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Air-to-air visual acquisition performance with TCAS II

November 7, 1984
  |
Project Report
Author:
John W. Andrews
Published in:
MIT Lincoln Laboratory Report ATC-130
Topic:
collision avoidance
R&D area:
R&D group:

Summary

The ability of pilots to visually acquire aircraft approaching on collision cources is analyzed using a mathematical model of visual acquisition. The model is calibrated by reference to subject pilot flight test data resulting from testing of the Traffic Alert and Collision Avoidance System (TCAS). Techniques are presented that allow the determination of the probability of visual acquisition for a range of intruder aircraft sizes and closing rates. The effect of visual range (atmospheric visibility) upon visual acquisition performance is analyzed.
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Summary

The ability of pilots to visually acquire aircraft approaching on collision cources is analyzed using a mathematical model of visual acquisition. The model is calibrated by reference to subject pilot flight test data resulting from testing of the Traffic Alert and Collision Avoidance System (TCAS). Techniques are presented that allow...

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Air-to-air visual acquisition performance with TCAS II

An automatic weather station network for low-altitude wind shear investigations

September 18, 1984
  |
Project Report
Author:
Diana L. Klingle-Wilson
…
Published in:
MIT Lincoln Laboratory Report ATC-128
Topic:
weather
R&D area:
R&D group:

Summary

During the summer of 1983 an experimental network of automatic weather stations (a mesonet) was operated in the vicinity of Hanscom Field, northwest of Boston, as part of a larger effort to collect Doppler radar and meteorological data on thunderstorms and other potentially hazardous weather events in this area. This report describes the mesonet system used and presents in detail the data collected on 21-22 July 1983. Conclusions about the limitations and the future use of the mesonet system are also included.
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Summary

During the summer of 1983 an experimental network of automatic weather stations (a mesonet) was operated in the vicinity of Hanscom Field, northwest of Boston, as part of a larger effort to collect Doppler radar and meteorological data on thunderstorms and other potentially hazardous weather events in this area. This...

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An automatic weather station network for low-altitude wind shear investigations

A comparison of storm tracking and extrapolation algorithms

July 31, 1984
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Project Report
Author:
John C. Brasunas
Published in:
MIT Lincoln Laboratory Report ATC-124
Topic:
weather
R&D area:
R&D group:

Summary

The FAA requires short-term forecasts of the development and motion of high reflectivity regions to plan for weather avoidance in the en route and terminal areas. Specific needs include choice of air routes and anticipating when to open or close approach/departure gates, descent corridors, and runways. This report compares storm-tracking algorithms for making short-term (0-30 minute) forecasts of high reflectivity areas, to serve these air traffic control needs. The area forecasts are made by moving the key features of the current reflectivity map according to the velocities derived from the storm trackers. The NEXRAD centroid, correlation, and Crane peak-cell trackers are compared against themselves, persistence, and a best-fit extrapolation. Two performance measures are used: (a) overlap of predicted versus actual areas (b) accuracy in flight-path choice. The second method is a new way of scoring the predictor performance and is particularly suited to aviation needs. Five storms are considered, three in Massachusetts and two in Oklahoma. The correlation and peak-cell trackers generally performed well in the Massachusetts storms, close to a best correlation fit extrapolator. The centroid tracker behaves erratically, due to contour merging and splitting. The centroid tracker performed well on compact, Oklahoma storms where the correlation and peak-cell trackers were misled by storm propagation, an effect to be expected when there is high vertical shear of the horizontal wind. It is recommended that either the correlation or centroid tracker be used, depending on the type of storm expected. The centroid tracker would be used on compact storms; the correlation tracker would be used on storms without substantial propagation. The forecasts appear to be skillful in predicting high-reflectivity areas; however, they are less skillful in anticipating flight-paths which do not intersect these areas. Inclusion of forecasts of storm growth and decay will probably be required to improve the performance; anticipating growth and decay will also be important for forecasts of greater than 30 minutes.
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Summary

The FAA requires short-term forecasts of the development and motion of high reflectivity regions to plan for weather avoidance in the en route and terminal areas. Specific needs include choice of air routes and anticipating when to open or close approach/departure gates, descent corridors, and runways. This report compares storm-tracking...

