Airworthy Cable Angle Measurement System For Slung Load Operations

One of the challenges of helicopter cargo missions is dealing with external slung loads. During flight, these loads often move in complex ways driven by forces generated by atmospheric effects and the helicopter’s downwash. A low-cost, accurate and airworthy system for measuring the load’s motion could allow for direct slung load stabilization by providing feedback to a human pilot, flight computer, or load feedback system. Advanced Optical Systems, Inc. will create an optical system capable of directly measuring not only the cable angle but also the load’s location and orientation, allowing us to determine if the load is rotating or undergoing a pendulum motion beneath the helicopter. This is more information than can be provided by a simple measurement of cable angle at the helicopter, and supports more sophisticated load stabilization approaches. The system will track loads through swings of 75° or more with an angular accuracy of better than 0.1°, and will be flexible enough to accommodate slings of varying lengths, from a handful of feet to 100 feet. By using LED or eye-safe laser diode targets on the load, we will be able to track the load even in degraded visual conditions such as brownout.