The perfect instrument pilot will gain nothing from Garmin´s new synthetic vision technology (SVT) displays. But, for the rest of us, the three-dimensional images of terrain and obstacles presented on the G1000 flat-panel displays will give us the information necessary to avoid, or a chance to recover from, a potentially disastrous mistake while flying in the clouds or darkness.
Instrument or night flying requires a pilot to match often abstract numbers on a chart to what we see on a variety of instruments in the panel. Failure to fly the published heading, course or altitude in IMC or on a dark night can be fatal. But we humans are more analog creatures than digital. We navigate best whether walking, driving or flying by being able to observe our surroundings and make subconscious adjustments to our path to avoid obstacles.
Synthetic vision takes advantage of our analog brain processing power to supplement the necessary digital nature of instrument flying. SVT isn´t guidance, it´s backup. Turn the wrong way toward terrain instead of away from it, and you will immediately see your error and have a chance to recover. Misread the altimeter or numbers on the approach plate and SVT shows you the mistake. This all falls under the overused term of "situational awareness," but unlike other awareness aids, such as two-dimensional moving maps or ground proximity warning systems, synthetic vision requires no extra brain processing power. You see the terrain or obstacle from miles away as though flying in good VFR, and the avoidance path is instantly obvious with no further integration of information sources.
Synthetic vision is not brand new, but what is remarkable about Garmin´s SVT is the detail of the images and overall capability at a price suitable for all kinds of airplanes from light piston singles to jets. It will be available soon in the Diamond DA40 single and the Citation Mustang light jet. And SVT can be retrofitted to any existing G1000 system with a software change. At this point individual airplane types require specific approval, but it is possible that the FAA will issue multimodel approvals to speed up availability for the many types that have G1000 systems.
Garmin chooses to call its system synthetic vision technology instead of the more common synthetic vision system because, well, it can trademark SVT, but not SVS, and because more capability is planned for the future, so it wants to keep the emphasis on "technology" instead of system.
Garmin has been working on SVT for about five years with much of the effort spent on creating the software to transform digital topographical data into electronic images of hills, valleys, rivers and mountains. But even more effort went into figuring out how best to present the synthetic view of the world on the primary flight display (PFD) so that it compliments the data we need to fly on instruments without clutter or distraction.
The actual terrain and obstruction data is already stored in the terrain awareness and warning system (TAWS) database. TAWS is the system that yells out "pull up" if you get too close to terrain. It also shows blotches of yellow and then red to indicate approximately where the threat lies. TAWS was already a part of the G1000 system so the information to create the SVT images is already there.
In order for SVT to represent a faithful view of what we see out of the windshield, the synthetic images must be shown relative to the heading and track of the airplane. Track is the path of the airplane over the ground, and heading is where the nose is pointed. Those images only line up when there is zero crosswind and the airplane has no crab angle. If SVT did not consider both heading and track, a runway or obstacle would not be in the proper relationship to the nose of the airplane, and that would be potentially confusing when you break out of the clouds or are peering through murk or darkness.
To keep the SVT display in proper orientation both laterally and vertically the system needs to calculate the airplane´s flight path in 3-D. The flight path is not where the airplane is pointed, but is its current trajectory projected ahead based on forces acting on the airplane. You need inertial sensors to calculate a flight path because it is the inertia, or energy, that propels the airplane on its path, not airspeed or attitude.
Because of the inertial sensing requirement, flight path calculations were reserved only for large airplanes that could carry large, heavy and very expensive inertial systems, until recently. But the miniature accelerometer sensors that make attitude-heading reference systems (AHRS) now both small enough and affordable enough for a G1000 system can provide the information to calculate flight path. An AHRS uses acceleration measurements to determine changes in the attitude and heading, and that same acceleration data can measure the flight path through the atmosphere.
Flight path information is critical to SVT because it projects where the airplane will be relative to the terrain, and thus you can see if you will miss the mountain or land short of the runway. Mere attitude doesn´t work. For example, if you pull the nose up to clear a hill depicted on the SVT the nose would appear to go over the hill, but there may not be enough energy available to climb even though the nose is raised. The flight path calculation determines where the airplane is actually going, up-down and right-left.