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A comparison of storm tracking and extrapolation algorithms

Rain rate climatologies over marine regions

May 1, 1984
  |
Project Report
Author:
Andreas K. Goroch
…
Published in:
no published logic to cover case - index 63
Topic:
weather
R&D area:
R&D group:

Summary

A method to relate archived marine meteorological observations to two-minute average rain rates is described. The method is used to produce maps that indicate the frequency of observation of critical rain rates (5, 8, and 15 mm/hr) for the Atlantic, North Pacific and Indian Oceans.
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Summary

A method to relate archived marine meteorological observations to two-minute average rain rates is described. The method is used to produce maps that indicate the frequency of observation of critical rain rates (5, 8, and 15 mm/hr) for the Atlantic, North Pacific and Indian Oceans.

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Rain rate climatologies over marine regions

Fundamentals of mode S parity coding

April 2, 1984
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Project Report
Author:
Jeffrey L. Gertz
Published in:
MIT Lincoln Laboratory Report ATC-117
Topic:
mode S data links
R&D area:
R&D group:

Summary

This report presents the details and basic theory of the coding scheme employed on Mode S uplink and downlink transmissions. Since ATCRBS interference is the main source of error for these signals, a cyclic burst detection code was chosen for Mode S. This code permits simple error detection at the transponder and more complex error correction at the sensor. The theory behind cyclic encoding and decoding as used for Mode S is presented first. Then, since polynomial multiplication and division are required for these processes, circuits for these operations are described. Finally, the last chapter describes the actual implementations specified for encoding and decoding in both the transponder and sensor.
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Summary

This report presents the details and basic theory of the coding scheme employed on Mode S uplink and downlink transmissions. Since ATCRBS interference is the main source of error for these signals, a cyclic burst detection code was chosen for Mode S. This code permits simple error detection at the...

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Fundamentals of mode S parity coding

Adaptive noise cancellation in a fighter cockpit environment

March 19, 1984
  |
Conference Paper
Author:
William A. Harrison
…
Published in:
ICASSP'84, IEEE Int. Conf. on Acoustics, Speech and Signal Processing, 19-21 March 1984.
Topic:
speech
R&D area:
R&D group:

Summary

In this paper we discuss some preliminary results on using Widrow's Adaptive Noise Cancelling (ANC) algorithm to reduce the background noise present in a fighter pilot's speech. With a dominant noise source present and with the pilot wearing an oxygen facemask, we demonstrate that good (>10 dB) cancellation of the additive noise and little speech distortion can be achieved by having the reference microphone attached to the outside of the facemask and by updating the filter coefficients only during silence intervals.
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Summary

In this paper we discuss some preliminary results on using Widrow's Adaptive Noise Cancelling (ANC) algorithm to reduce the background noise present in a fighter pilot's speech. With a dominant noise source present and with the pilot wearing an oxygen facemask, we demonstrate that good (>10 dB) cancellation of the...

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Adaptive noise cancellation in a fighter cockpit environment

A high stability TWTA for ground surveillance applications

March 13, 1984
  |
Conference Paper
Author:
C. E. Hayse
…
Published in:
Proc. 1984 IEEE Natl. Radar Conf., 13-14 March 1984, pp. 110-114.
Topic:
radar
R&D area:
R&D group:

Summary

A high stability, C-band transmitter capable of supporting -68 dBr subclutter visibility over a wide range of pulse widths and duty factors was developed for use in a multimode, battlefield surveillance radar. The transmitter was mode-switched between groups of 1/4, 20 and 65 microsecond radar pulses and long duration (100ms) FSK burst. A key feature was the use of a high speed, interpulse regulator to maintain proper TWT voltage and to limit ripple independent of waveform without the need for excessively large energy storage. Actual measured performance met the 100 mV cathode ripple specification without the use of PKF synchronization, independent of PKI, duty cycle and pulse width and was confirmed via direct evaluation of electrode voltages, serrodyne phase jitter and the radar pulsed-Doppler spectrum.
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Summary

A high stability, C-band transmitter capable of supporting -68 dBr subclutter visibility over a wide range of pulse widths and duty factors was developed for use in a multimode, battlefield surveillance radar. The transmitter was mode-switched between groups of 1/4, 20 and 65 microsecond radar pulses and long duration (100ms)...

