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In Plain SightIn Plain Sight

Enhanced vision systems to see the unseen The wind howled and the moon hid below the trees. It was not a good night in Nashua.

Enhanced vision systems to see the unseen

The wind howled and the moon hid below the trees. It was not a good night in Nashua.

But we taxied around the New Hampshire airport — Boire Field, known for its resident fauna — without worry, because we had a day's-eye view. The enhanced vision system (EVS) displayed what the infrared camera in the nose of the Cessna 340 saw, as we rolled toward a fuel truck that was running, its engine lit up like a hot coal, and as we turned onto the primary taxiway past rows of airplanes otherwise hidden in the dark. With our night eyes we searched for deer, although we found none. No matter — we could see the airport fence clearly, and the outline of the trees — even the clouds as they tumbled overhead in the tempest. Using our eyes alone, we could see nothing but the dingy yellow line on the asphalt outlined in the taxi light.

A couple of months ago, I witnessed a similar demonstration of the power of enhanced vision, out at Palm Springs, California. We took off after sunset in a Beechcraft King Air C90 into the black hole that is the bowl surrounding the desert city. Nothing outside according to the naked eye, but brilliant white outlines of the mountains all around us on the cockpit screen.

It reminded me of primary instrument training — one peek is worth a thousand cross-checks. Only in this case, we could see the mountains depicted on the sectional chart, but hidden from view out of the windshield.

Seeing in the dark

Forward-looking infrared (FLIR) technology began development in the late 1950s. A form of thermal imaging, FLIR detects — typically ahead of a vehicle — the heat emitted from virtually all people, animals, and objects, and it maps this rather than the visible light, allowing the user to "see" in low-light conditions (and the dark), and through light-scattering particulates like haze, and certain kinds of fog.

First developed for airborne use in combat and military targeting applications, FLIR took decades to gain purchase as a commercial product — although in hindsight, FLIR makes sense in cockpits from jet aircraft to helicopters to light airplanes on patrol. Two ranges of infrared cameras are widely available: long-wave infrared (LWIR) and medium-wave infrared (MWIR). LWIR senses at roughly the 8-to-12-micron range, and can detect heat emitted from several miles away; its use is limited at long distances by the scattering effect of air particulates. MWIR operates in approximately the 3-to-5-micron range and works more effectively in the face of scattering, but generally requires a lower-temperature sensor. Certain systems in production now have ranges in the near-infrared wave band, down to 1 micron, giving the ability to see not only terrain and airport infrastructures, but also approach and airport lighting.

A FLIR interfaces typically with a video display for viewing in the cockpit. Current systems use both analog and digital outputs, depending on the manufacturer and model, making them compatible with a wide variety of displays, from video monitors to multifunction displays (MFDs).

Another facet of FLIR that you may hear in the discussion: cooled vs. uncooled sensors. High-end systems found in business jet, airliner, and military applications use cooled sensors for high levels of sensitivity — they are literally air-conditioned, to maintain a consistent temperature across a wide range of environments (at temperatures as low as minus-60 degrees Fahrenheit). Uncooled sensors generally have much lower sensitivity but are far cheaper, lighter, and more compact since they require no cooling system.

The sensitivity gained by the cooled sensors allowed for their use as enhanced flight vision systems (EFVSs), as they were first recognized by the FAA. The EFVS (and some high-end systems known today simply as EVS) delivers a real-time, realistically framed video of the world in front of the infrared camera generally mounted on the nose of an airplane or helicopter. The view outside depicts the terrain, buildings, people, vehicles (especially if the engines are running), and animals otherwise obscured by darkness, haze, or fog. An EFVS provides Part 121 and 135 operators "credit" on instrument approaches down to 100 feet height above touchdown — somewhat akin to the ability to descend another 100 feet that a pilot gets for seeing the approach lights at decision altitude on a standard ILS.

Simpler EVS products have great application as well, for both personal and business use in Part 91 operations, as an enhancement to safety. Although typically delivered with uncooled sensors, these EVSs give the ability to see terrain and airport hazards in the dark (such as deer on the runway, or other airplanes on the taxiway) for a price that just keeps coming down.

You also can look forward to the EVS marriage with SVSs (synthetic vision systems), perhaps joining SVSs such as Honeywell's I-PFD (primary flight display) and Chelton's Flight Logic electronic flight information system (see " On Display: Chelton's Flight Logic Synthetic Vision," May 2003 Pilot) with rapidly advancing EVS technology. The union makes a lot of sense: The SVS supplies the terrain and navaid infrastructure (the constants in the picture outside), while EVS supplies the real-time, often-moving hazards, such as another aircraft taking the runway when you're on short final. The pilot also can compare the terrain and infrastructure that the EVS sees with what the SVS expects to validate each against the other.

