by
Darryl Phillips
It's fun, once in awhile, to gaze into a crystal ball and predict how aviation can use technology to increase the joy and utility of flight, and improve safety too.
Besides mundane flying chores like keeping the shiny side up and not running out of gas, there are five items of information the pilot needs. Where am I? Where is significant weather? Where is significant traffic? Where are significant "hard" obstacles? Where are significant "soft" obstacles? These have one thing in common, they fit together beautifully on a moving map display.
WHERE AM I? We have that solved today, the moving maps do a great job. Most of them use GPS position, but loran or inertial or GLONASS or other navaids or some combination of the above can be used to accurately determine present position.
WHERE IS SIGNIFICANT WEATHER? This is a job for datalink. An immense amount of weather data exists on the ground, and it should be broadcast and displayed on the moving map in the cockpit. Unfortunately, the datalink experiments being carried out by Lincoln Labs and AOPA Air Safety Foundation use addressed datalink, not broadcast. But in my crystal ball, the information that applies to everyone must be broadcast to everyone simultaneously, just as ATIS or VOR or GPS signals are broadcast today.
If the same picture is sent to everyone, there is plenty of time to uplink pictures from all over the nation before it's necessary to update with fresh ones. Most pictures would go in the bitbucket, but if the pilot wanted to see the weather at Omaha or Fort Lauderdale it would be available. Precip radar, Doppler, lightning strike, we need to see them all.
On the other hand, if a separate copy of the picture is sent to one aircraft at a time, the ground-based resources will be badly strained during times of peak traffic. As more and more planes request data, the system will slow to a crawl. At some point certain participants (read: little airplanes) will be crowded out just as we are at busy airports today. It's true that concrete is a limited resource, but radio signals should be accessible to everybody, not just one recipient at a time.
From the FAA's point of view, the system being tested in Maryland has the advantage that all the recipients are known. Every aircraft has a unique electronic "address". Every plane is individually identified. That means that ATC will be able to charge each pilot for the services rendered. Whether you're in favor of privatized ATC or prefer socialized ATC the message is the same. If they can bill you for it, they will. That's why it's important to let the alphabet organizations know how you feel about addressed (Mode S) datalink before they give it their blessing.
WHERE IS SIGNIFICANT TRAFFIC? The pilot needs to see all traffic that might interfere with his flight. This is not a job for a ground based datalink. Many midairs (and a lot of near misses) happen below radar horizon, often in the pattern at outlying airfields. There is no way for ATC to uplink information about planes it cannot see. And it's stupid to utilize an overworked middleman when the two planes can electronically communicate directly with each other.
Eventually what will develop is something akin to "TailLight". The ad hoc collision avoidance working group headed by Phil Hodge came to the conclusion that datalink and collision avoidance are two distinct subjects. Phil coined the term TailLight to describe a low cost simple GPS-based box that constantly broadcasts it's three dimensional position and vector. Surrounding aircraft for ten or fifteen miles can receive each other's TailLight signal, just as we would see their strobes on a crystal clear night if we had perfect vision throughout the 360 degree sphere.
Strobes are not license plates. When we maneuver to allow for another aircraft we don't worry about it's registration number. The fact that he exists is sufficient, we don't need his identification. Likewise with TailLight, it is limited to the information the other pilots need. We shouldn't clutter the airwaves with unnecessary or undesirable data.
TailLight can display the traffic on a moving map. Or, the data can be used in a low cost box to announce the traffic audibly. Collision avoidance is different than datalink.
Is there a frequency available for TailLight? Yes! At the low end of the DME band are a number of channels that belong to the FAA and aren't being used. TailLight would fit on any one of them. For instance, channel 6X (967 MHz) is already assigned by ICAO to the individual nations to use as they wish, it is outside the military JTIDS activity, and it is eternally free of DME since it's paired with 1030 MHz. It is available.
All that is necessary for TailLight to become a reality is for FAA to say OK. No taxpayer dollars, no government involvement. Just allow us to use a frequency that's empty now. General aviation can develop TailLight to meet our flight safety needs, we can do it at a price that little airplanes can afford, we can do it quickly. All we need is for FAA to get out of our way.
A big advantage of the 967 MHz frequency is it's proximity to the cellular telephone band. There is immense R&D going on to produce cheap, low power, exotic performance semiconductors and other components for this band, and the benefits of this research are directly transferable to TailLight.
Likewise, it will be easy for FAA to use the existing cellular network to receive TailLight and relay the data to ATC. The infrastructure already exists. It's certainly cheaper than radar, and it works on both sides of the hill.
Air Traffic Control only has one function, to keep airplanes from bumping into each other. FAA spends thousands of millions of dollars each year to keep planes apart. TailLight will greatly increase air safety, and it won't cost the government anything.
