Enhanced Vision: Final Link in Situational Awareness?

Over the past 100 years of flight–and, no doubt, for hundreds of years to come–an airplane pilot’s uppermost concern has been, and will continue to be, the need to maintain situational awareness. Where am I, relative to where I should be? How is the vehicle performing? What unknown or unseen hazards are out there? How safe am I? These are the essential questions that pilots instinctively, and continuously, ask themselves, from engine start at departure to shutdown at destination.

Indeed, loss of situational awareness is most often the causal factor in airplane accidents, from the student pilot who allows his airspeed to fall and stalls on the approach, to aviation’s worst disaster, when two Boeing 747s collided on the runway at Tenerife 26 years ago, killing 583 passengers and crew.

Unquestionably, avionics developments have done much to increase situational awareness and overall safety. Yet modern, well-equipped aircraft still have been involved in fatal accidents, particularly in poor visibility or at night. There are plenty of well-known instances, for example, the Boeing 757 that struck high ground during its night landing descent to Cali, Columbia, an accident replicated at Aspen, Colo., by a Gulfstream corporate jet. Tenerife was echoed at Milan, Italy, when an MD-87 on its takeoff roll collided with a Citation business jet that inadvertently entered the fog-bound runway. And at Taipei, Taiwan, where a Singapore Airlines Boeing 747 struck construction equipment when it attempted to take off on the wrong runway, during a rain storm at night.

Even in good visibility at night, threats remain. At Los Angeles International (LAX), a landing Boeing 737 hit a commuter Metroliner that was holding on the runway for takeoff clearance. And at Fort Lauderdale, a landing Boeing 767 narrowly missed a Boeing 737 that had taxied into takeoff position without air traffic control (ATC) clearance. In both cases, the runway lights made the aircraft invisible to the landing pilots.

A New Approach

All of these incidents had one common thread. In each case, disaster could have been averted by the use of infrared (IR) technology. Commonly called enhanced vision, IR allows pilots to see through rain, fog and darkness. Potentially, this technology could be the missing link in situational awareness.

For example, IR-enhanced vision provides a powerful safety-monitoring tool in non-precision approach operations, where no electronic descent path guidance is available and pilots must fly a series of progressively lower "steps" to reach the runway. These approaches have long been decried as the most hazardous of aviation’s landing procedures. Sometimes called the "dive and drive" process, the non-precision approach at Guam airport was a significant factor in the crash of a Korean Air Boeing 747 in August 1997, in which 225 passengers and crew were killed.

However, Larry White, a chief pilot who flies a Falcon 50 for Mariner Air, Seattle, gives evidence of enhanced vision’s benefit during an approach. "On a straight-in, non-precision approach to the Lawrenceburg, Tenn., airport, a relatively short runway for us, the IR clearly depicted a power line close to the approach end of the runway that we flew over," he recalls. "We adjusted our descent to hold a higher altitude until we cleared the power line. Even on the usual straight-in ILS [instrument landing system] approaches that we do most often, actually seeing the underlying terrain and obstructions provides excellent situational awareness."

Non-HUD Approach

Until recently, however, enhanced vision system (EVS) equipment was complex, costly and almost exclusively associated with sophisticated head-up displays (HUDs) in high-end corporate jets, where its use is tightly governed by Federal Aviation Administration (FAA) certification standards. The HUDs in top-of-the-line Gulfstream corporate jets, for example, use EVS sensors built by Kollsman Inc., of Merrimac, N.Y., while Bombardier’s Global Express uses an EVS sensor from CMC Electronics in Montreal. But because of their critical landing guidance functions and other characteristics, these EVS systems are both complex and costly, reportedly adding some $500,000 to the price of the HUD.

Now, Max-Viz Inc., a small company in Portland, Ore., has pioneered cheaper, compact EVS solutions that do not require a HUD. They use conventional, head-down multifunction or similar cockpit displays and therefore are not subject to rigid landing guidance criteria. In fact, FAA views head-down EVS as being similar to a TV camera through which the pilots can view the outside world. Unlike the HUD/EVS, Max-Viz’s solutions can not be used for primary guidance.

An STC Will Do It

Correspondingly, only a supplemental type certificate (STC) governs the installation of non-HUD EVS equipment to meet airframe airworthiness standards. As a result, the Max-Viz EVS-1000 system’s installed price, including an STC’d installation kit, runs about $120,000, depending on the specific airplane or helicopter.

