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Filling A Need
October 6, 2011

Chief Test Pilot Says Partnership Engaged Students And Offered An Example Of What Flight Test Is All About

William Gray, U. S. Air Force Test Pilot School chief test pilot with a group of students.William Gray, U. S. Air Force Test Pilot School chief test pilot with a group of students. (NASA Photo) › View Larger Image X-Press editor Jay Levine recently talked with William Gray, the U.S. Air Force Test Pilot School chief test pilot and staff advisor for Project Icarus: A Limited Handling Qualities Evaluation of Cross-Coupling. Gray talked about the value the project had for students in their partnership with Dryden researcher Bruce Cogan.

What was the biggest benefit to the TPS with this research project?
Every student in every class is involved in a student test-management project. It's always a real-world test project. We want it to be something that is important, valuable and new. There is a wide variety of these projects. This particular one was really good for us because this kind of research had never been done with fixed-wing aircraft and it needed to be done. It was a chance for our students to be involved in a project that would, no kidding, affect future planning and design of aircraft.

For them, it's just a fascinating project and they get the additional motivation of "it matters." It's not a make-believe thing. We don't do many make-believe things, but some things are more interesting than others and this is a particularly interesting one."

How were students selected for this project?
Students have opportunities to request the projects they work on, and this one was a match for several who were selected for it. It was a chance for them to work with engineering and sciences for which they had a lot of education. There was a lot of benefit to bringing home their education and a lot of benefit in terms of bringing home some of the stuff we teach them here about aircraft flying-and-handling-qualities testing.

        What were the biggest challenges?
From my point of view, the biggest challenge on any project like this is scoping it. Because to really, fully answer the questions that [Dryden researcher] Bruce [Cogan] had, that NASA had, and that we had, would have taken easily 10 times more flight hours and man hours to do. We had to scope it into something the students can do while they were still attending school eight hours a day. This is something that they do in addition to their regular schoolwork. We had to scope it [the project] to the point where they had a chance to get good, solid answers and not be overwhelmed with the amount of data or preparation. Nevertheless, they had to work hard. This was not a simple subject.

        What was the biggest success from a TPS standpoint?
There were problems they had to solve and whenever they are solving problems, they are learning. From the standpoint of the school, once again, we are producing information that is adding to the body of knowledge on how aircraft fly and how pilots interact with aircraft. We learn a lot when we put together a project like this.

       How did the aircraft fly with the algorithms?
We had to build these algorithms so that we could change the way the airplane flew in predictable ways. The big question was, if a pilot is controlling the pitch by pulling back on the stick to raise the nose, what if the airplane also rolls? So now the pilot would have to control that, too. It could roll a little bit, or it could roll a lot. It could roll so much that the pilot would lose control of the airplane. Vice versa, what if the pilot goes to roll the aircraft and it pitches too? Same thing. If it pitches a little bit, the pilot may not notice it. If it pitches a lot, it may give the pilot problems. If it pitches too much, the pilot may lose control of the aircraft. We looked at both of those factors from [the standpoint of] how much any given change would affect the flyability of the aircraft.

There were numerous times where we would run the algorithm on the NF-16D VISTA control laws, and students who were doing the flying in the front seat would lose control of the aircraft and the safety systems in VISTA reverted back to standard controls. It was very physically demanding.

How did it fly?
Sometimes it flew really well, sometimes really, really bad. They needed those data to see how the aircraft would fly with a certain amount of cross control.

        What do you think about the prospects of the flight experiment?
Data obtained from the flights resulted in development of a credible preliminary [flight] envelope. In a nutshell, designers could use the information in determining how an aircraft would fly with certain damage and the extent to which it could be controlled.

We understand the problem better now. A lot of times, when you are just starting out research, you sometimes create more questions than you answer but it just brings you that much closer to solving the original problem. With the guidance they have come up with, I think we are pretty far down the path toward having useful information for future designers.

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