Brief summaries are given of research activities at the Massachusetts Institute of Technology (MIT) under the sponsorship of the FAA/NASA Joint University Program. Topics covered include hazard assessment and cockpit presentation issues for microburst alerting systems; the situational awareness effect of automated air traffic control (ATC) datalink clearance amendments; a graphical simulation system for adaptive, automated approach spacing; an expert system for temporal planning with application to runway configuration management; deterministic multi-zone ice accretion modeling; alert generation and cockpit presentation for an integrated microburst alerting system; and passive infrared ice detection for helicopter applications

Simpson, Robert W.

English

NASA Technical Reports Server

M S ~ - ~ c ~ j s ~  
AN INVESTIGATION OF 
AIR TRANSPORTATION TECHNOLOGY 
MASSACHUSETTS INSTITUTE OF TECHNOLOGY 
 robe^ W. Simpson 
Flight Transpodation Laboratory 
M.I.T., Cardridge, MA 02139 
SUMMARY OF RESEARCH ACTIVITIES 
There are three completed projects and three continuing research activities 
under way under the sponsorship of the FAA/NASA Joint University Program 
as the 1990-91 period ends. There were a number of publications du:ring the 
year and a set of Annotated References to them is provided in Section 3. As 
well, the complete conference paper is included for a few of these references. A 
brief summary of the continuing research activities is provided in the next 
section. 
2. REVIEW OF CONTINUING RESEARCH ACTIVITIES 
2.1 Wanke, C., and Hansman, R. J., Hazard Assessment and Cockpit Presentation 
Issues For Microburst Alerting Systems. 
Introduction 
Low altitude wind shear events, and in particular microbursts, are the leading 
weather-related cause of fatal aviation accidents in the U.S. For this reason, 
wind shear hazard detection and alerting system development is a very active 
area of research, and has been a focus of the Joint University program for 
several years. The variety of systems under development for wind shear 
detection and ground-to-air datalink, combined with the advent of electronic 
cockpit instrumentation, allow many options for implementation. of an 
https://ntrs.nasa.gov/search.jsp?R=19920008743 2020-03-17T12:39:17+00:00Z
intiegrated microburst warning system. Recent work at MIT has concentrated 
on two facets of this problem: (1) microburst hazard assessment, and (2) cockpit 
display of microburst alerts to flight crews. 
Microburst Hazard Assessment 
The first task for microburst alert generation is to combine data from several 
systems, which use different measurement techniques, into an estimate of the 
hazard posed to aircraft by a particular wind shear event. This must be done as 
accurately as possible to minimize both missed and unnecessary alarms. 
Holwever, the danger to aircraft posed by a microburst is not a directly 
measurable quantity. Thus, a microburst "hazard criterion" is needed, a 
quantity which can be directly measured or inferred from the available 
measurements. One example of such a criterion, currently used by the 
Terminal Doppler Radar System (TDWR) is maximum wind change across the 
miczroburst. Alternatives to this are shear-based or energy-based criteria which 
are more difficult to measure but relate rncre directly to the effect of the 
wi~~dfield on the dynamics of an aircraft. 
A technique based on batch flight simulation has been developed to evaluate 
sorne candidate hazard criteria.' Simulated approaches through numerically- 
modeled microbursts are flown, and a quantitative measure of approach 
degradation due to the windfield, a "microburst impact parameter," is 
computed. This measure includes both glideslope deviations and airspeed 
losses. The candidate microburst hazard criteria are then correlated with this 
microburst impact parameter. The value of the linear correlation coefficient is 
indicative of the usefulness of that criterion for evaluating the microburst 
hazard to aircraft. 
The results, using 12 modeled microburst windfields in several geometrical 
configurations, indicate that shear-based (airspeed change per unit distance) 
anti energy-based measures correlate very well with the microburst impact 
parameter. Also, maximum wind change was found to correlate very poorly. 
Further work is being done to extend these results to cover additional high- 
re~~olution microburst windfields, and to use these results to define "hazard 
thr~esholds" for accurate alert generation. 
