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.