Charles Lindbergh knew it, and every pilot who has come after him has known it, too: if only there were some way of seeing through the clouds, of turning a black night into a sunshiny day, flying would be a far simpler, and by extension safer, endeavor.
The Sperry artificial horizon, introduced in 1929, at least gave pilots an idea of which way was up when they ventured into the milky white of an overcast day. But decades later, ADIs and modern EFIS still provided only this basic information, offering pilots little more than a rudimentary depiction of the world with a blue sky on the top, a white horizon line in the middle and a flat and featureless earth below.
Now that’s all changing, thanks to the arrival of LCD flight displays, computer processors, graphics adapters, GPS position and database models of terrain, obstacles and airports. The new technology, called synthetic vision, holds the promise of doing for pilot situational awareness what TCAS did for traffic surveillance, what weather radar did for storm avoidance and what gear warning horns did for belly paint.
The idea behind synthetic vision is to provide a virtual presentation of the world on the primary flight display that accurately recreates hills and mountains, lakes and rivers and even runways. A decade’s worth of work spent refining the corresponding databases means that errors have been all but eliminated, at least in populated parts of the world. As a result, many experts are convinced that synthetic vision will rank among the most important safety innovations of our time.
“If you can see the mountain in front of you, you aren’t going to run into it,” said Daniel Baize, synthetic-vision project manager at NASA’s Langley Research Center in Virginia. “With older technologies, the flight crew has to manually scan the instruments and integrate a picture of their current situation within their head.” But synthetic vision, he noted, provides the flight crew a real-world scene that greatly eases the task of, say, making an approach in the soup to minimums at an airport tucked in a mountain valley.
This is precisely the reason Gulfstream is going to such lengths to bring the technology to its top models, in the form of the integrated primary flight display (IPFD) under development with avionics maker Honeywell. Gulfstream announced that synthetic vision will be a feature of the PlaneView avionics system in its biggest jets by the end of next year, prompting rival Dassault to say it won’t be far behind with a similar project. Business jets from both manufacturers fly with versions of Honeywell’s Primus Epic avionics system, which supports the synthetic-vision technology.
Honeywell gave the trade and general press a chance to check out an early version of its system on the eve of NBAA’06. NBAA Convention News was among the first group of journalists given the chance to fly with the IPFD system, in Honeywell’s Citation V test airplane from Phoenix Deer Valley Airport. Although this was a prototype of the system presented on the Citation’s 8-inch by 10-inch primary displays, all the crucial elements were included, Honeywell promised. (The version of the technology that’s intended for certification in the big Gulfstream jets will be presented on the 14-inch-diagonal PlaneView displays, making for an even more impressive presentation, Honeywell said.)
Flying with SVS
For those seeing it for the first time, “impressive” is probably the word that best describes the IPFD concept. Where Chelton Flight System’s FlightLogic synthetic-vision system (the industry’s first certified SVS) offers a fairly elementary view of the world ahead, the Honeywell integrated display system is a far more compelling and true-to-life presentation. Hills and mountains in the Honeywell cockpit are recreated with illusory depth and texture cues that include an azure sky projecting a perfect, daylight VFR world, except for a thin haze far in the distance that, in truth, only adds to the feel of realism.
Honeywell’s SVS receives terrain, obstacle and airport data directly from the company’s enhanced ground proximity warning system (EGPWS), introduced in 1996 and flown more than 500 million hours in the real world since then. Noting that the EGPWS database has been refined and adjusted countless times to correct errors, Jary Engles, Honeywell’s chief pilot, said the SVS presentation is extremely close to actual terrain, even though it isn’t the real world. “It’s a model of the world,” he said, “but we’ve worked hard to ensure the model” is as free of errors and anomalies as possible.
Taking off at twilight from Deer Valley’s Runway 25L in the Honeywell Citation, Engles set the airplane on a course that would take us directly over Phoenix Sky Harbor Airport and on toward Williams Gateway Airport, where we planned to shoot an ILS approach. Traveling from the East Coast early that morning on a commercial flight, I’d been up since about 1 a.m. Phoenix time not counting a short nap that morning. By the time we were airborne in the Citation, at around 7 p.m. local, I was feeling tired but was also excited to try Honeywell’s SVS.