Cotrkpit Display of Microburst Alerts 
Once alerts are generated, they need to be quickly and effectively disseminated 
to the Right crew. Recent work at MIT on this issue has focused on use o f  a 
dig;ital datalink and electronic cockpit displays to graphically present microburst 
alerts to the pilot. A previous piloted simulator experiment performed earlier 
in this program demonstrated that graphical alerts are significantly more 
Wanke, C., and Hansman, R.J., "Alert Generation and Cockpit Presentation for an Integrated 
Microburst Alerting System," AIAA Paper 91-0260, January 1991. 
4 
effective than verbal or alphanumeric alerts.2 A second experiment to further 
explore the use of graphical alerts was then designed and run in June of 1991. 
This experiment tested several different graphical alert formats using the MIT 
Advanced Cockpit Simulator, a part-task simulator of a modern transport 
aircraft with electronic cockpit displays. Alerts were presented on the Elecbonic 
Horizontal Situation Indicator; an example of a multi-level alert format is 
shown in Figure 1. Some of the issues being examined in this experiment are: 
Is presentation of microburst alerts on the EHSI display clear and effective? 
Should the available measurements be used with a hazard threshold to 
generate a single-level alert for "hazardous" microbursts only, or should 
multiple levels of intensity be displayed? 
Should measurements from all of the available sensors be combined to 
form a single "fused" alert, or should alerts from different sources be 
independently displayed? 
What are the procedural implications of displaying graphical alerts, i.e., does 
the positional information present in these alerts cause the pilot to 
significantly alter his avoidance strategy? 
Analysis of the data from this experiment is in progress; nine active airline 
pilots have participated to date. The experiment involves flying a tcttal of 12 
approach scenarios with the simulator, using a variety of graphical alert 
formats. Preliminary results indicate that multi-level alerts are more desirable 
than single level alerts, and that display of alerts on the EHSI was found to be 
very clear and useful by the pilots. Further analysis is underway, and results 
will be presented at the next JUP quarterly meeting. 
2.2 H a h ,  E., and Hansman, R. J., The Situational Awareness Effect of Alltomated 
ATC Datalink Clearance Amendments. 
Introduction 
Among the capabilities envisioned for the future datalink (i-e. digital g;round to 
air communications) system will be the use of these aircraft specific 
communications to supplement and possibly replace most routine A.ir Traffic 
Control (ATC) messages. By reducing the volume of ATC communications, 
including en route and terminal clearance amendments, datalinlk would 
relieve the already congested VHF voice frequencies. Additionally, having 
information being received in digital form makes it extremely easy for the 
Wanke, C., Chandra, D., Hansman, R. J., and Bussolari, S.R., "A Comparison of Voice and Datalink 
for ATC Amendments and Hazardous Wind Shear Alerts," 4th International Symposium on Aviation 
Space Safety, Toulouse, France, 20-22 November, 1990. 
aircraft Flight Management Systems to read the information directly, increasing 
efficiency and reducing data transfer errors. However, the automation of 
tlatalinked ATC clearance amendments could adversely affect the flight crew's 
siituational awareness by reducing their level of involvement in the 
amendment process. This project is investigating the effects of information 
~7resentation mode and amendment procedures on situational awareness of 
l>ossible implementations of datalink. 
(3urrent Work 
Work is proceeding on a part-time simulation study using the MIT Advanced 
Cockpit Simulator. The experiment centers on the information presentation 
rraode and amendment procedures in possible ATC datalink implementations. 
Data is collected on the error detection capabilities of pilots when the procedure 
is altered to change the number of times the airline pilot subject must review 
the data during the process. In particular, the need for keying in of data and 
ailso the need for a readback to ATC is varied independently between scenarios. 
In addition, the mode of presentation is also independently varied between 
verbal, textual, and graphical formats to investigate whether one presentation 
rnode is better than others. Data will also be collected on the pilot's time 
~wrformance and subjective preferences. 