Choices now

Ten years ago, the only EVS you saw regularly was on CNN, used by our military forces overseas. But companies have entered the market on both ends to provide general aviation aircraft owners and pilots with a list of EVS options that continues to grow.

In 1997, Gulfstream Aerospace debuted its Gulfstream V ultra-long-range business jet with the first EVS to be FAA certified on a civil aircraft. EVS I is now standard on the Gulfstream 550 and 450, and an option on the 500 and 350. Owners of large-cabin Gulfstreams (Vs and IVs) can retrofit the system.

The EVS originally certified on the Gulfstream V has been improved since then to an EVS II system, operating in the 1-to-5-micron range, at half the weight and one-quarter the volume of the initial system. The EVS II, developed by Kollsman (the company that you might have heard of when setting your sensitive altimeter — the Kollsman window displays the pressure), uses a sapphire window (up to one-quarter-inch thick), and has a digital video output. Noise equivalent temperature differences (NETDs), the smallest difference in temperature that an EVS can distinguish, are one-third that of competing systems, and the dynamic range (a sensor's ability to adequately image bright light and shadow in a scene) is greater. EVS II is now going into the FedEx fleet on Boeing 757s and 777s, McDonnell Douglas MD-11s, and Airbus A300 and A310s. It's scheduled for certification on several Gulfstream models this year.

If you're not in the market for a GV or 777, Kollsman has another option. The GAViS (General Aviation Vision System) is an EVS using an uncooled sensor to deliver the primary benefits of FLIR (the ability to see terrain and hazards in the dark) without the weight and cost. The antenna-like fairing houses the camera and weighs less than 4 pounds. Although the sensitivity is far less than that of EVS II (35 mK vs. less than 5 mK for EVS II), it still uses Kollsman's proprietary gain control algorithms for clarity. Kollsman has obtained parts manufacturing approval on the GAViS to allow for its installation in a wide range of aircraft; the current supplemental type certificate for Cessna Citations lists for $92,500 with the installation kit.

As noted before, Kollsman is teaming up with Chelton Flight Systems to link SVS and EVS using Kollsman's GAViS and Chelton's Flight Logic EFIS (electronic flight information system). Flight Logic is STCed in more than 740 aircraft; the marriage will utilize a new type of VGA screen on the system, and the latest Flight Logic software. At press time, the companies were not projecting an expected delivery date for the combined system.

For those pilots seeking to obtain most of the benefits of EVS in lighter aircraft, there is one more option for the time being. Almost three years ago, Forward Vision debuted a low-cost FLIR. The Forward Vision FLIR uses an uncooled sensor in the LWIR (7 to 14 microns), and a germanium lens to generate a 320-by-240-pixel image. Installations of the Forward Vision started on experimental aircraft, and continue with field approvals on production aircraft. Cost of the system is $14,995 plus installation and video monitor (several options are available through the company).

Max-Viz, suppliers of EVS to business aircraft and helicopters, has focused on EVS for the aviation industry exclusively for 15 years. Its EVS-1000 and EVS-2500 both use uncooled sensors (the 2500 has two); the 1000 utilizes LWIR and the 2500 combines LWIR with short-wave infrared for greater sensitivity at a maximum range. The products also include an upgradeability path that allows a user to move from a 1000 to a 2500 system if need arises, and for future upgrades to millimeter (super-long-wave) sensors that allow for greater penetration through clouds and fog, currently under development.

Forward Vision is now teaming up with Max-Viz to enhance both companies' product lines and plans an upgrade path for its systems in concert with Max-Viz, recently announced at the Sun 'n Fun Fly-In in April. Forward Vision debuted its EVS-100 long-wavelength (8 to 14 micron) infrared imaging system (a descendant of Max-Viz' EVS 1000 and Forward Vision's FLIR) with an integrated power supply and an RS170 video output. The EVS-100 comes enclosed in an aerodynamic pod for exterior mounting and weighs less than 1.25 pounds, according to the manufacturer. Price has been maintained at $14,995 plus installation and compatible display.

L-3 Communications has recently joined the EVS scene with its IRIS infrared imaging system, about to enter the STC market beginning with turboprops; the first STC goes on the Beech-craft King Air C90. IRIS uses uncooled sensor technology in the LWIR (7 to 14 microns), and a barium strontium titanate (BST) detector to generate a 320-by-240-pixel image. According to L-3, the BST detector is immune to solar radiation — the flash of the sun rendered traditional FLIRs blind with too much heat energy. Most modern EVSs accommodate for solar radiation in some way to minimize its effects. The IRIS installation we tested in flight was displayed on a Honeywell Bendix/King MFD. Retail price on the C90 is planned at $14,995 plus installation; the display is not included.

E-mail the author at [email protected].

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