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A high stability TWTA for ground surveillance applications

Development of surveillance techniques for TCAS II

March 5, 1984
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Conference Paper
Author:
William H. Harman III
Published in:
IEE Colloquium on Airborne Collision Avoidance, London, Uk, 5 March 1984, PP. 2/1-2/4.
Topic:
collision avoidance
R&D area:
R&D group:

Summary

In the development program of airborne collision avoidance, the equipment intended for installation on air carriers is designated TCAS 11 in the United States. A TCAS 11 installation my be thought of as consisting of two major subsystems: (1) air-to-air surveillance, and (2) control logic (including the logical tests that decide when another aircraft is dangerously close, algorithm that select an appropriate vertical resolution advisory, and a display of the advisory to the pilot). This paper focuses on the air-to-air surveillance subsystem. It identifies the disturbance phenomena that affect performance, presents a number of techniques that have been developed to overcome these difficulties, and presents performance measurements made through airborne testing. A TCAS II installation carries out surveillance in both Mode S and Mode C. The former is used for all Mode S aircraft, including other TCAS II aircraft. The latter is used for all other aircraft, provided they are equipped to reply in Mode C. This paper concentrates on surveillance in Mode C, which is by far the more demanding case.
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Summary

In the development program of airborne collision avoidance, the equipment intended for installation on air carriers is designated TCAS 11 in the United States. A TCAS 11 installation my be thought of as consisting of two major subsystems: (1) air-to-air surveillance, and (2) control logic (including the logical tests that...

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Development of surveillance techniques for TCAS II

Flight testing of TCAS II with subject pilots

March 5, 1984
  |
Conference Paper
Author:
John W. Andrews
Published in:
IEEE Colloquium on Airborne Collision Avoidance, London, UK, 5 March 1984, pp. 3/1-3/4.
Topic:
collision avoidance
R&D area:
R&D group:

Summary

All safety benefits to be derived from the Traffic Alert and Collision Avoidance System (TCAS) are dependent upon the aircraft crew understanding and reacting appropriately to the TCAS advisories. For this reason it is important to display the TCAS information so that it can be promptly and unambiguously understood by the crew. It is also important that the crew be able to integrate the TCAS advisory information with information from other sources so that TCAS becomes a compatible addition to pre-existing safety procedures and not a contending alternative. Because crew response to TCAS is strongly influenced by visual cues received from outside the cockpit, testing in actual flight has proven important. Under sponsorship of the Federal Aviation Agency (FAA), Lincoln Laboratory conducted a series of flight tests with an experimental TCAS II unit to investigate crew response issues.
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Summary

All safety benefits to be derived from the Traffic Alert and Collision Avoidance System (TCAS) are dependent upon the aircraft crew understanding and reacting appropriately to the TCAS advisories. For this reason it is important to display the TCAS information so that it can be promptly and unambiguously understood by...

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Flight testing of TCAS II with subject pilots

General aviation TCAS avionics (GATCAS)

February 27, 1984
  |
Project Report
Author:
Randal L. Briggs
…
Published in:
MIT Lincoln Laboratory Report ATC-115
Topic:
collision avoidance
R&D area:
R&D group:

Summary

Experimental Traffic Alert and Collision Avoidance System (TCAS) avionics developed for the FAA at MIT Lincoln Laboratory are described. The objective of the program under which this equipment was developed was to assess the feasibility of providing a small, low-cost unit for general aviation usage. The experimental general aviation TCAS (GATCAS) avionics incorporates a new system architecture using a microprogrammed sequencer, a 16-bit microprocessor and a low-power, solid state sransmitter appropriate to the class of aircraft expected to employ GATCAS. The general aviatio unit is designed to operate below 10,000 feet in densities of up to 0.02 aircraft/nmi^2, and to provide a pilot warning time (TAUR) of 25 seconds. Assuming a track acquisition time of 10 seconds and a maximum closing speed of 300 knots, the required theoretical range of GATCAS is 3.4 nmi. The report includes (as an appendix) a cost analysis for general aviation TCAS avionics.
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Summary

Experimental Traffic Alert and Collision Avoidance System (TCAS) avionics developed for the FAA at MIT Lincoln Laboratory are described. The objective of the program under which this equipment was developed was to assess the feasibility of providing a small, low-cost unit for general aviation usage. The experimental general aviation TCAS...

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General aviation TCAS avionics (GATCAS)
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