The scenarios will simulate the Northeast Corridor during heavy traffic and 
thunderstorm conditions in order to increase the number of clearance 
a.mendments given to the pilot. Each is designed around two separate kinds of 
errors: the aircraft will be cleared into heavy thunderstorm cells and also will 
kbe routed incorrectly (i.e. to the wrong airport, the wrong approach fix, or on an 
i:18ogical path). Each subject pilot will fly ten scenarios, each of which will have 
a. different combination of presentation mode and amendment procedure. 
Elighten subjects are currently being sought to participate in the experiment. 
The testing stage of the experiment is projected to terminate in September. 
3, ANNOTATED REFERENCES OF 1990-91 PUBLICATIONS 
3.1 (:hi, Zhihang, A Graphic Simulation System for Adaptive, Automated Final 
kipproach Spacing, Flight Transportation Laboratory Report 91-3, June 1991, 
E:li&t Transpo~at ion Laboratory, MIT, Cambridge, MA, 02139 
As airline industry grows and air traffic increases drastically, terminal airspace 
a.round busy airports is becoming more and more crowded. To accommodate 
t:he soaring demand for use of airports, a plausible and profitable way is to 
i:mprove the efficiency of existing airports. An automated final approach 
spacing system can improve the efficiency as well as alleviate the workload of 
a.ir traffic controllers. 
In this research we develop an automated adaptive and interactive Final 
Approach Spacing Advisory (FASA) system to be used in future at busy 
airports. Our system is able to generate and update final arrival paths for 
aircraft and guarantees that the aircraft land as scheduled and safely spaced. It 
prompts air traffic controllers for calls of turns and speed reductions until they 
merge into the approach center line. These automated prompts are adapti.ve to 
errors in the execution of the arrival paths due to winds or pilot response. Also 
our system grants the controllers the ability to manually alter the la~ading 
schedule without violating constraints and regulations. 
It is assumed that a separate metering system has developed a plan for landing 
aircraft. This landing schedule is represented to the ATC controller in FASA as 
a sequence of "schedule boxes" or "slot markers" moving dong the extended 
center line. The ATC controller has some degree of control over the planned 
landings by moving these slot markers. A range of feasible changes in the slot 
position ("feasible interval") can be displayed. If a slot is moved rearwards to 
delay its landing, or if it arrives late for its slot 'on the center line, all subsequent 
slot markers will automatically shift rearwards to maintain safe spacings, and 
the automated prompts are then based on the new plan. If an aircraft arrives 
early, slots are not shifted frontwards automatically, but if any aircraft arrives 
ahead of its slot and will violate safe separations before touchdom, an alert is 
given to the controller. The mathematical methods used to implement this 
system are capable of incorporating a large variety of constraints and other 
interactive features. 
The FASA system was implemented on an Apollo Unix workstation in the C 
language and a graphical simulation using X-Windows was developed to test 
prototypical traffic situations for a single runway. The images of the elennents 
of the FASA system, such as aircraft, slot markers and extended runway oenker 
line, are drawn in different colors on the color display of the Apollo 
workstation. The images of aircraft move along the runway center 'line. 
Prompts for calls of turns and speed reductions are implemented as the 
blinking of the images of the relevant aircraft. Error alerts are implemented as 
the change of colors of the relevant images. The user of our sirnuliltion 
program is given the ability to mouse any slot markers, drag them along the 
runway center line and put them anywhere within the feasible interval 
mentioned earlier. 
The future research effort will extend the logic to incorporate plannini; for 
takeoffs, interactive insertion of missed approaches into the landing plan, and 
multiple runway operations. All of these features are easily implementablle by 
extending the methods used in this thesis to develop FASA. 
3.2 :Hazelton, Lyman R., An Expert System for Temporal Planning with an 
.Application to Runway Configuration Management, Flight Transportation 
'Laboratory Report 91-1, February 1991, Flight Transportation Laboratory, MIT, 
Cambridge, MA, 02139. 
