Choices that air medical operators will make about investing limited resources in safety equipment are price-sensitive. For this reason, enhanced-vision systems without night-vision goggles’ expensive recurrent training requirements may be seen as a more viable alternative by many EMS operators. However, in addition to choosing NVG or EVS, some HEMS operators are flying with both.

One such is the Lee County, Fla. EMS operation, whose Eurocopter EC 145, the first of the type in commercial use in North America, is so equipped. Rick O’Neal, the Lee County EMS manager of aircraft operations, told HAI Convention News, “The Max-Viz [EVS] display is particularly useful close to the ground during approach and landing. A quick glance at the screen will confirm that the area is clear or reveal people, vehicles or obstructions. Both NVGs and the Max-Viz display have limitations; fortunately one’s weakness is the other’s strength. We feel that combining the two technologies gives us a complete picture.”

The NVGs amplify visible light and, like the human eyeball that they replicate, can have their vision degraded by smoke, haze, mist and dust–particularly the “brownout” phenomenon that can be encountered by a helicopter in a hover over bare ground. EVS, on the other hand, detects thermal energy at wavelengths outside the human vision spectrum, often “seeing through” such obscurants to produce an image in visible light. General aviation EVS cameras are fixed on “boresight” with a field of view ranging from 30 to 53 degrees, while the NVG allows the pilot or observer, with head movement, to scan 90 degrees or more to either side. The NVG will also pick up a faint “cold” light that an EVS camera may not.