Distributed processing and fiber optic communications in air data measurement

This paper describes the application of distributed processing, fiber optics, and hardware redundancy to collecting airstream data in Princeton's digitally controlled Variable-Response Research Aircraft (VRA). Microprocessor-controlled instrumentation packages in each wingtip of the aircraft collect angle-of-attack and sideslip data in digital form; after scaling, filtering, and calibrating the data, they send it to the aircraft's microprocessor Digital Flight Control System (micro-DFCS) via digital fiber optic data links. Each wingtip's package is independent of the other; therefore, the system has dual hardware redundancy. The fiber optic link design is presented as well as a description of the calibration and communications software. Translation of the system's dual redundancy into fault tolerance is also covered. Results of preliminary flight tests are included.