SOLAR GLARE AND FLIGHT SAFETY

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Tags: Issue 3, 2017

A fair reflection?

Solar glare is a comparatively new and complex phenomenon affecting aviation; one that has become more widespread with the successful expansion of solar energy.

Given the relative infancy of regulation on solar glare, new problems are still being identified. In 2014, pilots complained about the level of glare radiating from the Ivanpah solar thermal plant in Nevada. None of the issued guidelines from the FAA were applicable, given its location away from airports and that it would not impact approach procedures to the nearest aerodromes. Yet a specific, government-backed glare study confirmed pilot complaints of significant ocular impact with potential for afterimage.

Our own work in this area, on behalf of Ingegneria Dei Sistemi SpA (IDS), concluded that given the line of sight and overall dimensions of a proposed solar plant in Italy, visual conditions for pilots on approach to a nearby aerodrome could be a hazard to aviation safety. Glare would occur, and be intense, creating discomfort for pilots on a range of approach types. Under such conditions pilots could experience temporary inability to scan the sky for other aircraft, significant distraction and discomfort, temporary inability to read instruments while manoeuvring and difficulty identifying navigational landmarks.

A traditional ATM safety approach deals essentially with systems failures, procedures, and human factors with regard to system usage, ergonomics and communications. Sunlight does not belong directly to any of these categories, so that glare from the sun is not included in a traditional safety study as a parameter. Instead, there are standards to make sure that cockpit instruments remain visible when in direct sunlight, for example, and pilots are submitted to medical tests. However, it has already been proven that glare from natural sunlight has contributed to aviation accidents (FAA study, 2003). As such, reflection should be considered as an aggravating factor in a safety study.

Our study with IDS involved complex geometric analysis, computing luminance, evaluating glare and simulating effects, testing against scenarios, and identified significant glare issues. The final report was accepted by the Italian CAA, including our proposed operational mitigations, but ultimately, the plant was not built due to other constraints.

This kind of work highlights the importance of properly evaluating impacts of new technologies, and of updating ATM safety procedures to take account of innovations, like solar energy plants.

For more information please contact Philip Church.

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