COMBINED VISION SYSTEM (CVS): A CVS such as the one pictured here lets a pilot see a mashup of infrared imagery in the screen's center square and 3-D graphics around the edges. Image: Courtesy of NASA Langley
When large airliners approach an airport for a landing, a combination of radio signals and high-intensity lighting shows the pilot exactly where the runway is, even at night or in fog. But millions of people a year fly on smaller commercial planes, many private, that do not have such technology. The pilots of those craft must rely on less sophisticated instruments, along with their cockpit window view during landing, a situation that can be fatal in bad weather. In 2011 alone four such commercial jets crashed into terrain or an obstacle, killing 140 passengers and crew, according to avionics-maker Honeywell and aerospace research firm Ascend. The accidents are known as "controlled flight into terrain."
Landings could be safer if new navigation displays featuring nighttime infrared imaging and 3-D graphics that accurately portray an aircraft's surroundings become standard equipment on smaller commercial and private planes. In addition to the potential safety benefits, Gulfstream, Bombardier and other makers of small and midsize business jets are also learning that the same technology can save time and money by keeping flights on schedule even in the face of weather that would normally require runway circling or flight rerouting.
The new technology, which this writer observed firsthand during a recent test flight (see video below), actually combines and leapfrogs two earlier technologies only recently being installed on smaller commercial craft. Synthetic vision systems (SVSs) use terrain data culled from actual flights and stored in a database to create a 3-D graphical interface (think Windows or Mac OS) on a screen in front of the pilot and co-pilot, enabling them to see a digital model of their surroundings even when their vision is obscured by darkness or clouds. SVSs also include information about the location of airports and runways, to help guide pilots until they can establish visual contact with their landing destination.
"The primary purpose of SVS is to provide pilots with situational awareness—where the aircraft is, in relation to the terrain," says Randy Bailey, lead aerospace engineer for flight deck interface technologies in NASA's Aviation Safety Program at the agency's Langley Research Center in Hampton, Va. Situational awareness is an issue primarily for pilots of lower-end aircraft that do not have the autopilot or automated landing systems of high-end corporate jets or jumbo airliners. NASA has been studying SVS since the mid 1990s as part of a larger aviation safety program aimed at devising ways of reducing accidents in which a normally functioning aircraft slams into the ground, water or an obstacle.
Enhanced vision systems (EVSs) use infrared cameras located on or near the aircraft's nose to enable nighttime vision on the pilot's screen. EVS has gotten strong backing by the Federal Aviation Administration. According to FAA rules, by the time pilots descend to within about 60 meters of the ground they must be able to see the runway—or at least the runway lights at night or in cloudy conditions—in order to land their aircraft. But recently the FAA has made exceptions for EVS-equipped aircraft. Even if a pilot cannot see the runway or its lights at 60 meters, he is allowed to continue descending using the EVS until he gets to an altitude of about 30 meters. At that point, if he can see the runway or lights with his own eyes (not via EVS), he can land. Otherwise, he has to abort and take another approach, or circle and wait for the sky to clear. If most planes had this capability, more landings would occur first time and fewer planes would remain in the sky burning extra fuel.
Only about 1,000 aircraft are equipped with EVS today, and probably only three-to-four times as many SVS-equipped aircraft are in the air, Bailey says. Other aircraft in the same class do not have either system because the technology is expensive, yet these aircraft are the ones that often have the controlled-flight-into-terrain crashes.
By the end of February NASA will release the results of its latest commercial aviation safety research, which will analyze, among other things, the impact of pilot disorientation. Bailey says he cannot share specifics about the report before its release, but he does say, "Loss of control is diminishing, but unfortunately loss of state awareness, whether it's [fatigue] or attitude awareness, is not where it should be, and we're looking at potential technology interventions that might improve aviation safety."
Although SVSs and EVSs can each improve safety, a newer technology that incorporates the two may eclipse them both. Honeywell Aerospace, which sells an SVS for several Gulfstream and Dassault Falcon business jets and is developing an EVS, is one of a handful of companies pushing the development of a "combined vision system" (CVS) in which the pilot can see a mashup of 3-D graphics and infrared imagery. Individually, SVS and EVS have limitations. Because SVS is driven by stored databases, it may not display the latest changes in terrain, obstacles and urban feature data. And the infrared cameras in EVS cannot see through clouds or fog, and they also have a limited field of view that restricts the image to a small area.
Honeywell has been flight-testing its CVS since June 2010. In this research version, the pilot's screen features an infrared EVS image embedded within a larger SVS image. The EVS image can vary in size but is trimmed during landings to a narrow area in front of the aircraft to help focus the pilot's attention on the runway "without distracting him or her from other unnecessary clutter," says Trish Ververs, a technology fellow in Honeywell Aerospace's Advanced Technology division specializing on crew interface and platform systems. The CVS is expected to become part of Honeywell's SmartView product, although it must first be certified by the FAA.
Although this writer did not directly observe Honeywell's CVS during the company's test flight between Morristown, N.J., and Rutland, Vt., last month, both EVS and SVS were on display. The EVS monitor in the Gulfstream G450's cockpit provided a clear, sepia-colored view of the sky ahead and terrain below. Its use was limited for lack of necessity due to the clear day, which afforded visibility of about 60 kilometers. The SVS looked much like a flight simulator video game, except with a detailed portrayal of the actual terrain in 3-D relief bordered above by a bright blue sky. The screen included white indicator lines marking the Gulfstream's distance from features on the ground, including hills, lakes and runways.
Honeywell will have company when its CVS hits the market, most likely in a few years. Ensco, Inc., is likewise developing a CVS that extracts data and imagery from enhanced and synthetic views to form a combined image. Ensco's CVS, however, fuses both together over the entire screen. A full-screen combined EVS and SVS seeks to envelop the pilot in this information, Bailey says, adding that the advantage is providing a larger field of view for the pilot. There is a potential disadvantage, however, if some sort of mismatch between EVS and SVS information arises that could mask a problem.
Regardless of the details of how they are designed, CVS is the future of aviation safety, even if it will take a few years before it is commercially available, Bailey says. "Synthetic and enhanced vision systems are two different technologies but they're actually complementary," he adds. "What makers of CVS technology are trying to do is develop one display that has the best of both worlds."