Military

Military Spin

By Maj. Steve Colby | June 1, 2004

 

Panoramic NVG

Helicopters have long led the aviation pack in Night Vision Goggle (NVG) use, benefiting the most from the safety improvements that they provide. Obstacle and terrain avoidance, and terminal approach visibility are unsurpassed when used in concert with other spectral imaging devices such as Forward Looking InfraRed (FLIR).

To date however, goggle employment has been constrained by the device's physical limitations. Those limitations include field of view, image collimation, light magnification, and image blooming or halo effects around light sources. Further, it takes significant training and experience to learn how to cross check cockpit instruments effectively under the goggles. The military recently tested, and is starting to field, a generation of goggles that improve the field of view from 40 degrees circular to 95 + 5 degrees in azimuth by 38 + 2 degrees in elevation. This generation of goggles provides the helicopter operator unsurpassed image clarity and flexibility in goggle operations. They are called Panoramic NVGs

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The base model tested provided a frame in which four image intensifier tubes were mounted. The eyepiece optics are specially manufactured, blended optics that provide a smooth transition when moving the gaze back and forth from the outer to inner tubes. On the original model, the focus for the outer tubes was fixed. This is remedied in the current models, particularly through the design of the goggle tubes. These NVGs use "folded" optics, much like a pair of binoculars, to shorten the overall length of the goggle from eyepiece to objective. Although they outweigh a pair of F-4949 goggles by 50 grams, the short length of the moment arm makes them feel lighter to the pilot by reducing neck strain and the need for counterweight. The overall power consumption is greater than a standard F-4949 goggle in low illumination but a gated power supply uses less power in high illumination conditions. Best results were obtained using a 3.6V LS14500 Lithium battery and resulted in 4-hour battery life in low-illumination conditions.

The most noticeable improvement in these goggles was the dramatic increase in situational awareness afforded without having to move one's head. The pilot could position his head 45 degrees angle off the approach heading and move his eyes left and right to perceive closure and drift without moving his head to pick up the cues. This allows the benefit of good approach speed and drift situational awareness without the accompanying inner ear induced erroneous cues from rotating the head rapidly from front to side view while decelerating.

These goggles have an additional ability to integrate critical flight information screens into the image tube. The data is focused at infinity to allow the pilot to view the overlay symbols without having to refocus the eyes. This revolutionary Heads Up Display (HUD) technology has been around for years with fiber optic combiners. However, it is now a digital reality with active matrix electro luminescent (AMEL) or newer generation color screens integrated into the image tube. The obvious benefit to enhanced NVG HUDs is the ability to gather critical information like power, radar altitude, drift cues, pitch and bank, without looking back in the cockpit under the goggles. The safety benefits of HUD-based drift cues in a hovering helicopter are obvious. Hovering landings in brown-out/white out conditions are made simpler by using the HUD cues directly in front of your eyeball to stop drift prior to touchdown. Aircraft equipped with drift sensing capability like INS or Doppler and a data bus can integrate the HUD cues. When all crewmembers are HUD-equipped, a CRM technique to assign one member to audibly call out drifts in excess of pre-briefed parameters may dictate a go-round. This divides aircraft landing safety responsibility to the crew.

I see this technology having huge crossover (military to civil/para-public) applicability. Improving situational awareness and safety through technology is a means to improve our success in the Global War on Terrorism. To find out more about the manufacturers and availability, contact Martin Andries, Lead Engineer, ASC/FBXP, DSN 986-5169. Telephone: 937-656-5169 or e-mail martin.andries@wpafb.af.mil

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