Historically, transmission towers were only climbed to repair or replace hardware or light members. In recent years, formal condition assessment programmes have been introduced, whereby towers are climbed and inspected on an8 yearly cycle. This increased the amount of tower climbing considerably but it was not until tower painting of the galvanized lattice steel towers started in earnest in the mid 1990’s that the numbers of workers on towers grew enormously. The tower painting process includes a number of climbing operations including the initial assessment for painting, a number of quality assurance inspections, a final practical completion inspection and future defect liability inspections. Some of these inspections could be carried out using unmanned aerial vehicles (UAVs) Unmanned aerial vehicles or drones have been developing in the last few years at an exponential rate. In the case of electric propulsion vehicles the advent of lighter lithium polymer power packs has helped increase payload sizes and flight duration. The selection process for a suitable platform and accompanying recording/image capture equipment for the intended role was in itself an exhaustive exercise. Some of the aspects that were considered included the equipment cost, availability, durability, payload capacity and power consumption/flight duration. There is a large number of helicopter type UAVs in operation around the world, with numerous configurations from single rotor (traditional helicopter style) through to multiple (up to 9) rotor platforms. The flight control systems range from a simple radio control through to complex multi facet arrangements with GPS, navigation and autonomous flight capability. With the development of UAVs, aviation regulatory authorities have difficulty keeping up. Whilst there are no formal requirements in place currently, the company decided that working with the New Zealand Civil Aviation Authority (CAA) was essential, however it was an arduous task to finally obtain CAA approval. Several examples of condition assessment survey work were carried out using the Cyberquad on transmission structures. There are considerable benefits of having a platform Operator (Pilot) and payload Operator who are both qualified inspectors and condition assessment specialists with many years industry experience.
-Michael Boardman
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