To the average citizen, one aspect of Sunday’s air collision over the Los Angeles suburb of Cerritos was more than horrifying--it was offensive.
How in the world could a private aircraft blunder into the path of an airliner? Why couldn’t the air-traffic-control system keep them apart? Don’t we have rules and systems to prevent such things?
As with any responsible accident investigation, it will be many months before we know why the pilot of the Piper flew into reserved airspace, why the Aeromexico crew did not see him in time, or exactly what the air-traffic controller saw on his radar screen.
What we do know is that our methods for keeping high-speed airline traffic and low-speed private traffic apart is neither perfect nor (it would seem) adequate.
Certainly such actual midair collisions are rare, but the type of near-disaster that has been erroneously labeled the “near-miss” occurs more often these days. Even though certain blocks of supposedly inviolable airspace have been set aside for aircraft in contact with air-traffic control, other airplanes--usually small private ones--violate those areas constantly. Controllers will tell you privately of raised heartbeats and momentary panic as unknown targets “pop up” on their screens. Maybe the target is at a safe altitude, far below or above the controlled aircraft.
And maybe it isn’t.
On Sunday the altitude was the same.
Radio calls pointing out conflicting traffic are made constantly to airliners and other aircraft flying under the radar guidance of (and in radio contact with) air-traffic control. Every airline pilot is all too familiar with the difficulty of actually spotting such “targets” against the background of a city below or through the haze that characterizes the Los Angeles basin.
The dilemma is that once in a while one of those “targets” may actually be an airplane flying at the wrong altitude, and the airline crew may not see it in time.
That may have been the case on Sunday. Pilots, whether private or commercial, are supposed to be able to read their maps and follow the rules. Certainly if the rules had been followed the Piper would never have come close to the Aeromexico DC-9.
The rules, however, are an incredibly complex maze of lines and circles and numbers on an aviation map of the Los Angles area. Such a map is so complex on its face that human mistakes are not just possible, they’re guaranteed.
In other words, it is essentially a human problem. When human failure is certain (and the facts prove that such failures occur all the time), the solution is to build enough of a safety buffer into the system that even the worst imaginable blunder by a pilot will not metastasize into an accident. In the area of the Cerritos disaster the protected slice of air space looks like a pie-shaped wedge, each side roughly 15 miles long. The startling thing is that this specific wedge of California sky is only 1,000 feet thick--from 6,000 to 7,000 feet in altitude. This means that private aircraft, or anyone flying by visual rules and talking to no one, can fly over or under that thin corridor even though it is used constantly to funnel positively controlled air traffic into LAX. As Sunday’s tragedy proved, it is far too easy for a pilot to climb or descend right through that space by mistake. And since controllers are used to seeing unidentified traffic passing above or beneath the area, it is standard procedure for them to assume that none of those uncontrolled targets are at the wrong altitude.
The built-in confusion of what appears on the map to be a jigsaw puzzle of protected air-space segments, each with different altitude restrictions (and only a few extending from the surface up), must be simplified. Pilots should be able to know what areas are restricted by easy reference to their charts and to features on the ground. The number of places in which uncontrolled traffic can fly under or over controlled traffic must be minimized.
Other measures also can be taken. There now are calls for quick approval and installation of collision-avoidance systems (now in development) in all planes operating within high-density areas. This is a necessary goal, but it will take years to even begin to install such a system, and the cost of collision-avoidance devices may range as high as $50,000 per unit for commercial aircraft and $2,000 each for private craft. And there is another fallacy to this solution: It works only if all aircraft in the area are equipped with the same system. Let one single-engine airplane fly through the area without such equipment and it may be undetectable, which means that we are back to square one.
There are, however, measures that can improve the situation immediately:
--Do not permit any uncontrolled traffic to fly over or under a Terminal Control Area without the type of radio transponder that reports the aircraft’s altitude to the controller on each sweep of the radar beam.
--Educate private pilots about the vital responsibility of avoiding TCAs when not properly cleared. (Most private pilots are highly capable people who educate themselves on these issues, but the record is clear that there are too many exceptions.)
--Coordinate a campaign to track down and take action against pilots who do blunder into TCAs.
Studying the problem for five more years or waiting for the future deployment of some collision-avoidance system will not be enough to assure the citizenry that a Cerritos-style accident will not recur.
After all, the one constant in a human system is human failure.