WHERE ARE SIGNIFICANT HARD OBSTRUCTIONS? These are mountains and towers and those abominable aerostats. Things that can kill you. I used to think that these obstructions needed TailLight beacons, but wiser heads have convinced me that most obstructions should be contained in the database.
Paper maps show obstructions, right? So it makes sense that the electronic equivalent should contain the obstructions as well. Of course some of the moving maps already do.
This brings us back to datalink. Mountains don't move, new towers are only constructed occasionally, perhaps an aerostat will appear from time to time. Things change slowly. It's appropriate to keep all that data onboard, with uplinked revisions as needed. Pilots are accustomed to buying new paper charts and we're starting to get used to the idea of purchasing subscriptions to keep the GPS database up to date. But there is a better way. Datalink.
In the future, datalink should be used to keep the onboard database updated. Most information doesn't change, so it's a trivial job to uplink the few changes in the background, when nothing more important is happening. Gone will be the day when we have to revise approach books weekly or purchase those expensive database cards for the GPS. This is a use of datalink that many pilots won't mind paying for. Won't it be great to fly into a terminal area knowing that the latest changes are in the database and the moving map is 100% current? Even if a new approach has just been approved this morning, it will already be available to you.
WHERE ARE SIGNIFICANT SOFT OBSTRUCTIONS? "Soft" obstructions are things like Special Use Airspace, temporary restrictions (the prez, forest fires, concerts, olympics, all that), the status of military airspace, and so on. This is an uplink function.
NOTAMS are one of the biggest jokes in aviation. FAR 91.103 requires each pilot to be familiar with all AVAILABLE information concerning the flight. But "available" is subject to a wide range of interpretation. If just one FSS or FSDO knows something that pertains to your flight and you don't happen to talk to the right office, was that information "available"? Many NOTAMS are regional and not accessible prior to flight. But does that mean they weren't "available"?
In my crystal ball, I see a time coming when all this data is available via datalink. NOTAMS will be a thing of the past. If the FAA didn't value the information enough to put it in the computer, it's not the pilot's fault. And if the President suddenly decides to visit your region and a 25 mile radius is restricted, you'll be instantly aware.
Eventually, the whole idea of removable database cards should be obsolete. All revisions can be uplinked in the background and the distinction will blur between hard and soft obstructions, between NOTAMS and ATIS. If it pertains to your flight then it will be available.
If a particular aircraft chooses not to datalink, then he will either use paper charts or update his own database. Just as today. He will check NOTAMS on the telephone, just as today. Without datalink the pilot will probably be denied access to JFK or LAX, but there is nothing new about that.
Datalink and TailLight will reinforce each other, particularly in the IFR environment. Any aircraft with datalink capability can, on electronic request, downlink it's GPS position. The ATC radarscope can then keep the TailLight position tagged, and need only request an update if there is a potential for confusion, for example when one track crosses another. (Even then, the two aircraft had different altitudes so there isn't really "track crossing", it just looks that way to those who think in two dimensions.) In any event, ATC can reverify whenever it wants, but the datalink frequency isn't constantly overloaded with position reports from every aircraft.
In time, the present TCAS will become obsolete because it's capabilities will be much improved with TailLight. Datalink and TailLight will replace the transponder, and ATC can junk those expensive and obsolete rotating dishes.
Many police departments, fire departments, and ambulance districts keep track of their vehicle locations without radar. Aviation can too.
The obvious question is how do we get from here to there. I believe TailLight should be marketplace-driven. Immediately, flight schools that operate fleets of training aircraft would benefit from collision avoidance. Other TailLight users would be anyone who flies and does some other job at the same time. Fish spotters, traffic copters, all that sort of thing. They can benefit before the rest of us get around to installing TailLight.
Likewise, some military training commands would love to get TailLight. They are presently investing heavily in passive TCAS but they really need something better. Military acceptance of TailLight would provide a big push to those groups that are inertially gifted.
Simultaneously, the GPS/moving map people add the few chips it takes to implement TailLight. As more and more of these are installed, the number of aircraft we can see continues to grow.
The market segment I'm interested in uses no picture at all. There are reasons why some pilots will choose to not equip with a moving map. I want to build equipment that reports traffic audibly. This can be inexpensive as it needs no cosmetics, just a hidden black box that connects to the antenna and power and audio. Voice synthesis can be found in $20 toys at WalMart today, so it's certainly affordable.
We must put enough benefits in TailLight, at a low enough price, to get the vast majority of pilots to voluntarily equip. Loran and GPS have shown that the aircraft owners are eager to spend their money on products that provide tangible benefits.
The challenge to the FAA is simple: Lead, follow, or get the hell out of the way.