U.S. Patent  5,566,073   Oct 15, 1996    Pilot Aid Using A Synthetic Environment

The basic idea in flying an aircraft is to land in one piece without killing anyone and, hopefully, without damaging the aircraft.

There are two ways to fly an aircraft: Visual Flight Rules (VFR) and Instrument Flight Rules (IFR).

In VFR, you look out the cockpit window and figure out where you are and where you have to point the aircraft to get where you want to go.

The other reason you look out the cockpit window is to avoid flying into the ground, a mountain, or another aircraft.

In IFR you have the same goal, but in this case you do it by relying on instruments. There are instruments to tell you your altitude, your air speed, your heading, your orientation, and where you are.

In the old days you determined where you were by using a system of VHF radio beacons and a paper map. The map also gave you detailed information such as the height of the terrain, objects to avoid (like mountains or radio towers), airport approach patterns, and control tower frequencies.

Nowadays, with the Global Positioning System (GPS), it's much easier. Assuming everything's working and you are receiving the signals from the required number of satellites (and your GPS receiver isn't falsely telling you that the signals are ok), you just look at the readout for your latitude and longitude. There are even systems that provide a digital  map with the same detailed information provided by the paper map.

That should make flying easy, but it doesn't.

Flying under IFR requires that a pilot look at the readings from several instruments and mentally integrate them to determine the aircraft's orientation and position.

When a pilot is under stress it becomes difficult to do this. This is especially true when it comes to the aircraft's orientation. Because of how the human sense of balance works (the inner ear) it is easily misled.

The classic (and easy) experiment is to sit in a swivel chair and, with your eyes closed, rotate the chair a few times. Then stop. You will feel like you are now turning in the opposite direction even though you are not actually moving at all. With the 3D motion possible in an aircraft it is even easier to become disoriented.

Unfortunately, when this happens, pilots have a tendency to believe that their senses are correct and that the instruments are wrong. When pilots can see the outside world (VFR), they generally believe the outside world, but in IFR you cannot see the outside world.

This leads to pilots flying upside down or even straight into the ground. This is called "controlled flight into terrain" (CFIT) and includes the situation when a pilot isn't where he thinks he is and flies directly into the side of a mountain.

You might think that with modern technology this would be a rare occurrence. It isn't. An article in Aviation Week & Space Technology (AWST, 16 August 1999) reported, "According to the National Transportation Safety Board, in the past decade, CFIT caused 60% of air fatalities and 30% of U.S. general aviation accidents."

When John Kennedy Jr. was killed last year it was because he flew into bad weather, lost visual contact with the world, became disoriented, and flew straight into the water.

This doesn't happen just to private pilots.

In 1996 the pilot of a military aircraft flying into the Dubrovnik airfield in Croatia wasn't where he thought he was and flew into the side of a mountain, killing all souls onboard, including Secretary of Commerce Ron Brown.

In the early 1980s, Dean Martin's son (Dean Paul Martin) was flying a California Air National Guard F4. He wasn't where he thought he was and flew into the side of a mountain. (He was killed.) This was the same mountain where, several years earlier, Frank Sinatra's mother was killed in a private jet. The same thing happened, only from the other side of the mountain.

There is a technological solution to prevent this from happening.

In U.S. Patent  5,566,073  I came up with a method whereby I use a system like GPS to determine the aircraft's position as well as the standard instruments to determine the aircraft's orientation.

This information is used with a 3D description of the terrain to produce a synthesized 3D projected image of the outside terrain on a video screen.

The idea is that if you see an object on the display screen you should avoid flying into it.

The database is generated from several sources. The major one is a Digital Elevation Database consisting of an array of regularly spaced terrain elevations. The Department of Defense has a Digital Elevation Database for the entire United States where the elevations are spaced 1 meter apart. The U.S. Geological Survey  has a version of this database with the elevations spaced 30 meters apart.

Last year's Space Shuttle mission (STS-99) used a radar system to produce a digital elevation database for most of the world.

There are companies that make systems like the type I have proposed. Unfortunately, they cost around $1M apiece and require that a database be generated for each mission.

This is because the amount of data is so large.

A digital elevation database for points spaced 30 meters apart for the entire United States would require around 20 GBytes. It would also require a great deal of runtime processing.

I have come up with several methods for compressing the data. One method would put the entire database on slightly more than one CD-ROM. A DVD-ROM  would hold the database very nicely. This method is shown in U.S Patent  6,023,278  DIGITAL MAP GENERATOR AND DISPLAY SYSTEM. An alternative method is shown in U.S. Patent  5,974,423  METHOD FOR CONVERTING A DIGITAL ELEVATION DATABASE TO A POLYGON DATABASE.

Other advantages of my system are that it allows the pilot to select several feature such as pan, tilt, and zoom which would allow the pilot to see a synthesized view of terrain that would otherwise be blocked by the aircraft's structure, especially on a low-wing aircraft. The pilot can also preview the route either inflight or on the ground. Because the system has the ability to save the flying parameters from a flight, the pilot can replay all or part of a previous flight, and can even take over during the
replay to try out different flight strategies. Through the use of a head-mounted display with a head sensor, the pilot can have complete range of motion to receive a synthesized view of the world, completely unhindered by the aircraft structure.

It would also make a terrific Flight Simulator program for the consumer market. Witness the popularity of the Microsoft Flight Simulator.

My system can be implemented with a modern laptop PC, ruggedized to be used in an aircraft. A ruggedized version is necessary because unpressurized aircraft operate up to 15,000 feet. The lower air pressure at this altitude reduces the cooling efficiency inside the notebook. Even pressurized aircraft operate with cabin pressures of several thousand feet. Another area of concern is with the LCD displays. LCDs are made with glass plates that are hermetically sealed. The pressure and temperature changes cause the glass to expand and contract, weakening the seals until they fail.

The larger the display, the worse the problem becomes.

Fortunately, there are companies that make aircraft-rated LCD panels.

Another solution is to use a micro display.

A micro display is a small display (about 1" square) that is mounted very close to the user's eye, typically on a headset similar to a set of earphones. A lens system produces a virtual image that is equivalent to, for example, a 15" display 3 feet away. Current systems use either LCDs or the Micro Mirror Display pioneered by Texas Instruments. Current systems are also expensive, but a 1 square inch display has got to become less expensive than a 100 square inch panel (10" x 10"). Eventually, they should become very cheap.

The patent also contains a description of how 3D graphics works.

   5,566,073   Oct 15, 1996 
Pilot Aid Using A Synthetic Environment
Full Patent Image (1.7 MB PDF)

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Copyright 2001 Jed Margolin