Increasingly, business aircraft operators make new technologies buy their way onto their aircraft. Combined vision systems (CVS), ones that offer both a synthetic vision guidance system (SVGS) using a digital database and an enhanced flight vision system (EFVS) using infrared and visible light sensors, have potential to deliver that cost benefit.

Recently, we had the opportunity to fly Rockwell Collins’ Challenger 601, fitted with the latest HGS-6605 head-up display that has the CVS upgrade. The flight also enabled us to compare it to Dassault’s FalconEye HUD/CVS gear that we evaluated earlier this year.

HGS-6000- series HUDs have a 42-deg.-wide-by-30-deg.-high field of view, one of the largest of any HUD in current production. The projected CVS imagery, behind the primary guidance symbology, is a 30-deg.-wide-by-24-deg.-high background insert.

Both the Rockwell Collins and Dassault FalconEye SVS will have the requisite symbology, data integrity, performance monitoring and annunciations to qualify as SVGS and EFVS.

EVFS is provided by a triple-sensor EVS-3600, a more advanced version of the ES-3000 we’ve flown with Rockwell Collins’ compact HGS-3500 HUD. EVS-3600 is tuned to detect light and heat energy in three bands: (1) visible light in the .52-to-.95-micron band, such as energy emitted from LEDs; (2) shortwave incandescent and halogen bulb infrared in the 1.1-to-1.9-micron band; and (3) thermal background IR in the 7.0-to-14.o-micron long-wave band that detects subtle temperature differences in pavement, vegetation and paint stripes. Like FalconEye, EVS-3600 doesn’t include an older-generation, broad-spectrum 1.0-to-5.0-micron medium-wave IR sensor that stretches at its limits to detect some incandescent or halogen energy and some thermal background radiation.

In contrast to FalconEye, though, EVS-3600 has a designated shortwave IR sensor that is fine-tuned to detect peak thermal radiation at 1.7 microns from incandescent or halogen approach lights. The powerful IR heat emissions of an approach lighting system usually penetrate through fog and haze better than visible light from LEDs or long-wave IR thermal background radiation, so this sensor is given priority when images from the three EFVS sensors are combined.

Beyond the detection range of EVS-3600, SVS provides situational awareness in all weather and daylight/nighttime conditions.

As the aircraft nears the destination airport, a keyhole cutout starts to appear in the SVS background imagery, allowing both EVS and natural-vision views of the landing runway. The cutout in the background also allows a clear view of crosswind runways—an important safety feature, as it enables pilots to spot potential runway intrusions.

The design of Rockwell Collins’ CVS emphasizes simple operation. The pilot has a choice of four backgrounds on the HUD: (1) clear, (2) CVS, (3) SVS or (4) EVS. There aren’t adjustable upper and lower windows for SVS and EVS, as there are with FalconEye, and there aren’t individual brightness controls for SVS and EVS when they are blended together in the CVS background image. There is a single brightness control for CVS, SVS or EVS.

Rockwell Collins engineers believe that stand-alone controls for SVS and EVS window size, plus adjustments for SVS and EVS brightness, would prove to be distracting in the high-workload environment of final approach in challenging weather conditions.

Using Rockwell Collins current CVS, it may be preferable to use SVS and EVS separately on many approaches, adjusting the brightness individually for each mode, depending upon the prevailing visibility and weather conditions at the destination airport.

As we started up on Atlantic Aviation’s ramp at Portland we could see outlines of nearby hilltops, thermal images of the pavement and paint stripes and heat signatures of line-service personnel and turbine engine exhausts on the big-screen monitors in the cabin. Quite clearly, EVS is a significant aid at night in seeing the airport environment, people and traffic.

As we turned final on the approach, we were reminded of how effective HUDs are at helping pilots to fly smoothly and precisely by hand. The SVS’s igloo over the airport and extended runway centerline were most useful in aligning the aircraft for landing.

With nearly full brightness dialed up, the heat image of the approach lights could be seen in the distance. But we also wish we could have used SVS with the brightness turned down to use the keyhole cutout to spot the runway in the midst of all the airport’s artificial light glare. In our opinion, separate concentric, or adjacent, brightness control knobs for the SVS and EVS would enhance the utility of the CVS system.

Combined vision systems are likely to become the new standard for head-up displays in the future, much the same as EFVS virtually has become baseline equipment on top-end business aircraft today. Once they’re approved for credit to fly to lower approach minimums, they may become as vital to everyday mission completion as ILS and WAAS avionics.