(a)
displays the FSI result in green, as shown in Fig. 8a.
Case B: The P-FSI and S-FSI do not match, but the P-FSI (i.e., should be in) reasonably follows the S-FSI (i.e., is operating in) result. For example, the pilot is still holding at the higher SCA
(b)
holding altitude, but there is no reason that the pilot can not begin the descent to the lower holding altitude. In this case, the S-FSI would be “Holding High.” The P-FSI would be “Descending.” For these situations, we display the procedure guidance as shown in Fig. 8b. It says to the pilot, “You are currently holding high, but you should (c) begin descending to the lower altitude.” The pilot advisory system may display a message to that effect explicitly. Figure 8. Examples of procedure
guidance on a pilot display.
Case C: The P-FSI and S-FSI do not match and the pilot seems to (a) P-FSI and S-FSI results are identical. be performing a procedure that the pilot should not be performing. Pilot is performing expected procedure. Figure 8c, for example, is displayed if the pilot seems to be (b) P-FSI result is a flight segment that performing a vertical entry, but should remain outside the SCA. nominally follows the S-FSI result. The pilot Notice that the top line, which in all three cases is the State-based can transition into the next flight segment. FSI result, changes to a yellow color. (c) P-FSI result and S-FSI result do not
match or follow the expected sequence. The
The design of the Procedure Guidance display based on S-FSI pilot seems to be transitioning into an and P-FSI results deserves more research. In fact, it is still an open unexpected flight segment. question about whether or not the FSI results should be displayed at all.
D. Path Guidance
In the SATS HVO application, the NC&UGP research system has S-FSI and P-FSI implemented for the NASA-defined procedures. The FSI results are inputs to the Pilot Advisor, providing a context for evaluating the expert system rules. The system also includes Procedure Guidance (i.e., the display of FSI results as described in the previous section.) There was one additional feature added late in the project – a “wouldn’t-it-be-cool-if-we-could-do-this” feature.
The P-FSI had been successfully implemented and flight tested in the NC&UGP research system. The system includes Highway-In-The-Sky (HITS) guidance based on Nav3D Corporation’s synthetic vision software as shown in Fig. 9. But, the P-FSI result was not being used to drive the HITS. While the P-FSI “knew” that the pilot should descend from 3,000 to 2,000, the HITS would continue to hold the pilot at 3,000’ until the pilot manually dialed down the altitude setting for the HITS holding pattern. The team decided to try connecting the P-FSI output to the HITS. The result was striking.
Again, performing formal experiments on the value of automating the HITS guidance was outside the scope of our SATS project. This is an area that deserves more research. But the subjective and anecdotal evidence from the flight tests suggests that this could be the most important application for FSI technologies. With the P-FSI commanding the HITS display, the HVO procedures could be flown by “following the magenta, wire-frame highway.”
Figure 9. Screenshot from NC&UGP displays, including Highway-In-The-Sky.
IV. Fuzzy Sets and Flight Segment Identification
Our approach to flight segment identification has been based on fuzzy sets. Fuzzy sets are useful for describing sets in which the boundaries between the sets can not be crisply defined. The concept was introduced by Lotfi Zadeh in 1965.L. A. Zadeh, “Fuzzy sets,” Information and Control, vol. 8, no. 3, pp. 338 -353, June 196510 According to Zadeh, the stated purpose of fuzzy sets is to deal with “classes” that have no “sharply defined criteria of class membership.” A fuzzy set is completely defined by its fuzzy membership function, m (x), which gives the degree of membership of an element, x, in a fuzzy set. The classic example is that of the set of tall people. The height of a person will indicate whether or not a person is tall, but the boundary between tall people and short people can not be drawn at some exact height. Fuzzy sets allow the construction of system models when the sets that comprise the model are not clearly defined.
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