'The centralized Air Traffic Flow Control system depends critically on correct 
(airport capacity estimates for its success. This requirement demands that area 
,supervisors, responsible for the control facilities of the airports, construct a 
realistic schedule of the runway configurations to be used during the next 
several hours of operation. Constructing such a schedule is a difficult task, as it 
depends on several time dependent, strongly interacting factors. These 
variables include the airport ceiling and visibility, the wind speed and 
direction, the operational status of navigational aids, the expected traffic 
demand, noise abatement procedures and time of day, runway maintenance 
and repairs, and snow and ice removal. A computer program to weigh these 
factors and generate such a schedule would be very helpful and could have a 
major economic impact. 
Significant problems stand in the way of creating a general scheduling program 
using standard techniques. Because each airport has difficult runway geometry, 
a different surrounding geography and population distribution, and different 
weather patterns, each scheduler program must be customized for the airport at 
which it is to operate. Using standard programming languages and techniques 
to create so many unique programs would be exorbitantly expensive. Further, 
the programs would require periodic updates to reflect changes in the economy 
and patterns of use at each airport, adding to the cost. Finally, some of the 
factors involved are not easily quantifiable, making the standard numerical 
methods of operations research difficult to apply. 
Rule based "expert system" programs "reason", using logic, about a problem 
rather than just computing numerical results. They possess abilities which 
give them distinct advantages in the kind of problem domain typically 
encountered in Air Traffic Control: their structure consists of a standardized 
central "inference engine" and an easily customized set of rules and facts about 
a particular application; they can be built incrementally and are more easily 
maintained than traditional programs; and they can provide explanations of 
the logical processes used to make a decision, which can immensely simplify 
debugging. 
At the time that this research was begun, there was a significant obstacle to 
using an expert systems approach, as well. While the program of runway 
configuration management clearly requires the ability to reason about time, 
there were no well defined mechanisms for carrying out this kind of reasoning 
in the logic of an expert system. In fact, there was almost no theoreecal work in 
the area of temporal logic upon which one might base such a mechanism. 
This research describes a number of powerful new ideas and techniques which 
extend the range of applicability of expert systems to temporally dependent 
problems. The most important of these is the description of a representation 
and a set of mechanisms which can be added to standard logic in order to 
reason about persistence. Also included are methods necessary to reason about 
irreversible actions. Implementation of these new ideas and mec:hawisms 
extends the temporal reasoning capabilities of an expert system inference 
engine so that it can successfully be applied to problems in Air Traffic Control 
such as runway configuration management. Indeed, they are of such a 
fundamental nature that they are applicable to awidevariety of planning and 
scheduling problems, perhaps including crew maintenance scheduling, space 
shuttle launch sequence scheduling, and autonomous robot task scheduling. 
3.3 Yamaguchi, K., and Hansman, R. J., Deterministic Multi-Zone Ice Accretion 
Modeling, AIAA-91-0265, AIAA 28th Aerospace Sciences Meeting, January 
1991. 
A multi-zone predictive analytical model was created to describe the growth of 
ice on aerofoil leading edges under glare icing conditions. Comparison with 
experimental ice shapes showed good agreement. (See copy of paper included.) 
3.4 Wanke, C., and Hansman, R. J., Alert Generation and Cockpit Presenta~tion for 
an  Integrated Microburst Alerting System, AIAA-91-0260, AIAA 28th Aerospace 
Sciences Meeting, January 1991. 
The issues of providing a cockpit alert for microbursts which combines ground 
and air-based detection systems are investigated. An experiment has been 
designed to evaluate candidate graphical cockpit displays which uses a part-task 
piloted simulator. (See included paper.) 
3.5 Dershowitz, Adam L., and Hansman, R. J., Passive Infrared Ice Detection for 
Helicopter Applications, paper presented at 46th Annual F o a m  of A~mexican 
Helicopter Society, Washington, DC, May 1990. 
A technique is proposed to detect remotely the icing on rotor leading edges by 
using passive infrared thermometry to detect the warning caused by the! release 
of the latent heat of fusion as supercooled water freezes. (See included paper.) 


An investigation of air transportation technology at the Massachusetts Institute of Technology, 1990-1991

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