Precision Path Autopilot (PPA)
There is a growing need for accurate measurements to assist in the study and understanding of dynamically changing Earth deformations resulting from disasters such as earthquakes, volcanic activity, and polar ice cap changes. Armstrong's PPA flight control system enables an aircraft to repeatedly fly nearly the same trajectory hours, days, or weeks later to obtain these measurements. The PPA consists of an embedded microcontroller-based flight computer and navigation algorithms that use externally provided attitude and differential GPS information to generate aircraft control commands. The system features a unique use of a controller area network (CAN) system and design interface to imitate an instrument landing system (ILS) and enable precise, repeat-pass flights.
Work to date: The technology was developed for NASA's Unmanned Aerial Vehicle Synthetic Aperture Radar (UAVSAR) program, which requires flight path repeatability. At 300-600 knots groundspeed, the PPA reliably keeps an aircraft within a 5-meter radius of a fixed line through space, whether the line is 30 or 200 miles long. This capability allows precise, repeat-pass interferometry for the UAVSAR program. The system has been used since 2007 in field science missions over Mount St. Helens, South America, Greenland, Iceland, Alaska, Japan, and all of California and Hawaii.
Looking ahead: The team continues to support the UAVSAR program in its science missions.
' The PPA system was designed, built, tested, and deployed at Armstrong. The supporting graphic displays and the pilot expertise required to efficiently collect data are key to its success. The system
has successfully supported the UAVSAR program in many science missions. '
Sean Clarke and Brian Strovers, PIs
Armstrong's Research and Engineering Directorate is responsible for the overall engineering content of flight research projects. Our engineers provide technical expertise in aerodynamics; guidance, navigation, and control; propulsion; static and dynamic structures; flight hardware and software; flight and ground test instrumentation and data systems; and system engineering and integration. They apply their expertise across the spectrum of Armstrong's many activities and also support the development and continual evolution of engineering tools and test techniques. Here are highlights from a few recent and particularly notable engineering success stories.