In contrast to the stiff, rigid wings found on most commercial aircraft, flexible wing technology is considered essential to next generation, fuel efficient aircraft. However, flexible wings are susceptible to “flutter,” or highly destructive aeroelastic instability. The Lockheed Martin X-56A multi-utility technology testbed (MUTT) unmanned aerial vehicle (UAV) – a modular high-altitude, long-endurance (HALE) technology demonstrator – was specifically designed with long, flexible, very high-aspect ratio wings in order to investigate and test active flutter suppression technology.

To better understand and mitigate flutter, engineers at NASA’s Armstrong Flight Research Center (AFRC) equipped the X-56A UAV, or “drone,” with fiber optic sensing (FOS) technology.

For the last decade, AFRC has utilized FOS technology to perform distributed strain sensing and real time structural health monitoring during flight. Compared to traditional sensors, FOS technology provides an unprecedented level of insight into the behavior of a structure: a single hair-like optical fiber spanning up to 40 feet can act similarly to 2,000 or more strain gauges without the cumbersome and weight prohibitive instrumentation wire. In addition to strain, FOS can be used to measure temperature, deflection, stress, load, stiffness, and various other critical engineering parameters.

Engineers installed a two-line fiber system on both the top and bottom wing surfaces of the X-56A to simultaneously monitor the bending and cross-sectional rotations of each wing. The distributed strain data was acquired along the wingspan and used to derive the oscillation velocity of the wings which is indicative of flutter onset. As each fiber line is comprised of hundreds of sensing points, the FOS setup provided significantly more data and greater insight than traditional sensors.

Read the full article in the Automated & Connected Knowledge Hub.

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Ryan Scurlock is an application engineer at Sensuron. He holds a Bachelor of Science in Mechanical Engineering from San Diego State University and a Master of Science in Engineering Mechanics from the University of Texas at Austin. Before joining Sensuron, he held several research positions and served as structural engineer for a worldwide defense technology provider.