Kollsman Helps See in the Dark; It Makes Virtual Vision a Reality

Gulfstream Aerospace has become the first airframe company to commit to certificating an infrared enhanced vision system (EVS).

In October, the company will begin flight tests of an IR sensor developed by Kollsman, in conjunction with the Honeywell /GEC-Marconi HUD 2020 head-up display. The company is working with avionics suppliers and the Federal Aviation Administration to define a test program, and EVS will be offered as an option on the Gulfstream IV-SP and V.

Gulfstream has set an internal goal for certification in June 1999, according to president and chief operating officer Jim Johnson, but that goal "is pretty aggressive," he said in an interview with Show News. "Our own requirements are more stringent than the FAA's."

In an EVS, a thermal image is displayed on the HUD combiner, allowing the pilot to see runway lights at a safe distance despite fog, rain or smoke, and continue an approach that would otherwise have to be aborted. Currently, in the U.S., there are only 50 runway ends where it is possible to land with a runway visual range (RVR) of 700 feet, and then only if the aircraft is equipped with Category III landing systems and the crew is trained to use them. With EVS, says Kollsman, a Category I aircraft and crew can use more than 700 approaches under such conditions.

EVS procedures are designed so that the system is not critical to safety. As in the case of a normal Category I approach, the pilot must be able to see the lights and other features at a 200-foot decision height--with EVS, however, the pilot will see these at a distance well above the unaided visual range. If the pilot loses sight of the lights between the decision height and the end of the runway, a missed approach is executed. If the EVS fails after the decision height, and the pilot loses the lights, it is tantamount to a failure in the lights or a sudden change in visual conditions.

EVS has been highly controversial since the early 1990s. Northwest Airlines and Sextant launched a program to fit EVS to its older Category I aircraft, but encountered problems and dropped the project. One major avionics company concluded that IR sensors could not penetrate weather to any useful extent, as has a leading HUD supplier.

A key difference in the Kollsman system, however, is that the IR camera itself is specifically designed for EVS applications, including a lens and image processor which are optimized for detecting runway cues at normal approach distances, while filtering out flare from runway lights. The camera is designed to be installed inside the radome, beneath the radar.

"There are two things that have increased my confidence level" in EVS, Johnson said. "The technology today can easily handle the spectrum of frequency and amplitude changes in the lights--the early systems did not respond fast enough." The other step forward, he said, is that the raster HUD has earned its way aboard aircraft like the Gulfstream IV and V, making it a much less expensive proposition to install EVS.

The Kollsman camera will be field-tested this winter in a light aircraft: one of the challenges in developing EVS is the need to test it in a variety of conditions. Fog varies in density and consistency according to temperature, altitude and humidity; not all runway lights have the same IR signature; and the IR image of the runway is dependent on surface material and temperature. Meanwhile, Gulfstream will use a simulator to refine EVS procedures.

Almost half of the customers for the Gulfstream V want EVS, according to Kollsman. American Airlines has ordered EVS-capable HUDs for its 737-800 fleet, and is considering a move to the new technology.

By Bill Sweetman