Publications

Refine Results

(Filters Applied) Clear All

The FAA Terminal Doppler Weather (TDWR) Program

February 3, 1989
  |
Conference Paper
Author:
Donald H. Turnbull
…
Published in:
Proc. Third Int. Conf. on the Aviation Weather Systems, 30 January - 3 February 1989, pp. 414-419.
Topic:
air traffic control
R&D area:
R&D group:

Summary

The Federal Aviation Administration (FAA) initiated the Terminal Doppler Weather Radar (TDWR) program in the mid-1980s in response to overwhelming scientific evidence that low-altitude wind shear had caused a number of major air-carrier accidents. The program is designed to develop a reliable automated system for detecting low-altitude wind shear in the terminal area and providing warnings that will help pilots successfully avoid it on approach and departure. Wind shear has caused more U.S. air-carrier fatalities than any other weather hazard. A 1983 National Research Council (NRC) study (National Research Council, 1983) identified low-altitude wind shear as the cause of 27 aircraft accidents and incidents between 1964 and 1982. A total of 488 people died in seven of these accidents, 112 of them in the 1975 crash of Eastern Flight 66 at New York and 153 in the crash of Pan American Flight 759 at New Orleans in 1982. Since the NRC study was completed, the National Transportation Safety Board (NTSB) has investigated at least three more wind-shear incidents. One of these, the crash of Delta Flight 191 at Dallas/Fort Worth on August 2, 1985, took another 137 lives. Wind shear is not a serious hazard for aircraft enroute between airports at normal cruising altitudes, but low-level wind shear in the terminal area can be deadly for an aircraft on approach or departure. The most hazardous form of wind shear is the microburst, an outflow of air from a small-scale but powerful downward gush of cold, heavy air that can occur beneath a thunderstorm or rain shower or even in rain-free air under a harmless-looking cumulus cloud. As this downdraft reaches the earth's surface, it spreads out horizontally, like a stream of water sprayed straight down on a concrete driveway from a garden hose. An aircraft that flies through a microburst at low altitude first encounters a strong headwind, then a downdraft, and finally a tailwind that produces a sharp reduction in airspeed and a sudden loss of lift. This deadly sequence of events caused the fatal crash at Dallas/Fort Worth in 1985, as well as a number of other serious air-carrier accidents. Wind shear can also be associated with gust fronts, warm and cold fronts, and strong winds near the ground. It is important for pilots to be trained in recovery techniques to use if they are caught in wind shear. But a sudden windspeed change of at least 40 to 50 knots, which is not uncommon in microbursts, presents a serious hazard to jet airliners, and some microbursts simply are non-survivable. The only sure way to survive wind shear in the terminal area is to avoid it. However, flight crews do not have adequate information available today to predict or detect wind shear. The primary goal of the IDWR program is to provide pilots with an objective, quantitative assessment of the wind-shear hazard. The TDWR system also will improve operational efficiency and reduce delays in the terminal area by providing air traffic control supervisors with timely warnings of impending wind shifts resulting from gust fronts.
READ LESS

Summary

The Federal Aviation Administration (FAA) initiated the Terminal Doppler Weather Radar (TDWR) program in the mid-1980s in response to overwhelming scientific evidence that low-altitude wind shear had caused a number of major air-carrier accidents. The program is designed to develop a reliable automated system for detecting low-altitude wind shear in...

READ MORE
The FAA Terminal Doppler Weather (TDWR) Program

Weather sensing with airport surveillance radars

February 3, 1989
  |
Conference Paper
Author:
Mark E. Weber
Published in:
Proc. Third Int. Conf. on the Aviation Weather System, 30 January - 3 February 1989, pp. 68-74.
Topic:
aviation weather
R&D area:
R&D group:

Summary

Modern airport surveillance radars (ASR) are coherent, pulsed-Doppler radars used for detection and tracking of aircraft in terminal area air space. The Federal Aviation Agency (FAA is procuring over 100 next-generation ASR-9 radars for major US. airports while relocating existing ASR-8s to secondary terminals. Thus within the next five years, almost every U.S. airport that supports commercial operations will be equipped with one of these sensitive, highly stable S-band radars. In view of their on- or near-airport location, rapid scan rate and direct data link to air traffic control personnel, it has been recognized that ASRs can also provide flight controllers with timely information on weather conditions that are hazardous to aircraft. An ASR's transmitted frequency, power, pulse-to-pulse stability and receiver sensitivity are well suited for weather sensing. Conversely, its broad elevation beamwidth, rapid antenna scan rate and non-uniform pulse transmission sequence introduce significant complications for the quantitative interpretation of echoes returned from weather. This paper reviews principal results of a four-year, FAA-sponsored program to evaluate the capabilities and limitations of ASRs for measuring storm severity.
READ LESS

Summary

Modern airport surveillance radars (ASR) are coherent, pulsed-Doppler radars used for detection and tracking of aircraft in terminal area air space. The Federal Aviation Agency (FAA is procuring over 100 next-generation ASR-9 radars for major US. airports while relocating existing ASR-8s to secondary terminals. Thus within the next five years...

