The intent was to build on our experiences from the previous semester and use a more powerful computer connected to an array of sensors on an airplane. The system would function much like the black box on a commercial airliner.
The AIP was required to be a self contained unit that recorded up to 10 channels of analog and digital data during flight. The maximum duration was 10 minutes, and the maximum sample rate was 10 Hz per channel. A Motorola 68000 microprocessor was specified. Data was to be stored in the computer until it could be downloaded after each flight via an RS-232 serial line.
For the aeronautical side of the project, a major objective was to demonstrate that a simple, low cost airframe could be built that would satisfy low labor requirements that were necessary in order to be practical in an academic environment. To that end, the fuselage was based on an aluminum ski pole, with the wing mounted on a pylon above the fuselage. The AIP box was mounted in front of the wing pylon. A foam nose was attached to the front of the box for streamlining and for absorbing energy in a crash.
The wing and empennage were of simple foam-core construction. The landing gear was constructed of piano wire and attached to the fuselage tube with hose clamps. A taildragger configuration was used.
An electric motor was used for propulsion. The rationale was that too often I'd seen students on previous projects spending too much time wrestling with small piston engines that were ill-behaved and unreliable unless they were treated with great care and skill.
Electric power was intended to sidestep that problem. Even though batteries had significantly lower energy density than fuel, I felt that disadvantage would be more than offset by fact that electric systems were easier to manage and were a better fit for an academic lab environment. For example, you could run the powerplant indoors without requiring special ventilation for the exhaust.
The airplane design had the motor mounted at the rear of the wing root facing aft. The motor used a pusher propeller that was just behind the wing pylon.
The following hardware was supplied by the Tucson Section:
By the end of the semester the ECE students had managed to get a breadboard version of the computer running, along with an electronic airspeed sensor that could be read by the computer.
In addition, the students had modified two servos so their positions could be read by the computer. Before the modifications, each servo had an internal potentiometer connected to the output shaft in order to provide position feedback to the servo electronics. The modification consisted of tapping into the pot with the intent of connecting it to an A/D converter on the computer.
It turned out that a flight-ready computer was not available by the end-of-semester deadline, so I substituted a Blue Earth microcontroller we had used on a previous semester's project. I connected one of the rate gyros to the microcontroller.
Although we hadn't installed the electric motor or control system by semester's end, the airplane, called the BA III, was ready for unpowered flight. We did perform some quick glide tests before the deadline, and we were able to download flight data from the rate gyro, which was configured to record pitch rate data.
Overall, the ECE students did an outstanding job, and Edward Lonsdale, the
professor teaching the course, had nothing but praise for them afterwards.
He also thought, as I did, that interdisciplinary projects like this were an
excellent idea.