. The NASA King Air B200 and Cessna 206 were also used to evaluate the human factors issues concerning cockpit displays for these classes of aircraft, which are also flown by some professional pilots. In addition to convective weather avoidance associated with thunderstorms or frontal activity, the study also explored clear air turbulence detection techniques. The detection of these events and the communication of this information to other aircraft in an automated Pilot Report format are being used to display danger areas to other pilots.
A limited set of radar and aircraft data acquired during the 1981 and 1982 Joint Agency Turbulence Experiment are used to compare incoherent and coherent radar methods for atmospheric turbulence severity estimation. Time series of ground-based radar in-phase and quadrature signal return data are processed by Doppler (Fast fourier tranform) and incoherent (R-meter with and without noise correction) methods to determine Doppler spectrum variance. These variance data serve as input to a turbulence algorithm to derive estimates of turbulence severity. Theses estimates are then compared with in-situ aircraft measurements. Results show the order of preference for the radar methods is Dopple, R-meter with noise correction, and R-meter without noise correction. The Doppler, R-meter with noise correction, and R-meter without noise correction. The R-meter without noise correction method must be considered unreliable since it results in large overestimates of turbulence severity when the signal to noise ratio is less than about 12 dB. The R-meter with noise correction, and R-meter with noise correction method generally duplicates well the results derived from Doppler analysis and may be considered a reasonable alternative when Doppler capability is not available. Keywords: Incoherent radar; Doppler radar; R-meter; Turbulence severity; Eddy dissipation rate; Composite severity class.
This publication is divided into two sections: detection of clear air turbulence; and operational aspects. Partial contents include: clear air turbulence problems and solutions a state-of-the-art report; the feasibility of optical radar to detect clear air turbulence; early warning of clear air turbulence by photometric measurements; analysis of clear air turbulence incidents and much more.
The combination of increasing airport congestion and the ad vent of large transports has caused increased interest in aircraft wake turbulence. A quantitative understanding of the interaction between an aircraft and the vortex wake of a preceding aircraft is necessary for planning future high density air traffic patterns and control systems. The nature of the interaction depends on both the characteristics of the following aircraft and the characteristics of the wake. Some of the questions to be answered are: What deter mines the full characteristics of the vortex wake? What properties of the following aircraft are important? What is the role of pilot response? How are the wake characteristics related to the genera ting aircraft parameters? How does the wake disintegrate and where? Many of these questions were addressed at this first Aircraft Wake Turbulence Symposium sponsored by the Air Force Office of Sci entific Research and The Boeing Company. Workers engaged in aero dynamic research, airport operations, and instrument development came from several count ries to present their results and exchange information. The new results from the meeting provide a current picture of the state of the knowledge on vortex wakes and their interactions with other aircraft. Phenomena previously regarded as mere curiosities have emerged as important tools for understanding or controlling vortex wakes. The new types of instability occurring within the wake may one day be used for promoting early dis integration of the hazardous twin vortex structure.
During the winter operations, from 1967 to 1971, of Clear Air Turbulence (CAT) research at Wallops Island, Virginia, the Weater Radar Branch of Air Force Cambridge Research Laboratories observed eighteen cases of significant turbulence, defined as cases of light-to-moderate or moderate intensity. The report presents the meteorological data for each of these cases, consisting of synoptic sea level and upper air charts and rawinsonde data, observations of clear air echoes with powerful radars, and aircraft data which are used to indicate the present location and intensity of the turbulence.