Max-Viz has STCs issued or under way for a wide variety of aircraft, from the Boeing 767 airliner to the Bell 206 single-engine helicopter. Owners of airplanes as small as the Cessna 182 also have shown "serious interest in the system," according to a company official. Max-Viz sees impressive potential in the non-HUD market although it also builds systems for integration with HUDs.

"The adoption of EVS throughout the aviation industry is happening much faster than we expected," says Jean Menard, director of sales. "Our customers include business jets of all sizes, VIP aircraft, commercial and government helicopters, and even high-end general aviation aircraft. Our goal is to see EVS on every aircraft."

Today, the company offers two systems, the EVS-1000 and the EVS-2000. The difference between them is that the EVS-2000 uses dual IR sensors plus "sensor fusion" and other critical software.

Infrared allows vision through fog and darkness because it relies on radiated energy, not reflected light. All objects, including airplanes, runways, the chair you may be sitting in, this copy of Avionics Magazine, and even you, yourself, continuously emit IR radiation. An object’s emission level runs roughly proportional to its temperature. An infrared sensor can measure these emission levels, and its output can be converted into the equivalent of a thermal image, or picture, of the area being viewed by the sensor. Cooler objects appear darker, and warmer objects are lighter. And with today’s sensors, capable of discriminating between temperature differences of a fraction of a degree, these images can be startlingly realistic.

But infrared is a rather fickle medium to measure. Radiating in a spectrum just below that of visible light, its emissions can only be detected through three narrow "windows," because of atmospheric effects. These windows occur approximately between 1 and 2 microns, between 3 and 5 microns, and between 8 and 14 microns. A micron is a millionth of a meter, and the three windows are sometimes described respectively as the short-, medium- and long-wave infrared bands.

The view through each of these windows is subtly different. While all of the windows portray a thermal image of the outside world, each band has unique characteristics. For example, approach and runway lights appear clearly in the 1- to 2-micron short-wave band but become virtually invisible in the medium- and long-wave bands. For their HUD-related systems, therefore, both Kollsman and CMC Electronics chose a single infrared sensor that covered the low- and medium-wave bands, from 1 to 5 microns.

Max-Viz, on the other hand, opted for two separate sensors for its EVS-2000. One is in the short-wave and the other in the long-wave band. The system then fuses the outputs for a composite picture.

But HUD-dependent EVS units have a very limited market. On the other hand, the number of non-HUD-equipped airplanes that could benefit from EVS is enormous.

And this is why Max-Viz burst onto the scene in the fall of 2002 with its innovative EVS-1000 system for the non-HUD market. The company packaged a proven industrial IR sensor, known as a microbolometer, into a small tubular case. Its images can be displayed on a multifunction or similar display, or even on an electronic flight bag. The EVS-1000 sensor operates in the 8- to 14-micron long-wave band, which means that returns from approach and runway lights are minimized.

For operators wishing full-spectrum imaging, Max-Viz offers its EVS-2000 series, which covers both the short- and long-wave infrared bands. Cessna has chosen the EVS-2000 as its standard enhanced vision system for its Sovereign and Citation X, with retrofits available for Citation Xs in service.

In selecting an industrial microbolometer as its infrared sensor, Max-Viz took another pioneering step. It developed an uncooled sensor, when all earlier airborne infrared sensors required complex cryogenic cooling systems to achieve optimum efficiency. Max-Viz researchers found that, at the relatively short ranges required to avoid controlled flight into terrain (CFIT) accidents and for safety monitoring around airports and while taxiing, there is little significant difference in performance between cooled and uncooled systems. But there is a significant difference in cost.

Competition Emerging

Noting the EVS-2000’s forecasted mean time between failure (MTBF) of more than 15,000 hours, Cessna says it chose the Max-Viz system "due to the reliability of the uncooled systems, compared to cooled products on the market."

Interestingly, both Kollsman and CMC Electronics now plan to follow Max-Viz’s lead in adopting the 8- to 14-micron uncooled microbolometer in their own non-HUD designs. Kollsman’s Night Window and CMC’s SureSight M-series are expected to enter the market in mid-2004.

By the end of 2003, Max-Viz expected to have between 50 and 75 operators flying its new systems. Forecasting rapid growth in the years ahead, company officials appear undeterred by the future entry of two heavyweight competitors. "The potential market is bigger than all three of us," one official comments.