Though the flight path calculation is fundamental to the internal workings of the SVT display, Garmin also wanted to show the pilot his flight path. The company experimented with various symbols to show flight path but settled on what is the norm in head-up displays, which is a circle with short lines sticking out like stubby wings and a vertical tail. The flight path marker, as Garmin calls it, appears on the display as soon as the airplane is accelerating down the runway and it projects the airplane´s path during all phases of flight. The flight path marker will be centered only under steady state flight conditions with no wind. At other times it will be moving around the display showing where the airplane is going, not where the nose is pointed.
Having flight path information makes possible some kind of highway in the sky (HITS) presentation that combines both lateral and vertical guidance in a single symbol. All types of HITS symbols have been experimented with over the years, but the one that NASA and other researchers have found works best for the entire range of pilot experience is a series of boxes in space that you fly through using the flight path marker. The boxes can describe a curved flight path and of course provide guidance vertically.
But Garmin´s own testing revealed that the pathways -- as it calls the boxes -- are not ideal for every pilot. The company found that it was impossible to beat the conventional single-cue V-bar flight director when it comes to commanding the desired pitch and roll to stay on the computed course. The V-bar intuitively shows the bank angle and pitch needed to satisfy the command, while it takes some experience to know what kind of maneuvering will move the flight path marker into the boxes. Bottom line, Garmin SVT has the pathway boxes and the conventional flight director, and you can select the boxes on or off.
SVT displays traffic information in a way I haven´t seen before. Instead of the normal TCAS diamond symbol with a plus or minus sign in front of a number of hundreds of feet to show relative altitude of the target, SVT presents the threat in 3-D. For example, if the target airplane is in your 10 o´clock position 100 feet above you and moving left to right, that´s where the target shows up on the PFD display. The symbol grows in size and changes color as the threat intensifies, but just as with the synthetic view of the terrain, an avoidance maneuver is obvious, requiring no numbers to evaluate. Instead of reading the plus sign and understanding the airplane is above you, and then reading the number of hundreds of feet, with SVT you look at the target, see its relative position and motion instantly, and quickly assess the threat and calculate an escape exactly as you would with actual visual contact.
To see SVT in action Garmin´s chief of flight operations Tom Carr and I saddled up in a Cessna 182 that had been used for much of the development and test flying. The wind was howling over 30 knots from the south, so turbulence and lots of big crab angles were going to make the display interesting.
Terrain is displayed on the SVT as soon as the system is aligned. There is a small hill between Garmin´s ramp and the runway, and even at taxi speed I could see the terrain was above the zero pitch line and we would not clear it without a hard right turn to follow the pavement. At 30 knots of groundspeed on takeoff roll the SVT shows the runway under you and the flight path marker is active. Terrain near Garmin´s Olathe, Kansas, home is pretty flat, but the SVT image has nice texture so it looks much like the real surface beneath you. Gridlines on the terrain help provide distance and height perception, and actually look much like the "section lines" that are common across the broad center of the country.
Tom pointed me at a nearby broadcast tower that is more than 1,000 feet agl and I put the flight path marker on the tower symbol shown on SVT. With the very strong wind the nose was pointed at least 20 degrees left of the tower, both on SVT and visually out the windshield, but the flight path marker showed we were flying directly at the tower. As we neared the obstacle it grew in size on the display. When the TAWS system calculated we were less than 60 seconds from impact, the tower symbol turned yellow. Less than 30 seconds from impact the tower symbol turned red and grew in size to occupy most of the center display area. It took most of my willpower not to turn away from the tower, or climb, before the 30 second warning because the display on SVT is so compelling, and threatening. It would be impossible not to immediately understand the threat and see how to avoid it based on SVT alone without the added TAWS alerts.
I flew very low over one of the big reservoirs in eastern Kansas and was pleased with how the blue water display contrasted with the blue sky presentation. There was no mistaking the color and subtle texture of the water for the normal "blue is up" display of the PFD.
I aimed at the hilly shoreline of the lake and watched as the terrain on SVT turned yellow to show that I was less than 60 seconds from coming too close with my present flight path. Soon the terrain that I would not clear without a flight path change turned red. It was obvious to me just from looking at the SVT image that I was dangerously close to the terrain without the color warnings, but they do provide another level of alerting for a possibly confused or distracted pilot.
