Some have called enhanced vision the single most important advance in aviation safety since the introduction of airborne weather radar more than 40 years ago. And for good reason. Enhanced vision systems (EVS)–infrared cameras and/or millimeter-wave radar married to a HUD or MFD in the cockpit– provide pilots with outside visual reference from the start of taxi through takeoff, cruise and approach, right down to the landing flare. They let the pilot see the runway ahead, other aircraft and vehicles, and even terrain and obstacles in nearly all types of weather, day or night.
Gulfstream pilots who have flown with the FAA-approved Kollsman EVS, which projects a cooled FLIR camera image on a raster-capable Honeywell HUD, are effusive in their praise of the system. More than 40 such systems are awaiting installation at Gulfstream and production has been increased to meet demand for the $500,000 sensor package, now flying aboard larger Gulfstreams.
The FAA, meanwhile, has become so convinced of the operational and safety benefits of EVS that it drafted changes to the FARs that would allow the use of such devices during takeoff and landing, with “credits” granted for certain operations, such as descent below DH on a Cat I instrument approach. Taking into account the usual skepticism within the FAA of new and untested technologies, it becomes clear just how important the arrival of EVS really is.
Bones of Contention
But while industry reaction to the FAA’s proposed FAR changes has been largely positive, disagreements over a handful of the plan’s finer points have surfaced.
Current operating rules, for example, do not allow pilots to use EVS on approach when determining forward flight visibility as defined in the FARs. The proposed changes would permit descent below DH, DA or MDA (normally 200 feet on a Cat I approach) if the pilot can see the airport environment through the HUD even though it may not be visible to the naked eye–what the FAA now refers to as “enhanced flight visibility.” (The FAA proposes allowing a descent on a Cat I approach to 100 feet height above terrain.) But because the proposed language in the FARs deals only with Cat I approaches and HUD-equipped aircraft, several avionics manufacturers and aircraft builders criticized the notice of proposed rulemaking (NPRM) for being shortsighted.
In comments submitted to the FAA after publication of the proposed changes in February, equipment suppliers, business jet makers and industry groups voiced dissatisfaction over some of the perceived inadequacies of the proposal. Chief among the complaints was that the plan in some cases shortchanges commercial operators and that it fails to provide flexibility for the development of future technology such as short-wave radar and EVS systems that use displays other than HUD.
Consisting of 13 pages of definitions, explanations and revisions to FAR Parts 91, 121, 125 and 135, the NPRM serves as a comprehensive addendum to the current regulations, defining the new technology as enhanced flight vision systems, or EFVS–an acronym that is not expected to replace the widely accepted EVS. Industry players and trade groups have suggested several changes that are designed to improve operational benefits to operators while not compromising safety. Perhaps the most hotly debated was the flight visibility requirement of FAR 91.175(c)(2) and 91.175(d), long a sore subject with operators who argue that assigning a numerical value to a horizontal evaluation of flight visibility is simply not feasible. Several commenters suggested deleting the flight visibility requirement and instead allowing a crew to continue an approach if one of the 10 items (runway lights, threshold markings, VASI and so on) listed in FAR 91.175(c)(3) is identified.
Another criticism that appeared again and again (put forward by Gulfstream, Bombardier, NBAA, the General Aviation Manufacturers Association, CMC Electronics, Kollsman and others) centered on the fact that, as written, the rules would not allow a crew flying under Part 135 or 121 to start an approach if current weather is reported as being below published minimums. These are long-standing operating rules with which all commercial pilots should be intimately familiar. It was argued, however, that commercial operators flying with EVS should be permitted to begin the approach no matter what the reported minimums happen to be, as is the case under Part 91.
In its comments, Gulfstream said that unless these types of operational benefit are extended to Part 135 operators, “a business case for the inclusion of the technology in a revenue-producing aircraft cannot be made.” The airframe maker added that without the suggested change for Part 135 commercial operators, “adoption of the technology will be limited.” Others echoed Gulfstream’s attitude, writing that the NPRM should apply to commercial operators the same standards it applies to Part 91 operators.
Several commenters also wrote that use of EVS should be approved not only for Cat I instrument approaches, but for Cat II and III approaches as well. GAMA, for example, reasoned that because EVS provides increased situational awareness in poor weather, its use during Cat II and III approaches should be addressed. EVS manufacturer CMC Electronics took the argument a step further, saying that since EVS can be helpful even in zero-zero conditions, the pilot should therefore be permitted to use it.