But the final word should go to chief pilot Larry White. His Dassault Falcon 50 is equipped with an EVS-1000. Says White, "How did we ever get along without it?"

FAA Rule for EVS

For the past several years, enhanced vision systems (EVS) have dominated the announcements of new avionics at the National Business Aviation Association (NBAA) show. NBAA 2003, held in Orlando, Fla., in early October, was no exception. It was distinguished by the anticipative buzz of imminent new Federal Aviation Administration (FAA) standards regarding EVS.

According to a notice of proposed rule making (NPRM) issued in February 2003 (docket no. FAA-2003-14449), the pilot of an aircraft equipped with EVS and a head-up display (HUD) can "go through a similar decision making process as required by existing regulations to continue the approach from the DA [decision altitude], DH [decision height] or MDA/H [minimum descent altitude/height] and safely maneuver the aircraft for a landing on the intended runway." A revision of the regulations for takeoff and landing under instrument flight rules (IFR), the new rule will allow pilots operating aircraft under parts 91, 121, 125, 129 and 135 to use an EVS/HUD during straight-in Category 1 instrument approaches or non-precision instrument approaches.

Visual contact of the runway during a Category 1 instrument approach at the decision height (200 feet) need not be with the naked eye or, as it is referred to in the NPRM, with "flight visibility." If the pilot can see the runway in the EVS/HUD, he can proceed with the landing, according to the proposed rule. This gives aircraft operators distinct advantages, including greater situational awareness and margin of safety, plus the allowance of "operations in reduced visibility conditions that would not otherwise be possible," according to the NPRM.

The FedEx Buy

While announcements of new developments in enhanced vision systems have focused on the business aircraft market, the largest recent sale of EVS involved the commercial aircraft market. FedEx Express is the first air transport operator to acquire the technology, having ordered the Kollsman All Weather Window EVS for its widebody fleet. Systems will be installed (one per aircraft) in some 200 of FedEx’s about 600 aircraft, including the Boeing MD-10 and MD-11 and Airbus A300 and A310.

The EVS infrared imagery, along with flight guidance information, will be projected on a liquid crystal, head-up display, to be developed for FedEx by Honeywell Air Transport Systems. Honeywell and Kollsman plan to have certification of the HUD/EVS completed by 2006 and installations beginning in 2007.

With enhanced vision, the express cargo carrier hopes to reduce weather-related delays, improve landing and takeoff minimums, and diminish the risk of runway incursions.

In addition to the cooled All Weather Window IR system, Kollsman also offers its uncooled Night Window system, which is smaller and less costly. It consists of an 8- to 12-micron forward-looking infrared (FLIR) sensor with an integrated IR window and optional electronics processing/power supply box for interface flexibility.

The All Weather Window was first certified on the Gulfstream V in September 2001. It is standard equipment on the G550 and G450.

The M-Series Competition

Soon Max-Viz will not be alone in offering an inexpensive enhanced vision system (EVS) for aircraft not equipped with a head-up display. CMC Electronics is expanding its SureSight family of EVS infrared (IR) sensors with a less expensive version of its I-series. The new SureSight M-series, expected to be on the market in early 2004, is an uncooled IR system that weighs less than 5 pounds (2.7 kg), which is about one-fourth the weight of the cooled I-series system. The I-series operates in the 1- to 5-micron wavelength range, while the M-series is in the 8- to 14-micron range, which is less capable of penetrating humidity and fog.

The I-series is part of Thales Avionics’ EVS package for the Bombardier Global Express, the newly announced Global Express XRS and, as an option, in the Global 5000. CMC delivered the initial, first-generation SureSight I-series sensor to Bombardier in September 2003, for flight testing in the Global Express. The testing will be in preparation for the sensor’s certification, anticipated in the second quarter of 2004. Bombardier expects to have the entire package (sensor and HUD), which the airframe manufacturer calls the Bombardier Enhanced Vision System (BEVS), certified by the fourth quarter of 2004, with deliveries in production aircraft beginning in 2005.

CMC is developing a second-generation IR sensor, which it plans to have approved and ready for installation in the Global Express XRS. Like other EVS manufacturers, CMC also is looking at millimeter-wave (MMW) technologies. A CMC spokesman says the company is evaluating MMW radar, which emits pulses and therefore is an active system, and MMW sensors, which are passive EVS systems.