READ MORE
Weather sensing with airport surveillance radars

Advances in primary-radar technology

January 1, 1989
  |
Journal Article
Author:
Melvin L. Stone
…
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 363-380.
Topic:
surveillance
R&D area:
R&D group:

Summary

Current primary radars have difficulty detecting aircraft when ground clutter, rain, or birds interfere. To overcome such interference, the Moving Target Detector (MTD) uses adaptive digital signal and data processing techniques. MTD has provided the foundation for a new generation of primary radars called Airport Surveillance Radar-9 (ASR-9). In addition to achieving near-optimal target-detection performance, ASR-9 also provides timely weather information. The Federal Aviation Administration (FAA) is installing ASR- 9 systems at more than 100 airports across the United States.
READ LESS

Summary

Current primary radars have difficulty detecting aircraft when ground clutter, rain, or birds interfere. To overcome such interference, the Moving Target Detector (MTD) uses adaptive digital signal and data processing techniques. MTD has provided the foundation for a new generation of primary radars called Airport Surveillance Radar-9 (ASR-9). In addition...

READ MORE
Advances in primary-radar technology

Applying artificial intelligence techniques to air traffic control automation

January 1, 1989
  |
Journal Article
Author:
David A. Spencer
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 537-554.
Topic:
air traffic control
R&D area:
R&D group:

Summary

We have developed a computer program that automates rudimentary air traffic control (ATC) planning and decision-making functions. The ability to plan, make decisions, and act on them makes this experimental program qualitatively different from the more clerical ATC software currently in use. Encouraging results were obtained from tests involving simple scenarios used to train air traffic controllers.
READ LESS

Summary

We have developed a computer program that automates rudimentary air traffic control (ATC) planning and decision-making functions. The ability to plan, make decisions, and act on them makes this experimental program qualitatively different from the more clerical ATC software currently in use. Encouraging results were obtained from tests involving simple...

READ MORE
Applying artificial intelligence techniques to air traffic control automation

Experimental examination of the benefits of improved terminal air traffic control planning

January 1, 1989
  |
Journal Article
Author:
David A. Spencer
…
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 527-536.
Topic:
air traffic control
R&D area:
R&D group:

Summary

Airport capacity can be improved significantly-by precisely controlling the sequence and timing of traffic flow-even when airspace usage and procedures remain fixed. In a preliminary experiment, a plan for such sequencing and timing was applied in a simulation to a 70-min traffic sample observed at Boston's Logan Airport, and the result was a 13% increase in terminal throughput. A total of 2.2 aircraft flight hours were saved. Delays imposed upon arriving traffic in the simulation were much more equitably distributed than in the actual traffic sample. An even greater improvement may be possible if controllers are able to space aircraft more precisely on final approach than was achieved in the simulation. If the plan had been followed precisely, the throughput increase would have been 23%.
READ LESS

Summary

Airport capacity can be improved significantly-by precisely controlling the sequence and timing of traffic flow-even when airspace usage and procedures remain fixed. In a preliminary experiment, a plan for such sequencing and timing was applied in a simulation to a 70-min traffic sample observed at Boston's Logan Airport, and the...

READ MORE
Experimental examination of the benefits of improved terminal air traffic control planning

Electrical characteristics of microburst-producing storms in Denver

January 1, 1989
  |
Conference Paper
Author:
Earle R. Williams
…
Published in:
Proc. 24th Conf. on Radar Meteorology, 27-31 March 1989, pp. 89-92.
Topic:
aviation weather
R&D area:
R&D group:

Summary

Coordinated Doppler radar and electrical measurements of thunderstorm microbursts were initiated by Lincoln Laboratory and the MIT Weather Radar group in Huntsville, AL in 1987. These measurements were intended to identify electrical precursors to aviation hazards at ground level and to study the relationship between the state of cloud convective development and the prevalent lightning type. The results of the Huntsville Study (Williams and Orville, 1988; Williamd et al., 1988) showed pronounced peaks in intracloud lightning activity and radar reflectivity above the melting level 5-10 minutes prior to maximum outflow velocities at the surface. A similar behavior has been reported by Goodman et al. (1988) for a thunderstorm observed in COHMEX in the same region. These observations support a prominent role for ice, both in promoting the intracloud lightning aloft and in subsequently driving the outflow by virtue of the melting process. All Huntsville cases studied were 'wet' microbursts with maximum low level reflectivity factors greater than 50 dBZ. The parent storms were deep (H>11km) and electrically active (flash rate greater than or equal to 1min^-1). Recent microburst studies in Denver (Hjelmfelt, 1987); Biron and isaminger, 1989) have identified, in addition to a majority of 'wet' microbursts, substantial numbers of dry microburst-producing storms (Z<10^3 mm^6/m^3) with elevated cloud bases and modest radar cloud tops. The present studies were aimed at determining to what extent the electrical manifestations observed in Huntsville were prevalent in Denver. This paper presents some preliminary results for the Denver measurements from the summer of 1988.
READ LESS

Summary

Coordinated Doppler radar and electrical measurements of thunderstorm microbursts were initiated by Lincoln Laboratory and the MIT Weather Radar group in Huntsville, AL in 1987. These measurements were intended to identify electrical precursors to aviation hazards at ground level and to study the relationship between the state of cloud convective...