A fourth major point of contention was that the NPRM allows EVS to be used only with a head-up display. Max-Viz, for one, has already certified a basic EVS for use on an MFD, and airframe makers say they would like the option of additional display choices. Future display technologies, argued some, could offer even greater performance. Some requested a change to the language, warning that the use of the term HUD may not stand the test of time.
Three players have emerged to compete in the market for EVS, with each company having certified or about to certify a variety of EVS products for civil aircraft. They are Kollsman of Merrimack, N.H.; CMC Electronics of Montreal, Quebec; and Max-Viz of Salem, Ore.
Kollsman was the first to gain operational approval of an approved EVS, the culmination of an intense flight-test program at Gulfstream that introduced the aviation world to the All Weather Window. The system is the only commercially certified EVS used with a HUD. Its main component is a cryogenically cooled infrared sensor with sufficient sensitivity and resolution to detect terrain and airports in fog, haze, smoke and precipitation.
Gulfstream has asked Kollsman to increase production of the system, now certified in a variety of Gulfstreams. The Kollsman EVS is included as standard equipment in the G550 and is an option in the G500, G400 and G300. So far it has been installed in 25 airplanes, each equipped with a FLIR camera in the nose and computer processors that overlay the infrared image on a Honeywell 2020 HUD. FlightSafety has so far trained 125 Gulfstream pilots to fly with EVS.
Edward Popek, EVS product manager at Kollsman, claimed more than 200 systems are on order. He added that the company is developing a next-generation system that will be lighter and feature an improved sensor, which he said may be offered by Gulfstream. Kollsman has also introduced Night Window, targeted at operators seeking only improved situational awareness during clear night operations. Able to fit on smaller aircraft, the $80,000 uncooled night VFR system projects a photographic negative-like image of airport structures and ground features, either as a real-time overlay onto a raster HUD or displayed on an MFD.
CMC Electronics and Thales, meanwhile, are jointly developing EVS packages for Bombardier’s Global Express and Global 5000. Designed for use with a Thales HUD, the system will be standard equipment on new Global Expresses beginning with about S/N 150 and will be offered as an option to Global 5000 buyers. Certification of the CMC-designed sensor is expected early next year, according to Mike Venables, the company’s EVS marketing manager.
CMC plans to deliver flight-test hardware to Bombardier this summer, with the test program to continue through the fall. The company also plans to certify a head-down display version of the system, but it would not offer landing credits, said Venables.
He added that the company continues to explore new sensor technology such as millimeter-wave radar, but said the limitations are the antenna size, image quality and cost. The major advantage of short-wave radar is that it can see through all types of weather, whereas EVS has a difficult time looking through clouds.
Max-Viz, the third market entrant, recently became the second company to gain operational approval of an EVS, this one an EVS-1000 in a Challenger 601-3A that portrays its image on a cockpit MFD rather than a HUD. The $129,000 (installed) sensor and display package places a forward-pointing remote infrared camera in the top of the airplane’s tail fin and a dedicated 6.5-inch video-capable LCD in the cockpit. Max-Viz expects that STCs for a number of additional business jet types will be completed later this year, said Jean Menard, director of corporate sales.
The EVS-1000 uses an uncooled long-wave IR sensor that allows pilots to see through fog, haze and smoke during approach and landing. Cessna has selected Max-Viz to provide its dual IR sensor-based EVS as an option aboard the Citation X and Sovereign. The EVS-2000 will be offered beginning later this year on new Citation Xs and Sovereigns and for retrofit to Citation Xs in service.
Max-Viz has also been holding discussions with helicopter OEMs, including Bell, regarding making EVS a factory option. In January, Max-Viz sales manager Chuck Aaron conducted a series of day and night low-level development flights in a Bell Cobra north of Los Angeles, using a three-sensor array feeding video to a Cinerama-style triple-segmented screen mounted on the glareshield.
The five-inch-high screen, which folds flat when not in use, has a total field of view of 159 degrees laterally and 40 degrees vertically. A single-sensor EVS-1000 system will cost an operator $80,000 to $100,000, depending on complexity of the installation.