|Hardly a week goes by that
the evening news doesn't report another "near miss" (terminology recently
replaced by "near collision," for obvious reasons). Many involve
two airliners supposedly under "positive radar control."
Jets are invariably "on instruments" -- even in clear skies. Their flight crews operate busy cockpits, though, and depend, rightly or wrongly, on ground-based radar for "traffic advisories." Thanks to an unknowing electorate and Governmental neglect, all we really have is "see-and-avoid" (not "see and be seen," which is a silly phrase). Even under instrument flight rules.
Radar traffic advisories are often some help. Emphasis on "some." In the busier areas, traffic advisories are -- how can I put this? -- traffic advisories are hit-or-miss operations. When you need them most, the controllers are too busy to give them. And the particular pilots to whom controllers most need to talk may not even be tuned to the right frequency (along with most others here, this sentence deserves an exclamation point).
For decades, Government and industry have struggled with the problem of preventing mid-air collisions through airborne technology. The current proposal for CAS (Collision Avoidance Systems) is a grievous misnomer. "Avoidance" (the A in CAS) implies routine control, pre-planned and unexceptional -- the salutory properties of orderly flow. Instead we hear the frantic cries of CAS: "Pull up! Pull up!" "Collision evasion" would be a better term for the stuff.
As in all vital matters, there are at least three aspects: technical factors, economic issues, and human considerations.
The technical factors in airborne "black boxes" are formidable indeed. The instrument in each airplane has to measure its distance and direction to every other nearby airplane in three dimensions. The relative motions must then be determined. That's the "track-while-scan" mission dating back to the fifties all over again -- only from a moving platform. Reasoning from first principles, we quickly conclude that the problem has three parts: project, detect, and select. The equipment must project these airplane motions into the immediate future in order to detect potential conflicts and must then be empowered to select the proper "escape maneuver" for presentation to the pilot. Actually, pilots. We dare not permit the other plane approaching a deadly embrace to perform the wrong maneuver at the same time.
Any airborne system necessitates exchange of data from plane to plane. All planes, not just airliners. There is no benefit to anybody until everybody makes the requisite investment. Thus, the economic issues are plain enough. The cost of each box -- black or any other color -- can exceed the value of some of the planes that carry them. The common good would be served by a subsidy from the common wealth; however, unlike traffic signals, say, the analogous protection would have to be financed for installation in each and every vehicle, from eighteen wheelers to motor scooters.
Among the human considerations are what I call "the twin antagonists" -- False Alarm and Missed Threat. The smoke detector in your home should sniff a smoldering couch at the earliest moment but not sound off over burnt toast. You want the burglar alarm in your car to catch a nimble thief but disregard an innocent bump in the parking lot by a shopping cart. The biggest case of all: detecting the belligerent rocket as it emerges from its silo but not launching retaliatory strikes against a flock of geese maneuvering near the Arctic Circle.
Collision evasion is no exception. The system must achieve a balanced sensitivity. The requirements embrace the idea of discerning potential threats early enough to afford non-radical escape maneuvers -- while not crying wolf. After all, any airplane in the sky on a converging course might be considered a threat if your on-board system mindlessly projects its motion far enough into the future. Airline passengers will soon become fed up with sudden "pull-ups" (or, sooner with "push-downs"). Yet, we don't want pilots routinely "popping the circuit breaker" on the collision warning annunciator.
Whatever the merits of airborne collision evasion equipment, it is not a substitute for air traffic control, which in turn needs -- urgently needs -- improved collision avoidance equipment. The video game at your local pizza parlor has more advanced technology in it than the radars deployed throughout the entire ATC system. For self-evident reasons, most of the technology is best kept on the ground, but there are improvements sorely needed in avionics, too.
The current generation transponders are limited to 4,096 squawk codes. Pathetically few. The number is merely a vestige of the technological past, a time when, for each electronic "bit," we had to use one whole 12AT7 -- a vacuum tube about the size of your thumb. Now you can put thousands on a flake of silicon so small, a child's sneeze would blow it away.
With more codes, aviation authorities would surely assign a permanent identification for each airplane, an "electronic license plate," so to speak. Computers on the ground would then access tables of fixed data, including type and performance of each and every aircraft. Today's practice of repeatedly entering the information into the ATC system uses up critical radio capacity and imposes extra pilot and controller workload. More significantly, there exists no reliable "uplink" by which to communicate automatically with the pilot either for routine or emergency instructions. Let's fix that, too.
Even with today's primitive systems, much improvement is possible. For each parcel of sky, wouldn't it make sense to mandate some common frequency that each plane must monitor for traffic advisories? By the way, that is what they do -- in Australia.
Vehicles on the ground -- even pedestrians -- will some day have what's called "cellular telephony," which automates the connectivity protocol. Airplanes don't even have the equivalent of a phone number. Pilots still talk "half-duplex" on party lines -- the same as truckers over their cheap CB rigs. A plumber's pocket pager applies more sophisticated technology than the most advanced avionics to be found in airliners.
Aviation's priorities are scrambled. Collision evasion
systems will probably be shouting at airline flight crews before any other,
more effective measures become a reality. Wishful thinking has no
place in public safety. In a control environment characterized by
improved, ground-based automation -- true collision "avoidance" systems
that guide airplanes away from each other -- the airborne black box might
serve merely as a last-resort back-up. For safety's sake, let's start
using its proper name.