Terrain is shown in topographical color fashion with lower elevations in green changing to darker shades of brown as elevation increases. There is a color scale that shows range of elevations that each shade of color represents. The only thing missing on displays of tall mountains is a snow cap. The terrain data resolution is nine arc seconds for much of the world, though some remote areas are not surveyed at that detail. Nine arc second resolution causes some rounding of peaks or valleys on the display, but I found the resolution to be remarkable in showing the rolling small hills and valleys of what most of us think as flat Kansas farmland. The overall resolution and detail of SVT is much better than other light airplane synthetic vision systems I have flown, and impressively close to the remarkable system Gulfstream and Honeywell developed for that company´s large cabin jets.
I must say that I was prepared to hate the pathway box display because I have not liked them on any other HITS display I have flown. But after a few minutes I began to appreciate the usefulness of the pathway, particularly for those G1000 installations that don´t have a flight director, or for pilots who don´t like or are unfamiliar with flying flight director commands.
The pathway boxes are actually rectangles that represent a block of airspace 700 feet wide and 200 feet tall. The size of the boxes shrink on an ILS or LPV approach as you near the runway, and in no case will the boxes be larger than half-scale CDI needle deflection. The boxes are spaced 500 meters apart and are presented in magenta if the guidance is GPS based or in green if the source is VOR/ILS. The box colors match the colors of the course information shown on the normal instruments. When you are on course you see four boxes. As the one fades from view as you fly through it, a fourth one appears 2,000 meters ahead. The spacing shows progress at slow speeds, and is not too distracting at high speeds. When not on course -- intercepting a course, for example -- there is no limitation on the boxes in view.
When approaching a course to intercept, the boxes appear as a string of dots in space placed at the desired altitude above ground. As you shallow the angle of intercept you can see they are boxes, not dots, and begin to maneuver the flight path marker into the boxes. It´s important to understand that it is the flight path marker, not the center airplane symbol on the PFD, that must fly through the boxes to stay on course. I followed the boxes around a holding intercept, a missed approach turn back to a holding fix and on a T-bone GPS type of approach. The spacing on the boxes -- at least at Skylane speed -- made it easy to see how the next box was moving left or right, up or down to fly curved procedures.
Flying the pathway boxes was not any easier for me than flying the V-bar flight director commands, but then I have many thousands of hours behind a V-bar. But the pathway boxes are visually expanded so they actually command a very precise path through the air. Just as when flying the expanded scale of a HUD, or the flight path guidance of Falcon Jet´s EASy cockpit, I felt like I was not being very precise because the flight path marker kept moving around in the boxes in the turbulence. But when I looked at the conventional CDI and glideslope needle they were not moving. Having the flight path marker at the edge, or even a little outside the box, didn´t cause the CDI needle to move even a quarter of its width. I think I would probably turn off the pathway markers after intercepting an ILS, for example, to remove clutter, but for terminal area maneuvering they really do work.
As you approach a runway that has been selected it appears much larger than actual scale on SVT. If it were shown in scale the runway would be a speck from 20 miles away. As the approach continues the actual runway appears on scale inside the expanded runway box, and on short final you see the runway number and the texture of the pavement of the actual runway in faithful size and perspective. Nobody would recommend using SVT for an actual zero-zero landing, but I bet I could make a survivable touchdown with it in an emergency.
Because SVT is being individually certified in each G1000 application, pricing and availability will be dependent on the airplane manufacturer. Every company that equips its airplanes with G1000 is doing its best to make SVT available as soon as possible and the upgrade can be performed at Garmin dealers with no hardware changes. Diamond was first to announce an SVT price of about ,000 for new deliveries and retrofit in the DA40, but each G1000 application is custom and unique to each airplane, so expect considerable variance in pricing.
It is tempting to believe that SVT will be useful only when flying near mountains because they provide all the visual drama on the display and are an obvious hazard. But the flying reality is that a 500-foot high hill is equally deadly if you are at 400 feet. Flying in clouds, reduced visibility or darkness is always more risky than flying in visual conditions because our natural orientation facilities are inhibited. SVT returns a pilot to a more natural world, one where our instincts can backup our procedures and provide reassurance that we are really headed for where we want to go. I find the capability, clarity and usefulness of SVT amazing at any price, but that such capability is possible for piston singles is something I never expected to see. And, most telling, when you push the button that turns the SVT images off and you are looking at only a brown and blue presentation of the PFD, it feels like you just flew into a cloud on an otherwise nice VFR day.
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