Engles handed over the controls and explained some of the system’s symbology, which I’d been briefed on in a sim on the ground. The display had the usual tape readouts of airspeed and altitude, but that’s about where the direct similarities between a traditional EFIS and this system ended. The real world ahead was nothing but blackness in front of the airplane, but as we left the shimmering lights of Phoenix behind us we could see the SVS’s virtual presentation of mountains in the distance, the foothills nearer and even a river below.
Also included on the display were guidance cues taken from Honeywell’s 2020 head-up display. Scanning the screen I noted there was a flight-path vector, a velocity vector and a speed chevron, all similar to the HUD symbology I’d experienced flying the Falcon 900EX EASy simulator at FlightSafety.
From the very first moments I took the controls, hand flying the Citation using the SVS display was simple and straightforward. Because I knew exactly where the threatening terrain was–and knew I could easily steer clear of it–situational awareness was high and workload reasonably low. The speed vector and chevron allowed for precise airspeed control, making for another item I didn’t have to worry about very much. Also, the flight-path vector made the task of altitude-keeping really not much of a chore at all.
On our approach to Williams Gateway Airport, a small airplane symbol appeared on the display just below the flight-path marker. There are hash marks on either side of this symbol (representing a traditional CDI’s dots) and a solid line showing the ILS inbound course. Put the airplane symbol on the line and you’re on course, Engles explained.
Williams Gateway Airport has three parallel runways. We were shooting for the center one, Runway 12C, a 10,000-foot strip used to train tens of thousands of Army Air Corps and Air Force pilots beginning in 1941. On the display each of the runways were easily discernable, but just to be sure there was no mistaking which one was dialed into the FMS, the SVS drew a green box around Runway 12C. Glideslope presentation was similar to that shown on a regular EFIS and, using the velocity chevron to maintain a precise approach speed, the ILS was about as uneventful as they come.
Rather than touching down, we performed the missed approach, which involved a climbing turn to the right. Engles explained that a Beech 18 many years ago flew this same procedure directly into the side of a mountain after continuing its turn to too far. As an exercise designed to show the value of the SVS display, Engles had us continue the turn as well. Rolling out on about the same heading as the Beech 18 pilot, it was clear that we’d better continue turning or start a climb soon because of ominous-looking terrain dead ahead.
“Now take a look outside,” Engles suggested. I did, and saw nothing but inky blackness.
If we had continued toward the mountains, the peaks would have started changing colors, Engles explained, from the sectional-chart-like brown hue to red and yellow, the same warning colors the EGPWS uses. An overhead plan map that always appears on the PFD would also show the red and yellow danger areas, as would the moving map on the MFD. In fact, just about all of the information provided on the 3-D synthetic display is also provided to the crew elsewhere in the cockpit. The difference is the pilots have to piece together a mental picture in their heads of their situation from disparate information, while the SVS performs the task for them.
On the way home Engles pressed a button and the SVS picture reverted to a regular ADI with its standard blue-over-brown horizon. “How’s that?” he asked. Interestingly, I immediately felt the fatigue from the long day closing in around me. It was uncanny. Without the 3-D picture of terrain, I was suddenly left to wonder where the mountains were, and it made my brain work and that made me feel tired.
Sure, I could glance over at the EGPWS display on the MFD, but that meant going back to a traditional instrument scan–something I hadn’t bothered with until now. I had also lost the use of the flight-path-vector marker when Engles hit the reversion button, meaning I had to pay closer attention to altitude. The speed trend vector was gone as well, and, even though I hadn’t touched the throttles, maintaining airspeed was one more thing to think about. “Hey, no fair,” I protested. With another press of the same button and a low chuckle Engles turned back on the sun and the world reappeared. The tiredness I had felt a split second before vanished as quickly as it had come.
On the descent back to Deer Valley Airport, Engles had us start down a little sooner than we otherwise might. We were pointed at a mountain ridge that lay between us and the lights of Phoenix. When I glanced outside over the nose, the high ridgeline was indistinguishable from the surrounding desert. Yet on the flight display we could easily see it and, more important, ensure we would safely clear the terrain by keeping our flight path vector and the solid white horizon line above it.
An approach to Deer Valley was a cinch thanks to a three-degree hash line that appears on the display below the flight-path marker when visual approach mode is selected. To plant the wheels on the touchdown zone, all the pilot has to do is wait for the hash line to reach the runway end and then push the nose over to put the flight-path vector on the runway end. The instrument scan on approach is kept to a tight focus. As long as the flight-path marker, three-degree hash line and runway end are aligned, you know you’re on the proper descent path. Lindbergh would have loved it.