A lightweight, robust fiber-optic system is the technology behind a new method to compute wing deflection and slope from measured strain of an aircraft. This state-of-the-art sensor system is small, easy to install, and fast, and offers the first-ever means of obtaining real-time strain measurements that can accurately determine wing deflection and slope during flight. Such measurements are particularly useful for real-time virtual displays of wing motion, aircraft structural integrity monitoring, active drag reduction, active flexible motion control, and active loads alleviation.

Armstrong’s technology can be used to calculate a variety of critical parameters, with specific wing deflection and slope measurements including complete degrees of freedom, i.e. three translational degrees of freedom (tx, ty, and tz) and three rotational degrees of freedom (rx, ry, and rz). These deflections are computed from the strain on the wing, which is traditionally measured using a strain gauge. However, such devices require measurements of multiple strain gauges over the wing, each requiring multiple wires. This increases weight and complexity, and it makes the measurement unwieldy in many applications with limited space. Armstrong’s technology requires only one wire per fiber-optic strain sensor for accurate measurement, decreasing weight and improving applicability.

From measured strain, an included computer program calculates wing deflection and slope along the line of the fiber-optic strain sensor. This enables real-time virtual displays of wing motion as well as accurate measurements of wing load. Accurately computing the load on the aircraft wing requires complete degrees of freedom at all structural finite element nodal points. Traditional methods are capable of measuring only sectional loads over the wing, without discernment between inertia load, drag load, etc. Armstrong’s approach enables measurement of the load over the entire wing, and it enables differentiation between different types of load. This has the potential to reduce fuel consumption by reducing structural weight through the use of active flexible motion control and by reducing wing-drag load.

This work was done by Chan-Gi Pak of Armstrong Flight Research Center. For more information, contact the NASA Armstrong Technology Transfer Office at This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to DRC-013-019.