The advent of computers in the cockpit and electronic flight displays had opened up tremendous new opportunities for conveying information to pilots. In the 1970s, the TCV program had conducted a lot of research into different display formats, but the focus had been primarily on flight and navigation displays. In 1987, however, a NASA researcher in Langley's Aviation Safety/Automation program, Terence S. Abbott, began working on a new format for displaying engine instrumentation information. The display was called the Engine Monitoring and Control System (EMACS).

Abbott's focus was actually on developing a more effective format for any kind of display. As opposed to electromechanical instruments, which could only present raw sensor information, computerized, electronic displays had the capability of processing that information into a more useful form for the pilot. Specifically, Abbott wanted to evaluate the advantages of "taskoriented" displays, which would, as the name suggested, take the end task the operator needed to perform with the information and design the display to support that task. He chose an engine instrumentation display as an application with which to experiment because the tasks pilots had to perform with engine information were relatively simple, but they still involved both monitoring and control functions.

The primary control task pilots had to perform with aircraft engines was choosing and setting the power level. Conventional, electromechanical engine instruments gave the pilot direct readings of the engine pressure ratio (EPR), which measured the difference in pressure between the engine inlet and outlet, the speed of the low pressure engine compressor (N1), and the speed of the high pressure engine compressor (N2). The pilot would use these readings to interpret and adjust the amount of power, or thrust, the engine was developing. Abbott's design, on the other hand, used a computer to process all that information for the pilot. Using a model of the engine's performance and vertical bar graphics, EMACS showed the pilot the actual thrust commanded (presented as a percentage of full takeoff power), as well as the thrust the engines were putting out at the moment.

The second aspect of EMACS addressed the engine monitoring functions pilots had to perform. To insure that the engines were operating properly, pilots had to constantly monitor readings of exhaust gas temperature, engine oil pressure, oil temperature, and fuel flow, in addition to the EPR, N1 and N2 gauges. The conventional, round electromechanical instruments showed the numerical value for each parameter and would indicate if that number was in a caution or alert range. The only way for a pilot to detect small deviations from a normal reading, however, was to know, from past experience, what a normal reading at that power setting should be. Small deviations were significant because they were often early indications of engine trouble.

The EMACS format was based on the assumption that knowing the actual numerical value of any engine parameter was not as critical to the pilot as knowing whether the reading was normal or not. To give the pilot that information, EMACS presented the engine readings in a format called a "column deviation graph." The display represented each engine parameter as a separate vertical column on a common graph. The readings were synchronized so that, regardless of the actual numerical value, the middle line of the display represented zero deviation from a "normal" reading at a given power setting. The first lines above and below that line represented a caution level, and the lines beyond that signalled a warning level. The column graphs for each parameter would extend up or down from the middle line for any high or low deviation from the ideal value. For more specific information, each column was labelled and the numerical value of each parameter was displayed in digital form above the appropriate column. [Ref 6-9]

Displays of normal engine power-up for takeoff; top-traditional display, bottom-Engine Monitoring and Control System (E-MACS) display, designed for easy reading.

This display had several potential advantages. First, it enabled pilots to detect even small deviations in engine behavior easily, before they reached a caution level. Second, it allowed pilots to scan all the instrument readings quickly and almost instantaneously determine if all the parameters were within limits. Several behavioral studies had indicated, in fact, that a column deviation graph format allowed a user to process up to 18 different elements in the same amount of time it took to process one, because the entire graph was perceived as a single item. [Ref 6-10]

Abbott started work on the concept in 1987 and began tests of the system in the TSRV fixed base simulator at Langley in the summer of 1988. A total of 16 NASA, airline and United States Air Force pilots participated in the study, which used the cathode ray tube (CRT) displays in the simulator to compare modern, conventional engine instrumentation displays against the EMACS concept. The results were striking. Using the conventional instruments, the pilots missed 43% of the engine faults introduced into the system. With the EMACS display, however, every single fault was detected, no matter how small.

In a particularly dramatic aspect of the experiment, the researchers introduced a similar kind of fault as the one identified as the cause of the Air Florida crash on the 14th Street Bridge in Washington, D.C., January 13, 1982. The problem on the Air Florida B737 jet was that the forward probe for the engine pressure ratio was blocked by ice. As a result, the EPR reading in the cockpit was erroneously high. Since pilots use the EPR gauge to set the engine power, the pilots of the Air Florida jet thought they had full takeoff power when, in fact, they did not. While the other gauges, such as the fuel flow, N1, and exhaust gas temperature, would have shown lower than normal readings because of the low power setting, they were not low enough to indicate a caution level, and the Air Florida pilots did not catch the problem in time. Using the conventional display format, the evaluation pilots in the NASA simulation study all missed the error, as well. With the EMACS display, however, the pilots caught the problem in time on every single run.

The pilots in the study reported that the EMACS display was significantly easier to use for both engine control and monitoring, and they showed an overwhelming preference for the EMACS format for fast detection of fault conditions. [Ref 6-11] Clearly, the technology had promise. The system was put on the TSRV 737 airplane in February 1991 to see if it would still work in realistic flight conditions. Since the objective of the flight tests was validation of the basic technology only, the tests did not include any industry pilots. Further flight tests were scheduled, but the push to finish the airborne windshear detection flight testing forced the EMACS research to be rescheduled.

Although the technology showed significant promise, the major airframe manufacturers still had some concern about the system's ability to judge ideal engine performance accurately over the life of an engine. Typically, as an airplane engine aged, its maximum performance would deteriorate, so the "normal" readings would change. Although NASA researchers believed that the parameters between a "normal" reading on the display and a cautionary one were sufficiently broad enough to allow for engine degradation, the concern remained. Nevertheless, the McDonnell Douglas Corporation did include an EMACS concept in the tentative baseline cockpit design for a future air transport airplane it planned to build, designated the MDXX. [Ref 6-12]

Interestingly enough, the most rapid application of the EMACS concept was not in the air transport industry at all, but by a general aviation avionics manufacturer. Representatives from ARNAV Systems, Inc. saw a NASA display of EMACS at the Experimental Aircraft Association annual convention in Oshkosh, Wisconsin in 1989. They liked the idea so much that they adapted the concept into a design for general aviation piston engines, and began marketing it as a component of the company's MFD 5000 Cockpit Management System in 1992. To cope with the problem of engine performance degradation over time, ARNAV developed an artificial intelligencebased computer program that would modify the ideal values as the engine aged. Although the initial version of the MFD 5000 did not incorporate all the elements of the EMACS display, it included the basic column deviation graph, and the company eventually planned to implement the entire EMACS concept. [Ref 6-13]

Displays of incorrect sensor readings during engine power-up for takeoff, similar to that experienced during the 1982 Air Florida accident at Washington National Airport. Top--Traditional display. Bottom--Engine monitoring and Control System (E-MACS) display. Note the visual superiority of E-MACS to warn flight crews of hazard.

The EMACS research illustrated an interesting aspect of technology transfer. Although the major manufacturers considered putting the technology on a nextgeneration airplane, that application process would take five or more years and would still be dependent on whether or not the technology proved itself costeffective enough to be included in the final cockpit design. EMACS was accepted immediately and enthusiastically, however, by a smaller company outside the mainstream air transport industry. Ever since Thomas S. Kuhn introduced his concept of "paradigms," theorists have argued that new ideas are often accepted first at the edges of an organization or industry. Smaller companies could generally move faster, had less inertia supporting the status quo, and had less to lose by incorporating new technologies or concepts. [Ref 6-14] While the theory did not necessarily apply in every case, the rapid transfer of the EMACS technology to ARNAV illustrated at least one example where the theory held true.