READ MORE
Electrical characteristics of microburst-producing storms in Denver

Multisensor surveillance for improved aircraft tracking

January 1, 1989
  |
Journal Article
Author:
Jeffrey L. Gertz
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 381-396.
Topic:
aircraft
R&D area:
R&D group:

Summary

Cross-range measurements of aircraft travelling at distances of 50 to 200 miles include significant errors. Therefore, heading estimates for medium-to-long-range aircraft are not sufficiently accurate to be useful in conflict-detection predictions. Accurate crossrange measurements can be made-by using two or more sensors to measure aircraft position-but such measurements must compensate for the effects of system biases and aircraft turns. A set of algorithms has been developed that are resistant to system biases, that detect turns, and that track successfully through both biases and turns. These algorithms can be incorporated into a complete multisensor system, with good intersensor correlation of aircraft tracks and no added delays to the air traffic control processing chain.
READ LESS

Summary

Cross-range measurements of aircraft travelling at distances of 50 to 200 miles include significant errors. Therefore, heading estimates for medium-to-long-range aircraft are not sufficiently accurate to be useful in conflict-detection predictions. Accurate crossrange measurements can be made-by using two or more sensors to measure aircraft position-but such measurements must compensate...

READ MORE
Multisensor surveillance for improved aircraft tracking

Parallel runway monitor

January 1, 1989
  |
Journal Article
Author:
Raymond R. LaFrey
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 411-436.
Topic:
air traffic control
R&D area:
R&D group:

Summary

The availability of simultaneous independent approaches to parallel runways significantly enhances airport capacity. Current FAA procedures permit independent approaches in instrument meteorological conditions (IMC) when the parallel runways are spaced at least 4,300 ft apart. Arriving aircraft must be dependently sequenced at airports that have parallel runways separated by less than 4,300 ft, a procedure that reduces the arrival rate by as much as 250h. The need for greater airport capacity has led to intense interest in new technologies that can support independent parallel IMC approaches to runways spaced as close as 3,000 ft. This interest resulted in several FAA initiatives, including a Lincoln Laboratory program to evaluate the applicability of Mode-S secondary surveillance radars for monitoring parallel runway approaches. This paper describes the development and field activities of this program.
READ LESS

Summary

The availability of simultaneous independent approaches to parallel runways significantly enhances airport capacity. Current FAA procedures permit independent approaches in instrument meteorological conditions (IMC) when the parallel runways are spaced at least 4,300 ft apart. Arriving aircraft must be dependently sequenced at airports that have parallel runways separated by less...

READ MORE
Parallel runway monitor

Propagation of mode S beacon signals on the airport surface

January 1, 1989
  |
Journal Article
Author:
M. Loren Wood Jr
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 397-410.
Topic:
air traffic control
R&D area:
R&D group:

Summary

Many airports across the United States will soon be equipped with Mode S, a next generation beacon (or secondary) radar system. One feature of Mode S is that it provides a data link between airborne aircraft and air traffic controllers. If Mode S could be used to communicate with aircraft on the airport surface, the radar system would improve airport safety and efficiency on runways and taxiways. The airport surface, however, is a hostile propagation environment. This article outlines a candidate design for the propagation of Mode-S beacon signals on the airport surface. Data that support the feasibility of Mode S for surveilling runways and taxiways are presented.
READ LESS

Summary

Many airports across the United States will soon be equipped with Mode S, a next generation beacon (or secondary) radar system. One feature of Mode S is that it provides a data link between airborne aircraft and air traffic controllers. If Mode S could be used to communicate with aircraft...

READ MORE
Propagation of mode S beacon signals on the airport surface

Multipath modeling for simulating the performance of the Microwave Landing System

January 1, 1989
  |
Journal Article
Author:
James E. Evans
…
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 459-474.
Topic:
aviation weather
R&D area:
R&D group:

Summary

The Microwave Landing System (MLS) will be deployed throughout the world in the 1990s to provide precision guidance to aircraft for approach and landing at airports. At Lincoln Laboratory, we have developed a computer-based simulation that models the performance of MLS and takes into account the multipath effects of buildings, the surrounding terrain, and other aircraft in the vicinity. The simulation has provided useful information about the effects of multipath on MLS performance.
READ LESS

Summary

The Microwave Landing System (MLS) will be deployed throughout the world in the 1990s to provide precision guidance to aircraft for approach and landing at airports. At Lincoln Laboratory, we have developed a computer-based simulation that models the performance of MLS and takes into account the multipath effects of buildings...

READ MORE
Multipath modeling for simulating the performance of the Microwave Landing System
2001-2010 of 2301