Low-visibility approach tests by NASA and Rockwell Collins suggest that combining synthetic and enhanced vision systems so that the different image sources are apparent to the pilot is preferable to creating a fused picture. The flight tests, in a Gulfstream V business jet, evaluated ways of combining images from an infrared sensor and an onboard database on head-up and head-down displays.
The GV flights at Reno, Nevada were conducted under the SE-Vision project jointly funded by Collins, NASA and the US Air Force Research Laboratory. The aircraft was fitted with Collins head-up and head-down displays and weather radar for the test. The Kollsman infrared sensor for the GV's existing enhanced vision system (EVS) was retained.
Infrared-based EVS improves situational awareness in low visibility, but is degraded by weather. A synthetic vision system (SVS) offers immunity to weather, but requires highly accurate database and position information. "If you fuse the images, it is difficult for the pilot to understand the errors," says Tim Etherington, principal systems engineer at the Rockwell Collins advanced technology centre.
Combining rather than fusing the database-derived SVS image of the outside world with the image from an EVS infrared sensor provides greater integrity. Any discrepancy, or misregistration, between synthetic and enhanced elements of a combined image during low-visibility approach alerts the pilot to problems like loss of GPS position information, Etherington says.
More tests are planned for November in the US Federal Aviation Administration's Boeing 727 testbed, which will be fitted with the Collins HUD and radar and a Max-Viz dual-band infrared sensor. The 727 trial will include using Collins' WXR-2100 MultiScan radar as a forward database integrity monitor, looking ahead of the aircraft to confirm that obstacles and runways are where the SVS says they are. Air-to-ground detection of vehicles will also be tested.
GRAHAM WARWICK / WASHINGTON DC
Source: Flight International