|InfoVis.net>Magazine>message nº 176||Published 2005-11-28|
|También disponible en Español|
The digital magazine of InfoVis.net
Recently the Portuguese aviation authorities issued their final accident report about Air Transat flight TS 236 of August 24, 2001. Said flight was close to ending in tragedy since the plane, in flight from Toronto (Canada) to Lisbon (Portugal) flamed out both jets due to a complete loss of fuel over the Atlantic Ocean.
The pilots were unable to correctly identify the loss of fuel that happened in one of the turbines. This fact produced strange readings in the oil temperature indicators. Moreover they acted from memory, without following the written procedures that describe how to act when a fuel imbalance appears between the two fuel tanks of the plane.
The plane ran out completely of fuel over the ocean, at night, 120 km away from the Terceira island (Azores). The pilots headed towards the island and were able to land safely with only minor injuries to 18 people during evacuation, thanks to the high flying skills of the pilots after a tense glide for 19 minutes, with reduced instrumentation fed by the battery and with the hydraulic system fed by an emergency Ram Air Turbine that uses the wind as an energy resource.
This is a clear example of the importance of situation awareness. The pilots thought for a long time the oil temperature readings and remaining fuel were wrong due to the unusual situation and the causes that led to it. Nevertheless the information systems of the plane an Airbus A320-243 that had suffered a change of engine using inadequate procedures, were accurately reporting the situation.
There's no other place where information visualisation plays a clearer role nor a more critical one than in the cockpit of a plane. Unlike automobiles where engine parameters are almost irrelevant for us, attending only the speed, the proper handling of a plane requires being aware of a non negligible amount of flight and engine performance parameters without which knowledge flying can become an experience of undetermined ending.
Even the simplest ultra-light planes offer a quantity of information about these parameters that easily quadruples those of the average car.
Flight information systems have become increasingly more sophisticated as the digital world has incorporated data presentation displays that make it possible to see seemingly the flight parameters or a moving map centered in our GPS localization.
Around 1980 it was discovered that human beings extract the global aspects of a scene before perceiving the details of the same. Consequently these global aspects predominate when processing the information they provide. Moreover, it's believed that this type of analysis is preemptive, i.e. it happens without the cognitive effort associated to the sequential search of features followed by their individual analysis. An example of preemptive perception is the virtually instantaneous recognition of a face, that happens without the need to think, in an almost automatic way.
It appears then logical to think that information systems, be them for controlling an airplane, a nuclear plant or a company involved in the market should offer a clear representation of the global aspects which then allow the user to go into more detailed features. This, on the other hand, matches well with the famous mantra of Ben Shneiderman:
"Overview first, zoom and filter, then details-on-demand"
This wasn't what typically happened in the plane cockpits prior to the digital era. Their control panels where full of circular dials (btw. a fantastic visual metaphor that of the clock) that presented a huge amount of detailed information.
The advent of digital systems has enabled the the creation of multifunction displays that considerably reduce the cognitive overload (there are typically about 5 of them) and make it possible to show any data in graphic format. It's even possible to make searches in the flight or operating manuals, looking at plans and layouts of the machine, if needed.
These systems enable the user to see on the screens the most relevant set of information for the flight while the rest of it stays in the background, except when an alarm occurs. This way the pilots provide themselves with a situation awareness that instead of clogging their cognitive system, frees it from the overload other systems impose.
The amount of visual metaphors that can appear in the same display are very different. They cover from a GPS moving map, dials or tapes showing fuel level, oil temperature or airspeed, among many others.
Active work is under way in order to improve situation awareness, especially for critical fields, like landing on aircraft carriers (see the artícle* by C. Aragon and M. Hearst) where turbulence produced by the ship's infrastructure together with the wind can create vortex and strong local descents that are invisible and dangerous for the pilots.
There are also studies to create sensor systems capable of tele detection of air flows that enable the visualisation of potentially dangerous areas for landing, allowing the pilot to avoid them.
As we have seen information visualisation is present in aviation, as a factor to improve safety. We have spoken only of one example among the many that are using InfoVis. Nuclear plant control , improving driving conditions and battlefield situation awareness are just a few other fields that exemplify that the use of Information Visualistaion is becoming steadily more present in these critical issues.
Cecilia R. Aragon and Marti A Hearst. Improving Aviation Safety with Information Visualization: A Flight Simulation Study. CHI 2005, April 2-7, Portland Oregon USA.
C.M. Hoffman, Y.J.Kim, R.P. Winkler, J.D. Walrath & P.J.Emmerman Visualization for Situation Awareness ACM Proceedings of the 1998 workshop on New paradigms in information visualization and manipulation, Washington, D.C., United States, Pages: 36 - 40, 1998 ISBN:1-58113-179-8
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